b. determine the volume of water irrigated, v w, for each...

1006 Chapter 17 Agricultural Uses of Reclaimed Water

Irrigation Available Change in Cumulativevolume, Vw, reclaimed water, storage, �S, storage,

Month � 103 m3 Qi, � 103 m3/mo � 103 m3/mo ��S, � 103 m3

(1) (2) (3) (4) (5)

Sep 111.1 135.9 24.8 0Oct 57.3 118.9 61.6 24.8Nov 0 90.5 90.5 86.4Dec 0 94.0 94.0 176.9Jan 0 93.0 93.0 270.9Feb 0 90.5 90.5 363.9Mar 0 116.9 116.9 454.4Apr 72.5 113.2 40.7 571.3May 55.2 117.2 62.0 612.0Jun 256.6 135.9 �120.7 674.0a

Jul 463.4 135.9 �327.5 553.3Aug 361.7 135.9 �225.8 225.8

Annual 1377.8

aStorage volume requirement, Vs(est).

b. Determine the volume of water irrigated, Vw, for each month. For themonth of April, Vw is calculated as:

Vw � (Aw)[Lw(1)] � (1.576 � 106 m2)⋅[46 mm (10�3 m/mm)] � 72.5 � 103 m3

The values of Vw for each month are presented in column (2) of thefollowing table:

4. Estimate the net change in storage volume, �S. The net change is obtainedby subtracting Vw (column 2) from Qi (column 3). The calculated values areshown in column (4) in the computation table prepared in Step. 3. Note thatthe starting month in the table is rearranged such that the month when �Sturned from negative to positive is listed first.

5. Calculate the cumulative storage volume and the corresponding surfacearea of the storage reservoir. In this example, the cumulative volume inSeptember is set to zero, which represents an empty reservoir at the end ofthe irrigation season.a. The cumulative storage volumes are shown in column 5 in the computation

table prepared in Step. 3. The maximum value of the cumulative storagevolume is the estimated storage volume requirement, Vs(est), for thereclaimed water irrigation system. In this example, Vs(est) � 674.0 � 103 m3.

b. Determine surface area of the storage reservoir, As. Using the assumedstorage reservoir depth, ds, of 3.7 m, the surface area for the storagereservoir can be calculated as:

As � Vs(est)

ds�

674.0 � 103 m3

3.7 m� 165.4 � 103 m2 � 16.5 ha

Metcalf_CH17.qxd 4/1/07 01:03 PM 006Agricultural Uses of Reclaimed Water

17-3 Elements for the Design of Reclaimed Water Irrigation Systems 1007

6. Determine the adjusted field area by considering the net monthly gain orloss in storage.

a. Using the required surface area, determined in Step 5, the net gain orloss in storage volume, �Vs, due to precipitation (P), evaporation (ETres),and seepage can be estimated. The value for ETres can be estimatedusing the ETo data multiplied by the crop coefficient for a free water sur-face (generally 1.05 to 1.15). In this example, ETres was computed asETres � 1.1 � ETo. The monthly gain or loss from the storage reservoirfor April can be computed as follows:

�Vs � (P � ETres � seepage)(10�3 m/mm)(As)

� [38.1 mm/mo � 1.1 � 119.9 mm/mo) � 0] (10�3 m/mm)(165.4 � 103 m2)

� �15.5 � 103 m3/mo

The computed values of �Vs for each month are shown in column (3) ofthe following table.

Net gain or loss Adjusted Change CumulativeETres, in storage, volume, in storage, storage,

Month mm/mo �Vs � 103 m3/mo Vw � 103 m3/mo �S � 103 m3/mo ��S � 103 m3/mo(1) (2) (3) (4) (5) (6)

Sep 151.7 �24.4 97.6 �13.9 �8.0a

Oct 102.3 �12.5 50.4 56.0 13.9 Nov 46.1 0.9 0 91.4 69.8Dec 27.4 9.0 0 95.0 161.3Jan 29.1 11.5 0 104.5 256.3Feb 51.4 3.2 0 93.7 360.8Mar 88.6 �6.4 0 110.4 454.5Apr 131.9 �15.5 63.7 34.0 564.9May 180.8 �27.8 48.5 40.9 598.9Jun 214.6 �34.8 225.6 �124.5 639.8b

Jul 228.5 �37.8 407.3 �309.2 515.3Aug 194.5 �32.0 317.9 �214.1 206.1Annual �166.7 1211.1

aError due to adjustment. Assume zero.bMaximum design storage volume.

b. Determine the adjusted field area required. Using the values of net gainor loss of water, the adjusted storage area requirement can be estimatedusing Eq. (17-15). The adjusted field area, A′w is:

� 1.385 � 106 m2 � 138.5 ha

Aw¿ �Q � �Vs

Lw(1) � 10� 3 � (1377.8 � 103 m3) � (166.7 � 103 m3)

(874.5 mm) � (10� 3 m/mm)

Metcalf_CH17.qxd 4/1/07 01:05 PM Page 1007Agricultural Uses of Reclaimed Water


Based on the above calculation, the final area required for irrigation is reducedfrom 157.6 ha to 138.5 ha.

7. Determine the adjusted storage volume required.a. The adjusted volume of water irrigated each month, Vw, is calculated

using the irrigation area determined in Step 6b. The computation for Aprilis as follows:

Vw � (Aw)[Lw(1)] � (1.385 � 106 m2)⋅[46 mm (10�3 m/mm)] � 63.7 � 103 m3

The values of Vw for each month are presented in column (4) of the tablepresented in Step 6.

b. The changes in storage, �S is a calculated as Qi � �Vs � Vw. The com-putation for April is as follows:

�S � Qi � �Vs � Vw � 113.2 m3 � (�15.5 � 103 m3) � 63.7 m3 � 34 m3

The values of �S for each month are shown in column (5) of the tablepresented in Step 6.

c. The final design storage volume is determined to be 639.8 � 103 m3 bysumming the �S values for each month, as shown on column (6) of thetable presented in Step 6.

Comment

Theoretically, the adjusted field area, A′w, could be used to recalculate the irri-

gation water volume to further refine the design volume. However, the computedvalues are a conservative estimate, and an additional adjustment of irrigationarea and storage volume is usually not necessary.

The amount of water applied during each irrigation period, and the timing and fre-quency of irrigation are determined by the ability of the soil to hold water in the rootzone, the allowed water deficit in the root zone between irrigation periods, and the ETof the irrigated area. Because irrigation scheduling is site-specific, involving consid-eration of a number of complex issues, a detailed discussion is beyond the scope ofthis textbook. Information relevant to irrigation scheduling may be found in guidancemanuals and handbooks such as Pettygrove and Asano (1985), U.S. EPA (1981), andUSDA (1997).

17-4 OPERATION AND MAINTENANCE OF RECLAIMED WATER IRRIGATION SYSTEMS

An operation plan for the irrigation systems should be prepared by the designer at thetime the construction plans and documents are prepared. A list of information to beincluded in the operation plan is presented in Table 17-23. Operational issues discussedin this section include management of (1) demand and supply, (2) nutrients, (3) cropand soil, and (4) public health protection. Maintenance issues including monitoring andirrigation system maintenance are also discussed.

IrrigationScheduling

Metcalf_CH17.qxd 4/1/07 01:05 PM Page 1008

Agricultural Uses of Reclaimed Water

Blending reclaimed water with water from other sources is a common practice wherereclaimed water production during peak irrigation period is less than irrigation demand.Blending of different waters is beneficial for (1) increasing irrigation water supply reli-ability, and (2) improving irrigation water quality. Water from multiple sources can beblended in the reclaimed water storage facility or added to the irrigation system throughthe use of approved connections, such as air-gap separation.

The rate of fertilization varies greatly with crop type and local conditions. As an exam-ple, common fertilization rates in California for several crops are shown in Table 17-24.By appropriate irrigation and fertilization management, the amount of fertilizer applied

17-4 Operation and Maintenance of Reclaimed Water Irrigation Systems 1009

Demand-SupplyManagement

NutrientManagement

1. A map of the irrigation area showing the following information:a. Field or plot numbers, area, and cropb. Irrigation system layout and controlsc. Drainage system layout and controlsd. Other pertinent information

2. Soil profile information:a. Textural changes with depthb. Available water capacityc. Management-allowed deficiency before irrigation is scheduled

3. Crop information:a. How to establish the cropb. Crop rotations if necessaryc. Rooting depthd. Critical growth periods

4. Irrigation water to be used:a. Source (reclaimed water or blend of reclaimed and fresh water)b. Irrigation water quality constituentsc. Flowrates and time available for irrigationd. Operating pressuree. Control of flowrate or pressure

5. Schedule irrigation periods6. Procedure to stop irrigating7. Determining the number of fields to be irrigated at the same time8. The order of fields to be irrigated9. Operating sequence for starting the irrigation system

10. Operating sequence for stopping the irrigation system11. Safety checks12. Maintenance procedures and frequency13. Monitoring schedule required by regulatory agencies and/or for crop management14. As-built plans of the system (prepared after construction and added to the

operation plan)

aAdapted from Smith et al. (1985).

Table 17-23

Information to beincluded in anoperation plana



when irrigating with reclaimed water can be reduced significantly, or even eliminatedin some cases. It should be noted that crops may not exhibit an observable difference inresponse to nutrients in reclaimed water during the first year of irrigation withreclaimed water, especially tree crops (Edraki et al., 2004).

NitrogenNitrogen will be beneficial in the early stages of crop growth, but it is much less benefi-cial toward maturity. In some cases, however, application of nitrogen in the maturitystage causes excessive vegetative growth, delay in maturity, or reduction in crop quality(Ayers and Westcot, 1985). Generally, a concentration in the reclaimed water below 5 mgN/L will have little or no adverse effect on crops. Sensitive crops may exhibit adverseeffects such as reduced yield, late maturing, or poor crop quality, above 5 mg N/L, andabove 30 mg N/L for most other crops (see Table 17-5). Excessive application of nitro-gen to pastures may result in accumulation of nitrogen in forage and cause adverse healtheffects on ruminant mammals (Ayers and Westcot, 1985).

Blending reclaimed water with water containing a lower level of nitrogen or changing thewater source during the later stage of growth may be helpful for the sensitive crops. Use ofreclaimed water for crops that are less sensitive to nitrogen concentrations throughout thegrowth stages is another option. Many water reclamation plants constructed recently haveincorporated nitrification and denitrification to comply with the waste discharge permits(i.e., NPDES), and nitrogen concentrations in the reclaimed water are often less than 5 mg/L.

PhosphorousIf the concentration of phosphorous in reclaimed water is 5 mg/L, 1.0 m of irrigationwith reclaimed water per season will provide 50 kg-P/ha of phosphorous to the irrigatedland. Depending on the types of the irrigated crops, the amount of phosphorous removedwith the harvested crop can be less than what is added by reclaimed water irrigation (seeTable 17-24). Excess phosphorous will therefore be accumulated in the soil. Even thoughaccumulated phosphorous may not cause immediate adverse effects for most crops,some plant species are known to be sensitive to high phosphorous concentrations.


Common application rate, kg/haCrop or

crop category Nitrogen (N) Phosphorous (P) Potassium (K)

Citrus and subtropical 137 110 78Field crops 124 58 116Fruits and nuts 141 78 253Pasture 62 35 14Turf 523 124 247Vegetablesb 50–300 50–200 0–300Grapes 54 27 126

aAdapted from Rauschkolb and Mikkelsen (1978).bApplication rate is dependent upon the vegetable type.

Table 17-24

Typical fertilizationrates in Californiaa



Exposure to reclaimed water is controlled through regulations and guidelines to mini-mize potential health risk to the public and farmers. The requirements imposed at thesite of reclaimed water irrigation include irrigation methods, setback distance from theirrigated land, and the timing of irrigation. Generally the requirements are specifiedaccording to the crop to be irrigated and the method of irrigation. It is important tonote that water reuse for agricultural irrigation has been practiced widely in theUnited States, and other countries. No evidence has been reported that irrigation withreclaimed water has caused adverse health effects in 30 to 40 yr of experience.

Setback Distance from Irrigated LandRequirements for the setback distance from the area irrigated by reclaimed water arespecified in many state regulations and guidelines for the management of public expo-sure to reclaimed water. Setback distance requirements of selected states are given inTable 17-25.

Potential Health Effect of Trace Organic CompoundsAdverse effects of trace organic compounds through nonpotable water reuse applica-tions are considered to be minimal because water containing these chemicals will notbe ingested by humans. To date, limited information is available on the uptake of refrac-tory trace organic contaminants by food crops via reclaimed water irrigation, or onassociated human health effects from consumption of crops irrigated with reclaimedwater. Various impacts of trace organics have been reported in several studies, but littleor no controlled experiments have been conducted.

Short-term issues with the use of reclaimed water have been studied extensively anddesign considerations of reclaimed water irrigation systems are well established. Controlof salt is the primary issue in agronomic requirements, whereas public health protectionis the basis for the regulations and guidelines of reclaimed water use. Long-term effectsof reclaimed water irrigation have not been studied as extensively as the short-termeffects, but the effects are not considered to be significantly different from those withconventional irrigation waters.

Source Water ConsiderationsThe quality of source water and reclaimed water in southern California is shown inTable 17-26. As reported, both the salinity and sodicity of the reclaimed waterexpressed in term of TDS and SARadj, are both higher than the three major potablewater sources. Although the salinity and sodicity of the reclaimed water are withinacceptable ranges for most crops and plants, long-term salt accumulation in the rootzone and leaching to groundwater should be monitored to ensure sustainability of thewater reuse system.

In Israel, where about 70 percent of wastewater is reused for irrigation, the accumula-tion of salt is becoming a critical issue. Salinity is managed by strict source control,such as prohibition of brine discharge to the wastewater system, changes in water soft-ening agents and detergents, and strict discharge requirements for industries (Weber andJuanico, 2004). Desalination of high salinity wastewater has also been proposed(Rebhum, 2004) to reduce salt in Israel’s water recycling system.

17-4 Operation and Maintenance of Reclaimed Water Irrigation Systems 1011

Public HealthProtection

Effects ofReclaimedWaterIrrigation onSoils andCrops



Tab

le 1

7-25

Set

back

dis

tanc

e re

quire

men

ts fo

r co

ntro

lling

hum

an e

xpos

ure

to r

ecla

imed

wat

er in

food

cro

p ir

rigat

iona

Min

imum

set

back

dis

tanc

es,m

(ft)

Sec

onda

ry e

fflu

ent

Sec

onda

ry e

fflu

ent

Tert

iary

or

high

er tr

eatm

ent

with

out d

isin

fect

ion

with

dis

infe

ctio

nw

ith d

isin

fect

ion

From

From

From

From

dom

estic

From

From

dom

estic

From

From

dom

estic

impo

undm

ents

From

wat

erim

poun

dmen

tspu

blic

wat

erim

poun

dmen

tspu

blic

wat

erto

dom

estic

publ

icR

estr

ictio

ns to

su

pply

to d

omes

ticac

cess

supp

ly

to d

omes

ticac

cess

supp

ly

wat

erac

cess

irrig

atio

n m

etho

dsS

tate

wel

lw

ater

wel

lar

eaw

ell

wat

er w

ell

area

wel

lw

ell

area

and

timin

g

Cal

iforn

iaN

Ab

NA

NA

30 (

100)

c45

(15

0)c

30(1

00)c

15 (

50)

30 (

100)

NS

dIr

rigat

ion

met

hods

sp

ecifi

ed

depe

ndin

g on

re

clai

med

wat

er

qual

ity a

nd

irrig

ated

cro

ps.

Flo

rida

NA

NA

NA

NA

NA

NA

23 (

75)e

61 (

200)

Low

Ir

rigat

ion

met

hods

tr

ajec

tory

spec

ified

nozz

les

depe

ndin

g on

requ

ired

recl

aim

ed w

ater

with

in

qual

ity a

nd30

mir

rigat

ed c

rops

.(1

00 ft

)

1012



Haw

aii

45 (

150)

305

(100

0)N

S30

(10

0)91

(30

0)15

2 (5

00)

15 (

50)

30 (

100)

NS

Irrig

atio

n m

etho

ds

spec

ified

depe

ndin

g on

recl

aim

ed w

ater

qu

ality

and

irrig

ated

cro

ps.

Irrig

atio

n tim

ing

spec

ified

.

New

Jer

sey

NA

NA

NA

NA

NA

NA

23 (

75)e

NS

30 (

100)

Irrig

atio

n m

etho

ds

spec

ified

de

pend

ing

on

irrig

ated

cro

ps.

Was

hing

ton

NA

NA

NA

30 (

100)

15 (

50)

15 (

50)

NS

NS

Eff

luen

t qua

lity

requ

irem

ents

for

proc

esse

d fo

od

dete

rmin

ed o

n a

case

-by-

case

basi

s.

a Ada

pted

from

U.S

.EPA

(20

04).

b NA

�no

t allo

wed

.c Fo

r sp

ray

irrig

atio

n.d N

S �

not s

peci

fied.

e From

irrig

atio

n si

te a

nd r

ecla

imed

wat

er tr

ansm

issi

on fa

cilit

y to

pub

lic w

ater

sup

ply

wel

l.

1013


Reclaimed water quality should be monitored to ensure public heath protection andhealthy plant growth. Generally, 24-hr composite or grab samples are taken to monitorvarious water quality parameters. Sampling frequency for the different water qualityparameters and the list of the parameters vary in state regulations, and many of them areto be identified on a case-by-case basis. The sampling frequency should be decided tak-ing into account health risks associated with the reclaimed water applications, the size ofthe project, and the population exposed. Typical minimum monitoring requirements andsampling frequency in reclaimed water irrigation systems are shown in Table 17-27.Results should be checked against the numerical limits set for different reuse applications.

Two control points should be considered in the water quality monitoring: (1) the point wherereclaimed water leaves the reclamation system (treatment plant plus storage, if the storageis included in the treatment process) and (2) the final point of use. Current regulations andguidelines generally require water quality monitoring at the point where reclaimed water isproduced, and the monitoring at the final point of use is conducted most commonly byreclaimed water purveyors on a voluntary basis. An approved laboratory should be used toanalyze the samples and the results submitted to the appropriate regulatory agency.

When a potable unconfined aquifer exists below agricultural sites irrigated withreclaimed water, a groundwater monitoring program should be conducted. The moni-toring based on a set of wells and piezometers has to be defined on a case-by-case basisdepending on the reclaimed water quality and the hydrogeological context.


Table 17-26

Water quality data from a water district in southern California

Source A Source B Source C (Surface water)a (Groundwater) (Groundwater) Reclaimed water

Constituent Unit Range Average Range Average Range Average Range Average

pH — 8.9–8.2 8.2 6.8–9.0 8.0 7.7–7.8 7.8 6.5–6.8 6.6

Sodium mg/L 55–87 68 34–141 57 97–130 116 116–142 129

Calcium mg/L 24–56 37 2.8–65 31 42–100 75 37–68 49

Magnesium mg/L 12–23.5 17.5 ND–14 6.2 11–32 19 11–26 18

Chloride mg/L 67–105 81 12–35 19 51–71 62 102–183 137

Sulfate mg/L 41–177 109 4.7–131 47 110–400 267 110–248 163

Alkalinity mg/L 73–112 89 109–269 153 179–193 186 101–150 127as CaCO3

TDS mg/L 278–528 384 188–432 267 450–850 670 566–812 680

SARadj — 2.2 2.7 3.7 4.2

% of total % 45 50 5supply

a26–100% from State Water Project (water from northern California), 0–74% Colorado River water.

ND � not detected.

MonitoringRequirements



17-5 CASE STUDY: MONTEREY WASTEWATER RECLAMATIONSTUDY FOR AGRICULTURE—MONTEREY, CALIFORNIA

Monterey Wastewater Reclamation Study for Agriculture (MWRSA) was the first largescale study designed to investigate the risk and effects of irrigation with reclaimed water onfood crops that included raw-eaten vegetables. The MWRSA started in 1976 and the finalreport of MWRSA was published in 1987. The report has been used as a standard for studydesign of agricultural irrigation with reclaimed water not only within the United States butalso in different countries. A brief overview of the MWRSA is described in this section.

17-5 Case Study: Monterey Wastewater Reclamation Study for Agriculture—Monterey, California 1015

Table 17-27Typical minimum monitoring requirements and sampling frequency in water reuse systems for irrigationa

Raw wastewater and Groundwater

Parameters reclaimed water Receiving soils Shallow aquifers Deep aquifers

Coliformsb Weekly to montly — Bi-annual AnnualTurbidity On-line for unrestricted — — —

irrigationChlorine residual On-line for unrestricted — — —

irrigationVolume Monthly — — —Water level — — Bi-annual —pH Monthly Annual Bi-annual AnnualSuspended solids Monthly — — —Total dissolved solids Monthly — Bi-annual AnnualElectrical conductivity Monthly Bi-annual Bi-annual Annual

(ECe)BOD Monthly — — —Ammonia Monthly — Bi-annual AnnualNitrites Monthly — Bi-annual AnnualNitrates Monthly Annual Bi-annual AnnualTotal nitrogen Monthly Bi-annual Bi-annual AnnualTotal phosphorous Monthly Bi-annual Bi-annual Annual

(extractable P)Phosphates (soluble) Monthly Bi-annual Bi-annual AnnualMajor solutes (Na, QuarterlyCa, Mg, K, Cl, SO4,HCO3, CO3)Exchangeable cations — Annual — —(Na, Ca, Mg, K, Al)Trace elements Annual — — —

aAdapted from Lazarova et al. (2004).bUnrestricted irrigation of landscape and food crops may require higher sampling frequency and additional monitoring parameters.

Metcalf_CH17.qxd 12/12/06 06:07 PM 15


The area around Castroville in Monterey County, California, is a national center forartichoke production. The area also is a major production site for various food cropsincluding broccoli, asparagus, carrots, cauliflower, celery, spinach, several varieties oflettuce, and more recently, strawberries. Agriculture is a major business in MontereyCounty, generating almost $3 billion/yr as of 2004.

Until the 1980s, groundwater was the primary source of irrigation water in MontereyCounty. Intensive groundwater withdrawal resulted in depletion of groundwater levelsthat resulted in seawater intrusion, rendering some well water unsuitable for irrigation.Meanwhile, expansion of the wastewater treatment facilities was required because theexisting facilities in the region were reaching full capacity. The Water Quality ManagementPlan by the California Central Coast Regional Water Quality Control Board recom-mended that water reclamation be proven safe before regional implementation could beconsidered. This recommendation became the incentive for conducting the 10-yrMWRSA project to assess the safety and feasibility of agricultural irrigation withreclaimed water (Sheikh et al., 1990).

The ultimate objective of the MWRSA was to demonstrate the overall feasibility of waste-water reclamation in northern Monterey County. The three primary concerns were:

1. Wastewater constituents

2. Agronomic concerns

3. Feasibility and public acceptance

Various federal, state and local agencies, as well as local farmers, participated in theMWRSA, with the Monterey Regional Water Pollution Control Agency as the leadingagency.

Wastewater ConstituentsBefore Monterey County started the development of water recycling projects in 1980s,the Castroville Wastewater Treatment Plant was the main treatment plant, treatingwastewater at a capacity of 1.5 � 103 m3/d (0.4 mgal/d). The treatment plant was mod-ified and upgraded as a field-scale pilot plant with the process specified in the originalCalifornia Wastewater Reclamation Criteria (Title-22 process), and a less extensive fil-tration process (FE process):

• Title-22 process: coagulation, flocculation, sedimentation, filtration, and chlorination• FE process: coagulation, flocculation, filtration, and chlorination

Dechlorination of the final effluent was practiced for the first 3 yr of the study but dis-continued thereafter to prevent microbial regrowth and to ascertain the effects of chlo-rine residual on crops (Sheikh et al., 1990).

The parameters monitored for the study were:

• Inorganic and organic chemical constituents including heavy metals• Microbial quality including viruses, bacteria and parasites


Setting

WaterManagementIssues

Implementation



Groundwater quality data were collected over the 5-yr study period. Microbialquality of aerosols generated by sprinklers was studied in the early stage of theoperation.

Agronomic ConcernsThe 5-yr field study began in June 1980, after construction of the pilot treatmentplant described above. The 12-ha (30-ac) field was divided into two parts: demon-stration fields and experimental fields. Three water types (Title-22 water, FE waterand well water), and four fertilization rates (no fertilizer, 1/3, 2/3 and 3/3 of fulllocal fertilizer rate) were tested in the study. Three separate irrigation systems con-sisting of an underground distribution system with portable aluminum pipes wereconstructed to supply different water types to each experimental plot. The parame-ters studied were:

• Survival of viruses and coliform bacteria, and occurrence of other selected pathogens,in irrigation water and on vegetables

• Accumulation of metals in soils and plant tissues• Soil salinity and sodicity, soil permeability• Crop yield and crop quality

Plot Design and Crop RotationA split-plot design (Little and Hills, 1978) was used to assign randomly various watertypes and fertilization rates to the experimental plots. This experimental designallowed comparison of both irrigation with different water types and the comparisonof the effect of varying fertilization rates at the same time. The rates of fertilizerapplication varied with crop and year, but they were always based on standard prac-tice in the region. The three types of water were applied either by sprinkler or a fur-row irrigation system. The plot design is illustrated on Fig. 17-19. Artichokes weregrown on the half of the experimental plots according to normal farming practice inthe region. Other vegetables including broccoli, cauliflower, lettuce, and celery weregrown on the other half of the plots according to a rotation schedule. The crop rota-tion schedule is shown on Fig. 17-20. Local farming practices were followed through-out the project.

Feasibility and Public AcceptanceDemonstration of feasibility and public acceptance were primary objectives of thestudy. Two 5-ha (12-ac) plots in the vicinity of the experimental site were dedicated asa demonstration field to investigate large-scale feasibility. Crops in the demonstrationfields were grown using reclaimed water with normal local farming practices and thecrops were observed for appearance and vigor. Field observation days were held to showthe ongoing activities to local growers and news media. Feedback was obtained regard-ing their perceptions, questions, and concerns.

The pilot tertiary treatment facilities were operated nearly continuously during the periodof field study. The field studies began in 1980, and they were completed in 1985.


Study Results


The farm-scale feasibility study in the demonstration fields was discontinued inyears four and five because adequate data were obtained in the first 3 yr. Based onthe study results, it was demonstrated that reclaimed water (secondary effluent plustertiary treatment consisting of coagulation, flocculation, sedimentation, filtration,and disinfection) was safe to use for food crop irrigation. It was also demonstratedthat secondary effluent plus filtration and disinfection is sufficient for food crop irri-gation (Engineering-Science, 1987; Sheikh et al., 1990; Asano and Levine, 1996;Sheikh et al., 1998).

Wastewater ConstituentsThe chemical constituents in the irrigation waters used on the experimental plots are shownin Table 17-28. The levels of heavy metals were within the range highly suitable forirrigation water.

Microorganisms lavels in the aerosol from the reclaimed water sprinklers were not sig-nificantly different from those in the aerosols from the well water sprinklers. Further,there was no apparent evidence of the application of recycled water in the quality ofthe shallow shallow groundwater.

Analysis of ResultsAnalysis of variance (ANOVA) was used to determine the significance of differencesin soil and plant characteristics among the plots receiving different water types andfertilization rates. Although the SARadj values for Title-22 and FE process waters werewithin the range that could potentially cause problems, the relatively high levels ofTDS helped to countract the high SAR values (see Fig. 17-8) such that the waters fellwithin the favorable range for irrigation (Sheikh et al., 1990). No viruses were foundon samples of crops from the experimental plots irrigated with reclaimed water.


Drainage

ditch

Tembladeroslough

Farm

Rd.

A B C D E F G H I J K Lv1v2v3v4

a1a2a3a4

Artichoke plots

Vegetable plots

3 0 1 232 10

00

11

22

33

000

0

11

11

22

22

33

33

0 00

00

000

0000

00

00

11

11

1 1 11 1

11

11

111

2 22

2

22

22

2

2222

22

2

33 3

33

33

333

33

3

33

3

Well waterT-22 waterFE water

0 = 0/3 fertilization rate1 = 1/3 fertilization rate2 = 2/3 fertilization rate3 = 3/3 fertilization rate

Fertilization rates

Irrigation water

Figure 17-19

Experimentaldesign for testplots. (Adaptedfrom EngineeringScience, 1987.)



Levels of naturally occurring bacteria were not significantly different between well-water-irrigated crops and reclaimed-water-irrigated crops. The levels of heavy metals insoil were affected by the fertilization rates, but no measurable effect was observed withdifferent water types.

Feasibility and AcceptanceNo adverse health effects from exposure of reclaimed water constituents to farmers dur-ing conventional farming practices were detected. The quality, yield, appearance, andshelf-life longevity of all the crops irrigated with reclaimed water were equal to or bet-ter than those of the crops grown with well water. In the study report, it was concludedthat there would be no adverse economic effect. There was no regulatory requirementto label or separate the reclaimed water-grown products, and as long as the productswere not labeled, the marketability of the product did not seem to be diminished(Sheikh et al., 1990).


Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1980

1981

1982

1983

1984

1985

PlantingHarvest

Field preparation Artichoke growthCut back artichoke regrowthOther vegetable growth

Celery

Broccoli

Artichoke

Head lettuceCauliflower

Broccoli

CauliflowerCelery

Head lettuce

Cauliflower

Greenleaf lettuce

Red leaf lettuce

Green leaf lettuce

Red leaf lettuce

Cauliflower

Romaine lettuceButter lettuce

Artichoke

Artichoke

Artichoke

Artichoke

Figure 17-20

Experimentaldesign for croprotation schedule.(Adapted fromEngineeringScience, 1987.)




Table 17-28

Chemical constituents of irrigation waters used in the experimental fieldsa

Well water Tertiary effluent Filtered effluent

Parameter Unit Range Median Range Median Range Median

pH unitless 6.9–8.1 7.8 6.6–8.0 7.2 6.8–7.9 7.3Electrical conductivity dS/m 400–1344 700 517–2452 1256 484–2650 1400Calcium mg/L 18–71 48.0 17–61.1 52.0 21–66.8 53Magnesium mg/L 12.6–36 18.8 16.2–40 20.9 13.2–57 22Sodium mg/L 29.5–75.3 60.0 77.5–415 166 82.5–526 192Potassium mg/L 1.6–5.2 2.8 5.4–26.3 15.2 13–31.2 18Carbonate mg/Lb 0.0–0.0 0.0 0.0–0.0 0.0 0.0–0.0 0.0Bicarbonate mg/Lb 136–316 167 56.1–248 159 129–337 200Hardness mg/Lb 154–246 203 187–416 218 171–435 227Nitrate mg/Lc 0.085–0.64 0.44 0.18–61.55 8.0 0.08–20.6 6.5Ammonia mg/Lc NDe–1.04 — 0.02–30.8 1.2 0.02–32.7 4.3Total phosphorus mg/L ND–0.6 0.02 0.2–6.11 2.7 3.8–14.6 8.0Chloride mg/L 52.2–140 104 145.7–841 221 145.7–620 250Sulfate mg/L 6.4–55 16.1 30–256 107 55–216.7 84.8Boron mg/L ND–9 0.08 ND–0.81 0.36 0.11–0.9 0.4Total dissolved solids mg/L 244–570 413 643–1547 778 611–1621 842BOD mg/L ND–33 1.35 ND–102 13.9 ND–315 19Adjusted SAR unitless 1.5–4.2 3.1 3.1–18.7 8.0 3.9–24.5 9.9MBASd mg/L — — 0.095–0.25 0.14 0.05–0.585 0.15Cadmium mg/L ND–0.1 ND ND–0.1 ND ND–0.1 NDZinc mg/L ND–0.6 0.02 0.07–6.2 0.33 ND–2.08 0.20Iron mg/L ND–0.66 0.1 ND–2.3 0.05 ND–0.25 0.06Manganese mg/L ND–0.07 ND ND–0.11 0.05 ND–0.11 0.05Copper mg/L ND–0.05 0.02 ND–0.05 ND ND–0.04 NDNickel mg/L 0.001–0.20 0.04 0.002–0.18 0.04 0.004–0.20 0.04Cobalt mg/L ND–0.057 ND 0.001–0.062 0.002 ND–0.115 0.05Chromium mg/L ND–0.055 ND ND ND ND NDLead mg/L ND ND ND ND 0.001–0.70 0.023

aAdapted from Sheikh et al. (1990).bAs CaCO3.cAs N.dMethylene-blue active substance (MBAS).eND � Chemical concentration below detection limit. Detection limits are as follows: NH3�N � 0.02 mg/L; P � 0.01 mg/L;B � 0.02 mg/L; BOD � 1 mg/L; and MBAS � 0.05 mg/L; Cd � 0.01�0.1 mg/L; Zn � 0.02�0.5 mg/L; Fe � 0.03 mg/L;Mn � 0.05 mg/L; Cu � 0.001�0.02 mg/L; Co � 0.001�0.1 mg/L; Cr � 0.04�0.2 mg/L; Pb � 0.001�0.2 mg/L.



Cost of Irrigation with Reclaimed WaterEstimated costs of irrigation with reclaimed water were determined in the MWRSAproject. The present worth of 20 yr of operation was estimated for three treatment alter-natives: (1) original full treatment including coagulation, flocculation, sedimentationand filtration, (2) filtered effluent, and (3) filtered effluent with flocculation. The esti-mated costs are shown in Table 17-29.

The Monterey County Water Recycling Project (MCWRP), comprised of the SalinasValley Reclamation Project (SVRP) and the Castroville Seawater Intrusion Project(CSIP), emerged as a result of the MWRSA (Crites, 2002). The MCWRP involved con-struction of the Regional Treatment Plant, pumping stations, storage facilities,pipelines and other distribution systems, and environmental mitigation for the waterreclamation system. The Regional Treatment Plant began operation in 1988 and treatsabout 80 � 103 m3/d (21 Mgal/d) of wastewater with a capacity of about 110 � 103 m3/d(29.6 Mgal/d) (Monterey County Website). At capacity, approximately 25 � 106 m3/yr(20,000 ac-ft/yr) of disinfected tertiary recycled water is delivered for irrigation ofabout 4700 ha (12,000 ac) of food crops (Sheikh et al., 1999).

The Recycled Water Food Safety Study was conducted in 1997 to determine ifpathogens were present in disinfected tertiary-treated water produced at theRegional Treatment Plant. The efficacy of treatment processes for pathogen removalwas also assessed in the study. The hygienic evaluation demonstrated that noSalmonella, Cyclospora, or E. Coli O157:H7 were detected in tertiary recycledwater from the Monterey County Water Recycling Project (Sheikh et al., 1999). Themicrobial and chemical quality of disinfected tertiary-recycled water is shown inTable 17-30.

Currently, reclaimed water quality, including the occurrence of pathogens, is monitoredroutinely and reported on MRWPCA’s website. MRWPCA has worked to reduce salt lev-els by using more efficient water softeners and replacing sodium chloride with potassiumchloride for softener regeneration (Crites, 2002). No harmful effect of salinity has beenobserved in the sampling program started in 1999.


Treatment Process Estimated cost, $/m3

Filtered effluent 0.05Filtered effluent with flocculation (FE-F) 0.06Tertiary with 50 mg/L alum 0.09Tertiary with 200 mg/L alum 0.13

aAssumptions: Plant design flow of 114 � 103 m3/d; 28 � 106 m3/d ofreclaimed water will be delivered for irrigation; and for FE-F process, estimatedcapital cost is $11,170,000 and estimated annual O&M cost is $376,000(in 1990, Engineering News Records Construction Cost Index,ENRCCI � 5200).

bAdapted from Sheikh et al. (1990).

Table 17-29

Estimated costs ofreclaimed waterfor various tertiarytreatmentprocessesa,b

SubsequentProjects

Recycled WaterFood SafetyStudy

LessonsLearned



Important lessons learned in the implementation of the MWRSA are:

• The study design for the experimental plots set the standard for the investigation ofthe effect of reclaimed water on crop irrigation.

• Food crop irrigation with reclaimed water treated with original full treatmentrequired by the California Wastewater Reclamation Criteria, as well as the filteredeffluent, did not pose any detectable public health hazard in terms of pathogens orheavy metal exposure. The study results led to the modification of the criteria toallow filtered effluent for food crop irrigation.

• The marketability of the product irrigated with reclaimed water did not seem to bediminished.

17-6 CASE STUDY: WATER CONSERV II, FLORIDA

Water Conserv II is the first project in Florida to use reclaimed water to irrigate cropsfor human consumption. Primary purposes of Water Conserv II were wastewater dis-charge abatement, agricultural (predominantly citrus) irrigation, and groundwaterrecharge. Two water reclamation facilities, City of Orlando Water Conserv II WaterReclamation Facility, and Orange County South Regional Water Reclamation Facility,are providing reclaimed water in the project area. Owner agencies for the WaterConserv II are the City of Orlando and Orange County (the City of Orlando is locatedwithin the Orange County). A map of the project area is shown on Fig. 17-21. A briefoverview of Water Conserv II is presented in this section.


Table 17-30

Microbial and chemical quality of disinfected tertiary recycled water for the Monterey waterreclamation studya

E.Coli Fecal O157:H7, Legionella, Salmonella, Crypto- Cyclo- Coliform, ChlorineCFU/ 100 CFU/100 CFU/100 Giardia, sporidium, spora, MPN/ Turbidity, Residual,

Sample mL mL mL No./L No./L No./L 100 mL NTU mg/L

1 NDb ND — — ND — ND 1.9 142 — ND — — — — ND 1.7 6.23 ND ND — ND ND ND ND 2.7 —4 ND ND ND 0.03 ND ND ND 1.2 —5 ND ND — 0.08 ND ND ND 2.3 146 ND ND ND 0.09 ND ND ND 1.6 127 ND ND ND 0.05 ND ND ND 1.5 14

Average ND ND ND 0.06 ND ND ND 1.8 12

Range — — — ND–0.09 — — — 1.2–2.7 6.2–14

aAdapted from Sheikh et al. (1999).bND � Not detect.



Agriculture in the region is predominantly citrus farming. In 1979, a group called SaveOur Lake took legal proceedings against the City of Orlando and Orange County, call-ing for termination of wastewater effluent discharge from the two wastewater treatmentfacilities (McLeod Road Wastewater Treatment Facility and Sand Lake RoadWastewater Treatment Facility) into Shingle Creek. The court issued an injunctionagainst the city and county to cease effluent discharge into the creek by 1988 (Cross etal., 2000). To maximize federal funding, the city and county decided to initiate a jointproject: the Water Conserv II Water Reclamation Project.

After the court decision to cease effluent discharge, the city and county commissioneda federally funded regional wastewater plan, the Southwest Orange County 201Facilities Plan. The planners investigated different alternatives, and found that a com-bination of agricultural irrigation and rapid infiltration basins (RIBs) would be the mostviable and cost-effective alternative. The recommended alternative was expected toreduce demand on the Floridan aquifer by eliminating the need for well water for irri-gation, replenishing the aquifer, and stabilizing area lake levels (City of Orlando, 2006).

Construction of facilities continued until late 1986, and operation began in December, 1986.Agriculture and commercial customers use 60 percent of the reclaimed water, and theremaining 40 percent is recharged to groundwater through RIBs (Water Conserv II, 2006).

17-6 Case Study: Water Conserv II, Florida 1023

Seminole County

Orange County

1 km

Conserv IIWRP

Conserv IWRP

Figure 17-21

Schematic of theConserv II projectarea.

Setting


Implementation



In 1998, the project supplied reclaimed water to citrus growers, landscape and foliagenurseries, tree farms, landfills (one of which includes a soil cement production facility),an animal shelter, Mid-Florida Citrus Foundation (MFCF, for research on long-termeffects), a golf course, and RIBs (Cross et al., 1998).

Water Reclamation Facilities and Transmission Pumping StationsWater Conserv II utilizes reclaimed water from two reclamation facilities: City of OrlandoWater Conserv II Water Reclamation Facility, and Orange County South Regional WaterReclamation Facility. The average flows from the two reclamation plants varies from 114 to132 � 103 m3/d (30 to 35 Mgal/d). The permitted annual average daily flow (AADF) atbuild-out is 260 � 103 m3/d (68.3 Mgal/d) of which the Permitted Public Access Irrigationis about 180 � 103 m3/d (46.4 Mgal/d) and the permitted RIB flow is 83 � 103 m3/d(21.9 Mgal/d).

The Water Conserv II Reclamation Facility has two identical treatment process flowdiagrams that consist of screenings and grit removal, primary sedimentation, activatedsludge with fine bubble aeration, and secondary clarification. The effluent is filteredand chlorinated prior to being pumped to the distribution center for reuse.

A transmission pumping station was placed at each water reclamation facility. Peakpumping capacity is about 140 � 103 m3/d (37.5 Mgal/d) per pumping station, with atotal capacity of 280 � 103 m3/d (75 Mgal/d) (Water Conserv II, 2001).

Transmission Pipeline, Distribution Center and Distribution NetworkReclaimed water from two water reclamation facilities is sent to the distribution centerand RIB sites by 34 km (21 mi) of transmission pipeline. The transmission pipeline hastwo surge facilities for surge protection. The distribution center consists of a distribu-tion pumping station, four 3.8 � 103 m3 (5 Mgal) storage reservoirs, a central controlstation computer, and the operations and maintenance buildings (see Fig. 17-22).Reclaimed water is then distributed to 76 agricultural and commercial customers, or tothe RIB sites through a 79 km (49 mi) pipeline network (Water Conserv II, 2001). Themajor user of reclaimed water is citrus growers in the service area. Reclaimed water istransmitted through the distribution network and filtered before irrigation (see Fig. 17-12).

Supplemental Water WellsGroundwater is used in the Water Conserv II project to meet peak demands, notablyfreeze protection needs of the citrus (York and Wadsworth, 1998). Twenty five supple-mental water wells are strategically located on the distribution network to supplementwater supply. Peak supplemental water supply capacity is about 212 m3/min (56,000gal/min).

TurnoutsA turnout is a point of delivery from city- or county-owned facilities to private customeroperations and functions to monitor, record, and regulate flow to the customer. Theturnout is kept locked, accessed only by a contract operator. Customers turn on and offaccording to their needs and have access to the flowmeter for monitoring and record-keeping. Normal system line pressure is 550 to 830 kPa (80 to 120 lb/in2). Water leavesthe distribution center at 380–500 kPa (55–72 lb/in2) (Water Conserv II, 2001).





Figure 17-22

Views of Conserv II water reclamation facility: (a) signage for Conserv II, (b) control buildingwith radio tower (top cutoff) for control of reuse application facilities, (c) central pump stationat distribution center, (d) reclaimed water storage tanks (Coordinates: 28.473 N, 81.647 W),(e) typical rapid infiltration basin (Coordinates: 28.493 N, 81.620 W), and (f) orange treesirrigated with reclaimed water (Coordinates: 28.474 N, 81.658 W).

(a) (b)

(c) (d)

(e) (f)



Rapid Infiltration Basins (RIBs)During the investigation of alternatives, land about 16 to 24 km (10 to 15 mi) westof McLeod Road and Sand Lake Road facilities was identified as an appropriate sitefor the RIBs because of conductive geological features. As of 2004, there were sevenRIB sites in Orange County (see Fig. 17-22). The total number of RIBs is 66, andeach RIB has 1 to 5 cells (total 135 cells). The total RIB bottom percolation area isapproximately 79 ha (195 ac), and the capacity infiltration rate is 83 � 103 m3/d(21.9 Mgal/d). Total site area is about 1170 ha (2900 ac) (Water Conserv II, 2001).A computerized management system, called Groundwater Operational Control System(GOCS) is used to control the flow of the RISBs. The system provides the capabilityto forecast the impact of RIBs on the regional groundwater system.

Public AcceptanceInitially, the project encountered strong resistance from citrus growers and residents(Cross et al., 2000). Growers were not convinced of the benefits of using reclaimedwater for irrigation. Residents mounted opposition by joining forces with the NIMBY(Not in My Back Yard) group (Cross et al., 1998).

The citrus growers accepted the project after the city and county provided researchdata by R. C. J. Koo, a leading authority on citrus irrigation at the University ofFlorida’s Lake Alfred Citrus Research and Education Center, on the effects of reclaimedwater on citrus production and fruit quality. The city and county also agreed to pro-vide funding for research on the long-term effects of the irrigation with reclaimedwater. The city and county provided two incentives: (1) reclaimed water would beprovided to growers free for the first 20 yr at pressures suitable for microsprinklerirrigation, and (2) water would be provided for enhanced cold protection (Cross et al.,1998).

The area residents accepted the project cautiously after the city and county providedassurances to address and be sensitive to concerns of the residents. The concernsfocused on the safety, health, and welfare of the residents and the need to minimizepotential adverse environmental impacts.

Study of Long-Term Effects of Irrigation with Reclaimed WaterMid-Florida Citrus Foundation (MFCF) is a nonprofit organization which conductsresearch on long-term effects of irrigating citrus with reclaimed water. The MFCF hasalso conducted research on the use of reclaimed water for other purposes, including dif-ferent crops and golf course irrigation.

New Options for Reclaimed Water UsesThe city and county realized the importance of diversification of their customer base(Cross et al., 1998). A golf course was constructed as an alternative user of reclaimedwater (see Fig. 17-23). Various crops are being investigated for suitability of irrigationwith reclaimed water. Residential and commercial development in western OrangeCounty seems inevitable. A new development of the “village” land use was adoptedin 1995. As of 2000, the construction was expected to start soon. The village will use




reclaimed water for landscape irrigation as well as commercial and light industrial uses(Cross et al., 2000).

The importance of Water Conserv II project for the City of Orlando and Orange Countyis as follows:

• The discharge of wastewater effluent to surface waters has been eliminated.• The RIB sites have provided a preserve for endangered and threatened species for

plants and animals, as officially cited by city and county decree.• The Floridan aquifer has been replenished through the discharge of reclaimed water

to the RIBs. The demand on the aquifer has also been reduced by eliminating the needfor well water for irrigation.

• Reclaimed water use applications have been expanded successfully to meet the zero-discharge requirement.

Important lessons learned in the implementation of Water Conserv II are as follows:

• Extensive scientific studies to demonstrate safety and benefits of reclaimed waterirrigation were needed to gain growers’ acceptance.

• Distribution of reclaimed water for agricultural customers requiring freeze protec-tion water was not feasible because of the high peak flows needed for freeze protec-tion and the high cost of operation and maintenance.

• Systematic upgrading and expansion of the project, including purchasing ofadditional RIB sites, was necessary to handle increasing population anddevelopment.


(a) (b)

Figure 17-23

Golf course irrigated with reclaimed water in Conserv II, Orange County, FL: (a) view of golfcourse looking toward club house (coordinates: 28.442 N, 81.626 W) and (b) rapid infiltrationbasin located at golf course.

Importance of Water Conserv II

LessonsLearned



17-7 CASE STUDY: THE VIRGINIA PIPELINE SCHEME,SOUTH AUSTRALIA—SEASONAL ASR OF RECLAIMEDWATER FOR IRRIGATION

The Virginia Pipeline Scheme is a large-scale water reuse project that utilizes seasonalaquifer storage and recovery. In this case study, the use of aquifer storage and recoveryfor agricultural irrigation and the study on water quality changes in aquifer are described.

Located in Adelaide, South Australia, the Bolivar Wastewater Treatment Plant (WWTP)has historically discharged 40 � 106 m3/yr (29 Mgal/d) of secondary effluent into thesensitive waters of the Gulf of St. Vincent. The location of the plant relative to the Cityof Adelaide and the agricultural hub of the Virginia Triangle are shown in Fig. 17-24.In this dry agricultural coastal region (rainfall 600 mm/yr, evaporation 2000 mm/yr),water availability is a limiting factor for crop production, and groundwater resourceshave been overdrawn for irrigation needs (Kracman et al., 2001). Consistent with aSouth Australia policy issued in 1993 to encourage sustainable water reuse, and the1995 Environmental Protection Act further promoting and regulating water reuse, theCity of Adelaide considered reclamation and reuse of the Bolivar WWTP effluent tosatisfy some seasonal irrigation demands, and to reduce adverse ecological effects causedby nutrients discharged in the marine environment.

1028 Chapter 17 Water Reuse Applications: An overview

Setting

St. VincentBasin

WillungaBasin

MurrayBasinM

ount

L

ofty

R

ange

s

ASR sitesOperationalProposed

0 20km

LakeAlexandria

VictorHarbor

Cape Jervis

Yankalilla

Strathalbyn

Mount Barker

Birdwood

Gawler

Nuriootpa

The LevelsPaddocks

Morphettvilleracecourse

Hegent GardensSouthParklands

Uttbrae

Clayton

Greenfields

ADELAIDE

Gulf ofSt. Vincent

Bolivarwastewatertreatment

plant

Andrewsfarm

Bolivar

Two WellsVirginiaTriangleHorticulturalArea

Figure 17-24

Virginia TriangleHorticultural Areaand aquifer stor-age and recoverysites. (Adaptedfrom Barnett et al.,2000.)



Beside aiming at providing reclaimed water for agricultural use during peak demandin the summer time, and minimizing year-round nutrient loads to Gulf of St. Vincent,the water reuse project also presented an opportunity for generating economic benefitsin the region, using taxpayer funds to both improve coastal water quality and promoteagricultural production, rather than simply building a nonrevenue-generating nutrientremoval upgrade for the Bolivar plant. To maximize the economic goals, plannersdetermined that reclaimed water should be stored during the low demand season, thusincreasing availability of reclaimed water for the summertime peak irrigation season.

Due to concerns over vast land requirements, recontamination risks, evaporative losses,and waterlogging of surrounding land, surface storage was ruled out (Barnett et al.,2000). Aquifer Storage and Recovery (ASR) had been used recently with success in theregion for drinking water applications, and was suggested as the preferred method forreclaimed water storage. The specific constraints posed by reclaimed water ASR justi-fied the launch of a dedicated research program to assess water quality and treatmentrequirements, to satisfy both public health and irrigation requirements, as well as sus-tainable long-term ASR wellfield operation.

The existing treatment process at the Bolivar WWTP included primary sedimentation,secondary treatment using biological trickling filters and stabilization lagoons. Theeffluent was discharged to the marine environment.

Toward safe use of reclaimed water for unrestricted irrigation, South Australianregulations imposed:

• Turbidity less than 10 NTU (mean), 15 NTU (max)• Fecal coliforms less than 10 FCU/100 mL (median)• Pathogens, less than 1/50L (objective zero)

The additional treatment steps needed to achieve this improved effluent quality wouldalso have to improve the effluent to minimize physical, chemical, and biologicalprocesses from occurring in the aquifer and in the injection and recovery wells. A con-sortium of several governmental and private entities undertook a 3 yr research projectto determine the technical feasibility, environmental sustainability, and economic via-bility of ASR. Research confirmed the viability of dissolved air flotation and filtration(DAF/F) followed by disinfection, as most effective method for polishing the lagooneffluent. The recommended process flow diagram is illustrated on Fig. 17-25.

A 120 � 103 m3/d (31.7 Mgal/d) DAF/F facility was constructed at the Bolivar site,along with a disinfection contact tank, balancing storage reservoir, and finished waterpumping station. As shown on Fig. 17-25, coagulant is added to the algae laden lagooneffluent, prior to dissolved air flotation. The treated effluent from the flotation processis then passed through a granular polishing filter, before undergoing chlorination andoperational storage.

Seasonal storage of reclaimed water during winter months is achieved by injection intobrackish limestone aquifers within the Port Willunga Formation. Because the background

17-7 Case Study: The Virginia Pipeline Scheme 1029


RegulatoryRequirements

TechnologyIssues



aquifer salinity prior to injection was 2100 mg/L, the groundwater was unsuitable for irri-gation. Creating a sufficient lens of fresher reclaimed water in the aquifer was key to limitmixing and diffusion phenomena and, thus, recover water suitable for irrigation(Vanderzalm et al., 2002). Views of some of the facilities of the Virginia Pipeline Schemeare shown on Fig. 17-26.

During the irrigation season, produced and extracted reclaimed water is distributed toabout 250 client sites through the Virginia Pipeline, a network of 150 km of PVC pipe.A contractor was selected to implement the pipeline under a concession scheme, whichincludes responsibility for reclaimed water sales. The general layout of the VirginiaPipeline is shown on Fig. 17-27.

The Bolivar/Virginia Pipeline project is the largest water reuse project in Australia, andthe largest ASR project in the world for irrigation quality reclaimed water. It is also oneof the first ASR projects to inject lower quality water into a deep confined aquifer torecharge brackish groundwater (Barnett et al., 2000). Key to the success of the projectwas the 3-yr research, education, and training program intended to gain insight into thesustainability of the project and lead to modernization of the practices involved (Kracmanet al., 2001). Monitoring was targeted strategically for cost effectiveness and earliestpossible warning of operational incidents and clogging phenomena.


Figure 17-25

Virginia Pipeline Scheme tertiary treatment process for unrestricted crop irrigation and ASR(Coordinates: 35.174 S, 138.595 E, view at altitude 100 km).

Implementation



Public acceptance and education on water reuse was considered extremely important tothis project. A primary goal was to encourage customers to see reclaimed water aspreferable to the continued use of groundwater, to make the project economically fea-sible and sustainable (Kracman et al., 2001). Reclaimed water samples were displayedat public meetings so that potential customers could understand what the waterwould look like after treatment. Assurances were given by the South Australian HealthCommission that the treatment process would produce a water quality suitable for irri-gation of several crops with minimal restrictions.

Over a period of 3 yr, public perception changed to accept reclaimed water as a goodalternative to groundwater, rather than as an inferior product. A community liaison pro-gram was also created to educate the community about the aquifer, and to consult with


(a) (b)

(c) (d)

Figure 17-26

Views of Virginia Pipeline Scheme: (a) sign at Bolivar wastewater treatment plant(Coordinates: 34.770 S, 138.583 E), (b) view of one of six large stabilization lagoonsused for the further treatment of the secondary treated effluent (Coordinates: 34.756 S,138.569 E), (c) canal for transporting excess reclaimed water from the lagoons to theGulf of St. Vincent through mangrove trees, and (d) project trailer at the aquifer storageand recovery trial.



the community on the risks and potential benefits of the ASR project. This program wasalso intended to provide information on use of the aquifer to assure that there was nocontamination of the drinking water supply.

The DAF/F plant was monitored during the early commissioning period and resultsshowed that the plant was performing as expected (Kracman et al., 2001). In 24-h com-posite samples, total suspended solids were reduced from 100–150 mg/L in the feedwater to an average of 11 mg/L. The 90th percentile value for fecal coliform was 38 col-iforms/100 mL.


Figure 17-27

General layoutof the VirginiaPipeline Schemewith potentiometersurface contoursfor the confinedaquifer. (FromBarnett et al.,2000.)

Performanceand Operations



The quality of the reclaimed water recovered from ASR was a key monitoring parame-ter, not only to satisfy stringent requirements for reuse, but because any degradation ofaquifer quality would indicate that the process was unsustainable. The main concernsassociated with injection and mixing of recycled water with ambient groundwaterinclude redox processes, mineral dissolution, precipitation reactions, ion exchange,clogging, and dissolution processes (Vanderzalm et al., 2002).

Water quality data collected during field trials at Bolivar indicated positive results for bothreclaimed water quality and aquifer stability. The injection of a total of 250 � 103 m3

(66.0 Mgal) of reclaimed water occurred between October 1999 and April 2001(Vanderzalm et al., 2002). After approximately 16 wk, 150 � 103 m3 (39.6 Mgal) of waterwas recovered from the aquifer. The concentration variations observed for the main con-stituents of interest are shown in Table 17-31. As expected, there were dramatic water qual-ity variations in the first 103 m3 water extracted, which are not reflected in Table 17-31.

The major changes in the recovered water in the field trial included decreases in dis-solved oxygen, nitrate, and organic matter, as well as some buffering of pH, calcium,and bicarbonate. Based on the data obtained from the field trials, it was possible toassess environmental concerns about the fate of disinfection-by-products in thereclaimed water injected into the aquifer, particularly trihalomethanes (THMs) andhaloacetic acids (HAAs). The concentrations of the major trihalomethanes of concern,including chloroform (CF), bromodichloromethane (BDCM), dibromochloromethane


Parameter Unit Ambient (n � 5)b Injectant (n � 15) Recovered (n � 8)

pH unitless 7.2–7.3 6.4–7.8 7.0–7.3EC dS/m 2.9–3.9 1.8–2.6 1.9–2.5DO mmole/L <0.02 <0.02–0.33 <0.02Cl� mmole/L 21–28 10–15 11–16SO4

2� mmole/L 2.0–3.2 2.0–2.4 2.3–2.7HCO3

� mmole/L 3.5–4.9 2.6–6.7 4–5Ca2� mmole/L 3.3–3.9 1.0–1.8 1.5–1.9Na� mmole/L 16–25 11–15 12–16Mg2� mmole/L 2.5–3.7 1.2–1.7 1.2–2.0K� mmole/L 0.24–0.38 1.1–1.5 1.0–1.3Fe-total mmole/L 0.015–0.024 <0.0005–0.37 0.007–0.12Sr-total mmole/L 0.011–0.013 0.0018–0.0046 0.0031–0.0061TOC mmole/L <0.025–0.04 1.1–2.0 0.9–1.2DOC mmole/L <0.025–0.04 1.0–1.9 0.9–1.2NH4

� mmole/L 0.003–0.02 0.004–2.1 0.1–1.0NO3

� mmole/L <0.0004 <0.0004–0.34 <0.0004–0.007LSIcCalcite 0.10–0.19 �1.44–0.13 �0.39–�0.07

aAdapted from Vanderzalm et al. (2002).bNumber of samples.cLangelier Saturation Index (see Chaps. 9 and 19).

Table 17-31

Water quality inambient ground-water, injectantand recoveredwater during theASR trial,Bolivar/VirginiaPipeline project,Australiaa



(DBCM), and bromoform (BF), over time at the ASR well and at an observation welllocated 4 m (13 ft) from the ASR well are shown in Tables 17-32 and 17-33, respec-tively, as reported by Nicholson et al., (2002).

Initially, the concentrations of some compounds increased due to the continued forma-tion of THMs as a result of the reaction between residual chlorine in the recharge waterand its organic matter content. A decrease of all THMs is observed over time. Becausedegradation of chloroform can only occur under methanogenic conditions, it appearsthat such conditions prevail at the ASR well and at the observation well. The lower rate


THM Concentration, mg/LChloride

Day CF BDCM DBCM BF Total conc., mg/L

0 33 8 46 58 145 4157 71 20 10 <1 101 382

12 46 6 3 <1 55 36028 12 2 3 <1 15 35869 4 <1 <1 <1 4 38782 2 <1 <1 <1 2 363

109 <1 <1 <1 <1 <4 370

aAdapted from Nicholson et al. (2002).bCF� chloroform, BDCM � bromodichloromethane, DBCM �dibromochloromethane, BF � bromoform.

cDay 0 represents the recharge water THMs on the last day ofrecharge.

Table 17-32

THM and chloridedata in an SARrecharge well during a storageperiod.Bolivar/VirginiaPipeline project,Australiaa

THM Concentrationb, �g/LChloride

Day CF BDCM DBCM BF Total conc., mg/L

0 41 56 40 6 143 3947 47 57 38 5 147 370

12 35 41 26 3 105 36028 33 27 12 1 73 38169 — — — — — —82 19 9 5 1 34 379

109 14 2 <1 <1 16 357

aAdapted from Nicholson et al. (2002).b CF� chloroform, BDCM � bromodichloromethane, DBCM �

dibromochloromethane, BF � bromoform.cDay 0 represents the recharge water THMs on the last day ofrecharge. Travel time between the recharge and observationwell is approximately 1 d.

Table 17-33

THM and chloridedata in an observation welllocated 4 m fromthe SAR wellduring a storageperiod, Bolivar/Virginia Pipelineproject. Australiaa



of degradation at the observation well suggests a lower biomass available to carry outthe reaction. Haloacetic acids, which are degraded under both aerobic and anaerobicconditions were found to be attenuated rapidly in the aquifer (Nicholson et al., 2002).

Important lessons learned in the implementation of the Virginia Pipeline Scheme are asfollows:

• A key to the success of the project was an extensive research, education, and train-ing program. Customer confidence was a vital element for the reclaimed water to bemarketable.

• Aquifer storage and recovery (ASR) has the potential to create a sustainable waterresource cycle, particularly in areas such as the State of South Australia, where amajor source of water is groundwater.

• The ASR can be used to provide multiple beneficial effects including protection ofthe sensitive environment, freshwater recharge of brackish aquifers, the preventionof unsustainable use of freshwater, and attenuation of reclaimed water constituents.

PROBLEMS AND DISCUSSION TOPICS

17-1 Referring to Fig. 17-3, classify soils containing (a) 30 percent silt, 60 percentsand, and 10 percent clay, and (b) 55 percent silt, 15 percent sand, and 30 percent clay.Will the composition of these two soils impact irrigation with reclaimed water?

17-2 Estimate the sodium adsorption ratio, SAR, and the adjusted sodium adsorptionratio, SARadj, of reclaimed water with the following chemical characteristics.

Problems and Discussion Topics 1035

LessonsLearned

Constituent Unit Value

pH pH-unit 7.2Sodium mg/L 143Calcium mg/L 58Magnesium mg/L 13Chloride mg/L 157Sulfate mg/L 123Alkalinity mg/L as 132

CaCO3

TDS mg/L 754

17-3 Using data given below and the crop coefficients given in Table 17-21, estimatethe agronomic water requirements for olive trees. Assume the leaching requirement is 10percent when irrigation is necessary, and irrigation efficiency is 75 percent throughout ayear. No irrigation is necessary when precipitation is greater than crop evapotranspiration.


17-4 Estimate the expected yield reduction due to salinity for orange trees irrigatedwith reclaimed water containing 650 mg/L total dissolved solids with a leaching frac-tion of 15 percent.

17-5 A crop is irrigated with reclaimed water whose salinity, measured by total dissolvedsolids, is 850 mg/L. If a crop is irrigated to achieve a leaching fraction of 15 percent, esti-mate (a) the salinity of water leached out of the root zone, and (b) the appropriate leachingfraction to maintain a crop yield above 80 percent. The crop is known to have a thresholdsalinity level of 4.6 dS/m and the slope of yield reduction curve is 7.6 percent per dS/m.

17-6 If the crop in Problem 17-5 is grown in a climatic condition provided in Problem17-3, calculate the agronomic water requirements assuming the crop coefficient is 0.8throughout a year.

17-7 If the crop discussed in Problems 17-5 and 17-6 is grown on a 10 ha field, cal-culate the amount of salt leached from the irrigated land each year. Discuss the long-term ramification of using reclaimed water for irrigation in terms of salinity, and themeasures that can be used to mitigate salinity issues.

17-8 Two methods of treatment are being considered for agricultural irrigation with(a) conventional activated sludge, and (b) activated sludge with biological nutrientremoval, followed by filtration. Typical total nitrogen and nitrate levels can be found inTable 17-12. Estimate the amount of nitrogen, in kg/ha, that will be applied to the irri-gated field from the above two types of reclaimed water when reclaimed water isapplied at an average of 150 mm/mo for the first 3 mo of the growing season.

17-9 Reclaimed water with an average TDS of 1200 mg/L is to be used to irrigate toma-toes. Evapotranspiration for the peak period is 12 mm/d, and the maximum water infiltrationrate below the root zone is 8 mm/d. Estimate the maximum crop yield that can be obtainedwithout causing a rise in the water table. Use Table 17-15 to estimate the yield reduction.


Reference Time, Precipitation (P), evapotranspiration

Month d/mo mm/mo (ETo), mm/mo

Jan 31 97.5 25.0Feb 28 90.0 44.0Mar 31 71.1 85.8Apr 30 25.9 139.1May 31 13.5 175.0Jun 30 5.1 206.4Jul 31 1.3 215.6Aug 31 1.5 189.9Sep 30 9.1 147.0Oct 31 22.6 107.6Nov 30 55.6 51.8

Dec 31 62.2 29.5



17-10 Reclaimed water with the following characteristics is to be used for agricultur-al irrigation. Estimate the sodium concentration based on the reported water qualitydata. Also, discuss what should be assessed for crop selection and the irrigation method.

Problems and Discussion Topics 1037

Constituent Unit Value

pH unitless 7.2Calcium mg/L 74.4Magnesium mg/L 14.8Ammonia-N mg–N/L 6.35Total nitrogen mg–N/L 10.86Suspended solids mg/L 2.6Total phosphorus mg–P/L 3.5Alkalinity mg/L as 191

CaCO3

TDS mg/L 1067

SAR – 4.05

17-11 An irrigation water with an EC of 1.8 mmho/cm is to be applied to productionof lettuce. Seasonal evapotranspiration is 650 mm, seasonal time of irrigation is to be165 h, and the water application rate, which is less than the average infiltration rate, is9 mm/h. Assuming the maximum yield is 450 kg/ha, estimate the expected crop yield.

17-12 Determine the allowable hydraulic loading rate for an irrigation operation basedon the nitrogen loading limit. Assume allowable nitrate concentration in percolating wateris: Cp � 10 mg–N/L, and nitrogen uptake by crop is 0.04 kg/m2⋅yr. An average totalnitrogen concentration in reclaimed water is 25 mg–N/L, and the fraction of applied nitro-gen removed by denitrification and volatilization is 0.24. Assume all of the nitrogen leach-ing out from the root zone is in the form of nitrate. The fraction of applied nitrogenremoved by denitrification and volatilization is: f � 0.20. The values of (ETc � P) areshown below.

Month (ETc � P), mm

Jan �20.5Feb �2.5Mar 35.2Apr 65.0May 73.4Jun �48.8Jul �42.5Aug �67.9Sep �50.5Oct 20.9Nov 3.8

Dec �22.6


17-13 For the evapotranspiration data in Problem 17-12, calculate the annualhydraulic loading rate based on the maximum infiltration rate using Eq. (17-13a) withmaximum allowable percolation rate of 13 mm/d, and neglect runoff and drift losses.Compare the results with the hydraulic loading calculated in Problem 17-12. Whichhydraulic loading should be used? Provide the reasons for your decision.

17-14 Determine the field area required for reclaimed water irrigation with the fol-lowing conditions:

• The annual hydraulic loading rate � 655.8 mm/yr.• The average daily flow of reclaimed water is 1000 m3/d.• Conveyance efficiency is 90 percent.• Neglect the loss or gain of stored reclaimed water.

17-15 In Problem 17-12, the hydraulic loading rate was determined assuming anallowable nitrate in the leaching water is 10 mg–N/L. Discuss the ramification of leach-ing 10 mg–N/L of nitrate from the root zone in terms of underlying groundwater quality.

17-16 Determine the area of an open storage reservoir for a reclaimed water irrigationsystem with the water balance data below. Use Eq. (17-12) to calculate the hydraulicloading rate. Leaching fraction and irrigation efficiency are 15 percent and 90 percent,respectively. The storage reservoir will have an average depth of 5 m. Neglect the waterloss by seepage.


Month (ETc – P), mm

Jan �84Feb �47Mar �22Apr 50May 132Jun 183Jul 219Aug 183Sep 98Oct 36Nov �21

Dec �47

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18 Landscape Irrigation withReclaimed Water

WORKING TERMINOLOGY 1044

18-1 LANDSCAPE IRRIGATION: AN OVERVIEW 1045Definition of Landscape Irrigation 1045Reclaimed Water Use for Landscape Irrigation in the United States 1046

18-2 DESIGN AND OPERATIONAL CONSIDERATIONS FOR RECLAIMED WATER LANDSCAPEIRRIGATION SYSTEMS 1047Water Quality Requirements 1047Landscape Plant Selection 1050Irrigation Systems 1054Estimation of Water Needs 1054Application Rate and Irrigation Schedule 1065Management of Demand-Supply Balance 1065Operation and Maintenance Issues 1066

18-3 GOLF COURSE IRRIGATION WITH RECLAIMED WATER 1070Water Quality and Agronomic Considerations 1070Reclaimed Water Supply and Storage 1072Distribution System Design Considerations 1075Leaching, Drainage, and Runoff 1076Other Considerations 1076

18-4 IRRIGATION OF PUBLIC AREAS WITH RECLAIMED WATER 1076Irrigation of Public Areas 1078Reclaimed Water Treatment and Water Quality 1079Conveyance and Distribution System 1079Aesthetics and Public Acceptance 1079Operation and Maintenance Issues 1080

18-5 RESIDENTIAL LANDSCAPE IRRIGATION WITH RECLAIMED WATER 1080Residential Landscape Irrigation Systems 1080Reclaimed Water Treatment and Water Quality 1081Conveyance and Distribution System 1081Operation and Maintenance Issues 1082

1043

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18-6 LANDSCAPE IRRIGATION WITH DECENTRALIZED TREATMENT ANDSUBSURFACE IRRIGATION SYSTEMS 1082Subsurface Drip Irrigation for Individual On-site and Cluster Systems 1082Irrigation for Residential Areas 1086

18-7 CASE STUDY: LANDSCAPE IRRIGATION IN ST. PETERSBURG, FLORIDA 1086Setting 1087Water Management Issues 1087Implementation 1087Project Greenleaf and Resource Management 1089Landscape Irrigation in the City of St. Petersburg 1091Lessons Learned 1093

18-8 CASE STUDY: RESIDENTIAL IRRIGATION IN EL DORADOHILLS, CALIFORNIA 1093Water Management Issues 1094Implementation 1094Education Program 1096Lessons Learned 1096

PROBLEMS AND DISCUSSION TOPICS 1097

REFERENCES 1099

WORKING TERMINOLOGY

Term Definition

Foliar damage Damage to leaves of landscape plants. Reclaimed water constituents such as chloridemay cause damage to leaves of landscape plants as a result of sprinkler irrigation.

Landscape coefficient Ratio of evapotranspiration of a landscaping site (ETL) to the reference evapotranspira-tion (ETo).

Restricted access Area where public access is limited, such as highway medians, cemeteries, and inside area of industrial areas.

Unrestricted access Area where public access is not limited, such as golf courses, parks, school yards,area commercial areas, and residential areas.

Urban uses of water Major urban uses of water include landscape irrigation, toilet flushing, air conditioning,street washing, fire hydrants, and some commercial uses such as car washing.

Xeriscape Landscaping with plants that require little or no water.

Because of its typical location of use, landscape irrigation with reclaimed water is oftencategorized as an urban water reuse application (U.S. EPA, 2004). Water quality andother agronomic considerations for landscape irrigation, however, follow the same prin-ciples used for agricultural irrigation that have been discussed in Chap. 17. Along withan overview of landscape irrigation with reclaimed water, special design and operational

1044 Chapter 18 Landscape Irrigation with Reclaimed Water


Landscape Irrigation with Reclaimed Water

considerations for landscape irrigation are discussed in this chapter. In addition, thefollowing landscape irrigation applications are discussed in detail: (1) golf courses,(2) public areas, (3) residential landscape, and (4) landscape irrigation utilizing efflu-ent from decentralized and onsite wastewater treatment systems in rural areas. Twocase studies are also presented to illustrate the use of reclaimed water for land-scape irrigation. Other urban nonpotable uses of reclaimed water are described inChap. 20.

18-1 LANDSCAPE IRRIGATION: AN OVERVIEW

Landscape plants provide various functions such as creating an aesthetically pleasingproperty; creating a buffer between streets, parking lots, and noncommercial areas; andproviding vertical and horizontal dimensions to a site. Ornamental plants also maintainmoisture and may be used to mitigate the effects of heat in urban areas.

Although the water demand for landscape irrigation varies greatly by geographicallocation, season, and the types of plants, approximately one-third of residential wateruse is for landscape irrigation, with significantly higher usage in arid urban areas (U.S.EPA, 1992). For example, the Irvine Ranch Water District in southern California esti-mates that more than 70 percent of their total water use is for landscape irrigation.

Components of landscape irrigation systems that should be considered include:

• A landscape design and selection of plants that require less water

• Use of irrigation methods that have a high irrigation efficiency

• Use of nonpotable water including reclaimed water

Landscape irrigation with reclaimed water is a viable option to reduce potable waterdemand, and also as an option to reduce or eliminate wastewater discharge to aquaticenvironment. Factors motivating many local governments to consider the use ofreclaimed water include: (1) the high water demand for landscaping, (2) increasing costof acquiring additional water in urban areas, and (3) stringent wastewater dischargerequirements (see Chap. 2).

Landscape irrigation, as used in this textbook, includes irrigation of restricted and unre-stricted areas. The definitions of “restricted” and “unrestricted” vary in different stateregulations and guidelines, but generally apply to the following applications:

• Landscape irrigation with unrestricted access areas such as:• Public parks• Playgrounds, school yards, and athletic fields• Public and commercial facilities• Individual and multifamily residences• Golf courses associated with residential properties

18-1 Landscape Irrigation: An Overview 1045

Definition ofLandscapeIrrigation



• Landscape irrigation with limited or restricted access areas such as:• Cemeteries• Highway medians and shoulders• Landscaping within industrial areas• Golf courses not associated with a residential community

The above categorization is based on California’s regulations. In Florida, the term“Public Access Areas,” applies to cemeteries, highway medians, and golf courses notassociated with a residential property (State of Florida, 1999). Examples of landscapeareas irrigated with reclaimed water are shown on Fig. 18-1.

The two largest users of reclaimed water for landscape irrigation in the United States areFlorida and California. Florida, the largest user, accounted for approximately 3.8 × 108 m3

(3.1 × 105 ac-ft) of reclaimed water in 2004, as compared to 1.4 × 108 m3 (1.1 × 105 ac-ft)in California. A comparison of the use of reclaimed water for landscape irrigationin California and Florida is illustrated on Fig. 18-2. In Florida, over 40 percent of the


(a) (b)

(c) (d)

Figure 18-1

Examples of landscape areas irrigated with reclaimed water: (a) golf course, Orlando, FL;(b) playground, Marin County, CA; (c) street median strip, Irvine, CA; and (d) residential homes,El Dorado Hills, CA.

ReclaimedWater Use forLandscapeIrrigation in theUnited States



reclaimed water is used for landscape irrigation in residential areas, a use not yet pop-ular in other states including California. Golf course irrigation is another major use forreclaimed water, comprising 50 and 36 percent of the total landscape irrigation use inCalifornia and Florida, respectively (see Fig. 18-2). Other states that are major users ofreclaimed water for landscape irrigation include Arizona, Colorado, Hawaii, Nevada,New Mexico, Texas, and Utah, most of which are located in arid regions. In recentyears, however, water-rich regions on the East Coast are using reclaimed water increas-ingly for landscape irrigation, partly due to stringent waste discharge requirements, andpartly due to localized water shortages in densely populated areas. Selected examples oflandscape irrigation with reclaimed water in the United States are shown in Table 18-1.

18-2 DESIGN AND OPERATIONAL CONSIDERATIONS FORRECLAIMED WATER LANDSCAPE IRRIGATION SYSTEMS

Design considerations for urban landscape irrigation systems using reclaimed water aresummarized in Table 18-2. For many urban landscape irrigation systems, either thereclaimed water system or the landscape area already exists. To convert these systems tourban landscape irrigation systems using reclaimed water, either the existing irrigationsystems need to be retrofitted for conveying reclaimed water, or new landscape areas needto be established adjacent to existing reclaimed water systems. In this section, factorsaffecting design and operation of landscape irrigation with reclaimed water are described.

Agronomic water quality requirements were described in Chap. 17 (see Table 17-5).Generally, tertiary treatment or an equivalent level of treatment is required for the purposeof public health protection in irrigation of landscape plants. Treatment processes usedto meet the water quality criteria for landscape irrigation are discussed in Chaps. 7 and 8.It should be noted that onsite treatment systems for subsurface irrigation of landscapingplants do not require the same water quality criteria (see Sec. 18-6). When establishing

18-2 Design and Operational Considerations for Reclaimed Water Landscape Irrigation Systems 1047

Freeway median, 3%

(a) California (b) Florida

Residential,43%

Golf course,36%

Golf course,50%

Mixed, other orunknown, 37%

Mixed, other orunknown, 21%

Public parks, schools,and playgrounds, 10%

Figure 18-2

Landscape irrigation in (a) California and (b) Florida. (Data from State of California, 1990;State of Florida, 2004.)

Water QualityRequirements




Table 18-1

Select examples of landscape irrigation with reclaimed water

Types of landscape Annual flow,State Location irrigation � 106 m3/yr Remarks

Arizona Mesa, the Southeast Golf course, residential 11a Also used for pondWater Reclamation replenishment andPlant (SEWRP) agricultural irrigation

Arizona Scottsdale Water Golf course irrigation 17 Excess water is furtherCampus treated with RO for

vadose zone rechargeto groundwater

California Irvine Ranch Water Area-wide reuse system: 11 Also used for agriculturalDistrict parks, golf courses, school irrigation, industrial water,

playfields, athletic fields, and toilet flushingand common areasmaintained by homeownerassociations

California The Vallecitos Water Hotels and resort venues, 3.5 Approximately 42 km ofDistrict and the parks, median strips, reclaimed waterLeucadia County shopping areas, freeway distribution system,Water District landscaping, and common supplying about 60(for City of Carlsbad) areas maintained by irrigation sites

homeowner associationsColorado Denver Parks, schools, golf 41a Also used for industrial

courses cooling water andenvironmental purposes

Florida City of St. Petersburg Residential and other public 50 One of the oldest andaccess area largest urban irrigation

systems in the UnitedStates

Georgia Forsyth County Park irrigation using 3.5 Membrane bioreactor issubsurface drip irrigation used to treat wastewater

Hawaii Kihei wastewater Golf courses, landscaping 2.2Ð2.8 Also used for agriculturalreclamation facility, of parks, residential areas, uses, dust control,Maui community center, schools, composting, toilet flushing

and public buildingsNevada Clark County Water Golf course 1.2 Reclaimed water is

Reclamation District blended with potable waterTexas Northwest 11 schools, 12 parks, 3 golf 24a Four water reclamation

Wastewater courses, cemetery, zoo, plants in the area provideTreatment Plant, residential area, small reclaimed water. Also usedEl Paso community for groundwater recharge

and industrial waterTexas San Antonio Golf courses, schools, 43 Other uses include

commercial sites, cemetery industrial cooling andstream augmentation

Utah Tooele City Golf course, county 3.1 Plans to irrigate residentialrecreation property landscape

aFlow capacity.



water quality goals, the impact of water quality on the irrigation system also needs to beconsidered. The impacts of water quality on operation and maintenance of irrigation sys-tems are discussed at the end of this section. A comprehensive salt management guide forlandscape irrigation with reclaimed water has been prepared by Tanji et al. (2006).

Agronomic water quality requirements depend on the tolerance of plants to reclaimedwater constituents, such as sodium, chloride, and boron, and the effects of salinity andsodicity on irrigated land and landscape plants. Long-term effects of reclaimed water


Table 18-2

Typical design considerations for urban landscape irrigation systems

System Specific consideration References

Treatment processes Selection of treatment system to meet quality Part 3requirements for landscape irrigation• Pathogens (evaluated by indicator organisms)• Nutrients• Suspended solids

Landscape area Water quality requirements Chaps. 17, 18Plant selection Chap. 18• Salt tolerance• Boron tolerance• Water needsIrrigation method• Required pressure• Irrigation efficiency• Exposure controlLeaching requirements Chap. 17Water application rates Chaps. 17, 18Operation and maintenance Chap. 18• Irrigation timing• Irrigation area restriction• Soil conditioning• Sprinkler and emitter clogging control• Monitoring

Distribution and storage Area-wide distribution main Chap. 14systems • Flow rate

• Pumping requirements• Peaking factorDemand and supply balance Chaps. 17, 18• Storage requirements• Blending with other water sources• Multipurpose use of reclaimed waterCross-connection control Chaps. 14, 15• Spacing between reclaimed water

and potable waterlines• Pressure difference• Backflow prevention (for potable system)• Coloring of reclaimed water pipes



constituents and requirements for leaching and drainage must also be considered whendetermining water quality requirements. Nutrients are usually considered beneficial, butexcess nutrients may cause biofilm growth in the reclaimed water distribution linesand algal growth in the open storage reservoirs. Because of stringent water qualityrequirements contained in wastewater discharge permits and the need to meet qualityrequirements of various water reuse applications, it is becoming more common forwater reclamation plants to provide nutrient removal.

Aesthetic Quality ConsiderationsSome aesthetic water quality parameters are also important but they are often not regu-lated. For example, odor control is important for public acceptance in reclaimed water irri-gation but the odor level is not specified in most regulations. Typically, reclaimed waterfrom a tertiary or equivalent treatment has no or only a slight musty odor, unnoticeablewhen the reclaimed water is used for irrigation. Odors, however, may be generated in thedistribution system when the reclaimed water becomes stagnant (see Chap. 14). Thedevelopment of odors, principally hydrogen sulfide, is of critical concern where the con-centration of the sulfate (SO4

2�) is greater than 50 mg/L and the chemical oxygen demand(COD) of the treated effluent is above 20 mg/L. Thus, water quality parameters that arenot regulated specifically may be as important as those that are regulated.

Public Health ConsiderationsPublic health considerations are presented in Chap. 4. Two specific concerns relevant tolandscape irrigation with reclaimed water are: (1) the health risk associated with poten-tial cross-connection and subsequent contamination of potable water systems, and(2) human exposure to reclaimed water and its constituents during and after irrigation.As of 2003, 28 states have either regulations or guidelines for irrigation of unrestrictedaccess areas, and 34 states have them for irrigation of restricted areas (U.S. EPA, 2004).Typically, the criteria include: (1) minimum treatment levels (2) requirements for dis-infection, chemical and microbial water quality, and monitoring, and (3) exposure con-trol measures such as setback distance and irrigation timing. The basis for regulationsand guidelines is to minimize the risk of exposure associated with reclaimed water use.

Treatment and Water Quality RequirementsTreatment requirements are specified in most states including Arizona, California,Florida, Hawaii, Nevada, and Washington. Tertiary treatment including filtration and dis-infection is required usually for unrestricted uses. In restricted access areas, human expo-sure to reclaimed water can be controlled more easily; thus, the quality and treatmentrequirements are typically less stringent than those required for unrestricted use areas.Treatment and water quality criteria in selected states are summarized in Table 18-3.

Selection of landscape plants is usually a landscape designer’s task, but it also affectsthe estimation of water demand and quality requirements. As described in Chap. 17, salttolerance is the most important parameter in plant selection. Salt tolerance of selectlandscape plants is shown in Table 18-4. Other parameters to be considered are:

• Tolerance to boron and other reclaimed water constituents• Water needs, drought tolerance• Native/nonnative to the region


LandscapePlant Selection



Par

amet

erA

rizon

aC

alifo

rnia

Flo

rida

Haw

aii

Nev

ada

Texa

sW

ashi

ngto

n

Unr

estr

icte

d ur

ban

uses

Trea

tmen

tS

econ

dary

Oxi

dize

d,b

Sec

onda

ryO

xidi

zed,

Sec

onda

ryns

cO

xidi

zed,

trea

tmen

t,co

agul

ated

,tr

eatm

ent,

filte

red,

and

trea

tmen

tco

agul

ated

,fil

trat

ion,

and

filte

red,

and

filtr

atio

n,an

ddi

sinf

ecte

dan

dfil

tere

d,an

ddi

sinf

ectio

ndi

sinf

ecte

dhi

gh-le

vel

disi

nfec

tion

disi

nfec

ted

disi

nfec

tion

BO

D,m

g/L

nsns

20d

ns30

530

TS

S,m

g/L

nsns

5.0

nsns

ns30

Turb

idity

,NT

U2

(avg

)2

(avg

)ns

2 (m

ax)

ns3

2 (a

vg)

5 (m

ax)

5 (m

ax)

5 (m

ax)

Col

iform

,Fe

cal

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lFe

cal

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lFe

cal

Feca

lTo

tal

MP

N/1

00 m

Lno

ndet

ecta

blee

2.2

(med

)f75

% o

f2.

2 (m

ed)f

2.2

(avg

)20

(av

g)2.

2 (a

vg)

23 (

max

)23

(m

ax in

30

d)sa

mpl

es b

elow

23 (

max

in 3

0 d)

23 (

max

)75

(m

ax)

23 (

max

)de

tect

ion

25 (

max

)

Res

tric

ted

urba

n us

es

Trea

tmen

tS

econ

dary

Oxi

dize

d an

dS

econ

dary

Oxi

dize

dS

econ

dary

nsO

xidi

zed

and

trea

tmen

tdi

sinf

ecte

dtr

eatm

ent,

and

trea

tmen

tdi

sinf

ecte

dan

dfil

trat

ion,

and

disi

nfec

ted

and

disi

nfec

tion

high

-leve

ldi

sinf

ectio

ndi

sinf

ectio

n

BO

D,m

g/L

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2030

TS

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5ns

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30

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idity

,NT

Uns

nsns

2 (m

ax)

ns3

2 (a

vg)

5 (m

ax)

Col

iform

,Fe

cal

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lFe

cal

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lFe

cal

Feca

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tal

MP

N/1

00 m

L20

0 (a

vg)

23 (

med

)f75

% o

f23

(m

ed)f

23 (

avg)

200

(avg

)23

(av

g)

800

(max

)24

0 (m

ax in

30

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mpl

es b

elow

200

(max

)24

0 (m

ax)

800

(max

)24

0 (m

ax)

dete

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n25

(m

ax)

a Ada

pted

from

U.S

.EPA

(20

04).

b Oxi

dize

d w

aste

wat

eris

was

tew

ater

that

is tr

eate

d to

oxi

dize

and

sta

biliz

e or

gani

c co

mpo

unds

,and

con

tain

s di

ssol

ved

oxyg

en.T

he te

rm Òo

xidi

zed

was

tew

ater

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use

d to

avo

id s

peci

ficat

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oftr

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t spe

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BO

De N

ot d

etec

tabl

e in

four

of

last

sev

en d

aily

sam

ples

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even

-day

med

ian.

Tab

le18

-3

Var

ious

sta

te w

ater

qua

lity

and

trea

tmen

t req

uire

men

ts fo

r un

rest

ricte

d an

d re

stric

ted

urba

n us

esa

1051

Metcalf_CH18.qxd 12/12/06 06:09 PM Page 1051Landscape Irrigation with Reclaimed Water

Sal

t tol

eran

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ical

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ese

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tive

sens

itive

tole

rant

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rant

tole

rant

Ale

ppo

pine

Pin

us h

alep

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s√

Alg

eria

n iv

yH

eder

a ca

narie

nsis

√c

Blu

e dr

acae

naC

ordy

line

indi

visa

√B

ouga

invi

llea

Bou

gain

ville

a sp

ecta

bilis

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rush

che

rry

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m p

anic

ulat

um√

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iza

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ophy

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tesc

ens

√C

herr

y pl

umP

rune

s ce

rasi

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cus

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sine

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hine

se h

olly

,cv.

Ilex

corn

uta

√B

urfo

rdC

rape

myr

tleLa

gers

troe

mia

indi

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ceum

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plan

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ocyc

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rand

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a√

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priv

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dum

√H

eave

nly

bam

boo

Nan

dina

dom

estic

a√

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an h

awth

orn

Rap

hiol

epis

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ca√

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n st

one

pine

Pin

us p

inea

√Ja

pane

se b

lack

pin

eP

inus

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nber

gian

a√

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nese

box

woo

dB

uxus

mic

roph

ylla

var

.√

japo

nica

Japa

nese

pitt

ospo

rum

Pitt

ospo

rum

Tob

ira√

Laur

ustin

us,c

v.V

ibur

num

Tin

us√

Rob

ustu

mN

atal

plu

mC

aris

sa g

rand

iflor

a√

Orc

hid

tree

Bau

hini

a pu

rpur

ea√

Ole

ande

rN

eriu

m o

lean

der

√

Tab

le18

-4

Rel

ativ

e sa

lt to

lera

nce

ofla

ndsc

ape

plan

tsa

1052



Ore

gon

grap

eM

ahon

ia A

quifo

lium

√O

rient

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rbor

vita

eP

laty

clad

us o

rient

alis

√P

hotin

iaP

hotin

ia x

Fra

seri

√P

inea

pple

gua

vaF

eioj

oa S

ello

wia

na√

Pur

ple

ice

plan

tLa

mpr

anth

us p

rodu

ctus

√P

yrac

anth

a,cv

.Gra

beri

Pyr

acan

tha

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tune

ana

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coto

neas

ter

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ster

con

gest

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nobl

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sp.

√R

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rosa

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mum

his

pidu

m√

Ros

emar

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inus

off

icin

alis

√S

outh

ern

mag

nolia

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nolia

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ndfil

ora

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outh

ern

yew

Pod

ocar

pus

mac

roph

yllu

s√

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ndle

tree

,cv.

Euo

nym

us ja

poni

ca√

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ndifl

ora

Spr

eadi

ng ju

nipe

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nipe

rus

chin

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r ja

smin

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des

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awbe

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utus

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Com

pact

Sw

eet g

umLi

quid

amba

r S

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a√

Tho

rny

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agnu

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laea

gnus

pun

gens

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lip tr

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ndro

n Tu

lipife

ra√

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ush

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mon

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inal

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nges

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mar

a√

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pted

from

Maa

s (1

986)

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ery

sens

itive

:Max

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w�

0.7

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/m

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sitiv

e:M

ax.E

Cw

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4 �

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dS/m

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erat

ely

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itive

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0 dS

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erat

ely

tole

rant

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w�

4.0

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5 dS

/m

Tole

rant

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w�

5.5

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8 dS

/m

Ver

y to

lera

nt:M

ax.E

Cw

> 6.

8 dS

/mc In

Flo

rida,

Alg

eria

n iv

y is

cat

egor

ized

as

a sa

lt-to

lera

nt p

lant

.

Not

e:E

Cw

�el

ectr

ical

con

duct

ivity

of

the

irrig

atio

n w

ater

.Sal

initi

es e

xcee

ding

the

max

imum

per

mis

sibl

e w

ater

sal

inity

(M

ax.E

Cw)

may

cau

se le

afbu

rn,

loss

of

leav

es,a

nd/o

r ex

cess

ive

stun

ting.

The

max

imum

val

ues

show

n w

ere

deriv

ed fr

om m

axim

um p

erm

issi

ble

EC

eda

ta b

y a

fact

or o

fE

Ce

�1.

5 E

Cw.

1053

Metcalf_CH18.qxd 12/12/06 06:09 PM Page 1053Landscape Irrigation with Reclaimed Water

Generally, plants with low water requirements and high salt tolerance are preferred foruse in landscape areas that are irrigated with reclaimed water. Xeriscape, the method oflandscaping with plants that require little or no water, is often recommended in arid andsemiarid regions to conserve water.

Plant species preferred for a specific area vary with climatic, geological, and culturalconditions. Guidelines and recommendations for plants are usually available from localnurseries, university extensions, and city agencies. In St. Petersburg, Florida, for exam-ple, large-scale research projects were carried out during the 1980s to investigate theeffects of reclaimed water on landscape plants. In “Project Greenleaf,” a total of 203plant species were examined for the tolerance to reclaimed water irrigation (Parnell,1988). A summary of the findings from Project Greenleaf is presented in Sec. 18-7.

Landscape irrigation systems with reclaimed water consist of a water reclamationprocess and a distribution system, including pumps, flowmeters, distribution piping andtubing, and the sprinklers/emitters. A summary of the typical components of a land-scape irrigation system is shown in Table 18-5.

In many states, irrigation methods are specified along with the reclaimed water qualityrequirements. As an example, the requirements for reclaimed water quality and the irri-gation methods in California are shown in Table 18-6. Various irrigation methods forlandscape irrigation using reclaimed water are summarized in Table 18-7, and furtherdiscussion is provided in Chap. 17. Surface sprinklers are used most commonly for turfirrigation. Microsprinklers and drip systems are becoming increasingly popular forlandscape irrigation because of high irrigation efficiency and low risk of human expo-sure to reclaimed water. A subsurface irrigation system practically eliminates humanexposure to reclaimed water. Examples of sprinklers and emitters used commonly forlandscape irrigation are also shown in Table 18-5.

The two essential parameters used to estimate the agronomic water needs for plants arethe landscaped area requiring irrigation, and evapotranspiration. The estimation of agro-nomic water needs is similar to the method used to estimate water needs for agriculturalirrigation (see Chap. 17). In this section, only the concepts specific to landscape irriga-tion are discussed.

Landscape EvapotranspirationThe evapotranspiration that occurs in a landscape area is affected by (1) the plant species,(2) density of vegetation, and (3) microclimate of the landscape site (University ofCalifornia and State of California, 2000). The crop coefficient (Kc) is used to account forthese effects for agricultural irrigation. For landscape irrigation, a landscape coefficient, KL,is used in lieu of the crop coefficient. The landscape coefficient is defined in Eq. (18-1) as:

(18-1)

where KL � landscape coefficientks � species factorkd � density factor

kmc � microclimate factor

KL � ks � kd � kmc


IrrigationSystems

Estimation ofWater Needs




Table 18-5

Summary of components used for landscape irrigation systems

Landscape irrigationsystem component Description

Dripline Dripline, constructed of UV-stabilized polyethelene plastic, isused for drip irrigation systems. Emitters may be embeddedinline, plugged into outside of tubing, or embedded in the wall oftubing. Some manufacturers produce tubing with biocide coatingto inhibit biofilm growth. For use with reclaimed water, driplinesshould be either colored purple or have a purple strip. Driplinesare typically installed at a depth of 150 to 300 mm (6 to 12 in.),with in-line emitters spaced at 450 to 600 mm (18 to 24 in.), anddriplines installed in parallel and are separated by 200 to 600 mm(8 to 24 in.)

Inline tortuous path emitter A tortuous path emitter controls the flowrate, based on turbu-lent flow through a restricted labyrinth pathway. The flowratewill vary with changes in pressure due to changes in elevationor pump output. Some emitters are coated with herbicide toreduce root intrusion or biocide to reduce biofilm growth.Emitters are operated at pressures ranging from 0.7 to 3 bar(10 to 45 lb/in.2)

Inline pressure compensating Pressure compensating emitters with an internal diaphragm produceemitter flow that does not vary with changes in line pressure. They are

used typically in areas where changes in elevation would causevariable flowrate in nonpressure compensating emitters. Emittersmay be less sensitive to biofilm-type clogging, due to flushingaction of diaphragm. Root intrusion may depress the diaphragmand reduce the pressure compensating feature. Some models arecoated with herbicide to minimize root intrusion or biocide forbiofilm control. Emitters are operated at pressures ranging from0.7 to 3 bar (10 to 45 lb/in.2)

Microsprinkler Microsprinklers, sprayers, and jets can be used with flower beds,ground cover, and orchards. Full-, half-, or quarter-circlesprayers can be used at pressures ranging from 0.7 to 2 bar (10 to 30 lb/in.2). Flowrate and the sprinkling radius will varywith the operating pressure, with typical flowrates ranging up to 110 L/h (30 gal/h)

Pop-up sprinkler Pop-up sprinklers can be used for a variety of plants includinggrass, ground cover, flowerbeds, and shrubs. The rotor type, com-monly used for lawns, can be operated at a radius of 3, 4, and5 m (10, 12, and 15 ft). Full-, half-, or quarter-circle sprinklers areavailable. For uniform distribution of water, pop-up sprinkler headsshould rise above the height of the plants (such as grass) to beirrigated. Operating pressures range from 2 to 2.8 bar (30 to40 lb/in.2)

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b. determine the volume of water irrigated, v w, for each...

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