Pertanika 1(1), 40-50 (1978)

Bacterial Fermentation of High AlkalineWastes from Irish Potatoes1

MOHAMED ISMAIL BIN ABDUL KARIMDepartment of Food Science and Technology, Universiti Pertanian Malaysia

Key words: Bacterial Fermentation, High Alkaline Wastes, Irish Potatoes

RINGKASAN

Satu penyelidikan telah dibuat untuk mengkaji: (1) kemungkinan menggunakan peragian bakteriasebagai satu car a meneutralkan sisa-sisa buangan ubi kentang yang berkeadaan alkali selepas diproses ; (2) tukar-an kandungan sisa-sisa buangan ubi kentang yang beralkali selepas diperam; (3) jenis-jenis mikroorganismyang banyak menghasilkan asid dari sisa buangan ubi kentang yang diperam; (4) keadaan yang baik atausesuai untuk menyimpan dan menjalankan peragian. Keadaan yang baik untuk menjalankan peragian adalahdidapati pada suhu 30°C. Didapati tidak ada perbezaan di antara proses peragian dengan oksigen dan tanpaoksigen. Sisa buangan yang berkeadaan alkali dari ubi kentang meragi lebih cepat kalau disemai dengan sisabuangan yang telah beragi. Perubahan karbohidrat dan sedikit perubahan kandungan mineral dan protintelah berlaku semasa peragian dan simpanan sisa-sisa buangan ubi kentang tersebut. Sebahagian besar tambahanasid lactic telah didapati di sisa buangan ubi kentang yang telah beragi. Bakteria gram positif berbentukbatang dan bulat telah diasingkan dari sisa-sisa buangan ubi kentang yang telah beragi dan nama bakteria yangdijumpai secara percubaan adalah Lactobacillus delbrueckii dan Streptococcus faecium.

SUMMARY

A study was conducted to determine: (1) the feasibility of utilizing bacterial fermentation as a meansof neutralizing the excess alkali of lye-peel wastes from potatoes ; (2) the compositional changes in the fermentedcaustic peel wastes; (3) the predominant types of microorganisms in fermented waste that are responsible foracid production; and (4) the optimum condition for fermentation and handling. The optimum condition forfermentation was found to be at 30°C. No difference was found between using aerobic or anaerobic fermen-tation. The lye-peel potato wastes fermented more rapidly when seeded with previously fermented waste.Significant carbohydrate changes and minor changes in mineral and protein content occurred during fermentationand storage of potato waste. A significant increase in lactic acid occurred in the fermented waste which pro-bably accounted for the reduction in pH. Gram positive rods and gram positive cocci were isolated from thefermented potato waste and they were tentatively identified as Lactobacillus delbrueckii and Streptococcusfaecium respectively.

INTRODUCTION

The white, or Irish potato (Solanum tubero-sum), is a native of South America. The potato,with a total production in excess of 202.3 millionmetric tons (Agricultural Statistics, USDA,1976), is one of the major food crops in the world.The demand for processed potatoes in the formof potato chips, French fries, potato flakes, flour,frozen potato products and many other processedproducts is increasing. Major emphasis shouldbe given to the tremendous amount of wastesand by-products obtained from potato processing.In processing of potatoes, 20 to 50% of the pro-cessed raw potato is discharged as wastes (Streebinet aL, 1971). Most of the wastes from potato

plants arise primarily from peeling, trimming,slicing, cleaning and rinsing operations. Thedischarge of these wastes creates a water pollutionproblem. To reduce the effluent volume andreduce pollution, alternative processing systemshave been designed (Graham et aL, 1969).

With a view to reducing pollution, Grahamet aL (1969), at the USDA's Western Utilizationresearch and Development Division, Albany,California, announced the development of a newpeeling method for potatoes. Their peelingmethod was based on the application of infra redheat to light caustic treated potatoes followed bymechanical peel removal. The successful deve-lopment of the "dry" caustic peeling method

Part of the Thesis for the degree of M.S, University of Arkansas, Fayetteville, Arkansas, U.S.A.

40

MOHAMED ISMAIL BIN ABDUL KARIM

now makes it possible to recover the peel wasteas a semi-solid by-product material, separatefrom the plant effluent. According to manyworkers (Adam et aL, 1960; Willard, 1971;Carlston and Smallwood, 1972; McFarland andThompson, 1972; Smallwood et aL, 1974) subs-tantial reductions in pollution load and wastetreatment costs are achieved by dry causticpeeling. The major portion of the peel and lyeis withheld from the effluent waste stream. Inthis process, water use, peel loss and lye con-sumption is also minimized. However, a largevolume of heavy viscosity peel waste is generated.Disposal of the high alkalinity wastes in landfillsis opposed by the EPA because the high sodiumcontent reacts with the soil making the clay stickyand impermeable.

A method of neutralizing excess alkalinityof the potato waste by bacterial fermentation ispossible. Vennes and Olmstead, (1961); Blochet aL (1973); Blackstock and Skiver, (1974); Geeet aL (1974); Sistrunk and Karim, (1977), havesuggested feeding potato waste to livestock asone potential method.

This study examines the feasibility of utili-zing bacterial fermentation as a means of neutra-lizing the excess alkali of lye-peel wastes frompotatoes; the compositional changes in the fer-mented caustic peel waste; the predominanttypes of microorganisms in fermented wasteresponsible for acid production; and the optimumconditions for fermentation and handling. If afeasible and economical method for neutralizationof the excess alkali of potato waste by bacterialfermentation could be achieved, then the neu-tralized caustic peel waste could be used as avaluable source of feedstuff for livestock.

MATERIALS AND METHODS

The lye-peeled potato wastes for this studywere obtained from commercial processors (ForestPark Canning Co., Steele Canning Co.) in North-western Arkansas. Steps were taken to collectseveral batches of fresh samples of potato wastesfor the experiment during the normal processingseason.

I. Determination of optimum conditions for fer-mentation of lye-peeled potato wasteSamples of lye-peeled potato waste were

prepared by blending them with sterilized distilledwater (1: 1 w/v) using a blender at low speed forapproximately 2 min. to obtain a homogenous pro-duct. The initial pH of the potato waste wasdetermined by a pH meter. Samples containing1 kg of the homogenate were placed in glass

bottles (2 kg capacity). Some of the bottles ofthe potato homogenate were flushed with nitrogengas and capped with anaerobe traps to create ananaerobic condition. Samples were stored underaerobic and anaerobic conditions at 20°, 30°, 40°,45° and SOX for 2, 4, 6, and 8 days. After theappropriate storage time, 10 to 20 g of the potatowaste were removed aseptically and the pHdetermined.

A similar experiment was conducted butwith the storage temperature narrowed down to20°, 25°, 30° and 35°C.

Fermentation studies using fresh lye-peeledpotato waste seeded with different percentagesof inoculum from the previously fermented wastewere conducted. A 14 kg batch of lye-peeledfermented potato waste was used as inoculumfor seeding into fresh lye-peeled potato waste.Fresh lye-peeled potato waste (pH 11.4 and 12.4)was seeded with 0%, 5%, 10%, 15%, 20%, 25%30%, 35% and 40% of inoculum from the pre-viously fermented waste. Each of the batches ofpotato wraste consisted of 4.5 kg placed in stonecrocks. The experiment was conducted in agreenhouse where the temperature was 25 Jt: 2°C.The pH of the treated potato waste was thendetermined at intervals of 0, 2, 4, 6, 8, 10, 12 and14 days. A sample of 10 to 20 g of potato wastewas taken from each treatment and the pH deter-mined with a pH meter. The experiment hadthree replications.

II . Changes in composition of lye-peeled potatowaste during fermentation

Compositional changes in carbohydrates,nitrogen content, organic acid, Ca, K, PO4 andMg were studied in fresh and fermented potatowaste.

In determinations of total sugar, starch,water-soluble pectin, hemicellulose, cellulose anddry matter, all the potato waste samples usedwere first mixed thoroughly to get homogenoussamples. Four g of each sample were weighedin centrifuge tubes and extracted twice with hot80% ethanol to remove sugars. Total sugarswere determined by the phenol method (Duboiset aL, 1956). The pellets were taken up in 9 mlof distilled water and digested with 1 ml of 2%Takadiastase for one hour at 55°C to hydrolyzestarch. The samples were extracted twice usinga solution consisting of 80% ethanol, distilledwater, IN NaOH, and 70% H2SO4. Determi-nation of starch, water-soluble pectin, hemi-cellulose and cellulose were carried out using theprocedure of Sistrunk, (1965 a).

41

BACTERIAL FERMENTATION OF HIGH ALKALiNE WASTES FROM IRISH POTATOES

The pectin fraction was determined by thecarbazole method of Dietz (1953), with minormodifications as described by Sistrunk (1965 b).

The dry matter content was obtained byweighing 10 g of blended samples in tared alumi-nium cups and drying them for 24 to 48 hoursat 60°C.

In determination of nitrogen, Ca, K, P andMg, 1.5 g of potato waste was weighed into 150 mlbeakers, dried overnight in an oven at 60°C andwet-ashed by the A.O.A.C. procedure (1965).For nitrogen determinations, 3 ml aliquots weretaken from the diluted wet-ashed samples into125 ml Erlenmeyer flasks and analyzed for totalphosphate (Standard Methods for the Examinationof Water and Waste-water 1971). Aliquots fromthe wet-ashed samples were then appropriatelydiluted and analyzed for Ca, K and Mg byprocedures of the Association of Official Agri-cultural Chemists (1965). An atomic absorptionspectrophotometer (Beckman model 1301 with amodel DB-G Grating) was used for the mineralanalyses.

In determination of organic acid, 10 g sampleswere extracted twice with 50 ml of 80% ethanol.Glutaric acid was added as an internal standardto the ethanol extract. The solutions were con-centrated under vacuum and separated into sugarand organic acid fractions by ion exchangechromatography. Organic acids were preparedby using the method of ion exchange chromato-graphy described by Kushman et al., (1968) andBeuscher (1975). Derivatives obtained wereprepared with Tri-Sil reagent (Pierce ChemicalCo.,) for subsequent gas-liquid chromatography.

III. Isolation, screening and identification of thepredominant microorganisms responsible foracid production found in the non-fermented andfermented lye-peeled potato wasteBacterial plating was done on the non-

fermented and fermented potato waste accordingto the procedure of Bacteriological AnalyticalManual for Foods (1973) using Standard PlateCount (SPC) agar, Tomato Juice agar and VioletRed Bile agar. In using Tomato Juice agar onlythe fermented potato waste samples was used.The plates were incubated aerobically and anaero-bically and bacterial plate counts were recordedafter 48 hours of incubation. Isolation of moldcultures using Potato Dextrose Agar (PDA) wasalso done.

Typical colonies of bacteria from the freshand fermented potato wastes were isolated fromthe plates of SPC and Tomato Juice agar media.

Screening of the potential bacteria and moldculture for production of acid was carried outusing sterilized Tryticase Soy Broth (TSB)media and samples of fresh and sterilized lye-peeled potato waste (121°C at 15 psi for 35minutes). The initial pH of the TSB media andpotato waste sample was adjusted aseptically bytitration with 0.1N NaOH to 12, 11, 10, 9, 8 and7. Bacteria and mold cultures were transferredinto the TSB media and potato waste sampleswere incubated at 30°C for a period ranging from2 to 8 days. The pH of the TSB media andpotato waste samples were determined periodi-cally using a pH meter.

Identification of the isolated bacteria wasdone using a series of physiological and bio-chemical tests. The isolated gram positive rodswere compared with the characteristics of Lacto-bacilli described by Rogosa et al. (1959) andBuchanan et al. (1974) in Bergey's Manual ofDeterminative Bacteriology.

In the identification of the isolated grampositive cocci, the physiological and biochemicaltests described by Sharpe et al. (1966) andBuchanan et al. (1974) were used.

RESULTS AND DISCUSSION

Optimum conditions for fermentationUsing incubation temperatures of 20°, 30°,

40°, 45° and 50°C for fermentation, it was foundthat the incubation temperature of 30°C was theoptimum for reducing pH under aerobic con-ditions (Fig. 1). Under anaerobic conditions, thereare slight difference in pH between the treatments,and none of the lots had a pH value below 11.

In comparing aerobic and anaerobic con-ditions there were no differences in reduction ofpH of potato waste incubated at 20° and 25°Cat the end of 8 days of fermentation (Fig. 2).Significant differences in pH were obtainedbetween 30° and 35°C except in the cases ofwaste incubated at 30°C on the 4th day and at35°C on the 6th day. Greater reduction in pHwas obtained in samples under aerobic conditionsthat were incubated at 30° and 35°C, but nodifferences was found between those samplesincubated at 20° and 25°C under aerobic andanaerobic conditions.

Fermentation studiesIt was found that the lye-peeled potato waste

fermented more rapidly when seeded with pre-viously fermented waste (Figs. 3 and 4). Therewas apparently very little difference in speed of

42

MOHAMED ISMAIL BIN ABDUL KARIM

6 -

Fig. 1 Effect of aerobic fermentation of Irishpotato waste on pH changes over a period of8 days at different incubation temperatures.

neutralizing the alkalinity beyond 5% inoculumafter 4 days with potato waste which had aninitial pH of 11.4 (Fig. 3). In potato waste whichhad an initial pH of 12.4, there was very littledifference in speed of neutralizing the alkalinitybeyond 15% inoculum after 10 days of fermen-tation (Fig. 4). It also took a longer time toferment the potato waste which had a higherinitial pH of 12.4 (Fig. 4) when compared tousing potato waste which had an initial pH of11.4 (Fig. 3).

Compositional changes of lye-peeled potato wasteduring fermentation

Significant carbohydrate changes occurredduring the fermentation process (Table 1). Therewas an increase in total sugar, water-solublepectin and hemicellulose of the fermented waste.The starch and cellulose were found to decreasein the fermented product. Dry matter was alsofound to decrease slightly by about 1% in thefermented product.

There was very little change in the mineraland nitrogen content of the fermented waste(Table 2). A slight increase in phosphate wasfound but the N, Ca, K and Mg content variedvery little in the fermented product.

Significant changes in the organic acid con-tent of the potato waste occurred during thefermentation. There was an increase in phos-phoric, citric and lactic acid content of the fer-mented product (Table 3). A decrease in succinic,fumaric and malic acid was also found in thefermented samples. A great portion of the organicacid found in the fermented potato waste was inthe form of lactic acid.

Isolation, screening and identification of the predo-minant microorganisms found in the non-fermentedand fermented lye-peeled potato waste

Using SPC agar and Tomato Juice agar theaerobic bacterial plate count on fermented potatowaste had more than 300 million organisms/gand the anaerobic plate had 25 million organisms/g. The non-fermented waste had an aerobicplate count of 350,000 organisms/g and theanaerobic plate had 200,000 organisms/g. Thusthe fermented waste had a higher count than thenon-fermented waste, and there were moreaerobic bacteria in the waste. Although VRBagar, which is an ideal media to support coliformgrowth was used, no bacterial growth was foundon either of the aerobic plates from non-fermentedand fermented waste.

Five types of gram positive rods (Ri, R2, R3,R4, R5) and 3 types of gram positive cocci (Ci,C2, C3) were isolated from the non-fermentedand fermented potato waste which were platedon the SPC and Tomato Juice agar media. Themold cultures isolated from the fermented potatowaste were identified by the morphological charac-teristics according to the guidelines describedby Frazier (1967), as genus Geotricum, Aspergillusand Penicillium.

Results of the isolated bacterial and moldculture grown in the TSB media and potatowaste samples which had an initial pH of 12under aerobic and anaerobic condition, did notshow much reduction in pH. However, oncethe initial pH was at 11 or below, greater reductionin pH was noted from some of the bacterialcultures. The gram positive rods (R2} R3, R4and R5) and the gram positive cocci (Ci, C2, C3)did reduce the pH of the TSB media and potatowaste samples significantly, indicating the poten-tial of these bacteria to produce acid.

Two of the isolated gram positive rods (R3and R5) showed high percentages of correlation(95% and 89% respectively) with Lactbacillusdelbrueckii on their differentiating characters(Table 4). Two of the isolated gram positivecocci (C2 and C3) showed a high percentage ofcorrelation (92%) with Streptococcus faecium(Table 5).

43

Aerobic

Anaerobic

H

i i

10

9

8

7

6

5

pH

11

0

9

8

7

6

5

2

VNX

- xb \

—

i

4 6DAYS

O

a 30 C

\ a\>

« \ N a

\ \\ \

b N

1 I

\\

b

8

1

1

pH

a*

I

I

0

9

8

7 -

6 ~

5 -

4 6DAYS

8

I I

4 6DAYS

8

\

—

\ a

I

\N

b

35°C

a

I 1

a

s a

b

4 6DAYS

8

Fig. 2 Changes in pH during aerobic and anaerobic fermentation of Irish potato waste at different incubationtemperatures over a period of 8 days,

44

0 DAYS DAYS

12

10

H 8

6

4 —

12

.0

PH 8

6

4

0 5 10 15 20 25 30% Inoculum

12

10

pH 8

6

4

—

4—

—

—

—

0 5 10 15% Ino

12DAYS

10

. pH 8

6

4

20 25 30culum

i

—

0 5 10 15 20 25 30% Inocu lum

8 DAYS

—

—

—

0 5 0 15 20 25 30% In ocu urr i

Fig. 3 Effect of amount of inoculum on speed of fermentation using potato of Irish having an initial pH of11.4 at 25°C.

0 DAYS

13

I I

pH 9

7

5

PH

13

1 1

pH 9

7

5

6 OA YSr-

-

-

-

-

5 10 15 20 25 30 35 40

% Inoculum

13

1 1

9

7

5

-

-

-

10 DAYS

i 11

PH

0 5 10 15 20 25 30 35 40

% Inoculum

0 5 10 15 20 25 30 35 40

% Inoculum

13

1 1

9

7

5

—

-

-

14 D A Y S

Mill0 5 10 15 20 25 30 35 40

% I n o c u l u mFig. 4 Effectofamount of inoculum on speed of fermentation using potato waste having an initial pH of 12 A

at 25° C.45

TABLE 1

Changes in carbohydrate composition of lye-peeled Irish potato waste during fermentation at 30 C for 8 days(fresh weight basis).

Treatment(Potato waste)

Non-sterilized

Non-fermented (control)

Fermented (aerobic)

Fermented (anaerobic)

Sterilized?

Non-fermented (control)

Fermented (aerobic)

Fermented (anaerobic)

PH

11.5

5.8

5.7

11.6

5.7

5.6

Tot.sugars

0.82bz

2.17a

2.11a

0.67b

1.80a

1.75a

Starch

5.13a

2.27c

2.75b

4.83a

2.16b

2.06b

Percent.

H2O sol.pectin.

0.56b

1.03a

0.94a

0.52b

0.89a

0.90a

Hemi-cellulose

0.52b

0.61a

0.61a

0.49c

0.59a

0.52b

Cellulose

0.36a

0.26b

0.27b

0.37a

0.25b

0.27b

Drymatter

17.29a

16.23b

16.38b

17.18a

16.09b

16.17b

z Mean separation in columns under nony Potato waste sterilized at 121 °C (15 psi) for 35 minutes.

TABLE 2

Changes in composition of lye-peeled Irish potato waste during fermentation (dry weight basis)

Treatment(Potato waste) pH % Nitrogen % Ca ",, K % PO4 % Mg

Non-fermented

Fermented

11.8

5.S

0.243

0.207

0.04

0.04

1.2

1.2

0.22

0.34

0.01

0.012

TABLE 3

Average concentration of organic acids present in the non-fermented and fermented lye-peeled Irish potato waste

Treatment

Non-sterilized

Non - fermented

Fermented

Sterilized^

Non-fermented

Fermented

pH of waste

11.6

5.2

11.4

5.3

Phosphoric

.039bz

.056a

.044b

.101a

Acid

Succinic

.069a

.039b

• 133a

•072b

concentration

Fumaric

.044a

.015b

.031a

.021a

(me/g dry

Malic

.133a

•085b

.193a

.145a

weight)

Citric

.093b

.217a

.141b

.205a

Lactic

.22b

1.80a

.255b

2.033a

Mean separation in columns under non-sterilized and sterilized waste by Duncan's multiple range test, 5%.

Waste sterilized at 121°C (15 psi) for 35 minutes.

46

TABLE 4

Comparison of the differentiating physiological and biochemical characteristics of the isolated unknown cultures

of gram -f- rods to L. bulgaricus and L. delbrueckii

Differentiatingcharacters:

Lact.zbulgaricus

Isolated gram + rods cultures

R2 R4 R3 RsLact.y

delbrueckii

Growth at 15°C

Growth at 45 °C

NH3 from Arginine

Hydrolysis Aesculin

Fermentation of:Cellobiose

Galactose

Lactose

Maltose

Mannitol

Salicin

Sorbitol

Sucrose

Raffinose

Rhamnose

Arabinose

Glucose (acid)

Glucose (gas)

Melezitose

Xylose

Ribose

% Correlation

% Correlation

~" ~"

100% 78%

73%

-

80%

84%

75%

95%

±

±

65%

89% 100%

z, y Differentiating characteristics of L. bulgaricus and L. delbrueckii (data taken from Rogosa and Sharpe, 1959and Bergey s Manual of Determinative Bacteriology, 8th Edit., 1974).

' The symbols used are: + = positive reaction by 90% or more strains; - - negative reaction by 90% ormore strains; ± = weak reaction. .

47

TABLE 5

Comparison of the differentiating physiological and biochemical characteristics of the isolated unknown culturesof gram + cocci to S. faecalis, S. faecalis var. liquifaciens and S.faecium.

Differentiatingcharacters:

Growth at 10°C

Growth at 45°C

Growth in pH 9.6

Growth in . 1 %methylene blue

Survival at 60°C/30 minutes

Strep.z

faecalis

+«++

+

Strep.yfaecalis varliquifaciens

Strep*faecium

Isolated gram + cocci

c3 c2 Ci

NH3 from Arginine

Growth in 6.5% NaCl

Hydrolysis hippurate

Hydrolysis Aesculin

Gelatin liquifaction

Fermentation of:glycerol (anaerobic)

Lactose

Sorbitol

Mannitol

Arabinose

Melezitose

Sucrose

Galactose

Cellobiose

Inulin

Raffinose

ND

ND

ND

ND

ND

ND

ND

ND

ND

± ±+ +

±±

% Correlation

% Correlation

% Correlation

100%

100%

100%

92%

65%

77%

92%

65%

77%

35%

41%

38%

z, y, x The differentiating characteristics of S. faecalis, S. faecalis var liquifaciens and S. faecium (data taken fromGibbs and Skinner, Identification Method for Microbiologist, 1966 and Bergey's Manual of Det. Bact.8th Edit., 1974).

zv The symbols used: -f = positive reaction by 90% or more strains; — = negative reaction by 90% or morestrains; ± = weak reaction; ND = no data available.

48

MOHAMED ISMAIL BIN ABDUL KARIM

CONCLUSION

Utilizing bacterial fermentation as a meansof neutralizing the excess alkali of lye-peel wastefrom potatoes is feasible. While it would appearthat the optimum incubation temperature forfermentation is at 30°C, for economic and practicalpurposes, an incubation temperature of 25°Cwould be acceptable. As there seems to be nodifference between the use of aerobic and anaerobicfermentation it would be practical to carry outfermentation of potato waste under aerobic con-ditions. Bacterial plate counts conducted onthe fermented waste were found to have morethan 300 million organisms/g compared to350,000 organisms/g (fresh weight) found on thenon-fermented waste.

Other conclusions that were derived fromthe study were:(i) the lye-peel potato waste fermented morerapidly when seeded with previously fermentedwaste, (ii) Significant carbohydrate changes andminor changes in mineral and protein contentoccurred during fermentation and storage ofpotato waste, (iii) Significant changes in organicacid content of the potato waste were noticedduring fermentation, (iv) Gram positive rodsand cocci were the predominant microorganismsfound in the fermented waste although mouldstrains of Geotricutn, Penicillium and Aspergillusappeared as well. The gram positive rods andcocci responsible for acid production in thefermented potato waste were tentatively identifiedas Lactobacillus delbrueckii and Streptococcusfacecium respectively.

ACKNOWLEDGEMENTS

The author wishes to express his sincereappreciation to his advisor Dr. William A.Sistrunk for his guidance and encouragementthroughout the course of this study. Thanksare due to Dr. Ahmad A. Kattan and Dr. RonaldW. Buescher for their encouragement and con-structive criticism and to Dr. Joel A. Collins forhis assistance and guidance in the bacteriologicalidentification studies.

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49

BACTERIAL FERMENTATION OF HIGH ALKALINE WASTES FROM IRISH POTATOES

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23. STANDARD METHODS FOR THE EXAMINATION OF

WATER AND WASTE WATER. (1971). 13th edit.,APHA. AWWA. WPCF., Washington, D.C.

24. STREEBIN, L. E., REID, G. W. and Hu, A. C. H.

(1971). Demonstration of a full-scale wastetreatment system for a cannery. W.P.C.R.S.12060 DSB 09/71.

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"Stablization of potato wastes". Official Bulletin:North Dakota Water and Sewage Works Con-ference.

(Received 3 February 1978)

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