I

P 05406 80 A COMPARISON OF TREATMENTS FOR HIGH STRENGTH

DISTILLERY SLOPS FROM THE SUGAR CANE INDUSTRY

HPctor M . Poggi-Varaldo, Associate Professor Center of Advanced Studies and Research,

CINVESTAV del IPN, Dept. of Biotechnology and Bioengineering MCxico D.F., MCxico

INTRODUCTION

The industrial activity is the main contributor to the water pollution in h4exiCo. The sugar cane processing industry is the major wastewater generation source with nearly 6OTo of the total dis- charges' (Figure 1 ) . The distillery slops from alcohol manufacture based on molasses fermentation account for an important amount of the organic load of these emissions.

The distillery slops, known as vinasses, can be very aggressii e to rhe environment N hen improperly managed. They have low pH and high contents of suspended and dissol\.ed organic matter and nutrients. On the average, each liter of alcohol distilled generates 12 lo 14 liters of vinasses. The potential en\:ironmental impact of a distillery manufacturing 5 0 0 m' alcohol/d.ay is equivalent to that of a city of 200,000 inhabitants.' In 1989, about 1,500,000 m3 of \inasses were discharged in Mesico in parallel to a production of 115,000 ni3 of alcohol.'*4

Recycling and resource recovery from vinasses is a very dynamic area of research.' Current experi- ments in the CINVESTAV in reusing/recycling vinasses for alcohol fermenration or single cell protein synthesis show promise (V. Lopez-Mercado and M. de-la-Torre, private communication, CINVES- TAV, 1992). Although reuse and recycle could alleviate the vinasses' pollurion problem in the future,

SUGARCANE 62 0%

DISTILLERY Alcohol i--r-i- Vinaase

I Tapwater Aneeroblc EffluenI

CHEMICAL 2.1% OTHERS 19.0%

PULP AND PAP 10.0%

TOTAL: ONE BILLION M3/YR

Aerobic Etfluent

t t t t LEACHATE

Figure 1. Industrial wastewater discharges in Figure 2. Experimental design flowsheet. hfexico-contributions of industrial sectors.

47th Purdue fndusirial lVus/e Conference Proceedings, 1992 Lewis Publishers, Inc.. Chelsea, Michigan 481 18. Prinred in U.S.A.

789

I 790 47TH PURDUE UNIVERSITY INDUSTRIAL WASTE CONFERENCE PROCEEDINGS

Table I . Reactor Characteristics ~~

Work Hydra u I Total Volume Retent

Volume FBED Time Temperature (L) Carrier (L) (Day) ( “ C )

A n a er o b i c I.luidized 300 Exchange 120 I k d Resin

1011 3.6

7.2 35 & 25

,\e r o b ic 1-1 uidized 2.65 Carbon t k d

Active 1 1.5 2

4 23

ilieir treatment is and \ \ i l l continue to be necessary. Among the menu of processes available, biologi- c.:ll treatment of the sugar industry effluents seems to provide both a sound degree of pollution irbatement and resourcelenergy recovery o p p o r ~ u n i t i e s . ~ - ~ Furthermore, effective full scale applica- lions ve re implemented since rhe early 8O’s.’3’~‘*

In 1987, the government-ouned company AZUCAR S .A. and three h4exican higher education ~~is t i tu t ions (Center for Advanced Studies and Research-CINVESTAV, National Autonomous Uni- \.crsity of i\lIexico-U.N.A.M, and the State University of San Luis Potosi-U.A.S.L.P) with the cooper- ;tiion of the Mexican sugarcane mill “Alianza Popular” launched a pilot scale experiment I O test the \,inasses treatability and the actual potential for resource and energy recovery using a combination of Iiigh-rate anaerobic and aerobic processes.”

This paper reports some results form the experiments conducted in the context of this Pilot Project. Ihe objectives of this particular \vork uere:

1. to determine the performance of series anaerobic-aerobic treatment of vinasses; 2. to examine the feasibility of anaerobic treatment of vinasses followed by irrigation.

MATERIALS A N D METHODS

b;sperimental Design

Figure 2 summarizes the experimental program. Raw vinasses \vere treated in a pilot scale Anaero- bic Fluidized BED reactor (ANFBED). The anaerobic effluent from this stage was fed to a bench scale Aerobic Fluidized BED reactor (AEFBED). Lysimeters containing soil of the region received other portions of the anaerobic effluent at hydraulic rates 5 and 10 cm/\sk. Two “control” lysimeters ere irr-igated with tap water and raw vinasses at 10 cm/wk (see Table 11). Irrigation tests lasted six months.

The ANFBED operated at 35°C and hydraulic retention times ( H R T ) of 1,2,3, and 4 days during the first campaign; in the second campaign the ANFBED run at 25°C (psychrophilic or sub-optimal icrnperature range) and H R T of 3.6 and 7.2 days (Table I ) . The AEFBED worked at 23”C, in the I-;rnge of 1 to 4 days HRT. Both the AEFBED and the lysimeters received anaerobic effluent from the x c o n d campaign.

17:iperimental Set-up

Table I shows the main characteristics of the fluidized bed reactors. The ANFBED has a tall column (1.30 m diameter and 4 m height with an expansion chamber at the top. I t contained ion exchange resin (\pent) of 700 pm average diameter as carrier for biological grolvth. The AEFBED was a tall glass

Table 11. Lysimeters

Type of Influent Hydraulic Rate

(cm/wk)

Anaerobic Effluent Anaerobic Effluent Raw Vinasses Tap Water

~

10 5

10 I O

I cngth = 1.5 m; Diameter = 0.1 m; Material = PVC.

I HECTOR M. POGGI-VARALDO 79 1

Table 111. Raw Vinasse Characterization

Parameter Average Value

Temperature, “C PH Total Alkalinity, mg/L C a C 0 3 Chemical Oxygen Demand, mg/L 0, Volatile Organic Acids, mg/L acetic Total Kjeldahl Nitrogen, mg,/L N Ammonia Nitrogen, mg/L N Sulfate, mg/L SO,

27

2250 69400 10820 1600

150 3 100

4.3

column 1.65 m height by 0.05 m diameter. I t had a shorter concentric internal glass column 0.50 cni height by 0.03 cm diameter, which allo\ved the reactor to w o r k in recirculating fluidized bed mode. I t contained 1 liter granular activated carbon (GAC) 500 pm al’erage a s carrier.

The lysimeters were slim plastic columns (polyvin)~l-chloride pipe) 1 . S m height by 0.1 m diameter. They had lateral outlets equally spaced 0.15 cm and bottom trays for leachate collection. More detailed descriptions of the reactors and lysimeters dimensions, lay-outs, appurtenances, and start-up can be found elsewhere.1’*13

Analyses

All the analyses followed Sraridard A4eihods’’ except \,olatile organic acids, which were determined by direct titration,15 and methane in biogas, N hich was estimated by 3 simplified syringe (Orsat-based) method. l 6

Climatological and Soil Characteristics

The sugarcane mill “Alianza Popular” is located at 21” 97’ 41” latitude North and 99” 23’ 00” longitude, 320 m above sea le\,el, in a temperate/subtropicaI region belonging to the state San Luis .Potosi, 34exico. During the experimental period, the average mean, rhe average maximum, and the average minimum temperatures \\ere 17“C, 29”C, and 16°C respectively. The average precipitation was 181 “/month, the average evaporation rate was 126 mm/month .”

The soil for the lysimeters came from a sugarcane field nearby the mill. I t has a loamy-clay soil, with high content of organic matter, relatively high p H . Cores of 1.5 m depth \\‘ere sampled and transferred to the lysimeters with the least disturbance as possible. In this work , three strata of soil were defined and analyzed: top (0 to 30 cm depth), middle (30 cm to 90 cm depth), and bottom (90 cm to 150 cm depth).

RESULTS A N D DISCUSSION

Raw Vinasse Characterization

Table I11 shows a typical average analysis of the raw vinasses treated in this s t ~ d y . ~ . ’ ~ It has a high strength effluent, corrosive, with a high content in volatile organic acids due to fermentation during the storage. The organic matter concentration fluctuated in a range from as low as 25,000 up t o near 100,000 mg 0 2 / L COD. The [total COD]/[total N] ratio was approximately 44. This value was judged sufficient for anaerobic treatment.I8

Although sulphate concentration was high, the COD/sulphate ratio was around 22, well above the 10 to 12 threshold value below which methanogenesis impairment by sulphide toxicity can be expected. l 9 Therefore, no special provisions to remove sulphides from the recirculating effluent flow of the ANFBED \vere undertaken.

Anaerobic Fluidized Bed Reactor (ANFBED) Performance

Figure 3 shows the results of the first campaign for the ANFBED in terms of C O D removal efficiency, unit removal rate, and biogas productivity as functions of the organic loading rate. During this period, the reactor operated at 35°C. The C O D reduction \vas between 65 and 7 5 % o n total COD basis; i t slightly decreased with the increase in loading rate. The biogas productivity reached a maximum of 8 m3/m3*day. The unit removal rate followed a slight curved hyperbola. I t fitted Converti’s model very well (Figure 4). Converti’s model is a semi-empirical kinetic relationship

. . I 792 47TH PURDUE UNIVERSITY INDUSTRIAL WASTE CONFERENCE PROCEEDINGS

/

0 10 PO 33 4 5 - u t 0

ORGANIC L O R O I f G ( K G COD FEO/M3 DRY)

Figure 3. Anaerobic treatment of vinasses in mesophilic conditions- pilot scale fluidized bed reac- tor (ANFBED) performance.

between the un i t removal rate and loading rate, based on an analogy of the \lichaelis-h?enten model for enzymatic catalysis.20 The ANFBED shouted some acidogenic excursions at loading rates near 38 kg COD/m3-day, which was estimated as the maximum intensity limit for the process in the conditions of the experiment.

The ANFBED operated for a second season at sub-optimal temperature of 25°C. Figure 5 depicts the average results of this period.The organic matter removal efficiency reached 62% on total C O D basis at a loading rate around 10 kg COD/m3-day. When accelerated u p to 17 kg COD/m3*day loading rate, the reactor showed acidogenic upsets resulting in a poorer COD removal (47% average). The reactor recovered from these excursions with alkalinity addition and loading rate a d j ~ s t m e n t s . ' ~

n F 0.15 - 0 0 0 0 Y \

U ?O.lO -

RflTE=207XLR/( 285tLR) n F 0.15 - 0 0 0 0 Y \

U ?O.lO -

E v

c

RflTE=207XLR/( 285tLR) 1 RflTE=207XLR/( 285tLR) 1

..

0.00 0.04 0.08 I/LR (m3 doy/kgCOD fed)

n. I2

Figure 4. Anaerobic treatment of vinasses in mesophilic conditions- ANFBED results fitted a saturation kinetic model.

I 793 HECTOR M. POGGI-VARALDO

TEMPERflTURE = 25 C 1 B p H / l o v Ia

0

* Y a

6 . -

v !-

z 3 0

4 E

2

0 9.64 17.2 LGADl NG RATE ( kg COD/m3 day)

Figure 5. Anaerobic treatment of vinasses at sub-optimal temperature (25'C)-AKFBED average result s.

Aerobic Fluidized Bed Recfor (AEFBED) Performance

The AEFBED was started-up and acclimated to increasing concentration of the anaerobic effluent in four stages (Table IV). Figure 6 portrays the performance of the AEFBED during the acclimation periods in terms of COD and colour removal. The COD reduction was above 85% (on total C O D basis) for all the stages. The overall C O D removal of the series ANFBED-AEFBED reached 96Vo when the AEFBED was fed dilute anaerobic effluent (stages 2 and 3). These results compared favorably to those reported by Yang et al.".who found that a series Upflow anaerobic sludge blanket-

Table IV. Aerobic Fluidized Bed Start-up Semysinthetic Wastewater Formulation and Operation

Stage Stage Stage Stage 1 2 3 4

Molasses, g /L 4 3 2 1 Anaerobic Effluent, L /L 0.1 0.3 0.6 0.8 Tap Water, L /L 0.9 0.7 0.4 0.2 Ammonium Phosphate, g/L 1 0.5 0.5 0.5 Hydraulic Retention Time, Day a2 4 4 4 Time, Day 10 10 10 10

40 150

cm INFLUENT e LOROIN; RRTE 0

Figure 6 . Aerobic treatment of the anaerobic effluent in the AEFBED -acclimation results.

794 4 7 ~ ~ P U R D U E UNIVERSITY INDUSTRIAL WASTE C O N F E R E N C E P R O C E E D I N G S

Entrapped Aerobic Fixed Bed reactors achieved 97% soluble COD removal treating a sugarcane mil wastewater (no vinasses in i t ) . The color removal (reported as luminance increase) reached 85 or mor( when the influent to the AEFBED contained between 30°10 to 60% of anaerobic effluent by volume However, during the stage 4 , when the anaerobic effluent in the feed was 80% by volume, the ~ 0 1 0 ~

reduction fell dramatically (Figure 6). No attempt to determine the relative effects of biodegradation. adsorption on the GAC, and bioregeneration of the carrier G A C on color removal was made. Whether adsorption and bioregeneration of the carrier were the main mechanisms of color removal and were outcompeted by the high loading rate of dissolved coloured substances in the influent o f stage 4 (and during the subsequent steady states) deserves further research.

The AEFBED removed nearly 50% of the total C O D during the steady states (fed 100% anaerobic effluent). Figure 7 shows that the C O D reduction was almost independent of the loading rate, in a ikide range going from 3 to 35 kg COD/m3*day. No appreciable color removal was detected. The reactor liquor was aerobic in the range of loading rates experimented.

Although the combined ANFBED-AEFBED process showed higher COD removals than either one- stage anaerobic (ANFBED) or one-stage aerobic (rotating biological contactor) t r e a t n ~ e n t , ~ the final effluent did not meet the criteria for direct discharge into water bodies. Further treatment for colour and the recalcitrant C O D removal should be necessary. A combination of physico-chemical treatmeni (including membrane separation) and innovative biotechnological processes could accomplish the desired pollution r e d ~ c t i o n . ~ ~ . ~ ~ The economic feasibility of such more complex approaches i: questionable.

Irrigation Results

Figure Sa presents the a\'erage results of organic matter loading (espressed on surface are basis) a n d remo\.al (in decimal 0 to 1 range) in the lysimeters. A comparison between lysimeters 1 and 2 (anaerobic effluent at 10 and 5 cm/wk respectively) showed a higher COD remo\al for the lysimeter 2 . The concentration of COD in the bottom leachate was almost proportional to the organic loading (Figure 8b). The lysimeter 3 irrigated with raw vinasses averaged a COD removal comparable to thar in lysimeter 2 but the dynamic performance showed a remarkable deterioration of C O D reduction in the last two months (down to 60%, data not shoiGn).

The overall C O D removal of the anaerobic pretreatment followed by irrigation at 5 cm/\\.k (ANFBED + 5 cm/wk anaerobic effluent irrigation, Figure 9) was the highest of the four alterna- tives. With the caution due to the impact in some physico-chemical characteristics of the soil (as discussed below) this combination seemed to be the most recommendable.

The effects of anaerobic effluent and vinasses application on the soil are discussed here in terms of the variation with time and depth profile of the following parameters: organic matter content, electrical conductivity and sodium adsorption ratio (SAR) of the soil extracts, and sodium and calcium ions concentrations (Figures 10 to 12). The bar denominated SOIL stands for the results of non-irrigated soil (or time zero). The other bars represent the results of lysimeters 1 to 4 (see Table 11) at the end of six months irrigation period.

I 1103 I I 1

o c m c K m a

u o o a

STER@Y STATES REFBEO

Figure 7 . Aerobic treatment of the anaerobic effluent in the AEFBED-steady state average results.

HECTOR M. POGGI-VARALDO 795

LYSIMETER IRRIGATION TESTS COD LOADING AND REMOVAL

' I

I I I

10000

8000

6000

4000

2000

0

f 1

4 LYS 1 LYS2 LYS3

COD CONCENTRATION IN LEACHATES

0

LOADING RATE (kg C 0 D/m 2. d )

COD REMOVAL

fl LEACHATE COD (mg/L)

LYS 1 LYS2 LYS3

Figure 8. Lysimeter irrigation tests: &-COD removal efficiency and loading rate; 8b-COD concen- tration in lysimeter leachates. Key: Lys 1: anaerobic effluent at 10 cm/uk: Lys 2: anaerobic effluent at 5 cm/wk; Lys 3: raw vinasses at 10 cm/wk.

Irrigation with anaerobic effluent and vinasses at 10 cm/wk increased significantly the organic matter content of the top and intermediate layers (Figure 10). Interestingly, the lysimeter 2 (anaerobic effluent at 5 cm/wk) showed the highest organic matter increase at the bottom. The electrical conduc- tivity of the top layer was not practically affected (Figure 1 la). However, this parameter increased significantly in the intermediate and bottom strata, especially for the lysimeters receiving anaerobic effluent at 10 cm/\vk and raw vinasses. In all cases, the electrical conductivity values of the top layers were below the recommended 4 to 5 mS/cm maximum."

Figure I I b shows a n outstanding increase in the SAR ratio, singularly in the lysimeters irrigated with anaerobic effluent. This effect was accompanied by an increase of one unit of pH (data not shown). The SARs were nearly three- to four-fold the maximum recommended value." Sodium accumulation and calcium washout suggested sodium (and potassium, data not shown) exchange by calcium, especially in the top layer (Figures 12a and b). This exchange acted synergistically to increase the experimental SARs. Sweeney and G r a t ~ ~ ~ reported similar increases in soil pH and monovalent cation concentrations in soils irrigated with anaerobically pretreated molasses stillage.

I t is well kn0u.n that high values of SAR are associated to decrease of the soil permeability and sodium toxicity to crops." The S A R results suggested that the hydraulic rate of the anaerobic effluent should be set considering the monovalent cation loading, in addition to the conventional organic matter and nutrient loading rite ria.^' The anaerobic effluent should be applied onto land at rates lower than 5 cm/\vk. The use of strategies combining effluent dilution, intermittent irrigation (one every other or t\vo years), calcium supplementation, and drainage would minimize long term detri- mental impact on soil properties and crop yields.'

796 4 7 ~ ~ PURDUE UNIVERSITY INDUSTRIAL WASTE CONFERENCE PROCEEDINGS

.. Y

J

> 0

UJ LT

0 0 0 J J

0: L L > 0

a

a

I I L I U L U i

-, ! i I

IRRIGATION 10 cdwk 5 cm/wk 1 0 cm/wk

RPJAEROB I C EFFLUENT V I I-IASSES

' J I fi6S';t TREfiT!.lEIL'TS

Figure 9 . Overall COD removal of the four alternatives.

On the other hand, the lysimeter receiving \inasses had a normal pH of 7 .7 and the distribution of sodium and calcium \\'as not so disrupted as compared to that in the soil before irrigation. The SAK values \vere below the maximum recommended level of 9 (Figures 1 l b and 12a and b). These results substantiated the findings of Tauk and Medeiros16 who reported increases in calcium and magnesium concentration in the top layer of a soil irrigated with a single dose of 80 m3/ha of ra\v \#inasses (equivalent to a 500 m3/ha*year or 0.2 cm/wk).

CONCLUSIONS

1. The anaerobic treatment of vinasses a t 35°C in a fluidized bed process was reliable and efficient, reaching 70% C O D removal and 8 m3/m3.day biogas productivity. The inten- sity limit for the process was approximately 38 kg COD/m3-day loading rate, beyond \vhich acidogenic excursions impaired the reactor performance.

6

0 0.15 0.6 1 2

AVERAGE DEVM (m)

W SOIL ~ V I N A S E TAP WATER

0 ANAJZREFFL@lOcmhv a ANAEREFFL@Scmhut

Figure 10. Organic matter contents profile in lysimeters. Key: SOIL: results in soil before irrigation. The other results were obtained after 6 months of irrigation with the corresponding influents.

HECTOR M. POGGI-VARALDO 79 7

E : t 0.1s 0.6 1.2

AVERAGE DEPTH (m)

a is @.6 AVERAGE DEPTH (m)

1

L2

Figure 11 . Conductivity and SAR profiles in lysimeters; Ila-Electrical conductivity in the extract; l lb-SAR in the extract. See Key in Fig. 10.

2. The performance of the ANFBED at sub-optimal temperature (25°C) w’as dependable at loading rates near 10 kg COD/m3.day. I t removed approximately 60Vo of the incoming COD and the biogas productivity attained 4 m3/m3.day. At 17 kg COD/m3*day the reactor showed acidogenic upsets.

3. The aerobic fluidized bed reactor removed more than 85% of incoming colour and organic matter when fed dilute anaerobic effluent (30% to 60% by volume) during the acclimation stages. At the time of receiving whole anaerobic effluent, the reactor did not accomplish any colour reduction. The C O D reduction was SO%, almost independent of the loading rate in Ihe range of 3 to 35 kg COD/m3.day.

4. The effluent from the series ANFBED-AEFBED would need further treatment for discharging into water bodies.

5 . The lysimeter irrigated with anaerobic effluent at 5 cm/wk showed the highest organic load removal (near 90% C O D reduction). However, the S A R reached very high values, sodium and potassium exchanged for calcium in the soil matrix, and the soil p H increased up to 9. The load of monovalent cations seemed to be the limiting factor of the irrigation rate.

6. The lysimeters irrigated with anaerobic effluent 10 cm/wk and raw vinasse exhibited organic matter accumulation and electrical conductivity increase, as well as inferior C O D removal.

798 4 7 ~ ~ PURDUE UNIVERSITY INDUSTRIAL WASTE CONFERENCE PROCEEDINGS

so

..1 0.6 1 . i 0.1s AVERAGE DEPTH (m)

loo ,

a 1s a6 AVERAGE DEPTH (m)

L2

Figure 12. Cation profiles in lysimeter. 12a-Calcium concentration; 12b-Sodium concentration. See Key in Fig. 10.

The series anaerobic-aerobic treatment did not produce an effluent quality for discharging in \\rater bodies. On the other hand, anaerobic treatment followed by irrigation at I O U rates could be a feasible alternative for vinasse treatment and disposal, provided close monitoring and irrigation strategies (combining anaerobic effluent dilution, calcium supplementation, intermittent irrigation and drain- age) are adopted to mitigate adverse impacts on soil structure and fertility.

ACKNOWLEDGMENTS

Financial support from the CINVESTAV, the Project TAEK-CIEA, and AZUCAR S.A. is grate- fully acknowledged. The authors thank Dr. Fernando Esparza-Garcia, Head of the Dept. of Biotech- nol. and Bioeng., CINVESTAV, for his continued support and understanding. The authors are indebted to Prof. Carmen Duran-de-Bazua, Faculty of Chemistry, UNA!vI, \ f r . Luis E. Zedillo, (at that time Director of R&D, IMPA, AZUCAR S.A.), Prof. A. Noyola, UNA\I, and Dr. S. Gonzalez, UNAM for their consistent help and encouragement; Dr. Pedro Medellin, Director of UASLP and staff of the UASLP for their significant contribution with soil analysis; and the managers and staff of the sugarcane mill “Alianza Popular” for logistics and laboratory support .

LIST OF ABBREVIATIONS

ANFBED Anaerobic fluidized bed reactor AEFBED Aerobic fluidized bed reactor

HECTOR M. POGGI-VARALDO 799

C O D Chemical oxygen demand C A C Granular activated carbon HR Hydraulic rate HRT Hydraulic retention time LR Loading rate LYS Lysimeter VOA Volatile organic acids SAR Sodium adsorption ratio

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12. Garcia, h4.A. “Treatment of Vinasses in a Pilot Scale Anaerobic Fluidized Bed,” B.S. Thesis, CINVESTAV and UASLP, S.L.P., Mexico (in Spanish) (1989).

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14. Sfandard Methods for the Examination of Water and Wastewater, 16th edition, Amer. Public Health Assoc., Washington, DC, 1985.

15. DiLallo, R. , and O.E. Albertson. “Volatile Fatty Acids by Direct Titration,” J . Water Pollut. Control f e d . , 33:356-365 (1961).

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17. SARH Bulletin of the Ministery of Agriculture and Water Resources, Mexico (1991). 18. Metcalf and Eddy “Wastewater Engineering: Treatment, Disposal and Reuse,” New Y o r k ,

McGraw-Hill, 2nd. edition, 1979. 19. Poggi, H.M., R . Hernandez, N . Rinderknecht, and J.F. Calzada. “Supplemented Kraft Conden-

sate Treatment in High Rate Anaerobic Processes,” Proceedings, 44th fndustrial If’aste Confer- ence Purdue Unirlersi[y, 1989, Lewis Publishers, Chelsea, hll1, 1990, pp.271-277.

20. Converti, A , , M . Zilli, M. Del Borghi, G . and Ferraiolo. “The Fluidized Bed Reactor in the Anaerobic Treatment of Wine Wastewater,” Bioprocess Eng., 5 (1):49-55 (1990).

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22. Ohmomo, S. “Decolorization of Molasses Wastewater by a Thermophylic Strain Aspergillus fumigatus,” Agric. Biol. Chem., 5 1 :3339-3345 (1988).

22(9): 123-130 (1990).

3 222-227 ( 1984).

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23. Rao, A.V.S.P., J . Karthikeyan, and L. lyengar. “Removal of Color from Distillery Wastewater,” Proceedings, 44th Pirrdue Industrial Wasre Conference, Lewis Publishers, Chelsea, MI ( 1 990.

24. Sweeney, D.W., and D.A. Graetz. “Chemical and Decomposition Characteristics of Anaerobic Digester Effluents Applied to Soil,” J . Environ. Qual., 17:309-3 13 (1988).

25. Crites, R.W., E.L. Meyer, and R.G. Smith. “Land Treatment of Municipal \Yastewater,” Process Design h4anua1, EPA 625/1-81-013, U.S.E.P.A., Cincinnati, OH, 1981.

26. Tauk , S . M , and Medeiros. “Nutrientes e atividade enzimatica em latossolo Vermehlo-Amarelo textura media, tratado corn vinhaqa, sob cultura de milho“, Ecletica Quim. 14:83-94 (Sa0 Paulo, Brazil; in Portuguese) (1989).