Disposal of Cheese Whey by DigestionAuthor(s): David BackmeyerSource: Sewage Works Journal, Vol. 20, No. 6 (Nov., 1948), pp. 1115-1118Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25030997 .

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Vol. 20, No. 6 DISPOSAL OF CHEESE WHEY BY DIGESTION 1115

This is not an entirely new prece dent since this division has made some

tests in the past on special occasions,

particularly for the Fire Prevention

Bureau, but has never had the person nel to do such work regularly nor in the amount requested.

It is recommended that a special assistant to the chemist be employed to do the. testing under the direct su

pervision of the chemist and the

undersigned. This assistant would also receive training in sewage labora

tory work to the end that he would be available to take over the duties of the chemist whenever that may become nec

essary. The cost of operating this bu reau would be negligible outside of the assistant's salary and the initial mod est expenditure for equipment.

A summary of plant operation data is given in Table IV.

TABLE IV.?Summary of Operation of the

Item Average

Rainfall (in.). 36.50

Design flow (m.g.d.): Mean D.W.F. 80.0

Max. D.W.F. 140.0

Raw sewage flow (m.g.d.). 46.3

Screenings (cu. yd. per month).... 204

Grit removed (cu. yd. per month).. 73

Suspended solids (p.p.m.) :

Raw sewage. 199

Plant eflluent.. 96

Per cent removal. 51.4

B.O.D. (p.p.m.): Raw sewage. 205

Plant eflluent. 96

Per cent removal. 34.4

Per cent volatile solids:

Raw sewage. 65.4

Digested sludge. 44.4

Digested sludge (cu. yd.) :

To marsh. 30,525

(Ohio) Sewage Treatment Plant for 1947

Item Average

To drying beds. 11,440 Tons dry sludge pulverized for

fertilizer. 915 Tons fertilizer sold. 950

Total sales ($). 9,525 Bay View pumping station costs

($ per m.g.) :

Purchased power. 0.30

Supplies. 0.33

Supervision and labor. 3.38

Total. 4.01

Sewage works costs ($ per m.g.): Power. 0.008

Supplies. 1.15

Supervision and labor. 5.86

Total. 7.02

Gas engine economy ($) :

Pumping cost if power purchased 23,638.49 Actual pumping cost. 6,058.91 Gas engine saving. 17,579.58

DISPOSAL OF CHEESE WHEY BY DIGESTION By David Backmeyer

Superintendent, Water and Sewage Treatment Utilities, Marion, Ind.

The sewage treatment and garbage

disposal plant at Marion, Indiana, was

completed and placed in operation in

July, 1940. This plant, which utilizes

activated sludge for secondary treat

ment, is equipped with complete fa

cilities for separate sludge digestion of

both sewage and garbage solids, to

gether with gas engines for utilization

of the digestion gas. The resident

population of Marion in 1940 was

26,676. The total gas production in

1947 was 23.167 million cu. ft., which

is the equivalent of 2.37 cu. ft. per capita per day.

Whey Waste Problem

During the past 3 years the sewage plant has been seriously overloaded

during the spring months of each year from cheese whey discharged to the

sanitary sewer by one of the local milk

processing plants. As the treatment

plant had been disposing of digested sludge in liquid form by hauling in tank trucks (Figure 1), the facilities of

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1116 SEWAGE WORKS JOURNAL November, 1948

^v*' '

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FIGURE 1.?Liquid fertilizer tank trucks used for hauling whey to sewage plant.

the sludge disposal plant were offered to the industry in an effort to com

pletely eliminate the discharge of the

whey to the sewer.

In March, 1947, arrangements were

made with the industry to haul the

whey from their storage tank directly to the sewage treatment plant in city tank trucks. The whey is unloaded at the plant directly into the garbage

well from which it is pumped to the

sludge digestion units. In this way the soluble B.O.D. load does not mix

with the raw sewage flow and cannot, therefore, reach the activated sludge secondary treatment units.

Whey Mixed With Garbage

In the processing of the garbage at the treatment plant, the green gar bage is unloaded from the collection trucks onto an open platform at grade level, and is then shoveled into the

hammermill grinder hopper. Sluicing water is added in the grinding process to bring the final slop to a solids eon tent of from 5.0 to 7.5 per cent, on dry solids basis.

After some experimentation it was

found that the liquid cheese whey made

an ideal substitute for the sluicing water. The temperature of the whey

was always from 100? to 140? F. when

unloaded from the tank trucks. This warm liquid would serve as a temper

ing agent when added to the garbage being ground, particularly in the cold

months of November and December. Instead of pumping garbage slop to the digesters at 55? F., it was possible to maintain the temperature of this

mixture of ground garbage and whey at 90? to 95? F. by unloading the whey tank truck as the garbage was fed to the grinder.

Whey Increases Gas Production

Cheese whey contains from 4.5 to 7.0 per cent total dry solids, and only about 8 or 9 per cent of the solids is

inorganic ash. The other constituents,

sugar, protein and fat, are readily di

gestible and are easily converted into

gas in the sludge digesters. By sub

stituting whey for water in the gar

bage grinding process it was further

possible to recover valuable gas from the whey without overloading the plant digesters from the standpoint of liquid

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Vol. 20, No. 6 DISPOSAL OF CHEESE WHEY BY DIGESTION

TABLE I.?Effect of Whey on Plant Operation

1117

Plant Operation Data Before and During Whey Discharge to Sewers

Batch Discharge of Whey

to Sewers, June 23 to

July 7, 1946

Continuous Discharge of Whey to Sewers

Feb. 18 to Mar. 12, 1947

May 18 to 30, 1948

Average for

1946

Average for 76 Months

Prior to Jan. 1, 1947

B.O.D. (p.p.m.): Raw

Settled Final

% Reduction

232 162

7 96.8

212 182 31 85.4

219 149 29 86.7

174 152

13 92.8

188 134

13 93.4

Sludge Index (Mohlman) 138 118 107 91 81

D. 0. Aerator Effluent

(p.p.m.) 1.8 0.9 0.8 3.1

Activated Sludge Volatile Solids (%) 65 75.7 68.4 61.5 58.9

Air Supplied, Cu. Ft./Gal.

Sewage 1.04 1.06 1.32 0.90 0.89

volume fed daily into the digestion system.

A sharp rise in the gas production rate was evident within 30 minutes after the garbage-whey mixture was

pumped to the digesters. On several

days when peak loads of whey were

handled it was necessary to pump the

pure whey to the digesters without the addition of ground garbage. Gas pro duction volumes on these days soared to as much as 108,000 cu. ft. per 24 hour period.

Although the addition of whey to the already heavily loaded digestion system made it extremely difficult to

withdraw clear supernatant from the

digesters, at no time was there any evi dence of foaming or excessive volatile acid accumulation in the digestion sys tem. The carbon dioxide content of the gas produced would increase from 33.0 per cent when small volumes of

whey were being handled to about 36

per cent when large volumes were taken and gas production was at its

peak. No difficulty was encountered in using this fuel in the plant gas en

gines.

Effect of Whey on Plant Operation

Two tables of plant operation data are presented. Table I shows the

effect of the whey on the activated

sludge units when it is dumped to the

city sanitary sewers. When whey reaches the aerators a series of rapid changes takes place. The color of the

activated sludge will change in a 12

hour period from chocolate brown to

slate gray. The volatile content of the

sludge rises rapidly within a period of 6 to 10 days. It is almost physically

impossible to supply enough air to

maintain dissolved oxygen in the

mixed liquor. Septic conditions, of

course, lead to black sludge and the

complete loss of the active sludge if

part of the load is not diverted by by passing after primary treatment.

The plant effluent becomes murky and B.O.D. reduction drops sharply. The sludge index rises rapidly and within several days, if the overload

continues, a reduction in flow volume to the final tanks must be made.

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1118 SEWAGE WORKS JOURNAL November, 1948

TABLE II.?Whey Discharged to Digesters During 1947-48

Month I Loads Thousand Gallons

Per Cent Dry

Solids

Thousand Pounds

Dry Solids

Per Cent Volatile

Solids

Thousand Pounds Volatile

Solids

Thousand Pounds Sludge

Dry Solids, to Plant

Percentage Whey Solids

of Sludge Solids

B.O.D. of Whey (p.p.m.)

1947 March

April May

July August

September October

November

December

1948 March

April May

Average

23

27

43

34

25

2

61

73

103

76 88 10

47

29.7

36.9

43.0

34.0

25.0

2.0

61.0

73.0

103.0

76.0

88.0

10.0

48.5

5.60

5.74

6.31

6.03

5.50

6.48

5.65

5.19

5.13

4.73

4.90

6.14

5.61

14.2

17.8

23.0

17.0

11.5

1.1

28.8

31.3

43.9

26.2

14.5

4.6

19.5

92.0

91.5

91.7

91.5

91.0

94.5

92.5

90.9

91.1

89.4

91.1

95.4

91.7

13.1

16.3

21.1

15.5

10.4

1.0

26.6

28.4

40.0

23.4

13.2

4.4

17.8

223.1

113.6

205.5

288.6

292.3

276.8

236.2

176.7 277.6

275.5

259.1

253.8

239.0

6.35

15.70

11.20

5.89

3.92

0.39

12.16

17.70 15.85

9.53

5.57

1.83

8.80

33,100 46,200 36,300 34,700 33,200

34,700 32,340

35,700

Shock loads resulting from dump

ing of batches of whey to the sewers

may result in an immediate overload on the plant as high as 60 to 70 per cent above the normal load. If these loads were to be treated successfully, the operator needs three additional treatment plants as stand-by units to

handle them. The solution to the

problem is to completely eliminate the

dumping of any whey to the sewer.

Digester Organic Loads

Table II is presented to show the volume and extent of the organic load

contributed by the whey waste to the

digesters during several months of 1947 and 1948. In the third column from the right the pounds of normal

dry sludge solids removed from sewage are shown so that a comparison can be

made indicating the extent of the dry solids load which resulted from the

handling of the whey. During the

peak month of November, 1947, the volatile organic load from whey was

greater than the equivalent load from all the garbage ground and added to the digesters.

Whey Disposal Charge

A charge of $1.00 was assessed for each 500 gal. of whey hauled from the

dairy plant. The B.O.D. strength varied from 18,000 p.p.m. to 46,000 p.p.m. as shown in the right hand col umn of Table II. The net cost to the

industry was, therefore, $6.50 to $13.00 per 1,000 lb. of B.O.D. removed, de

pending upon the concentration of the

product hauled. The wide variation in solids content and B.O.D. was due to the fact that some of the whey was acid treated at the milk plant to re

move the casein, and not all of the

liquid hauled was whole whey.

Summary

This method of final disposal of cheese whey has been satisfactory from the standpoint of accomplishing a

temporary solution to a difficult indus trial waste problem. Utilization of the cheese whey by the dairy industry is

certainly a more logical solution. The

industry may then expect to realize some net revenue from the product, and the sewage treatment plant will not have to expend money for special treatment of a waste that is extremely high in B.O.D.

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