Agricultural Wastes 3 (1981) 285-296

AEROBIC A N D ANAEROBIC BIOFILTRATION OF AGRICULTURAL EFFLUENTS

JAN A. OLESZKIEWICZ~

Research Institute on Environmental Development, Wroclaw Division, 51-616 Wroclaw, Rosenbergow 28, Poland

ABSTRACT

Based on a pseudo-first-order model of organics removal in biological filters the data for various agricultural wastes are interpreted. It is evidenced that the model is applicable to both anaerobic and aerobic biofilters. Various advantages of biofiltration are presented in applications to the agricultural industry. Anaerobic and aerobic biofilters have been successfully applied to treatment of dilute piggery wastes. It is postulated that a series of anaerobic and aerobic biofilters could offer a short- detention-time system for strong agricultural effluents, capable of attaining high effluent quality from operations where traditionally suspended-growth systems are used.

NOMENCLATURE

A H K k L N Q s, So Se

Specific surface area (m 2 m - 3). Dep th of the biofilter (m). Gross removal coefficient (kg m - 3 d - 1). Specific removal coefficient (kg m - 2 d - 1). Volumetr ic organic loading applied (kg m - 3 d - 1). Recirculat ion rat io = Qrec/Qraw (--). Hydraul ic loading per cross-section (m 3 m - 2 d - 1). Influent, mixed applied concent ra t ion (rag d m - 3 ) . Influent raw wastes concent ra t ion (mg d m - 3 ) . Effluent concent ra t ion (mg d m - 3).

t Present address: Duncan, Lagnese & Associates, Inc., 3185 Babcock Boulevard, Pittsburgh, PA. 15237, USA.

285 Agricultural WastesO141-4607/81/O003-0285/$02.50 © Applied Science Publishers Ltd, England, 1981 Printed in Great Britain

286 JAN A. OLESZKIEWICZ

& T AT ®

nf f

arec Qraw F I g

Intercept with S e axis (mg dm-3). Temperature (°C). T - 20 (°C). Temperature correction factor (--). Not filtered mixed sample. Filtered sample soluble concentration. Recycle flow rate (m 3 d-1). Incoming raw waste flow (m 3 d - 1). Food to microorganisms (biological slime) ratio, expressed for biofilters per surface area of the media assumed to be evenly covered with slime (kgm-2d- 1).

INTRODUCTION

The agricultural industry is usually comprised of small production plants where maintenance of wastewater treatment facilities is considered an additional burden. The personnel are often poorly qualified to maintain sophisticated aerobic or anaerobic biological-culture reactors such as activated sludge and other treatment systems, particularly in the case of rapidly biodegradable substrates such as food- processing-industry wastes. The recent revival of interest (Hemming & Wheatley, 1979; Porter & Smith, 1979) in the heterogeneous reactors, i.e. anaerobic and aerobic biological filters, for use in smaller facilities is due to several reasons:

(i) maintenance of a well designed biofilter is simple; it is confined in practice to maintaining an appropriate flow regime;

(ii) shocks can be easily absorbed by changing the flow regime from the plug- flow to the pseudo completely mixed regime by increasing recycle;

(iii) recovery of the attached slime biota after the upset is faster and the operation of the plant requires less skill than in suspended-biological-sludge plants;

(iv) the nature of certain agricultural wastes (e.g. potato) makes the use of activated-sludge systems not feasible due to bulking problems typical of high-carbohydrate systems (Allen, 1972; Eckenfelder et al., 1974; Smith et al., 1978)

The paper will demonstrate some full-scale and pilot-scale data on application of biofilters to treatment of several agricultural effluents. The data will be interpreted by the first-order model derived by the author, which correlates removal with applied organic loading.

The aim of the paper is to show the advantages of the biofilters when used for treatment of small or large volumes of agricultural wastes; to demonstrate the methods of data interpretation (the biofilter design is still based on empirical

BIOFILTRAT1ON OF AGRICULTURAL EFFLUENTS 287

evidence and a variety of models that fail to yield comparable results); and to suggest the possible use of the common model for both aerobic and anaerobic biofiltration.

M A T H E M A T I C A L MODEL

A pseudo-first-order model was used, as introduced by Oleszkiewicz & Eckenfelder (1974).

SJSa = exp ( - K/L) (1)

where S~ and S, are effluent and mixed influent concentrations (mgdm -s) respectively.

S o + NS~ S a - ( 2 )

I + N

where S O is the raw wastes concentration. The value of the volumetric organic-substrate loading L (kgm-3d -1)

corresponds to the food to microorganism ratio concept (F/M) where

L = QS~ n (3)

o r

and thus

L F/M=~

Sc/Sa=exp(-k F~M) (4)

assuming that the microorganism's biomass is evenly distributed on the surface area of the media (Oleszkiewicz, 1977).

The model (eqn 1) has been derived on the basis of data from highly loaded, oriented, plastic-media, aerobic trickling filters; however, interpretation of nitrifying, low-loaded, aerobic biofiltration data by this formula has also proved effective (Oleszkiewicz, 1976). It will be demonstrated that the model is applicable also to anaerobic biofilters operating both under high loadingand in the denitrifying stage.

The complicated nature of the three-phase regime of the biochemical changes in the filter has precluded researchers and designers alike from finding a model that is mechanistically accurate. Analysis of the existing empirical models against eqn (1) (Oleszkiewicz et al., 1976), has proved that the latter fits data more flexibly, although exceptions are noted (Moodie & Greenfield, 1978).

The applicability of the model is further verified by the Maclaurin series

288 JAN A. OLESZKIEWICZ

expansion of the exponent which, for low values of K/L , reduces to the most popular empirical correlation

(S O - Se)/So = K / L (5)

used by Imhoff, Rincke and others, as well as by the filter media manufacturers, based on full-scale experience.

Taking into account the temperature correction factor ®, found (Oleszkiewicz & Eckenfelder, 1974) to be equal to 1.035 or higher for aerobic trickling filters, the working equation takes the form

S J S a = exp ( - kAHOar /QS~) (6)

where K = kA . The temperature correction factors need further verification in the case of anaerobic biofilters.

AEROBIC BIOF1LTRATION

The wastes from canning operations have a long history of aerobic biological treatment (Loehr, 1974; Lund, 1971), with trickling filters being the preferred system due to ease of maintenance, possibility of absorbing shock-loads and weekend shutdowns.

Figure 1 illustrates the kinetics of BOD removal from a factory processing fruits and vegetables into jams, juices, soft drinks, wines and powdered products, and discharging wastes with BODs, S O = 200-700 rag® 2 d m - 3. The wastewaters were treated in one and two-stage pilot=scale biofilters (Wolski, 1960). The need based on this data for recycle, frequently questioned and criticised by researchers (e.g. Moodie & Greenfield, 1978), should be strongly emphasised. Figure 2 illustrates the effects of increasing recycle on'the BOD removal efficiency in the above described installation at Tymbark.

Similar results were obtained by the author for other effluents treated on plastic media (Oleszkiewicz, 1975). The studies have indicated the existence of a plateau and a decrease of removal efficiency with increase of N. The plateau varies with the nature of the wastes; for substrates resistant to biodegradation the optimum recycle ratio may reach Nov t = 4 to 5. In agricultural wastes these values are lower, Nop t = 1 to 2.

The results of the above studies have been fully verified in the full-scale installation. In another study, Wolski (1971) has again proved the excellent applicability of the trickling filter to the canning wastes. The pilot-scale coke biofilter, having a depth of 6 m and an area of 0.8 m 2, was loaded with Q = 1-35- 2.0 m 3 m - 2 d - 1 and the raw waste concentration of BOD 5 = 200-600 mgO 2 dm - 3, and yielded consistently good removals (from 60 to 91 ~) based on BOD 5. The results are presented in Fig. 3: the removal coefficient is k = 0.027 kg m -2 d -

1 0 0 0 ~

800

6 0 0 f

GO0~

2OO

E

100 E

- - 80 o o 60

d

20

Fig. 1.

10 0

I t I I I I I

• NO RECYCLE

• TWO STAGES

o ONE STAGE

• . O K = 2"30 A = 80 mS/m s

k 0 ,0y8 k g l m 2 d

_- ' ~ o o

-- • K: 1,0 •

I I L I I I i

0.2 0.4 06 0,8 1,0 1,2 1,4 1,6

l l L ( m 3 d / k g )

Tymbark fruit processing and distillery wastes treatment on coke media.

100

8 0

6O

u

>~ z.0 o IE uJ

o 20 o

Fig. 2.

F - - ] 7 - 1 I

I

y,

I _ I _ _ I I _ _ [ 0 100 200 30O

RECYCLE RATE N (°/o)

Effects of recycle on efficiency of Tymbark wastewater treatment.

290 JAN A. O L E S Z K I E W I C Z

1000

700

500

400

300

20O

o co

I00

70

50

i I

O N = 3

• N = 2

0 N= 1

40

30 0

K : 2.1B

o k = 0 .027 k g l m 2 d

o

"2 o

I ~ I 1 I i • 1

0.4 0,B 1.2

l l L (rn3d I kg )

Fig. 3.

1,4

Cannery wastes biofiltration on coke media.

( K = 2 . 1 8 ) , a value similar to that obtained in Fig. 1 for similar wastewaters. Interpretation of the fruit- and vegetable-waste treatment data for a plastic-media biofilter reported by Askew (1966, 1967) and NCA (1971) yielded similar values of K, although the correlation was not as good as in Figs. 1 and 3.

Yeast factory wastes are usually high in organic solids, particularly those from the first separation by centrifuging. These concentrated streams are usually separated and anaerobically pretreated before mixing with other plant effluents. The pilot- studies data on yeast factory effluent biofiltration reported by Wolski (1960) have yielded good correlation according to eqn (1) (Fig. 4). The influent wastes contained anaerobically digested, first-yeast-separation stream and other raw streams which diluted the concentration to S O = 400-1500 mgO 2 dm- 3 (BODs)" Very high recycle ratios were practised (N = 3-6), which decreased the applied wastes BOD s to S a = 160-470 mgO2dm -3. The gross removal rate coefficients for the higher loadings were KI = 0.56 and K 2 = 0.21 kgO 2 m - 3 d - 1, and k 1 = 0.007 and k 2 = 0"003 kgO 2 m- 2 d - 1 for coke media.

Another example of successful biofiltration application is for the treatment of piggery wastewaters. The piggery wastewaters frequently induce activated-sludge bulking. If the farm maintenance is not careful enough with disinfecting and cleaning agents, foaming may also occur during aeration (Jones & Patni, 1972). Thus,

BIOFILTRATION OF AGRICULTURAL EFFLUENTtl 291

500

400

~ 300

o~200 E o

100 i . -

~ 8o 3 ~ 60

Fig. 4.

S'-0 = 321

I I I I I

1 2 3 " 5 1 / L (m3d / kg BOD )

Biofiltration of anaerobically pretreated yeast plant wastes.

the future aerobic treatment of diluted piggery manures should not overlook the trickling filters. Results o f treatment on an experimental brushwood-media biofilter are presented in Fig. 5. The gross removal coefficient is K 1 = 21.3 k g m - 3 d -1 for high-loadings, roughing treatment, and/ (2 = 3.22 kg rod- 3 d - 1 for loads below 10 kgO 2 m - 3 d - 1. The removals varied from 75 to 97 % as B O D 5 (Oleszkiewiez, 1976).

Fig. 5.

10000

7 000 ~•

5 000 ,ooo

3 000 - -

~ ' 2 000

(:3

o o m 1000

7 0 0 u. u . ua

500

4OO 0

I I I I I

AVERAGE S o : 15500 q /ms

0,1 0,2 0,3 0,4 0,5

1 I L (mt'd I k g )

Piggery manure treatment on experimental brushwood-media biofilter.

292 JAN A. OLESZKIEW1CZ

In another study on biofiltration of piggery manure where influent COD averaged 54,000mgO2dm -3 (range 32,000-119,000) and BOD s averaged 15,600mgO 2 dm-3 (range 11,800-19,250) the removals attained were even higher. At variable loadings (in the range below i.0 kgO z m-3 d-~ COD) the effluent quality ranged from 230 to 2900 mgO 2 dm- 3 COD, and BOD S was usually contained within 100- 300 mgO 2 dm- 3 (Hepherd & Charlock, 1977).

ANAEROBIC BIOFILTRAT1ON

Certain agricultural effluents contain substances aerobically non-biodegradable or for which long retention times are required, making the process uneconomical. Anaerobic pretreatment is practised to break down these substances, as well as to reduce the overall organic load in the case of concentrated effluents. Full-scale anaerobic pretreatment has been practised since the early 1950s for meat packing and slaughterhouse wastes, and is presently gaining popularity for treatment of olive-processing wastes and distillery slops (Michelli, 1979) and for yeast and concentr, ated brewery effluents (Wolski, 1960).

Recently, anaerobic treatment has been introduced as a preparatory method for agricultural utilisation of effluents, since nitrogen resources pass the anaerobic stage undiminished.

This discussion will be confined to the studies of anaerobic biofiltration of piggery wastes. Large piggery effluents usually yield a very loosely knit bacterial sludge, with bulking tendencies, while the introduction of the solid surface media in the biofilter creates a more balanced and stable environment which makes the anaerobic biofilter a highly reliable treatment unit.

The biofilters have been used in both the roughing mode, as full raw wastes treatment units, and as denitrifying-polishing units. The raw waste treatment data from a bottom-fed pilot-scale biofilter is presented in Fig. 6. Since the filter was packed with plastic balls of specific surface area A = 90 m 2 m- 3, the value of k is equal to 3 .1 /90=0 .034kgm-2d -1. The filter yielded excellent removals at uncontrolled room temperatures of 22-26°C, as shown in Table 1.

The loadings that can be applied to an anaerobic biofilter are much higher and the attractiveness of the system lies in this flexibility of operation which is frequently needed in the varying raw waste loading conditions of the agricultural industry. At low loadings quite high removals were obtained (over 90 ~ on the COD base), with good gas production. At higher loadings, above 6 kgm-3 d-~, over 60 ~ COD removals were still obtained, which makes the anaerobic biofiltration an excellent roughing or pretreatment unit of very low retention time (at retention times below 12 h excellent methanogenesis was still observed), low area needs and relatively low energy requirements. Screening is the only preliminary process required. It is already established that fine, dynamic screens are standard in piggery waste treatment plants; thus they can be excluded from the economical analysis.

10

8

z,, E E

o ~ o, 3

03

° o 2

£3

0,8

0,6

0,5

Fig. 6.

r q FILTER 1 2 3

So< lOkg /m 3 • • •

~ o t l So>lOkg/m3 0 o ,*,

D 0 D

OA D

~ , ,A _ ~ •

zx • ~ _ K = 3.1 kg / mZ'd

0 • • o o \ 0

0 0

0

0 0,2 0,4 0,6 0,8 1,0 1,2 1,4

I / L (m~d Ikg COD )

Anaerobic lab. biofiltration kinetics--raw pig wastes.

TABLE 1 PERFORMANCE OF AN ANAEROBIC BIOFILTER TREATING RAW PIGGERY EFFLUENT: AVERAGED DATA, ONE RUN LASTED 3 0 - 4 5 DAYS (I.E. STEADY

STATE)

COD loading Effluent filtered (kgm-a d -1) COD (mgO2dm -3)

Removal efficiency (%)

Non-filtered Filtered COD COD

0'35 436 91 "2 88.7 0"71 369 93.6 89'8 1.61 596 88"3 87.7 2"01 1010 71.6 72.3 3.23 1143 76-1 60'8 3.48 2363 61-4 48.5 5.66 2477 66.3 46.2 7.29 2318 63.3 53.7

Note: Influent COD varied: filtered COD = 3650-4600 mgO2 d m - 3; non-filtered COD = 8600-9700 mgO 2 d m - 3.

294

1000

J A N A. O L E S Z K I E W I C Z

B00

600

400

E 300 "tin

O 200

E

100 D

o 80 U

60

w

u_ 40 u - w

20

O O

"0

O O

SelSo= exp(-K/L)

0

0 0 0 - 0

t I I I I I I I

0,2 0,4. 0,6 0,8 1,0 1,2 1,4. 1,6 1 ,B

LOAD FUNCTION I / L ( m 3 d / k g C O D )

Fig. 7. Removal kinetics in full-scale anaerobic polishing biofilters.

Anaerobic biofilters have been successfully applied to final treatment of the piggery wastes after a chemical-biological treatment train. The BODs,nf concentration of effluent from the activated-sludge tanks which entered the anaerobic biofilters averaged 180mgO 2 dm -3 (BODs, e = 61), while the average COD,f was 394 mgO 2 d m - 3 with COD e = 200 mgO 2 dm- 3 (Oleszkiewicz et al. , 1979, 1980).

Figure 7 illustrates the kinetics of COD removal on a coke-filled, top-fed, biofilter. The bed was 0.80 m high and was placed on 20 cm of gravel underlayer. The effluent quality was (on average) 39mgO2dm -3 BODs,nf (18 BODs.f) and 223 mgO 2 dm-a COOn e 057 CODe), i.e. some 73-78 % BOD 5 removal and 20-40 % COD removal, in spite of the uncorrected carbon/nitrogen ratio, which is typically unfavourable in the case of piggery wastes.

DISCUSSION AND CONCLUSIONS

The nature of food-processing wastes frequently dictates the application of trickling filters, particularly since the data on suspended-culture process upsets has been

BIOFILTRATION OF AGRICULTURAL EFFLUENTS 295

made known (Eckenfelder et al., 1974). Reliable treatment effects for wastes from these industries have been presented with conventional media biofilters; the introduction of plastic media expands the range of loadings that can be applied and decreases the pretreatment requirements. The somewhat lower treatment efficiency (by 5-10 %) of aerobic biofilters when compared with dispersed-growth reactors is offset by lower energy requirements of up to one-half of that of the activated-sludge system. Aerobic biofiltration has been applied successfully also to treatment of screened animal wastes considered not suited for trickling filters by some workers (Loehr, 1974). Oriented plastic-media filters are more suited for high-rate and roughing, aerobic treatment of agricultural wastes, while polishing aerobic biofiltration is better realised on random media. Recent successful experience with meat-processing-wastes nitrification at very low loadings (L = 0.04 kg BOD 5 m- 3 d-1, 0.035 kg NH 3 m-3 d-1) applied on slag media indicates the wide range of possible applications of the aerobic process to agricultural wastes (Stracey, 1975).

Anaerobic biofiltration has gained some attention only recently (Mosey, 1977); the potential of the process in treatment of high-strength agricultural wastes has so far been documented in full scale for slaughterhouse wastes and yeast and brewery effluents. In this paper, piggery waste anaerobic biofiltration data are presented, with results showing that both anaerobic and aerobic biofiltration are capable of removing the carbonaceous and nitrogenous BOD at relatively high rates and with low energy requirements.

Frequently reported difficulties with handling of the excess biological sludge from treatment of agricultural wastes are not a problem in the case of biofiltration which yields a dense and fully stabilised sludge due to the high solids retention time in the biofilter.

The biofilter offers the operator a much greater flexibility than the suspended- culture reactor. Through recycle, almost continuous transfer from the plug-flow to the completely mixed flow regime can be achieved, which allows for utilisation of the benefts of both systems in one unit, depending on the changing conditions in the manufacturing plant.

The importance of proper design that allows for at least 200-300 % recycle of clarified effluent is emphasised by the presented data on easily biodegradable wastes, contrary to some literature information advocating against recycle. The value of the potential design/recycle ratio (N) should increase with the decrease of biodegrad- ability, the increase of the manufacturing product changes and with the increase of the variability of incoming raw waste loading (RWL). Usually, larger agricultural manufacturers have smaller variability in wastewater quality and then the recycle plays mainly the role of enzyme replenishment, slime wetting during dry periods, and is the basic operator's control of the sloughing (unloading) of the inert biomass which may accumulate randomly due to RWL variations or environmental changes.

In summary, aerobic biofilters are very well suited for much wider application in the agricultural industry waste treatment. Recent energy shortages have improved

296 JAN A. OLESZKIEWICZ

the e c o n o m i c feas ibi l i ty o f the a n a e r o b i c sys tems. T h e ease o f m a i n t e n a n c e and g o o d

p e r f o r m a n c e o f f ixed-bed a n a e r o b i c r eac to r s m a k e s t h e m a des i red p r e t r e a t m e n t , o r

s e c o n d a r y t r e a t m e n t a l t e rna t ive , in the case o f s t r o n g so lub le o r g a n i c was tewa te r s .

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ASKEW, M. W. (1966, 1967). Plastics in waste treatment. Process Biochemist ry, No. 12, 1966; No. l, 1967. ECKENFELDER, W. W., ROTH, J. A., MCMULLEN, E. & OLESZKIEWICZ, J. A. (1974). Effluent quality in the

frozen potato processing industry. Tech. Report 2, CIWQ Mgmt, Vanderbilt University, Nashville. HEMMING, M. L & WHEATLEY, D. (1979). LOW rate biofiltration system using random plastic media. War.

Pollut. Control, 54-68. HEPrERD, R. Q. & CHARLOCK, R. H. (1977). The performance of an experimental high-rate biological

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MOODIE, S. P. & GREENFIELD, P. F. (1978). Treatment of abattoir effluent by trickling filtration. J. Wat. Pollut. Control Fed., 50, No. 12, 2741-51.

MOSEY, F. E. (1977). Anaerobic biofiltration: A biological process for warm trade waste waters. Tech. Report 48, Water Research Centre, Stevenage, UK.

NATIONAL CANNERS ASSOCIATION. ( 197 I). Trickling filter treatment of fruit processing wastewaters. US EPA WPCR Series 12060 EAE 09/71, Washington.

OLESZKIEWlCZ, J. A. & ECKENFELDER, W. W. (1974). The mechanism ofsubstrate removal in high-rate plastic media trickling filters, Vanderbilt University Press, 277 pp.

OLESZKIEWICZ, J. A. (1975). Et~ciency of plastic media trickling filters operating under extreme organic loadings. Progress War. Technol., 7, No. 3/4, 607-15.

OLESZKIEWICZ, J. A., KOZIARSKI, S., JANOWSKI, K., JANICZEK, A., DOMARADZKI, R. & RYZNAR, G. (1980). Piggery wastewater treatment in Poland: Full scale practices and promising future techniques. ASAE Animal Waste Mgmt Conf. Proceed., Amarillo, Texas, 14-18 April 1980.

OLESZKIEWICZ, J. A., KOZlARSK1, S. & KWIATKOWSKI, Z. (1979). Chemical-biological treatment of piggery wastewaters. Environ. Protection Engng, 5, No. 2, 109-25.

OLESZKIEWICZ, J. A. (1976). Rational design of high-rate trickling filters, based on experimental data. Environ. Protection Engng, 2, No. 2, 85-105.

OLESZKIEWICZ, J. A. (1977). Theory and design of high-rate plastic media trickling filters. Prog. War. Technol., 9, 777-85.

PORTER, K. E. & SMITH, E. (1979). Plastic-media biological filters. Wat. Pollut. Control, 371 81. SMITH, D. W., et al. (1978). Treatment of effluent from a potato processing plant. War. Pollut. Control,

379-83. STRACEY, J. G. (1975). Treatment of abattoir and meat-processing effluent at Haverhill Meat Products,

Ltd. War. Pollut. Control, 74, No. l, 101-8. WOLSKI, T. (1960). Biofiltration of yeast industry and fruit and vegetable processing wastes (in Polish).

Prace lnstyt, i Laborat. Badaw. Przemys¢u Spozywcz., 10, No. 4, 628.3. WOLSKI, T.'(1971). Treatment of fruit and vegetable industry wastes. Part II. Biofiltration (in Polish).

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