CHARACTERIZATION AND TREATMENT OF BRFWERY WASTES

Henry G. Schwartz , Jr .* and Richard H. JonesM

INTRODUCTION

The brewing industry i n t h i s country has grown steadi ly i n recent years, with t o t a l production i n 1971 amounting t o 135 million barrels (Mbbl) (1). t h i s growth. breweries, it i s now increasingly dominated by a re la t ive ly small number of regional and national brewers. e i ther been absorbed by the larger firms or have ceased operating ent i re- l y i n the face of strong competition.

Amarked change i n the character of the industry has accompanied Where the industry once consisted of many small local

hbst of the small breweries have

A s the nature of the industry has changed, so have the individual brew- er i6s . The smaller f a c i l i t i e s are ineff ic ient and the cost of moderni- zation i s prohibitive. with much greater capacities are being constructed. there were only a few breweries with capacities over 1.0 Mbbl/year while today v i r tua l ly every new brewery has a capacity i n the range of 1.5 t o 4 .O Mbbl/year .

These breweries are being abandoned and new plants Twenty years ago

This trend t o larger breweries creates fewer, but much more substantial waste sources. d i f f i c u l t pollution abatement problems, par t icular ly i n view of increas- ingly stringent effluent standards.

The purpose of t h i s paper i s two-fold, f i r s t t o review brewery waste treatment practices throughout the country and, secondly, t o present the resu l t s of p i l o t plant studies a t one specif ic location. it i s hoped tha t future brewery waste treatment designs will benefit from past experiences.

These high-volume, high-strength wastes give r i s e t o

In so doing,

WASTE CHARACTERISTICS

Brewery effluent can generally be characterized as high-strength organic wastes with moderately high suspended sol ids concentrations. The wastes are generated from a number of plant operations as indicated i n the accompanying flow diagram, Egure 1.

q e a d , Environmental Engineering, Sverdrup & Parcel and Associates, xnc., St. Louis, Missouri

Florida V i c e President, bvironmental Engineering, Inc . , Gainesville ,

371

l O n t ALL WOCESS E Q U I M I I T REQUIRES CAUSTIC V l O h K I D .

D I S?OSIL

I

WASTf 8EER. R I Y S E WATER. UIMIIIO SOLUTIONS. LTC.

FIGURF: 1 BASIC BREWERY FLOW DIAGRAM

372

Beer has a BOD of about 100,000 t o 150,000 mg/l and, thus, one 12-02 bot t le of beer has jus t a l i t t l e l e s s BOD than the da i ly per capita domestic waste load. Wash-water from the various brewing vessels, gen- e r a l plant washdown, and waste beer from breakage and spi l lage in the packaging l ines , therefore, contribute large waste loads.

Perhaps the la rges t single waste source is press l iquor from grain dry- ing. Rather than s e l l the wet grain slurry, some brewers e l ec t t o pa r t i a l ly dry the spent grain using large mechanical presses. presses has a very high BOD content and may const i tute 25 percent or more of the t o t a l plant BOD load.

Spent grain from the l au te r tun is normally sold as feed.

The l iquor from these

The eff luent character is t ics from ten breweries are given i n Table 1. The data presented i n t h i s table were collected during plant v i s i t s , supplemented by limited information i n the l i t e r a t u r e ( 2 ) ( 3) (4), and demonstrate the high BOD and suspended so l ids leve ls i n brewery wastes. Those breweries w i t h r e l a t ive ly low BOD l eve ls generally do not press the spent grains, although the concentration depends also on water usage. Water consumption i n the industry ranges from 5 t o 1 5 bbl/bbl of beer.

Individual waste parameters f luctuate considerably over the brewing day because of the batch type of operation. from the use of sulf'uric acid, sodium hydroxide, and other cleaning com pounds. Measurements taken a t Brewery A, Figure 2, shuw changes of 10 pH un i t s within a ?&minute period. for a three-hour period while the 24.-hour composite had a pH of about 6.0.

Wide var ia t ions i n pH r e s u l t

A pH of about 4.0 was observed

Other data gathered a t Brewery A, see Table 2, indicated a C0D:BOD r a t i o of about 2:1, but t h i s factor was somewhat variable. s t i t u t ed about 75 percent of the t o t a l BOD. Dissolved so l ids concentra- t ions averaged 1520 mg/l w i t h peak values up t o 2190 mg/l.

Soluble BOD con-

PRESENT WASTE TREATMENT PRACTICES

The current state-of-the-art i n brewery waste treatment is much l e s s advanced than might be anticipated. wastes in to large municipal sewerage systems i n which the specif ic e f fec ts of the great ly di luted brewery wastes a re d i f f i c u l t t o ascer- t a in . ent ly hm t o receive a substant ia l proportion of brewery wastes i n t h e i r t o t a l flaw. portion is defined as ten percent or more by volume. plants currently receive only brewery wastes.

Most breweries discharge t h e i r

A t l e a s t nine treatment plants throughout the country are pres-

For purposes of t h i s discussion, a substant ia l pro- Four of the nine

During the course of these studies, each of the nine plants was v is i ted a t l e a s t once. A brief description of the nine treatment f a c i l i t i e s i s presented in Table 3 . d i f f i c u l t i e s i n t rea t ing the brewery discharges.

A l l of them have experienced varying degrees of

373

TABLE 1

B-RY EFFLUENT CHARACTERISTICS

Total Flow

Brewery mgd

A 2.7

B 3.4

C 1.2

D 0.35

E 0.85

F 3.2

G 1.5

H 1.0

I 5.&*

J 1.6

Average BOD A 1000-1400

900

8 50

2000-2 300

2800-2900

1500-2200

6000-8000

210CL430W

l o o w 980

Peak BOD LQdL

2 700

-

4800

- 5000

5000

11,000

19, OOW

- -

Average Suspended

Solids A 500- 700

500

- 800-1400

700- 1600

200- 400

2 600- 2 700

- 4503tn

365

*COD *Design values

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FIGURE 2 pH FLUCTUATIONS OF RAW BREWERY W A S T E

375

TABLE 2

WASTE CHARACTERISTICS - BREWERY A

Characterist ic ODeratinP Data*

Flaw - average 2.65 mgd

BOD - average range

Suspended solids - average range

Temperature - average range

pH - average range

w-Dissolved sol ids - average range

=COD - average range

1000-1400 mg/l 400-2700 mg/l

500-700 mg/l 140-1340 mg/l

9 4OF 88-102OF

5.5-6.2 3- 12

1520 mg/l 770-2190 mg/l

2290 560- 3800

w-COD:E?OD r a t i o 2.0: l

*Soluble BOD:Total BOD r a t i o 0.75:l

*Based on six-month operating record except as otherwise noted **Results of eight-day sampling program during plant evaluation

study

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Activated Sludge Systems

Eight of the nine treatment plants use some form of the activated sludge process. The Kraus process or a modification thereof is used at three older installations, B, C, and D. Interestingly, these three systems were all originally designed and/or operated as conventional activated sludge systems and were later converted to the Kraus process. In each case, sludge bulking became a major problem when the conventional sys- temwas used. The Kraus process has been the only successful means of controlling bulking at these plants. for control of filamentous organisms was tried at one location without success. A s used at Plants B, C, and D, the Kraus process has generally proved to be an effective method for treating brewery wastes. It should be noted, however, that these three systems also receive mnicipal wastes.

Chlorination of the return sludge

The only complete-mix activated sludge system, Plant I, has been in ser- vice only a few months and operating data are unavailable. the treatment plant receives only brewery wastes although municipal wastes will soon be added. Because of the low flows, the detention time in the force main is about six hours and the waste is septic when it arrives at the treatment facility. The resulting odors are very prevalent near the primary clarifiers.

The complete-mix system at Plant I was designed for a food:microorganisms ratio of less than 0.4 lb of BOD removed/lbs mixed liquor suspended solids. A chlorination system for the return sludge has been provided to control sludge bulking should it occur. To date, no such problems have arisen; however, the true test will not occur until the system approaches design loadings.

Presently,

On three occasions, acid conditions in the influent waste stream, i.e., pH values below 4.0, have killed the activated sludge system. charges are now being neutralized at the brewery. The thickener appar- ently has very little effect on the waste activated sludge. BOD levels in the effluent are reported to be below 25 mg/l, but the secondary clarifier overflaw has a noticeable suspended solids content.

Such dis-

A conventional plug-flaw activated sludge system is used at Plant F, which has been in operation for about two years. tion basins, nutrient addition, and a roughing filter ahead of the acti- vated sludge system, severe sludge bulking has occurred as it has at many brewery waste treatment plants. Anaerobic conditions, causing rising sludge, clearly exist in the primary clarifiers, and the combined primary and waste activated sludges cannot be thickened in the conven- tional gravity unit. Fortunately, the flexibility and large capacity of the treatment system will enable some of these problems to be solved by operational changes.

In spite of equaliza-

Plants A and H employ contact stabilization following roughing filters. The contact stabilization process is particularly suitable for wastes with high proportions of suspended and colloidal BOD, but its applica- tion to the highly soluble BOD waste from breweries warrants examination. --

380

The overall treatment efficiencies at Plant A have been below expecta- tions, with BOD removals of about 80 percent and suspended solids reduc- tions in the 30 to 70 percent range. Studies at the plant show an effective loading rate of 0.78 lb BOD/lb MIXS based on contact and re- aeration tank volumes. Sludge bulking is a periodic problem at this very high loading rate, as evidenced by poor suspended solids removals. Modifications are presently being made to this treatment system in accordance with the results of pilot plant studies to be discussed in a subsequent se et ion.

Plant H is very similar to Plant A in the basic process sequence, but the results at Plant H are markedly superior. This facility has been in operation about 1* years, with treatment efficiencies well above 90 percent. tors, not the least of which is the in-house control exercised by the brewery. ment plant at a constant rate seven days a week. practiced for spent caustic solutions.

The excellent performance can be attributed to several fac-

Press liquor is pumped to a holding tank and fed to the treat- Similar controls are

A second factor contributing to the performance is a ten-acre polishing lagqon with a 15-day minimum detention time. The lagoon follows the main treatment operation and serves as added insurance against plant u p sets. In fact, it was observed that the effluent from the secondary clarifiers contained appreciable suspended solids which were later re- moved in the lagoon.

The final major factor influencing the plant performance is the fact that the present loading on the plant appears to be well below design levels. The design was based on a BOD:MUS ratio of 0.38.

Trickline: Filter Systems

Conventional trickling filters for complete secondary treatment have been used in the past at Plants D, E, and G. was abandoned in favor of the present Kraus system after several years of difficulty. handle the combined domestic and pretreated brewery wastes. The overall treatment efficiencies are 60 to 70 percent for BOD and 35 to 60 percent for suspended solids. Plant G recently upgraded its trickling filter system by adding activated sludge in series to the treatment sequence and by covering the filters with Styrofoam domes to contain odors. doubtedly, the extensive modifications to Plant G have significantly improved treatment performance, but data on the new system are not available. brewery wastes has been mediocre at best. been well below current acceptable levels and offensive odors have compounded the problems.

The trickling filter at Plant D

Plant E currently uses two large filters in series to

Un-

The performance of trickling filter installations handling Treatment efficiencies have

Plastic media trickling filters are used as roughing units at fow loca- tions, Plants A, E, F, and H. designed to remove 45 to 60 percent of the BOD, is to reduce the high- strength of the influent brewery wastes to more manageable levels.

The purpose of these roughing filters,

381

Generally, the roughing filters seem to have met the design criteLLLI., but not without some problems. With the exception of Plant H, the fil- ters all generate objectionable odors, at times discernible for several miles. The septic nature of the waste as it leaves the primary clari- fier and the anaerobic conditions in the roughing filter result in significant odor generation. Measurements at two of these plants show- ed zero dissolved oxygen in the wastes throughout the roughing filters. Little or no odor can be detected from the roughing filters at Plant H, possibly a reflection of lower loading rates at present.

Sludge Disposal

The disposal of primary and secondary sludges from brewery waste treat- ment operation is a severe problem, as it is at many treatment plants. The high BOD and suspended solids content of brewery wastes, however, results in a much higher solids production per unit volume of waste than many other wastes. for brewery wastes with mixed results.

A variety of sludge disposal methods have been used

Gravity thickening has been used with little success on both combined and waste activated sludges. Three plants presently use dissolved air flotation for thickening waste activated sludge with similar results, gpecifically a discharge solids content of about three to four percent.

Plants C, D, E, and G, use anaerobic digestion as their main sludge dis- posal method. The digestion systems perform quite satisfactorily in terms of volatile solids reductions, but little solids separation is achieved in the second stage digesters. Three of the four plants use sludge drying beds, while the digester liquor from Plant D is discharg- ed to a sludge lagoon which creates odor problems, particularly in the spring. Notably, the percentage of brewery wastes and, hence, brewery sludge is much higher at Plant D than at the other plants using anaer- obic digestion.

Aerobic digestion is used at Plants A and H, but is soon to be replaced with incineration at the former. Plant A resulted in only partial digestion and stabilization. plants initially discharged the digested solids to sludge lagoons, but severe odor problems eventually forced an end to this practice. application of lime, masking agents, and other chemical controls failed to eliminate or even markedly improve the situation.

Insufficient digestion capacity at Both

The

Plant H is now experimenting with spray irrigation for disposing of the digested sludge. Spray irrigation is also used at Plant I, but without digest ion.

Plants B and F use vacuum filters and dispose of the filter cake in landfills. A thermal sludge-conditioning unit was installed about two years ago at Plant B to reduce or eliminate the high operating cost of chemical conditioning. At the same time, the heat-treatment decant liquor was substituted for digester liquor in the Kraus process.

loaded the activated sludge system and caused a precipitous drop in the

The --high strength, resolubilized BOD in the decant liquor apparently over-

382

overall plant efficiency. Moreover, the heat treatment process generat- ed very objectionable odors. exchanger fa i led as a r e su l t of corrosion and the system was abandoned. Interestingly, while the systemwas i n service it yielded a f i l t e r cake with about 40 percent solids w i t h no chemical conditioners. This r e su l t is t o be compared with a 1 5 percent sol ids content i n chemically condi- tioned f i l t e r cake using 1 5 t o 20 percent lime and '7 t o 9 percent f e r r i c chloride a t the same plant.

Within six months, the carbon s t ee l heat

PILOT PLANT STUDIES

Since system start-up i n 1969, Plant A has experienced a ser ies of oper- ational d i f f i cu l t i e s , some of which have been discussed previously. A f l a w diagram of the treatment system, previously described i n Table 3, is shown i n Figure 3. a t present, although domestic wastes w i l l be added i n the near future a t about a 1:l ra t io .

The treatment plant receives only brewery wastes

One of the major concerns a t Plant A has been the inabi l i ty of the system t o consistently achieve sat isfactory treatment levels . Extensive f i e ld studies of the existing system indicated tha t the contact s tab i l iza t ion prqcess was poorly suited t o the high soluble-BOD nature of the brewery wastes, especially a t the very high loading ra tes experienced, i.e., 0.78 l b BOD/lb MLSS . A s a r e su l t of these problems, a se r ies of p i l o t plant studies were undertaken t o evaluate the t r ea t ab i l i t y of the waste using the complete- m i x activated sludge process. Studies were conducted with raw brewery wastes, t r ickl ing f i l t e r effluent, and a mixture of domestic and brew- ery wastes. In addition, a brief experiment was run on aerobic sludge digestion. following sections.

Results from the p i l o t plant studies are presented i n the

Experimental Fac i l i t i e s

The f i e ld studies conducted a t the P l a n t A s i t e were i n two p i l o t units. P i lo t Plant No. 1 consisted of a 650 gal, 18.0 f t 2 surface area primary c l a r i f i e r ; a 1,970 gal aeration tank; and a 512 gal, 16.0 f t 2 surface area secondary c l a r i f i e r . P i lo t Plant No. 2 consisted of a l 4 O gal, 6.0 f t 2 surface area primary c l a r i f i e r ; a 419 gal aeration tank; and a l 4 O gal, 6.0 ft2 surface area secondary c l a r i f i e r . t ion tanks and sludge return l i nes was provided by individual compres- sors for each unit.

A i r for the aera-

Samples were composited by automatic sampling devices where feasible and most chemical analyses were conducted on s i t e in a mobile labora- tory. the Examination of Water and Wastewater, 12th Ed,, with the exception of dissolved oxygen, which was measured by a dissolved oxygen probe calibrated against the standard Winkler t i t r a t ion .

All t e s t s were conducted i n accordance with Standard Methods for

-*

383

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I Digest ion I n To

S1 udge D i sposal

Bas i ns

Supernatant A

Reaeration

Bas i ns

/ \ Secondary Contact C1 a r i f i e r Bas i n

4

-- FIGURE 3 WASTE TFCEAWNT F L O W D I A W FOR BFEWERY A

384

Treatment of Raw Brewery Waste

P i lo t Plant No. 1 was used for the experiments on the treatment of raw brewery waste. The un i t was placed into operation by f i l l i n g the aera- t i on tank with se t t led brewery waste and seeding w i t h 600 gallons of re turn activated sludge from Plant A. The activated sludge system was acclimated stepwise over a 17-day period t o a n hydraulic feed r a t e of 1500 gal/day, which gave an average loading r a t e of 0.21 l b BOD/lb MLSS. Ammonium n i t r a t e was added t o supplement the low l eve l of nitrogen, about 1 - 6 mg/l as N, i n the influent waste.

After the system was s tabi l ized, 24-hour composite samples were analyzed over an eight-day period. Subsequently, the average loading r a t e was increased t o 0.56 l b BOD/lb MLSS and samples were collected and analyzed for an additional 12-day period. The data gathered during these experi- ments are summarized i n Table 4 for runs A 1 and A2 and are presented graphically i n Figures 4 and 5.

The r e su l t s of these p i l o t plant studies indicate tha t raw brewery waste can be eas i ly biodegraded by the complete-mix activated sludge process. A t the lower loading r a t e of 0.21 l b BOD/lb MLSS, the soluble BOD in the eff luent was always l e s s than 20 mg/l and averaged 8.0 mg/l. hig'her r a t e of 0.56 l b BOD/lb MLSS, the eff luent soluble BOD averaged

A t the

14 %/I.

The soluble BOD removal r a t e , K 2 , was calculated based on the equa- t ions ( 5) :

Lo - Le Le = K 2 Sa t

where : K2 = removal r a t e constant Lo = influent soluble BOD Le = eff luent soluble BOD Sa = mixed liquor suspended so l ids t = time under aeration, detention time 0 = 1.056 ( 20° t o 3OoC) 8 = 1.135 (4' t o 2OoC)

Average values calculated for the several runs are given i n Table 5.

I n view of past experience with sludge bulking, one of the major items of i n t e re s t i n these studies was the sludge volume index (SVI). SVI averaged 230 for the lower organic loading r a t e and 346 a t the high- e r ra te . A sludge with a n SVI of 230 can be se t t l ed i n a conservatively designed secondary c l a r i f i e r , but it is d i f f i c u l t t o achieve adequate liquid-solid separation consistently with a n SVI of 346.

The

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-- F I G U R E 4 BOD REDUCTION I N P I L O T PLANT TREATING SETTLED BRFWERY WASTE. AVERAGE LOADING RATE - 0.21 lb BOD/lb MLSS/day

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Treatment of Trickling F i l t e r Effluent

The experiments on treatment of t r ickl ing f i l t e r effluent were conducted in P i lo t Plant No. 2, which was operated concurrently with P i lo t P l a n t No. 1. The system was placed i n operation by f i l l i n g the aeration tank with f i l t e r effluent and 100 gallons of return activated sludge seed. The t r ickl ing f i l t e r effluent was fed direct ly into the aeration tank a t a r a t e tha t was increased t o 700 gpd by the end of the acclimation period. Composite samples were collected and analyzed over a n eight-day period. The average loading r a t e was then increased t o 0.54 l b BOD/lb MLSS. After the system stabil ized a t the higher loading rate , composite Sam- l e s were collected for 13 additional days.

This r a t e gave a n average loading of 0.18 l b BOD/lb MLSS.

Results of the t e s t runs A3 and A 4 are also given i n Table 4 and shown i n Figures 6 and 7. A t the lower loading ra te , the treatment e f f i - ciency was excellent with an average effluent t o t a l BOD of 18 mg/l. soluble BOD was always below 1 5 mg/l and averaged 6.0 mg/l. When the loading was increased t o 0.54 l b BOD/lb MLSS, the effluent quali ty decreased markedly with an average soluble BOD of 33 mg/l and a t o t a l BOD of 83 mg/l. Removal r a t e constants for the soluble BOD were cal- culated and are shown i n Table 5.

The

The-SVI a t the 0.18 l b BOD/lb MLSS loading r a t e f a i r l y consistently averaged 215. widely from 92 t o 317. f icu l ty i n se t t l i ng a t the higher loading rates .

A t the higher loading ra te , however, the SVI varied Once again, the data indicated increased d i f -

Treatment of Combined Wastes

P i lo t P lan t No. 2 was used for the experiments with a 1:l mixture of t r ickl ing f i l t e r effluent and se t t led domestic sewage. Following the studies on t r ickl ing f i l t e r effluent, se t t led sewage was added t o the influent waste stream. The feed r a t e of each waste was s e t a t 650 gpd t o produce a detention time of 7.7 hours and a loading r a t e of 0.32 l b BOD/lb MLSS. secondary effluent were collected for nine days and the data summarized as run A5 i n Table 4 and shown i n Figure 8.

Composite samples of the two influent streams and the

During t h i s t e s t run, a Styrofoam dome was placed over the roughing f i l - t e r t o control odors, and the effluent BOD increased significantly. The average f i l t e r effluent BOD during the p i l o t plant t e s t was 723 mg/l with BOD concentrations greater than 1,000 mg/l on two separate days. The average t o t a l BOD in the p i l o t plant effluent was 35 mg/l, giving a t o t a l BOD removal efficiency of approximately 92 percent. The sol- uble BOD i n the effluent remained below 10 m g / l , with the exception of the l a s t two days of operation when the f i l t e r effluent BOD in- creased t o over 1,000 mg/l. mixture of se t t led sewage and brewery waste can be effectively treated by the complete-mix process.

The resu l t s of t h i s study indicated tha t a

Of s-pecial note, the SVI during t h i s experiment averaged 183, which is considerably below the values recorded for brewery wastes alone. This

390

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T I M E - D A Y S

FIGURE 6 BOD REDUCTION IN PILOT PZANT TREATING TRICKLING FILTER EFFLUENT. LOADING RATE - 0.18 Ib/BOD/lb MLSS/day

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T I M E - D A Y S

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T I M E - D A Y S

FIGURE 8 BOD REDUCTION I N PILOT PLCLNT TREATING 1:l RATIO SETTLED SEWAGE AND FILTER EFFLXENT LOADING RATE - 0.32 lb BOD/lb MLSS/day

393

result indicates improved settleability for the combined wastes, perhaps a significant factor in achieving good plant performance.

Aerobic Digestion of Sludge

The first test conducted on aerobic sludge digestion was in Pilot Plant No. 1 on a semicontinuous feed basis. Initially, 30 gallons of primary sludge and 150 gallons of waste activated sludge from Plant A were added to the aeration basin. Every second day thereafter, 180 gallons of feed were added to the tank with a corresponding removal of effluent. procedure resulted in a suspended solids concentration of approximately 1.0 percent with a 22-day hydraulic retention period. concentrate the sludge by raising the average influent BOD and suspend- ed solids, the feed rate was changed to 70 gallons of primary sludge and 120 gallons of waste activated sludge.

The volatile solids loading on the aerobic digester averaged 0.075 lb/ ft3/day over the testing period. Reductions achieved by the aerobic digester were 36 percent in volatile solids and 40 percent in BOD. summary of the pilot plant performance during this test is presented in Table 6. on aerobic digesters and indicate that this sludge may be successfully treated aerobically.

A brief test was conducted on the digester effluent for possible odor problems by drying six inches of digested sludge on a makeshift sandy earth bed. with no noticeable odor.

This

In an effort to

A

The data show performance comparable with published values

The sludge dewatered very rapidly and left a dry residue

Researchers have recently attempted to correlate the degree of sludge digestion with changes in sludge parameters such as pH, alkalinity, and nitrate content. A batch study was initiated in Pilot Plant No. 2 with 70 gallons of primary sludge and 120 gallons of waste activated sludge. Analyses were conducted on this sample during aeration to determine the parameters against which the degree of sludge digestion could be mea- sured. It may be seen that for this single sludge sample, essentially all of the BOD and volatile solids removal was completed by the sixteenth day of operation. Correspondingly, the pH had dropped to 5.0 by the eigh- teenth day of operation, and the total alkalinity was reduced from over 300 mg/l to less than 50 mg/l by the sixteenth day. results with alkalinity and pH data from the continuous feed test re- veals that with a pH of 5.0 to 6.0 and alkalinities around 40 mg/l, the continuous feed process accomplished essentially complete digestion within a retention period of 21 days.

The data obtained from the experiment are presented in Figure 9.

Comparing these

The indicated changes are explained by the fact that aerating a car- bonate-bicarbonate water removes carbon dioxide and gradually lowers the alkalinity. While the sludge is still actively digesting, carbon dioxide is being returned to the water. A sharp drop in alkalinity, therefore, does not occur until digestion is substantially slowed. Flurthermore, with the drop in buffering capacity of the liquid and the conversion of organic and ammonium nitrogen to the nitrate form, acid- ity increases and the pH drops to some new low level.

394

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T I M E - D A Y S

FIGURE 9 BATCH DIGESTION OF BREWERY WASTE SLUDGE

39 6

DISCUSSION

Based on the results of these pilot plant studies, design criteria for a complete-mix activated sludge system to handle brewery wastes have been established as follows:

1. Primary clarification, surface loading rate: 750 gpd/ft2 2, Aeration basin, loading rate: 0.25-0.30 lb BOD/lb U S

3. Secondary settling, surface loading rate: 400-500 gpd/ft2 (based on 2,500 mg/l MLSS)

Recommendations have been made and are being implemented to modify Plant A in accordance with the pilot plant studies. aerobic digesters will be converted to activated sludge basins with new sludge incineration facilities for sludge disposal. Because of piping restraints, the initial plant modifications will create an acti- vated sludge system more closely resembling stepfeed. Total conver- sion to a complete-mix pattern may be undertaken at a later date.

The existing

A relatively low organic loading rate appears essential if sludge bulk- iqg is to be controlled. improve sludge settleability significantly.

The addition of domestic wastes appears to

The use of a pure oxygen system may offer special advantages in con- trolling sludge bulking. often difficult, if not impossible, to maintain satisfactory dissolved oxygen levels throughout the aeration basin using conventional aeration equipment. At l ow dissolved oxygen levels, 0.1-0.2 mg/l, Sphaerotilus- type organisms compete very strongly and may give rise to sludge bulk- ing. possible remedy for this situation.

With a high strength brewery waste, it is

The use of pure oxygen in place of aeration is suggested as a

CONCLUSIONS

The treatment of brewery wastes has proved difficult at numerous instal- lations throughout the country. loadings and sludge bulking, are repeatedly encountered.

Two major difficulties, high organic

Activated sludge systems seem to offer the best approach for handling the high soluble BOD wastes. sludge process are functioning reasonably well on brewery wastes without appreciable bulking. complete-mix activated sludge can perform equally well without bulking if the loading rate is kept relatively low, ?..e., about 0.3 lb BOD/lb MUS.

Several Kraus modifications of the activated

Pilot plant studies reported herein indicate that

Plastic-media tricuing filters have been used as roughing units at several locations. removals, most of these units have given rise to objectionable odors detectable outside the treatment plant property. Unless the odors can be eliminated, roughing filters appear to have limited application for brewery wastes.

Although the filters accomplish 45 to 60 percent BOD

397

Finally, in-plant control of some of the major waste streams can vastly improve the waste treatment plant operations. In particular, the collec- t ion and equalized discharge of press liquor and caustic and acid clean- ing solutions w i l l greatly reduce the treatment problems inherent with brewery wastes.

398

LITERATURE CITED

1. Internal Revenue Service, Department of the Treasury. f fFiscal Publica- year, 1970, alcohol and tobacco summary s t a t i s t i c s . "

t i on 67 ( 3 - 7 1 ) .

2. O'ROURKE, J. T., and TOMLINSON, H. D, ffExtreme variations in brewery waste character is t ics and t h e i r e f fec t on treatment." Proceedings of the 17th Purdue Industr ia l Waste Conference, Purdue University, May, 1962.

3. McWHORTER, T. R., and ZIELINSKI, R. J. fWaste treatment for the Pabst Brewery a t Perry, Georgia.If Indus t r ia l Waste Conference, May, 197l.

Presented a t the 26th Purdue

4. LEWIS, H. V. Golden, Colorado,If unpublished paper.

"Treatment of brewery waste a t Adolph Coors Co.,

5. ECKENFELDER, W. W. ffApplication of kinet ics of activated sludge t o process design,ff Pergamon Press, 277 (1963) . Advances i n Biological Waste Treatment,

399