poultry slaughter

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Poultry slaughter wastewater treatment with an up-flowanaerobic sludge blanket (UASB) reactor

C. Chavez P. a, R. Castillo L. a, L. Dendooven b, E.M. Escamilla-Silva a,*

a Departamento de Ingeniera Qumica, Instituto Tecnologico de Celaya, Ave. Tecnologico y Antonio Garca Cubas S/N, 38010 Celaya, Gto. Mexicob CINVESTAV-IPN, Departamento de Biotecnologa y Bioingeniera, Avenida Instituto Politecnico Nacional 2508, C.P. 07000, Mexico D.F., Mexico

Received 9 December 2002; received in revised form 27 August 2004; accepted 28 August 2004

Available online 4 June 2005

Abstract

Removal of organic material from poultry slaughter wastewater as determined by changes in biological oxygen demand (BOD5)

was investigated by adding three different types of inoculum combining cow manure, yeast extract or hydraulic residence time as

variables with response vector of reduction of BOD5. In a 3-l reactors, a 95% removal of BOD5from poultry slaughter wastewater

was obtained with organic loading rates up to 31kg BOD5m3d1 without loss of stability. This 95% removal was obtained between

25 and 39 C with a hydraulic residence time between 3.5 and 4.5h. The growth of the consortium of micro-organisms in the reactor

followed a first-order kinetic with a constant specific growth rate of 0.054h1. It was concluded that an inoculum from cow manure

added with nutrients and yeast extract allowed a 95% removal of BOD 5from poultry slaughter wastewater at ambient temperatures

within a hydraulic residence time of 4h, sharply reducing possible environmental hazards.

2004 Published by Elsevier Ltd.

Keywords: Poultry slaughter wastewater; Up-flow anaerobic sludge blanket (USAB) reactor; Biological oxygen demand (BOD5); Hydraulic resi-

dence time and cow manure inoculum

1. Introduction

One of the most important applications of biotech-

nology is the treatment of industrial and municipal

wastewater to reduce environmental pollution (Lettinga

et al., 1980). Effluents from industrial poultry, porcine,

or bovine slaughterhouses containing lipids, proteins,

blood, and other organic material, might cause environ-

mental damage if discharged untreated in rivers andcreeks. Processing a chicken for human consumption re-

quires 1012l of water so the overall water consumption

in a poultry processing plant is considerable. Sixty per-

cent of the water is converted into wastewater with pH

between 6.1 and 7.1, a biological oxygen demand

(BOD) between 4500 and 12,000mgl1 and a large per-

centage of solids, mostly clotted blood (more than 40%

in volume), with a high fat content (Mercado, 1995).

The rest of the wastewater is lost in the process through

run-off.

Most poultry wastewater is treated physicochemi-

cally, requiring large quantities of chemicals and energy

to dry the effluent and generating 20g of sludge per litre

of water. Deposition of the sludge is difficult, thus limit-ing the use of this technique. A better option to reduce

the generated biosolids might be an anaerobic digestion

using up-flow anaerobic sludge blanket reactors (UASB)

(Speece, 1983;Young and Dahab, 1983; Young, 1991).

In the USAB process, anaerobic bacteria convert

organic material into methane, carbon dioxide, and bio-

mass while purifying the wastewater (Del Nery et al.,

2001). USAB systems are known for their high volumet-

ric treatment rates, good CH4 productivity, and low

0960-8524/$ - see front matter 2004 Published by Elsevier Ltd.

doi:10.1016/j.biortech.2004.08.017

* Corresponding author. Tel.: +52 461 61 175 75x152; fax: +52 461

61 177 44.

E-mail address: [email protected] (E.M. Escamilla-Silva).

Bioresource Technology 96 (2005) 17301736
mailto:[email protected]:[email protected]


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sludge production, which makes the process economi-

cally and technologically attractive (Del Pozo et al.,

2000). Since 1982, the applicability of UASB systems

for the direct treatment of sewage has been tested (Lett-

inga et al., 1980;Lettinga and Pol, 1986). Investigations

in Brazil (Souza, 1986), Indonesia (National Institute

for Public Health et al., 1988), India (Siddiqi, 1990)and Colombia (Schellinkhout et al., 1985) showed that

a BOD reduction of 75% is possible under tropical con-

ditions with somewhat lower percentages in colder areas

(Vieira and Souza, 1986).

Because of the demonstrated capacity of UASB ap-

proaches for both domestic and industrial wastes, we

investigated, in a preliminary study, the performance

of a UASB treating poultry slaughter wastewater. Spe-

cifically, we examined the effect of different types of

inoculum on reactor performance as determined by

reduction in BOD5. A full factorial experimental design

was applied considering temperature, type of inoculum

and hydraulic residence time as principal variables with

response vector of reduction of BOD5.

2. Methods

2.1. Wastewater

Wastewater originated from a poultry slaughter com-

pany (Bachoco S.A. de C.V.) in Celaya (Gto., Mexico).

It was sampled from the container where the effluent

was separated from the larger residues such as feathers,

bones and meat every 6h for two weeks. A total of 100l

was obtained per day, homogenized and analysed chem-

ically and microbiologically (ALPHA AWWA WPCF,

1990).

2.2. Pre-treatment of poultry slaughter wastewater

The slaughter wastewater collected from an equaliza-

tion pond of 185.5m3 at Bachoco S.A. de C.V. to min-

imize fluctuations in wastewater characteristics thereby

providing optimum conditions for subsequent treat-

ment. Retention time in the equalization basin was

between 12 and 24h.

2.3. Sludge activation process and treatments

Three different inocula were produced and tested for

their suitability as follows:

(A) Ten litre poultry slaughter wastewater taken from

the equalization basin was added to a 15l closed glass

container, equipped with gassing out orifice and left to

stand. After five days, 50% of the concentrated slaughter

wastewater was replaced with fresh slaughter waste-

water and cow manure was added at a rate of 5gl1

(Rojas, 1988). Three days later 10 g yeast extract per litre

was added to the mixture (Stronach et al., 1986).

(B) Ten litre poultry slaughter wastewater taken from



stand. After five days, 50% of the concentrated poultry

slaughter wastewater was replaced with fresh poultryslaughter wastewater and three days later, 50mg ferric

chloride, 15mg sodium molybdate, 20mg cobalt chlo-

ride and 10mg nickel chloride were added as part of a

1l solution (Kennedy and Droste, 1991; Keemer and

McCallion, 1989).

(C) Ten litre poultry slaughter wastewater taken from



stand. After five days, 50% of the concentrated poultry

slaughter wastewater was replaced with fresh poultry

slaughter wastewater. One litre of fresh waste water

was amended with 5g cow manure, 50mg ferric chlo-

ride, 15mg sodium molybdate, 20mg cobalt chloride

and 10mg nickel chloride prior of being added to the

mixture. Thirty-six hours later, a yeast extract solution

(10g yeast extract per litre of poultry slaughter waste-

water) was added.

2.4. Reactor characteristics

A tubular glass bioreactor with 85cm height, 6.7cm

internal diameter and 9cm external diameter (CRODE;

Celaya, Mexico) and a 3-l working volume operating in

continuous flow through mode was used. Three pH sen-

sors were installed in the bioreactor while its tempera-ture was controlled by circulating water trough its

jacket with a peristaltic pump. Sub-samples were taken

each 15h and analysed for chemical oxygen demand

(COD) and BOD5.

2.5. Experimental process in bioreactor

A factorial experimental design L9 (34-1) in triplicate

(Montgomery, 1991; Moen et al., 1991) was used to

investigate effects of hydraulic residence time, tempera-

ture and inoculum type on decrease of organic material

as determined by changes in BOD5 in poultry slaughterwastewater (Table 1). BOD5was determined by measur-

ing dissolved oxygen with an OD YSI instrument

(model 50-B-ILL, USA) before and after an incubation

at 20 C for five days. The BOD5 was defined as (Stan-

dard Methods for the Examination of Water and waste-

water, 1989)

BOD; mg l1 D1D2

P ; 1

BOD; mg l1 D1D2 B1B2f

P 2

C. Chavez P. et al. / Bioresource Technology 96 (2005) 17301736 1731


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with D1 = dissolved oxygen of diluted sample immedi-

ately after preparation (mgl1); D2= dissolved oxygen

of diluted sample after 5d incubation at 20 C (mgl1);

P= decimal volumetric fraction of sample used;

B1= dissolved oxygen of seed control before incubation

(4d);B2= dissolved oxygen of seed control after incuba-

tion (mgl1) (4d), and; F= ratio of seed in diluted sam-

ple to seed in seed control = (% seed in diluted sample)/

(% seed in seed control).

The bioreactor was inoculated with 10% inoculum

(0.3l) types A, B or C. The response variable used was

BOD5. All statistical analyses were done with Statistica

(StatSoft, Inc., USA, 2000).

2.5.1. Start-up

The reactor was started-up by continuous feeding at a

flow rate of 1lh1 corresponding to a hydraulic resi-

dence time (HRT) of 2.38h. This high loading rate al-

lowed a progressive adaptation of the biomass to the

loading rate while preventing a washing out of the

micro-organisms and the biosolids. However, a scal-

ing-up of the system to an industrial level will require

an adjusted HRT.

The influent flow rate was steadily decreased while

keeping the time intervals constant between successive

increments. Time intervals were defined when stable

concentrations of COD and VFAs value in the effluent

under each operating conditions were obtained. Thisstep-by-step organic load increase allowed the biomass

to adapt continuously.

3. Results and discussion

Physicochemical analysis of poultry slaughter waste-

water obtained daily for 15 days showed that most

parameters were above permissible international dis-

charge limits for wastewater (e.g.USEPA, 2002) (Table

2). The main contaminant in the wastewater was organic

matter with BOD5s ranging between 4500 and 8700

mg l1, 1025 times larger than norms established by

USEPA (2002). Organic material thus has to be reduced

before the wastewater can be discharged in the drainage

system or reused as irrigation water. Other pollutants

such as fats, oils, and surfactants were also above norms

Table 1

Experimental factorial design (33) to investigate the effect of hydraulic

residence time, temperature and inoculum type on the poultry

slaughter wastewater treatment with an up-flow anaerobic sludge

blanket (UASB) reactor

Experiment Hydraulic residence

Time

(h)

Temperature

(C)

Inoculum

type

Real Codea Real Code Real Code

1 2.30 1 25 1 1 12 3.30 0 25 1 1 13 4.30 1 25 1 1 14 2.30 1 32.5 0 1 15 3.30 0 32.5 0 1 16 4.30 1 32.5 0 1 17 2.30 1 40 1 1 18 3.30 0 40 1 1 19 4.30 1 40 1 1 110 2.30 1 25 1 3 011 3.30 0 25 1 3 012 4.30 1 25 1 3 0

13 2.30 1 32.5 0 3 014 3.30 0 32.5 0 3 0

15 4.30 1 32.5 0 3 0

16 2.30 1 40 1 3 017 3.30 0 40 1 3 0

18 4.30 1 40 1 3 0

19 2.30 1 25 1 2 120 3.30 0 25 1 2 121 4.30 1 25 1 2 122 2.30 1 32.5 0 2 123 3.30 0 32.5 0 2 1

24 4.30 1 32.5 0 2 1

25 2.30 1 40 1 2 126 3.30 0 40 1 2 1

27 4.30 1 40 1 2 1

a Code interpretation:1: low level of the factor, 0: middle level ofthe factor, 1: high level of the factor.

Table 2

Physicochemical characteristics of poultry slaughter wastewater mea-

sured daily for 15 days

Characteristics Minimum Maximum Mean

pH at 25 C 6.1 7.1 6.6

Electrolytic conductivity at 25C

(mSm1)

86.1 14.7 11.7

Total solids dried at 103105 C

(mgl1)

1082 4558 2771

Total volatile solids (mgl1) 938 4402 2199

Total fixed solids (mgl1) 124 1492 572

Total suspended solids dried at

103105 C (mgl1)

726 1462 938

Volatile suspended solids (mgl1) 623 1310 821

Fixed suspended solids (mgl1) 66 172 124

Total dissolved solids (mgl1) 344 3600 1833

Volatile dissolved solids (mgl1) 174 3564 1378

Fixed dissolved solids (mgl1) 12 1324 455

Settable solids (mgl1) 10 33 20

Oils and grease (mgl1) 147 666 306

Biochemical oxygen demand

(BOD5) (mgl1)

4524 8700 5500

Chemical oxygen demand

(COD) (mgl1)

5800 11,600 7333

Sulphates (mgl1) 561 1496 1107

Total alkalinity (mgl1) 7.5 12.1 12.0

Phenolphthalein alkalinity (mg l1) 6.30 11.70 10.88

Methylene blue active

substances (mgl1)

5.47 11.21 7.76

Fluorides (mgl1) 3.25 15.50 7.62

Total phosphorus (mgl1) 7.17 12.74 9.52

Phosphate, P (mgl1) 2.75 7.81 4.58

Ammonium, N (mgl1) 6 95 62

Organic nitrogen (mgl1) 1.2 22.5 17.2

Total nitrogen (mgl1) 10.5 11,150 74.9

1732 C. Chavez P. et al. / Bioresource Technology 96 (2005) 17301736


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established by USEPA (2002). The mean BOD5:COD

ratio was 0.75 as calculated using data inFig. 1. A value

above 0.6 normally indicates that a biological treatment

is better to remove organic matter from the effluent than

a physicochemical one (Lettinga and Pol, 1991).

To overcome many of the problems of batch reactor

studies and simulate waste-treatment processes, the flow

reactor is widely used for kinetic studies. In general

terms, the macroscopic material balance around a flow

reactor is

rate of accumulation in reactor

rate of input rate of output reaction rate.3

If we consider a well-mixed reactor then the concen-

tration in the reactor is equal to the concentration in

the effluent. The material balance for biomass and sub-

strate are

VdX

dt Q0X0Q0XV

rate of biomass formation; 4

and

VdS

dt Q0S0 Q0S V

rate of substrate consumption; 5

respectively. Since substrate is consumed, the rate of

substrate consumption is inherently negative. If steady-

state conditions are maintained then the material bal-

ance Eq. (5) becomes

rate of substrate consumption

Q0V

S0 S S0 S

h 6

where h= fresh residence time; S0 BOD05; S= BOD5;

Q0= volumetric flow.

In the case that the kinetics follow a first-order in a

completely mixed reactor then we have

rate of substrate consumption k0S. 7

Substituting(6)into(7)gives

S0 S

S k0h. 8

Fitting the removal of BOD5 with Eq. (8) gave

k= 0.2914h1 with correlation coefficient R2 = 0.975

for 4 h of HRT (Table 5). The kinetic of BOD5 removalindicated that organic matter biodegradation depended

on concentration of BOD5through time and could thus

be described by a first-order kinetic (Fig. 2).

Start-up times were 1828 days for inoculum A, 715

days for inoculum B and 2.55 days for inoculum C.

The start-up time using the third inoculation method

was less than those reported in the literature for similar

2500

3500

4500

5500

6500

7500

8500

9500

10500

11500

12500

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time (days)

CODandBOD5(mgl-1)

COD

BOD5

Fig. 1. Concentrations of COD and BOD5 (mgl1) in poultry slaughter wastewater sampled daily for 15 days.

y = 0.2914x - 2.2009

R2= 0.9749

0.00

5.00

10.00

15.00

20.00

25.00

0 20 40 60 80

(h)

(S0-

S)/S

Experimental

Fig. 2. Removal BOD5 kinetics in a UASB bioreactor for poultry

slaughter wastewater.



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bioreactors (Souza, 1986;Noyola, 1992;Sanchez et al.,

1993). The low start-up time obtained with high cellular

reproduction load indicated that the system could sup-

port more organic load and remove it efficiently in a

short time.

Data of maximum BOD5 removal obtained in this

laboratory experiment will facilitate scale-up and designof an industrial bioreactor. Largest removal of BOD5was obtained in experiments 6, 9, 15 and 18 (Table 3).

Analysis of variance (ANOVA) showed that process

hydraulic residence time (A), temperature (B), inoculum

type (C) and interaction C C significantly affected re-

moval of BOD5 with inoculum type being the most

important (Table 4).

Through an analysis of the surface response and the

factorial graphics it was possible to select the value for

each variable that would remove the largest amount of

BOD5 (Figs. 3 and 4). The surface response curved

showed that at high temperatures and middle hydraulic

residence times, the removal of BOD5was optimal (Fig.

4A). The best inoculum was type 3 with a hydraulic res-

idence time of 4h (Fig. 4B). The two other inoculum

types were not as efficient to reduce BOD5 as type 3

nor was reducing or increasing hydraulic residence time.

Inoculum type 3 at the highest temperatures resulted in

the largest removal of BOD5 and again the two other

inoculum types were not as efficient to reduce BOD5

nor did decreasing the temperature (Fig. 4C).A confirmatory test with the optimal parameters was

done and corroborated that a 2.1% increase in reduction

of BOD5 was obtained with hydraulic residence time

of 4 h, inoculum type 3 and temperature 35C. The

hydraulic residence time of 4h was less than reported

byRao et al. (1999)for treatment of similar wastewater

and inoculum type 3, never reported before, removed

9597% of BOD5. The best removal of BOD5 was ob-

tained at 35 C. However, maintaining a bioreactor at

35 C is economically unsustainable considering that

mean outside yearly temperatures in this part of Mexico,

i.e. Celaya, is 20 C (http://inegi.gob.mx). The confirma-

tion test was repeated at 25 C: a temperature, which

would be obtained in the UASB bioreactor. Changes

in temperature had only a minimum effect on BOD5removal and at 25 C a 95.6% removal of BOD5 was

obtained, within the operational range of anaerobic

processes reported byLettinga et al. (1979) (Table 6).

It was concluded that type 3 inoculum derived from

cow manure added with yeast extract and nutrients with

a short hydraulic residence time of 4.5h allowed a 95%

removal of BOD5 at ambient temperatures sharply

reducing possible contamination of surface water with

poultry slaughter wastewater.

Table 5

Parameters obtained fitting a first-order kinetic to BOD5removal in a

UASB bioreactor for poultry slaughter wastewater with different

hydraulic residence times

Residence time (h) Removal

rate (h1)

Interce pt Corre lation

coefficient

3:00 0.307 (0.029)a 3.011 (1.257) 0.9053:30 0.310 (0.024) 2.081 (1.307) 0.9154:00 0.291 (0.028) 2.220 (1.192) 0.9754:30 0.364 (0.034) 3.151 (1.429) 0.9104:00 (repetition) 0.373 (0.027) 2.725 (1.164) 0.9494:30 (repetition) 0.306 (0.020) 2.420 (0.850) 0.951

a Standard error of the estimate.

Table 4

Statistical analysis of different factors used in the optimisation study

for the removal of BOD5from poultry slaughter wastewater in UASB

bioreactor

Source of variation Sum of

squares

Degrees of

freedom

F P

A: hydraulic residence time 1849 1 104.7 0.0000

B: temperature 902 1 51.1 0.0000C: inoculum 6253 1 754.0 0.0000

AB 7 1 0.4 0.5577

AC 309 1 17.5 0.0006

BC 43 1 2.4 0.1381

AA 21 1 1.2 0.2962

BB 2 1 0.1 0.7675

CC 6815 1 385.7 0.0000

Table 3

Results of the full factorial experimental (33) design for the removal of

BOD5 from poultry slaughter wastewater using an UASB bioreactor

Experiment BOD5 removal (%)

Replicate 1 Replicate 2 Replicate 3 Mean

1 39.85 40.82 39.84 40.18

2 62.00 62.52 62.18 62.23

3 76.40 76.21 75.88 76.34

4 55.33 52.36 51.98 52.22

5 72.25 72.21 72.21 72.22

6 90.18 89.96 89.86 90.00

7 65.42 65.10 65.12 65.21

8 85.11 85.15 84.98 85.08

9 92.29 91.94 91.77 92.00

10 75.20 75.07 75.11 75.12

11 80.48 80.03 79.97 80.16

12 90.90 90.50 90.21 90.53

13 78.43 78.08 77.59 78.04

14 86.40 86.02 85.91 86.11

15 92.45 91.82 91.73 92.00

16 83.26 83.32 83.10 83.23

17 89.96 89.89 89.87 89.91

18 94.31 94.23 93.63 94.05

19 20.23 20.30 20.06 20.20

20 26.52 26.89 26.88 26.76

21 32.32 32.26 31.75 32.11

22 27.31 27.32 27.36 27.33

23 34.91 34.83 35.25 35.00

24 38.06 37.92 37.78 37.92

25 30.38 30.10 30.14 30.20

26 42.65 42.72 42.68 42.68

27 47.95 47.91 47.90 47.97

http://inegi.gob.mx/http://inegi.gob.mx/


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Residence time (h)

0.000

65.573

90.000

Temperature (C) INOCULUM Desirability

0.

.5

1.

15.110

43.085

71.060

0.902

-1 0 1 -1 0 1 -1 0 1

Fig. 3. Factorial graphics showing the response of hydraulic residence time, temperature and inoculum type investigated with an experimental design

33 for poultry slaughter wastewater treatment.

Fig. 4. Surface response curve for the determination of optimal parameters in the poultry slaughter wastewater treatment: (A) temperature (C)

versus residence time (h), (B) residence time (h) versus inoculum type, and (C) inoculum type versus temperature (C).



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Acknowledgements

The research was funded by Consejo del Sistema

Nacional de Educacion Tecnologica (COSNET) grant

647.95-P (Mexico). C.C.-P. and R.C.-L. received

grant-aided support from Consejo Nacional de Ciencia

y Tecnologa (CONACyT, Mexico).

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Table 6

Removal efficiencies (%) and organic volumetric loading (kg BOD m3d1) at different residence times (h) and temperature (C)

Experiment Re sidenc e

time (h)

Initial

temperature (C)

Final

temperature (C)

Removal

efficiency (%)

Organic volumetric loading

(kg BOD m3d1)

1 1.5 24.0 25.5 40.00 86.6

2 1.9 22.0 23.5 65.01 64.4

3 2.5 24.0 25.5 71.43 52.8

4 2.9 25.0 26.5 79.00 44.35 3.0 24.5 26.0 87.00 42.8

6 3.5 26.0 27.5 95.01 53.8

7 4.0 27.0 28.5 95.00 47.1

8 4.5 25.0 26.6 95.56 26.0

9 4.0 26.0 27.5 95.01 30.8

10 4.5 23.0 24.7 95.00 28.7


poultry slaughter

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