Aerobic and anaerobic treatment of fruit juice industry effluents - NOPR

Journal of Scientific & Industrial Research Vol. 65, October 2006, pp. 830-837

Aerobic and anaerobic treatment of fruit juice industry effluents Emine Elmaslar Ozbas1,*, Nese Tufekci1, Gulsum Yilmaz1 and Suleyman Ovez2 1

Istanbul University, Faculty of Engineering, Environmental Engineering Department, Avcilar, 34320, Istanbul, Turkey Istanbul Technical University, Faculty of Civil Eng, Environmental Engineering Department, Maslak, 34469, Istanbul, Turkey

2

Received 02 December 2005; accepted 05 June 2006 This study investigates biological treatment of fruit juice industry effluents in sequencing batch reactor (SBR), activated sludge reactor (ASR) and anaerobic upflow sludge blanket reactor (UASB). At anaerobic biological treatability studies, seed sludge was acclimated to the medium and 95% of COD removal was obtained within a few weeks. At the end of anaerobic study, organic loading rate was increased to 5 kg COD/m3-day and the hydraulic retention time was decreased to 2.3 days. At the aerobic biological treatability studies, 90-95% soluble COD removal was achieved for both wastewaters (sour cherry and apple) in SBR and in ASR. In addition to aerobic biological treatability studies, microbiological investigation, and kinetic and stociometric coefficients were determined. At the end of microbiological examination, fungi overwhelmingly dominated the system. Keywords: Activated sludge, Anaerobic up flow sludge blanket reactor (UASB), Fruit juice industry wastewater, Sequencing batch reactor (SBR) IPC Code: C02F3/12

Introduction Wastewater effluents from the fruit juice industry contain primarily high concentrations of organic materials, which are occasionally discharged into the municipal wastewater collection system and processed in wastewater treatment plants along with domestic wastewater. Major problems in the treatment of raw effluents from the fruit juice industry are low pH values, imbalance of nutrients, and the very considerable fluctuations in the amount of effluent and waste matter produced1,2. Sequencing batch reactor (SBR) is successfully applied to the treatment of strong wastewaters with effective organic carbon and nutrient removal3-5. Anaerobic upflow sludge blanket reactor (UASB) is a simple and easily operated anaerobic system. In such systems, sufficient refining efficiency can be achieved at low temperatures, as well as high temperatures6. This study deals with the anaerobic and aerobic treatments of wastewater from fruit juice industry before it is discharged into the municipal wastewater treatment plant. In addition to treatability studies, kinetic and stociometric coefficients (maximum ___________ *Author for correspondence Tel: +90 212 4737070/17732; Fax: +90 212 4737180 E-mail: [email protected]

specific growth rate µˆm and endogenous decay rate bH) were determined for aerobic treatment systems. Materials and Methods UASB Reactor consisted of: total volume, 16.5 l; internal diam, 12 cm; and height, 150 cm. Feeds were prepared each day and pumped to the reactors using variable speed peristaltic pumps. Anaerobic reactor is thoroughly mixed due to influent input from the bottom of tank and gas emission during treatment, which also drag a portion of the biomass when rising. Gas bubbles that are separated from the liquid and solid phases at the bottom of the funnel, which is placed to the precipitation section, leave the system with the gas line. In the mean time, released sludge particles return to the body. Similarly, some amount of sludge, which is dragged with the hydraulic upflow, precipitates at the stable exterior part of the funnel and returns to the body section. The treatment efficiency is improved through efficient mixing and contact of the effluent with biomass in the reactor. Activated sludge reactor (ASR) and SBR were operated with a hydraulic retention time (HRT) of 24 h, sludge age of 10 days and F/M ratio 0.5 (Table 1). After start-up period (24 h), SBR was operated with a cycle time of 12 h.

OZBAS et al: AEROBIC & ANAEROBIC TREATMENT OF FRUIT JUICE INDUSTRY EFFLUENTS

Table 1Characteristics of activated sludge and sequencing batch reactors Characteristics

Activated sludge reactor

Liquid volume, l Internal diam (Φ), cm Height, cm Sludge age, day F/M (F= COD; M=MLVSS) ratio

Sequencing batch reactor

4 12 80 10 0.5

4 14 64.5 10 0.5

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Analytical Methods

The reactors’ pH and temperature were controlled continuously. The main parameters including COD, alkalinity, total suspended solids (TSS), volatile suspended solids (VSS) and sludge volume index (SVI) were measured. All analyses were carried out in accordance with Standard Methods7. Maximum growth yield and endogenous decay rate were determined by using respirometric method2. Wastewater Characterization

Table 2Characterization of wastewaters Parameters

Sourcherry juice wastewater Sourcherry juice concentrate Apple juice wastewater Apple juice concentrate

COD mg/l

TKN mg/l

TP mg/l

1000-8000

3.3-55

0.104-10

1.000.000

3000

95

1600-2500

73-114

0.63-0.98

124.800

5694

49.14

Table 3Biogas production in the UASB reactor Parameter

Min.

Max. Average

As fruit juice wastewater is poor in nutrients (Table 2), NH4Cl and Na2PO4 were added to influent to improve C:N:P in anaerobic studies (C/N/P=300/5/1) and in aerobic studies (C/N/P=100/5/1). Besides, in anaerobic studies, system was fed with NaHCO3 in order to provide enough alkalinity in the reactor and to buffer the CO2 and volatile acids. Temperature (35-37°C) and pH (6.5-7.8) within the reactor were maintained in anaerobic studies. pH was maintained around 7.0 by NaOH addition during aerobic studies. Reactors were inoculated with the sludge taken from Pasabahce Tekel Raki Factory.

St. deviation

Results and Discussion Volatile loading rate, kgCOD/m3 day Biogas production, m3/day

2.3

21.1

880 11.000

5.7

2.2

5.500

1.980

Fig. 1COD removal efficiency values determined in UASB reactor for fruit juice effluent. CODi: Influent COD; CODe: Effluent COD

Anaerobic Treatability Studies

During the start-up period, main parameters in reactor were: Organic loading rate (OLR), 1.40 kg COD/m3/day; HRT, 5.7 days; VSS concentration, 7700 mg/l; and pH, 7-8. In this period, the seed sludge was acclimated to the medium and 95% of COD removal was obtained within a few weeks (Fig. 1). This period was observed for 73 days with no problems. After the start up period, OLR was increased to 3.47 COD/m3/day and HRT was decreased to 2.3 days. In the first few days, the efficiency dropped due to instability of pH and increase in OLR was observed. Buffering the feeding effluent with NaHCO3 resulted in 90% of COD removal in the system within 10 days. During this period, OLR was kept at 3.37-5 kg COD/m3/day for 30 days and 90% of COD removal was obtained on the average. The effluent COD value was kept between 600-800 mg/l except for the over loadings (Fig. 1). During the study, biogas production in the UASB reactor was about 0.395 m3 CH4/kg COD removed and the average CO2 ratio in the biogas was 20% (Table 3).

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Table 4Main parameters of sour cherry juice for ASR Time days

CODi mg/l

CODe mg/l

COD removal efficiency, %

13 14 20 26 34 39 42 43 49 50 56 74 75 76 83 90 97 104 111 116 120 123 133 Average Standard deviation

2875 1145 1200 1400 1260 750 950 950 990

45 90 70 135 125 60 145 85

96 92 94 89 83 94 85 92

1145 1000 1310 1310 1085 1190 1500 1350

95 130 95 180 130 90 85 45

92 86 92 86 88 92 92 97

1030

45

96

1600 1100 1257 432.3023

75 50 93.42105 38.47

95 95 91.368 4.119

Aerobic Treatability Studies Studies with Sour Cherry Juice Wastewater

Reactors were operated using sour cherry juice wastewater during 133 days with HRT of 24 h and 80-96% COD removal. Aeration and settling period used in ASR were approx 23 h and 30 min, respectively. The durations for filling, aeration, settling and withdraw phases were 45 min, 22 h and 15 min, 30 min and 30 min, respectively, for SBR. After the start-up period, ASR was operated at: HRT, 24 h; aeration period, 23 h; and settling period, 30 min. After 45th day, SBR reactor was operated with a cycle time of 12 h. During second stage, the durations of filling, aeration, settling and withdraw phases for SBR were 45 min, 10 h and 15 min, 30 min and 30 min, respectively. After start-up period, average COD removal were achieved for ASR and SBR as 92% (Table 4) and 93% (Table 5), respectively. MLSS and MLVSS decreased after day 50, because a little amount of microorganism was removed from the reactor to maintain the sufficient settling (Table 4). When OLR changed, COD removal values decreased because of insufficient aeration. In SBR, when operating cycle was changed as 12 h, microorganism concentration increased rapidly. SVI

TSS mg/l

MLVSS mg/l

5890

5330

4520

4150

3600

3590

3540

3370

3940

3600

2760

2610

2990

2810

4320 2390 2990

4160 2310 2740

2550

2420

3080 3547.5 999.17

2870 3330 890.372

values varied for ASR (30-90 ml/g) and for SBR (30-80 ml/g). Studies with Apple Juice Wastewater

Reactors were fed with apple juice wastewater. In this period, ASR was operated with a cycle time of 24 h, and SBR with a cycle time of 12 h. The durations of filling, aeration, settling and withdraw phases for SBR were 45 min, 10 h and 15 min, 30 min and 30 min, respectively. After 35 days, the influent COD was increased from 1600 mg/l to 2750 mg/l. COD removal efficiencies were 90% or higher until 45 days of operation. After initial COD increased, COD removal decreased from 90% to 70-75% during 15 days in both reactors (Tables 6 and 7). Because of this, operation cycle time was increased (24 h) and VSS concentration was decreased (4000 mg/l) in SBR. Beginning from 65th day, COD removal values of both reactors reached 85% and above. COD removal values reached 90% in the 90th day (Tables 6 and 7). SVI values were recorded as 30 ml/g in ASR and 43 ml/g in SBR on the 36th day and remained at the same level until the 45th day. When initial COD values were increased, sludge settling was worst until 100th day. Beginning from 100th day, sludge settling


Table 5Main parameters of sour cherry juice for SBR Time days

CODi mg/l

CODe mg/l


TSS mg/l

MLVSS mg/l

13 14 20 26 34 39 42 43 49 50 56 74 75 76 83 90 97 104 111 116 120 123 133 Average Standard deviation

2875 1145 1200 1400 1260 750 950 950 990

305 55 70 70 75 145 80 105 90

89 95 94 95 94 81 92 89 91

2400

2310

2720

2550

3440

3030

3860

3440

3620

3360

1145 1000 1310 1310 1085 1190 1500 1350

50 130 110 160 70 105 50 45

96 86 91 88 93 91 95 97

3310

3130

3830

3580

5070 3360 4130

4800 3240 3840

1030

35

97 5850

5620

1600 1100 1257 432.3

40 65 92.75 60.94

98 94 92.3 4.193

4960 3879.167 996.415

4750 3637.5 972.776

Table 6Main parameters of apple juice for ASR Time days

CODi mg/l

CODe mg/l


TSS mg/l

MLVSS mg/l

3 7 8 10 15 16 17 22 23 31 36 39 43 45 49 51 52 56 58 59 61 62 65 69

1650 1625 1625 1600 1600 1585 1600 1600 1600 1600 1900 2735

55 90 60 90 95 105 105 55 70 208 195 400

97 94 96 94 94 93 93 97 96 87 90 84

2790

2490

3560

3440

6610

6450

2740

1440

48 5920 1980 2530

5800 1960 2440

4180

3910

3470

3250

2160

2040 (Contd)

1755

1130

60

2900

360

87

2970 2500

720 320

76 87

833


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Table 6Main parameters of apple juice for ASRContd Time days

CODi mg/l

CODe mg/l


72 78 84 91 97 98 116 117 125 131 139 Average Standard deviation

2650 2635 2500

405 300 240

85 88 90

2750 2470

216 130

92 95

2560 2500 2500 2166 527.51

110 144 125 286.72 339.88

96 94 95 88.32 11.589

TSS mg/l

MLVSS mg/l

2520 3400 3340 3270

2990 3100 3025

4220 4550 5290 5830 3860 1383.97

3980 4277 5025 5538 3732.188 1365.53

Table 7Main parameters of apple juice for SBR Time days 3 7 8 10 15 16 17 22 23 31 36 39 43 45 49 51 52 56 58 59 61 62 65 69 72 78 84 91 97 98 116 117 125 131 139 Average Standard deviation

CODi mg/l

CODe mg/l


1650 1625 1625 1600 1600 1585 1600 1600 1600 1600 1900 2735 2775 2740

55 45 70 50 115 110 80 55 80 208 184 761 640

97 97 96 97 93 93 95 97 95 97 90 70 76

1755

675

75

2900

1340

54

2970 2500

930 380

85

2650 2635 2500

70 375 380

97 86 85

2750 2470

192 217

93 91

2560 2500 2177 537.542

105 128 301.875 335.842

96 95 89.13043 10.943

TSS mg/l

MLVSS mg/l

4610

4460

5040

4650

4710

4500

8320

8060

11280 3780 4400

10290 3760 4200

3480

3340

4080

3880

3730 5170

3560 4900

4450 3440 3900 4610

3220 3600 4240

5170 6460 6560 5610 5200 1909.77

4940 6201 6232 5330 4964.611 1799.33


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Fig. 2Determination for sour cherry juice wastewater of: a) Endogenous decay rate; b) Maximum specific growth rate

Fig. 3Determination for apple juice wastewater a) Endogenous decay rate; b) Maximum specific growth rate

begun to be good. SVI value was 80 ml/g in SBR and 50 ml/g in ASR in the 125th day8.

Microbiological Examination and Monitoring of Aerobic Reactors’ Systems

Determination of Kinetic Coefficients Determination of Endogenous Decay Rate (bH)

A reactor (vol, 2 l; initial biomass conc, 2000 mg/l) was started for the determination of bH. Oxygen consumption rates (OCRs) were measured during 10 days for sour cherry juice wastewater. During 12 days, OCRs were measured for apple juice wastewater. Then, a graphic was drawn for each wastewater using these values (Figs 2a and 3a). Slope of the curve on graph is equal to bH, which for sour cherry juice wastewater and apple juice wastewater was 0.32 day-1 and 0.13 day-1, respectively. Determination of Maximum Specific Growth Rate (µˆm)

A reactor (2 l) with F/M=4 mgCOD/mgMLVSS was prepared for each wastewater. OCRs were measured during 1 h. A graphic was drawn using these values for each wastewater (Figs 2b and 3b). Slope of the curve on graph is equal to (µˆm-bH). The µˆm values were determined for sour cherry juice wastewater and apple juice wastewater as 5.15 day-1 and 6.18 day-1, respectively.

of:

Microbiological examination of apple juice production wastewater treatability research in both aerobic reactors was begun at 69th day and continued for the following 20 days. Most interesting observation was the overwhelming dominance of fungi, Aspergillus spp. (Fig. 4). This does not support the previous arguments that growth rates associated with bacteria are higher than fungi9. These filamentous fungi cells have septa and foot cell belonging to Aspergillus genus. Abundance of fungi filaments was classified10,11 as “excessive” or “dominant”. The number of the filaments was over 50 within each floc, almost completely covering them. This situation was probably caused by wastewater composition of fruit juice production and pH. Because the content of wastewater of fruit juice production had very rich fruit sugar and other carbohydrates. pH of the system has decreased to 6-6.5 and even under 6 even though the system pH was everyday adjusted to 7-7.5. Slightly acidic pH values and high carbohydrate concentration are very favorable to fungi, so they can multiply faster than other competitors and get advantage to dominate the system. Fungi can tolerate acidic conditions and

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Fig. 4Microphotos belonging to reactors

adverse environments better than bacteria. Another important cause of fungi domination is nutrient, especially nitrogen (N) and phosphorus (P) is that bacteria can flourish and multiply even in very low concentrations of N and P9. N and P concentrations in wastewaters of fruit juice production are very low (N: 3.3-114 mg/l; P: 0.104-0.98 mg/l). This kind of wastewater composition can provide advantage primarily to fungi. It can be said that fungi are good and valuable microorganisms to treat this kind of wastewaters. On the other hand, this can be a problem in aeration tank for bulking and in final sedimentation tank for settlement of solids. These problems can cause process control and low effluent quality problems11. Filamentous fungi (Aspergillus spp.) has increased rapidly and dominated to the systems after 78th day. Abundance of filamentous fungi reached “excessive” numbers and caused solid separation and bulking problems in apple juice production wastewater

treatability research. This problem has been determined by microscopic examinations of the activated sludge and the result of SVI measurements (>150 ml/g). Fungi domination has not caused significant decrease in COD removal yield other than some slight decline. Zoogleal floc structure of the activated sludge was very good and appearance was normal. During the microbiological examinations, a few kinds of ciliated, attached and flagellated protozoa, a filamentous bacterium species, a filamentous fungus, and gram-negative and grampositive bacteria have been observed in floc structure. An unidentified filamentous bacterium, which contributed to floc macro-structure with 2-3 filaments/flock in normal times, has helped to overcome settlement problem of the activated sludge. Filamentous bacterium has caused settlement problem when the filaments spread into bulk solution from the floc, causing a decrease in density of the floc. It has not caused settlement and bulking problems when it


stayed in the floc structure. Fungi filaments have increased their numbers overwhelmingly in 100th day of operation, and all flocs have been completely covered by fungi filaments and even flocs could not be seen due to the abundance of filaments. Fungi spores have also contributed to this structure. There was no settlement or bulking problems in these situations. Probably, the reason is that, eukaryotic cells (fungi cells) are bigger, heavier and longer than prokaryotic cells (filamentous bacteria), so they could settle easily. Whenever filamentous bacteria have increased their numbers and spread out from the flock towards the bulk solution, settlement and bulking problems have occurred. Conclusions In anaerobic treatment of fruit juice industry wastewaters (≥ 90%) COD removal efficiencies were obtained with an organic loading up to 5 kg COD/m3/day. In aerobic treatability studies, high COD removal (≥ 90%) was obtained at treatment studies of each wastewater at cycle time of 12 h in SBR. Sometimes, COD removal values decreased. When OLRs were changing and if there was not enough aeration, low COD removal values were observed. There were not settling problems in aerobic treatability studies. Sometimes, SVI values increased depending on pH. The difference in the endogenous decay coefficient and maximum specific growth rate constant for apple juice and sour cherry juice wastewaters was caused by the different easily biodegradable fractions of wastewaters. At the end of microbiological examination, fungi overwhelmingly dominated the system. But, there were no settlement or bulking problems in these situations.

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Acknowledgements This research was supported by the Research Fund of Istanbul University (Project Number: BYP281/03112003). References 1

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