Chair of

Ecological Purification System

http://www.cwsc.or.jp

New Concept and New Name

- Quest for Safe and Delicious Tap Water

Introduction to

Nobutada NAKAMOTO

Community Water Supply Support Center of Japan

Professor Emeritus of Shinshu University, Dr. Sci.

of Slow Sand Filtration

To make an clear sub-surface water in a flood plain.

１．What is Ecological Purification System? 1-1. Basic Concept

Sand filter : Habitat for biological community

Slow Sand Bed : to make sub-surface clean water in a flood plain of a river. This photo is shown a cross section of a filter under an improvement. Practical sand layer is about 1 meter.

Small animals among sand grains are important. Slow means safe habitat for small animals which are catchers and decomposers.

It is essential that presence of oxygen for biological community. Small animals are catcher of particulate matter. Food chain is important. Dissolved oxygen in the fecal pellets is almost consumed up. It becomes anaerobic condition.

Slow Sand Filtration : Not only mechanical filtration

塩素添加は必須

1-2. Comparison with Rapid Sand Filter

Ecological Purification System ：Key is aerobic condition. Faster filtering rate keeps aerobic condition.

He introduced sedimentation basins for turbid matters from the River Thames in January, 1829. Scraping technique of the surface dirty sand was also introduced to recover the filter clog.

Horizo

ntal

to Ve

rtica

l

2. History of Slow Sand Filter2-1. Origin of Public Water Supply

He made an artificial clear seepage water of the flood plain. At that time, clear water was made by the mechanical separation by gravel and sand layer.

John Gibb sold clear water to entire city of Paisley, Scotland, in 1804.

James Simpson’s Filter at London, UK.

Origin of the process name: Slow Sand FilterThey believed that clear bacteria free water was produced by mechanical filtration using fine sand and slow process.

1832 : The great common sewers discharged into the Thames river. This was the Source of the Southwark Water Works.

Monster Soupcommonly called Thames Water. A magnified drop of water is shown to contain grotesque aquatic creatures in this satire on the Metropolitan Water supply Commission, which reported in 1828.

Clear safe water was made from the dirty turbid water by the slow sand filtration at that time.

2-2. Refocus, Rediscovery

IS THE WATER SAFE TO DRINK?Robert H. Harris and Edward M. Brecher and the Editors of Consumer ReportsConsumer Reports 1974.Part 1: The Problem, 436-443, June.Cancer risk by chlorination, asbestos. Risk of bacteria, virus, heavy metal, hazards after the treatment.Part 2. How to make it safer, 538-542, July.Why use activated carbon now? A challenge to traditional treatment. Routs to safer water.Part 3. What you can do, 623-627, August.

A large outbreak of diarrhea was occurred in Milwaukee, USA, in 1993. Slow sand filtration system was refocused and a workshop on it was held at Salem city, Oregon state by American Water Association in 1993. Refocus, Rediscovery, Timeless Technology for Modern Application. However, people loves New Technology.

Scraping surface clogging material by machine. Salem, Oregon, USA

Am Water Works Assoc. 1997;89(12):8–9.

What is real risk? What is more safe treatment?

Contents１．What is Ecological Purification System?

1-1. Basic Concept1-2. Comparison with Rapid Sand Filter

２．History of Slow Sand Filter2-1. Origin of Public Water Supply2-2. Refocus, Rediscovery2-3. Ecological Purification System

３．Water Purification Plants(Japan, Oversea and JICA projects)

４．Summary

New water treatment plant of slow sand filtration was built at Central Bridge, New York, USA. Many cattle grazed the grass around the reservoir of the source water.

Bird flu also.

Swan is the most friendly bird at the Ashford Common Water Works, Thames Water Utilities, UK.

Slow sand filtration will not care about Cryptosporidium.

Continuous culture system of filamentous algae. Frequent scraping and high nutrient in water.

Trap SS among algal mat.Oxygen bubble formation by algal photosynthesis.

Attention to the role of algae and animal in this system.

Someya Waterworks, Ueda, NaganoEstablished in 1923

2-3. Ecological Purification System

Effective scum out.

Diurnal change of dissolved oxygen in inflow and in outflow water and the partial pressure change of oxygen in bubbles.

Active growth of algae on the sand bed. Oxygen bubbles are formed under super saturated condition.

Scum out of algae

Partial pressure of oxygen in bubbles.

Continuous culture condition of algae keeps aerobic condition in the filtrate even in the night.

DO

con

cent

ratio

n

saturationconcentration

Day Night

Inflow water

Filtra

te wat

er

Depth of active layer of biological communities is about upper several centimeters. The time passing this layer is only several minutes. The time of ecological purification is an instant purification. One meter depth of sand layer is for the safe and guarantee in case of emergency.

Wakata water works, Takasaki, Japan. Established in 1964.

A. Hazen 1905.

Algae produce oxygen and make better environment for animals. Algae is also food for animals.

Mechanism of Ecological Purification System

Food size and animal size

Anaerobic condition inside of fecal pellet.

Animal carries up to particles as fecal pellets.

Development patterns of algal biomass as Chlorophyll in February and August at Wakata water works, Takasaki.

8月

1

10

100

1000

0 10 20 30

2月

1

10

100

1000

0 10 20 30

Chl‐

a（ｍ

ｇ/㎡

）

Feb.

Aug.

Filter run in days

Growth rate 0.054

Melosira varians 2.5E＋09cells/㎡

Melosira varians 2.6E＋10cells/㎡

Growth rate 0.174

Chl‐

a（ｍ

ｇ/㎡

）

Slow growth algae in winter, high in summer.

0

5 0

1 0 0

0 1 0 2 0 30

0

50

100

0 10 20 30

Health index change of algal mat during filter run, Wakata water works. Algal mat becomes healthy during filter run in winter. However, algae in summer become active in short time but it becomes worth condition after the peak. Algae grazed by midge of Chironomidae.

（％）

（％）

Feb.

Aug.

Active condition of M.varians

Hea

lth In

dex

of a

lgae

(%) :

Chl

.a/(C

hl.a

+Phe

.a)

Filter run in daysInactive condition of diatom cells

Fecal pellets of Chironomid larvae.

DAYS OF FILTER RUN

Chl

orop

hyll

a，

mg

m -2

1

10

100

1000

0 10 20 30

％

0

50

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0 10 20 30

A

B

A

B

A ; Healthy algae

B ; Inactive algae

Alg

al b

iom

ass

Hea

lth In

dex

of a

lgae

Growth pattern of algal mat in summer at Wakata water works. Remarkable decrease of algal biomass in summer was caused by the grazing activity of Chironomid larvae.

Filter run in days

Filter run in days

水深

In order to grow well for algae, the water depth was change to shallow depth.

Wakata water works.

Algae can grow under shallow depth, even in cold season.

In order to reduce filter resistance of sand layer, large size of sand for rapid sand filter was placed about one meter depth on the original fine sand.

Shallow depth promotes algal activity.

Algae can not grow on the bottom of slow san filter in winter. However, algae can grow on the shallow model in winter.

Flood plain of the Chikuma river in winter.

Experiment in winter at Someya water works.

Grid :1mm interval

Algae and animal grow well at the shallow depth. Wakata water works.

：１００cm～１４０cm

：１４０cm～２００cm

Algal biomass is large at the shallow depth and small in deep depth on the filter bed after 7 days of filter run at the bottom.

Animal biomass is large at the shallow depth and small at the deep depth.

Healthy filamentous diatom is remarkable at the shallow depth.

Shallow depth makes healthy condition of algae and animals.

Inactive cells of broken or empty diatom are remarkable at the deep depth.

Filamentous diatom dominates under rich nutrient and under frequent scrapping.

Midge larvae graze well diatom in warm period. Abundant casting shells of midge are remarkable on the surface.

In case of long filter run, carnivorous animals are also remarkable such as mollusks etc.

Filamentous green algae (Cladophora, Spirogyra, Hydrodictyon, etc.) are remarkabe in warm period.

This phenomena is usual in warm region.

Pioneer algae is filamentous diatom such as Melosira varians. Diatom is the best food for grazing animals such as insect larvae. Then, green filamentous algae becomes dominant algae in long filter run and in warm period.

Filamentous green algae at Kenzaki, Takasaki in summer.

Green filamentous algae at Someya water works in summer.

Succession: from diatom to green algae in long filter run.

Someya wwks (alt. 500m) in 1988. Wakata wwks (alt. 150m) in 2004.

Filter run in days

Nor

mal

ized

Hea

d Lo

ss, c

m

Comparison of temperature and filter resistance at different water works where are at different altitude. Both wwks treated the surface water of the rivers.

Filter resistance increased when the surface of filter pond was frozen in cold season at Someya wwks. Biological activity was weak. The viscosity of water became large in cold condition.

In warm period, the viscosity becomes small. The all of biological community becomes active. Filters does not clog.

Small amount of suspended matters in source water does not affect on the filter resistance.

High temperature and high solar radiation promote biological activity. In warm period, filters does not clog.

inflowH

ead

loss

cal

cula

ted

at 4

.8m

/d

tem

pera

ture

slow

outflo

w

outflo

w

outflowinflow

inflow

inflow

fast

Flow rate

Effective scum out

Day Night

NightDay

Dis

solv

ed O

xyge

n co

ncen

tratio

n

Closed scum out

Effective scum out Closed scum out

Importance of effect of scum outlet and DO change related with flow rate.Large fluctuation is observed under low speed of filtering rate. Small fluctuation is observed under high speed.

Effective removal of floating scum is necessary to keep favorite DO condition in night. Algae produce oxygen when they grow. When they die, they consume much oxygen. Oxygen releases from the surface to atmosphere. During the night, oxygen consumption becomes high. Sometimes, low oxygen makes unpalatable effluent water under low DO concentration.

Biological community is sensitive to anaerobic condition.

Nabeya-Ueno water works in Nagoya city (established in 1914) recognized the importance of scum out. They remaked the vertically movable type for easy escape of surface floating scum at the corner.

Miyako- jima island is a raised coral island, in Okinawa prefecture. All of the water source for Sodeyama water works is underground water. It is a hard water originated from the raised coral reef. This water is affected to the agricultural activity. In the filter pond, heavy algal bloom is remarkable during the whole year.

Floating algae is harvested and it becomes a good fertilizer for the farmer. The supernatant water shifts to high pH condition. Calcium carbonate crystals are formed under high pH condition. This phenomenon is recognized under the microscopic observation. This is a bio-mineralization.

Biological action by algae (Growth of algae : absorption of nutrient, oxygen production, crystallization of calcium carbonate from hard water, etc.) Sodeyama water works, Miyako-Jima (coral island), Okinawa. JICA training was done in this island.

Addition of oxygen: Aeration is frequently used for treatment of groundwater (reduction of unpleasant tastes and odors, discoloration, precipitation of iron and manganese).

Heber 1985

Iron and manganese are oxidized and form nearly insoluble hydroxide sludge. They can be removed in a settling tank (or using a coarse filter).

Cascade aerationAeration filter

Treatment for anaerobic water.

Pre-treatment of cascade aerator using biological activity of bacteria, algae and animals.

Family use of an ecological purification plant treated high concentration of iron and manganese in a tube-well water.

Final treatment of slow sand filter.

Biological Phenomena of Ecological Purification System(EPS) related with algae

☆Oxygen Production by Photosynthesis

Gives a better condition for heterotrophs. (Decomposer: bacteria, small animals)

CO2+H2O→CH2O+O2↑

☆Reduction of Nutrients in Water by Algal Growth106CO2+16HNO3+H3PO4+122H2O+(micronutrients,energy)

↓ ↑

(CH2O)106(NH3)16H3PO4 + 138O2 ↑ + micronutrients↓ ↑

Photosynthesis respiration, decomposition

Oligo-trophication (opposite process of eutrophication :shift to less polluted water)

☆Production of Food and Energy Source for Heterotrophic OrganismsAlgae is one of the best food for animals in EPS.

☆Shift to High pH and High DO Concentration by Photosynthesis(Low CO2 concentration shifts to high pH condition)

Metal ions are easily changed to hydro-oxide compounds.Easily precipitate: bio-mineralization

Reduction of metal ions:Reduction of toxic heavy metals

Countermeasure for suspended matters and sudden change of water quality

Nabeya-Ueno water wks, Nagoya. Established in 1914.

Surface water from a river.→5 sedimentation basins(Torii-matu)

Kenzaki wwks,Established in 1910.

Surface water from a river.→3 sedimentation basins.→4 slow sand filters

From Google map

Sakai water works, Tokyo. Established in 1924.

Sedimentation basin for river water

In case of a reservoir as a water source. Phytoplankton from a reservoir is not serious problem. It is a food for animals in a filter pond.

the

100 % of tap water in London city is supplied by slow sand filter. Thames river water is eutrophic water. At first, river water stock for about one month in a reservoir. Then it is treated by a gravidity rapid sand filter without any chemical reagent to eliminate plankton. And ozone treatment, slow sand filtration are done. It flow rate is 9.6 m/d (40cm/hour). This is double rate of traditional standard rate.

3．Water Purification Plants(Japan, Oversea and JICA projects)

Surface Loading Rates for a SSF at Ashford Common AWTW during April and May 2006

0

0.05

0.1

0.15

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Surf

ace

Load

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Rat

e (m

3 /m2 /h

)

All the plant of Thames waterworks adopted 9.6m/d (0.4m/h). Higher flow rate makes better quality in the filtered water. Diurnal change of DO in effluent water becomes small. It is better to avoid low oxygen concentration in the morning.

Filamentous diatom is dominated in winter at Thames water works, UK. But filamentous green algae called as a blanket weed is remarkable in summer. It is caused by the grazing activity of insect larvae in summer.

Refocus on bank filtration: Artificial subsurface water is taken at Mulheim water works, Germany. Suspended free water can be easily taken.

Porous pipes were placed under the gravel bed in a river. Almost suspended free water is taken for a slow sand filter plant. This is an artificial subsurface water.

Water source for Akan water works, Kushiro.

Nishihara waterworks, Suzaka city, Nagano. Raw water: SS free of subsurface water. Over two years, there is no scrapping. This is almost no work to maintenance. One filter area: 6.8mx13.5m=91.8m2 One filter capacity : 459m3/d. One filter can supply for 1500 persons demand (0.3m3/d).

At the foot of mountain, there is a reed plant where underground water leaks out. Porous pipes were set to take the subsurface water which is suspension free water.

JICA trainers visited in 2007-2008.

The water sources of Kinuta (Kami) water works (established in 1928) and Kinuta (Shimo) water works (established in 1923) were taken by the bank filtration which drainage pipes were placed in the flood plain of the river Tama-gawa. Suspended free water is the best water source for slow sand filtration process. The standard flow rates are 8.5 m/d and 9.5 m/d.

Recently, bank filtration as a water source is refocus and re-evaluated in Europe and United states. In Japan, we can find some examples in some old water works.

JICA training in Miyako Jima, Okinawa, Japan

Up-flow elimination system of SS

Pressure control for constant flow

Sand size is not important: large size of sand is better.The grid interval is 1 mm.

Ecological Purification System can be made by yourself.

Mr. WRIGHT Filipo(Samoa)Mr. KAPHLE Ram Chandra(Nepal)Mr. PHIMMASONE Vilaykhone(Laos)

In case of mountain stream, the dissolved oxygen is always supplies. Running water is usually aerobic.

Sedimentation basin

A ball tap is also an useful technique to keep a water level.

Up-flow roughing filter using gravels.

Over flow

This treatment model was constructed by JICA training coerce.

Slow sand filter

The drain tap in case of filter clog.

Flow rate is controlled to keep the water level using an over flow pipe.

Model experiment : sub-surface water(low oxygen concentration)

An model of an Ecological Water Purification System

The essential condition is to keep almost constant flow for biological community in this system. It means safe and reliable condition for organisms. Running water makes aerobic condition.

Constant flow system using a float.

Up-flow roughing filter

Ecological purification tank (slow sand filter)

Storage tank for filtrate water

Snap switch for a pump

Water is circulated using a pump. This system needs a constant flow of water.JICA training in 2008

Samoa island is a volcanic island located in south pacific ocean.

This water works is very energy save system using the natural gravidity.

Black sand is used. The water quality is good, as an aerobic condition is kept in always under constant flow.

5 slow sand filters

One regulator house for 5 slow sand filters.

2 sedimentation basins

4 up-flow roughing filters

Floating scum is drained off by the water level shifts.

Seepage clear water above a lava terrace flow out and make a water fall.

Site visit after the JICA training.

Fecal coli form bacteria are not detected in this filtrate water. Water quality is clear in all parameters for drinking water. This delicious water is safe and reliable for the villagers.

Small water supply system for a small community less than 100 persons in a country side.

Raw water is taken using a porous pipe placed in a mountain stream.

The final filter is composed with sand and several sheets of thick felt carpets. Periodical washing of the top of two or three sheets of the felt carpets on the sand layer is conducted to keep well condition of the filter rate. This cleaning is done usually once a month. Washed sheets are placed back on the sand layer and rocks as weight are placed on the sheets.

Up-flow roughing filter using gravel.

Slow sand filter.

Filtrate tank.

Soil layer which is biological active layer is very thin.

The water passed the deep layer in a mountain contains much minerals originated from the rocks.

Subsurface water contains low concentration of minerals. The contact time to the rocks is shorter than the water from the deep layer. The depth of biological active layer is

very thin such as in the sand filter bed.

JICA trainers visited.

Ueda, Nagano

There are so many bacteria.→Medical doctor touches with patients. Doctor is safe.

１０６ １０３１０４ １０１１０２ １０-１１００１０５ １０-2 １０-3

Logarithmic bacteria number in 1 ml

１０７１０８

.....

....

....

１０-４ １０-５

Risk of germ bacteria in water.

water

EPS (SSF)

Wash hand

Coli-form bacteria are abundant in soil and are not germ bacteria.

Please compare the size and number of Cryptosporidium with bacteria in water. Risk?

100 1101,000 0.1 0.0110,000 0.001 0.0001

soil

0.00001100,0001,000,000

10,000,000100,000,000

Gen

eral

ba

cter

ia

Gen

eral

ba

cter

ia

Gen

eral

ba

cter

ia

Col

i-for

mba

cter

ia

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i-for

mba

cter

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Col

i-for

mba

cter

ia

Feca

l C

oli-f

orm

Feca

l C

oli-f

orm

Feca

l C

oli-f

orm

Ger

m :

Cho

lera

Ger

m :

Cho

lera

Ger

m :

Cho

lera

Elimination by biological community

We have to think about acceptable risk.

4. Summary (1/2)

May, 2002 August, 2005. Portuguese book is available in 2009. Chinese book is in preparation.

Not the Slow sand filter, Ecological Purification System: New Concept, New Name, New Idea of Timeless Technology from Japan.

Large sand (around 1mm) Biological community among the sand. No clog.

Shallow water depth (around 50 cm) Algae and animals grow well.

Faster flow rate (around 10 m/d) Keep the aerobic condition.

Against suspended matter, sedimentation basin and up-flow roughing filter.

Active utilization of harvested algal biomass.Frequent scraping is not good.

Requirement for verification of Ecological Purification System.

Biological purification under aerobic condition. The key is food chain.

Original Name is not Fair.

Change the Name!

●Concept

●Technical points

For More INFO

Comparison with the traditional slow sand filtration, rapid sand filtration, membrane technique, etc. under different conditions with special reference to the cost and maintenance. Technique for introduction and application of new technology etc.

●Others

This is the point!

4. Summary (2/2)