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International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 11, Issue 7, July 2020, pp. 317-328, Article ID: IJARET_11_07_032 Available online athttp://iaeme.com/Home/issue/IJARET?Volume=11&Issue=7 ISSN Print: 0976-6480 and ISSN Online: 0976-6499 DOI: 10.34218/IJARET.11.7.2020.0 32

© IAEME Publication Indexed Scopus

PERFORMANCE EVALUATION OF MODIFIED SEQUENCING BATCH REACTOR (MSBR) FOR

TANNERY EFFLUENT TREATMENT R. Senthilnathan* and K. Thirumavalavan

Department of Chemical Engineering, Annamalai University, Annamalai Nagar, Tamilnadu, India

*Corresponding Author

ABSTRACT The tanning industry in Tamilnadu is familiar with its being a potentially

pollution-intensive industry. Tanneries are such industries which contributes a major part in water usage. The results of the lab analysis of the industrial wastewater

effluent show that the contamination is mainly due to high levels of Sulfides with an average of 1288mg/l. Chromium (trivalent) in the tanneries effluent range from 1.5-157mg/l in the end-of-pipe effluent and the level of chromium(Cr) from the chrome

path effluent is around 10064mg/l. Analysis of COD and BOD during the process show that the levels of COD ranged in between 1564mg/l 53056mg/l with an –

average value of 13894 mg/l. However, the BOD values ranged between 420– 27050mg/l with an average value of 4704mg/l which are above the limits of the

standard for discharge to the wastewater sanitary network, while values of TSS, settleable solids, phosphorous and total Nitrogen(N2) are within the limits. The results obtained from the biological treatment indicates the high effectiveness of the process

to reduce mainly TSS, COD and BOD besides appreciable reduction of other parameters mainly sulfides and nitrogen. The overall results of the treatability study indicate that the suspended solids are removed with almost 99% efficiency while the removal of COD & BOD levels reaches 93-95%.

Key words: Sequential Batch Reactor, COD, BOD, TSS, Tanneries Waste Water Cite this Article: R. Senthilnathan and K. Thirumavalavan, Performance Evaluation

of Modified Sequencing Batch Reactor (MSBR) for Tannery Effluent Treatment, International Journal of Advanced Research in Engineering and Technology, 11(7), 2020, pp. 317-328.

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Performance Evaluation of Modified Sequencing Batch Reactor (MSBR) for Tannery Effluent Treatment


1. INTRODUCTION 1.1. SBR Reactor

Acrylic material was used for the fabrication of SBR of volume 5 litres. The reactor was provided with a sludge settling zone, clear water zone, outlet port and sludge with drawl port The oxygen needed for the oxidation of organics in wastewater was provided in the form of air supplied from the bottom of the reactor through spargers (5 numbers) at a pressure of 0.5 kg/cm2.

1.2. Wastewatcr The wastewater used in the present study was transported from a leather industry engaged in processing raw to El leather. The wastewater collected from the industry was transported to the laboratory immediately hi refrigerated vessels. The wastewater was screened to remove

coarse floating solids and fine grit like sand. The settled wastewater was fed to the SBR through a peristaltic pump to avoid shock load to the microbial mass.

1.3. Start up of SBR The sludge required for the seeding of the reactor was organized from the activated sludge process employed for the treatment of wastewater discharged from an industry processing raw goat/sheep skins to E.I leather. The sludge was acclimatized to the wastewater hi stage wise addition of tannin concentration of 50 mg/L- After the tannin concentration had reached the required level, the wastewater was applied as a bulk with the required addition of micro and macronutrients.

Among the entire industrial outlet, tannery effluents are stand as the highest pollutants of Red-

There are about2161 tanneries running in India apart from smallscale industry, which annually processes 500,000tonnes of hides and skins. Annual release of effluent from these

tanneries is about 9,420,000m3 , which provokes about 100,000m3 of waste water per day (Mohan 2006) and these industries generally situated in Tamil Nadu, West Bengal, et al.,

Uttar Pradesh, Andhra Pradesh, Karnataka, Rajasthan and Punjab (Lefebvre 2005). In et al., Tamil Nadu alone there are approximately 1120 tanneries concentrated in Vellore, Ranipet, Tirchy, Dindigul, Erode and Pallavaram in Chennai. There are about 49functional tanneries in

and around Dindigul town, Tamil Nadu. It was estimated that about 76,400-85,600kg of leather was produced in Dindigul town every day (Basker, 2000). Tanning process involves the use of huge amount of fresh water and various chemicals include lime, sodium carbonate, sodiumbi-carbonate, common salt, sodium sulphate, chrome sulphate, fat, liquors, vegetable oils, dyesetc. Tannery pollution has spread over about 100km2 in and around Dindigul town (Mondal 2005). et al.,

Groundwater in shallow dug well emits foul smell and colour has also become dark due to there lease of effluent. The effluent discharged from tanneries contains high value of pH, EC,

chlorides, sulphide, sulphate, carbonate, chromium, BOD,COD, oil and dyes. Due to the complex tannery pollutants, it was not suitable for cultivation and hence the income of the people of this area has been completely lost. The fauna and flora of the land to a radius of 6 kms are already affected(Apparao and Karthikeyan, 1990).

Sequencing Batch Reactor (SBR) is a modified activated sludge biological treatment process used in solving the low density bio-sludge and bulking problems due to a large

volume of the clarifier. SBR technology has higher COD and nitrogen removal rates at comparatively shorter HRT. It is also cost effective and flexible. Sequencing batch reactor is a fill and draw type sludge system which operates in time rather than in space. SBR performs

R. Senthilnathan and K. Thirumavalavan


equalization, neutralization, biological treatments and secondary clarification in a single tank using timed control sequence and in some cases primary clarification. Sequencing batch

reactor consists of single tank equipped with an inlet for wastewater, air diffuser with compressor and piping for aeration, sludge drawing mechanism for draining sludge, decant mechanism for drawing supernatant, stirrer for inducing aeration and control mechanism for operation control with respect to time and sequence. The objectives of the study are 1) To

evaluate removal efficiencies of organic content and Suspended Solids(SS) in Tannery wastewater using Sequencing Batch Reactor. 2) To optimize the Hydraulic Retention

Time(HRT), Volumetric Loading Ratio(VLR) for the primary treated Tannery effluent.

Advantages and Disadvantages Equalization, primary clarification (in most cases), biological treatment, and

secondary clarification can be achieved in a single reactor vessel. Operating flexibility and control. Minimal footprint. Potential capital cost savings by eliminating clarifiers and other equipment.

2. MATERIALS AND METHODS 2.1. Sample Pallavaram is a suburban town of Chennai Metropolitan. It is one of the important tannery

clusters in Tamil Nadu, India. There are nearly 119 Tannery units in and around Pammal/Pallavaram area.

2.1. Sludge for Acclimatization The return activated sludge to be used in the treatment process is also collected from the

secondary tank in the CETP at Pallavaram, Chennai, Tamilnadu.

2.2. SBR Reactor An acrylic reactor of diameter 10cm and height 90cm is fabricated. The total volume of the reactor is 7L, with a working volume of 5L. It is fitted with a motor to the stirrer for even distribution of air. Air supply is achieved through air pump and diffuser at bottom.

Figure 1 Experimental setup of SBR Reactor

Feed Tank

SBR Air Diffuser

Effluent Tank

Deccant Tank



The schematic representation of the experimental setup is shown in figure 2. The tanneries withdrawal outlet, effluent withdrawal and Decant outlet are placed at 2cm, 5cm and 15cm respectively from the bottom of the tank.

2.3. Methodology The major steps involved include the adjustment of MLSS for treatment, Treatment of the wastewater in the reactor for optimization and the study on removal efficiencies.

2.4. Operational Strategy of the SBR

Table 1

Parameter Condition Cycle Time(min) 720 Voulme Exchane Ration 0.4 HRT 30 Filling Phase min 5 Settling Phase min 45 Withdrawal min 15

2.5. Biological Treatment Clarified effluent from chemical treatment is then passed to a biological reactor made of glass cylindrical column with a size of 10cm diameter and 90cm height. The treatment process was conducted batch-wise according to the following stages:-

Sludge adaptation stage for a continuous period of 20 days where an amount of activated sludge is mixed with effluent to be treated and air is injected continuously. This stage allows the acclimatized bacteria to grow and multiply.

Treatment of effluent in batches each batch with a retention time of 18hours with injection of air to keep the dissolved oxygen at not less than 2mg/l.

Monitoring during the biological reaction for activated sludge concentration (MLSS) and dissolved oxygen (D.O) where carried out and at the end of reaction the MLSS reach about 3.5mg/l and D.O 2.3mg/l.

Settling of the activated sludge in the column and siphon out the clarified effluent. Refilling of the column with untreated effluent in the presence of sludge blanket

while, injecting air and the above stages was repeated. The results obtained from the biological treatment indicates the high effectiveness of

the process to reduce mainly TSS, COD and BOD besides appreciable reduction of other parameters mainly sulfides and nitrogen. The overall results of the treatability study are shown in table (11), which indicates that the chemical/biological treatment is an effective technique for removing pollutant from Tanneries effluent. The suspended solids are removed with almost 99% efficiency while the removal of COD & BOD

levels reaches 93-95%. The quality of the treated effluent is incompliance with regulatory limits for discharging industrial effluent to public sewer and these levels sustained for consecutive four weeks of feeding the reactor with chemically treated effluent.



3. RESULTS AND DISCUSSION 3.1. Sample Characterisation The study was conducted in CETP at Pammal in Chennai district. The treatment plant treats tannery effluent from tannery industries located in and around Pallavaram nicipality. The Mu

treatment system adopts activated sludge process. Wastewater was collected from the equalization tank, primary clarifier, aeration tank, secondary clarifier and treated effluent and

was characterized for pH, TDS, TSS, COD, BOD, chloride, sulphate, chromium as per standard methods of wastewater analysis (APHA, 2005).

Table 2 Wastewater characteristics

Parameters Influe nt

Chara eristics ct ofCETP

T era e mits ol nc Liaccording o

TNPCB pH 7.0-8.1 6.0-9.0 TDS 5500-8300mg/L 2100mg/L TSS 1000-2000mg/L 100mg/L COD 3500-5000mg/L 250mg/L BOD 1100-1600 mg/L 30 mg/L Chloride 1000-2000mg/L 750-2000mg/L Sulphate 40-50 mg/L 2 mg/L Chromium 0.01-0.02mg/L 2 mg/L

Table 3 Results of the Treatability Study

Parameters Initial After

Primary Setting

After Chemical Treatment

After Biological Treatment

Total Efficiency

(%) pH 10.5 9.5 7.5 7.2 - BOD mg/l 6721 3215 2500 485 92.7 COD mg/l 19628 10758 6958 1000 98.8 TSS mg/l 15824 2880 1160 186 98.8 Settable Soilds -10min, ml/l 478 0 0 0 100 Settable Soilds -30min, ml/l 485 0 0 0 100 Sulfides mg/l 1872 39 14 5 99.8 O &G mg/l 114 64 45 17.9 84.8 Phosphates mg/l 34.8 31 14 6.9 81.5 Cyanides mg/l 0 0 0 0 Total Nitrogen mg/l 251 85 59 11.8 95 Chromium(Cr) mg/l 152.91 153.74 0.38 0.11 99.9 Phenols mg/l 0.72 0.14 0.006 0 100

3.2. Acclimatization of Sludge The obtained sludge from Pallavaram CETP is acclimatized with the Tannery wastewater.

checked on a three days basis upto twenty seven days and the values are shown in the form of a graph in figure 2. MLSS concentration required to start the biological process in SBR is 3600 mg/L.



Figure 2 Variation of MLSS Concentration with Time

Biological process in modified SBR can be started once the MLSS reaches 3600mg/L. Variation of MLSS concentration with time is mentioned above. Hence, the reactor can be started.

3.3. Optimization Studies in SBR Optimization of parameters organic loading rate, residence time and volumetric loading rate were done in the modified sequencing batch reactor for tannery wastewater.

1) Effect of Organic Loading Rate(OLR) The effect of organic loading rate for the degradation of tannery effluent was studied for a HRT of 8 hours at a constant volumetric loading rate(VLR) of 85%. OLR was varied between 2.15, 3.24, 7.18 kgs of COD/m3/day. The effect of OLR on COD removal was tabulated in table 3. OLR is varied by using the dilution method.

Table 4 Effect of OLR on COD Removal

OLR (Kg COD/m3/day)

Influent (mg/L) Effluent(mg/l)

Removal Efficiency

in % 2.15 532 111 79.1 3.24 709 191 74.0 7.18 1064 374.35 64.1

Figure 3 Effect of OLR on COD Removal

1 3 6 9 12 15 18 21 24 27MLSS 1500 1650 1700 1850 2100 2300 2600 2950 3400 3600

0

500

1000

1500

2000

2500

3000

3500

4000

ML

SS C

once

ntra

tion

in m

g/L

Variation of MLSS Concentration with Time

2.15 3.24 7.18Removal Efficiency in % 79.1 74 64.1

0

10

20

30

40

50

60

70

80

90

Rem

oval

Eff

icie

ncy

in %

Effect of OLR on COD Removal



COD removal was due to the aerobic biological treatment where the biodegradable organics are degraded by the mixed population of microorganisms.

Table 5 Effect of OLR on BOD Removal

OLR (Kg COD/m3/day)


Removal Efficiency

in % 2.15 216 24 89.4 3.24 294 42 85.1 7.18 439 96 78.5

Figure 4 Effect of OLR on BOD Removal

BOD removal efficiency decreased from 89% to 85% when the organic loading rate increased from 2.15 to 3.24kgs COD/m3/day.

Table 6 Effect of OLR on suspended soilds Removal

OLR (Kg COD/m3/day)


Removal Efficiency

in % 2.15 612 93 84.6 3.24 824 138 82.8 7.18 1226 269 79.1

The removal efficiencies of COD, BOD and suspended solids are graphically represented in figure 4.

Figure 5 Effect of OLR on suspended soilds Removal

2.15 3.24 7.18Removal Efficiency in % 89.4 85.1 78.5

7274767880828486889092

Rem

oval

Eff

icie

ncy

in %

Effect of OLR on BOD Removal

2.15 3.24 7.18Removal Efficiency in % 84.6 82.8 79.1

7677787980818283848586

Rem

oval

Eff

icie

ncy

in %

Organic Loading Rate

Effect of OLR on suspended soilds Removal



It is known that increase in OLR decreases the COD removal rate. But, there is no significant difference in removal efficiency when the OLR is increased from 2.15 to 3.24kgs COD/m3/day. Hence, the optimum OLR is taken as 3.24kgs COD/m3/day.

2) Effect of Residence Time(RT) The effect of residence time on the degradation of tannery effluent was studied for 4, 6, 8 hours. It was noted that the degradation was effective at 8 hours.

Table 7 Effect of Residence Time on COD Removal

Residence Time (in Hours)


Removal Efficiency

in % 4 539 121 63.1 6 535 149 73.9 8 529 118 79.6

Figure 6 Effect of Residence Time on COD Removal

The COD removal increases with increasing time. Maximum COD removal was observed at 8 hours with an efficiency of 79.6 %.

Table 8 Effect of Residence Time on BOD Removal



Removal Efficiency

in % 4 294 67 78.9 6 288 56 83.2 8 275 33 89.9

Similar to COD removal, BOD removal also increases with time. Maximum BOD removal was seen at 8hours with an efficiency of 89.9%. Figure 4.3 shows the BOD removal efficiency with respect to time.

01020304050607080

4 6 8

Rem

oval

Eff

icie

ncy

in %

Residence Time in Hrs

Effect of Residence Time on COD Removal



Table 9 Effect of Residence Time of suspended Soilds Removal



Removal Efficiency

in % 4 819 65332 64.6 6 836 53202 79.7 8 828 29124 89.7

The removal of suspended solids increases with time. Greater the residence time, greater

is the time for degradation. Due to higher residence time, the organics were converted to biomass and they settle down as sludge. The organic and suspended removal rates are

represented graphically in figure 8.

Figure 7 Effect of Residence Time on BOD Removal & SS Removal

3) Effect of Volumetric Loading Rate(VLR) The tannery effluent was studied for optimum volumetric loading rate by varying the VLR between 65%, 75%, 85%, 95% using the optimum residence time of 8hours. The results were discussed for COD, BOD and Suspended solids(SS) removal.

Table 10 Effect of VLR on Removal COD

Volumetric Loading Rate

in %


Removal Efficiency

65 291 61 79.2 75 279 43 84.7 85 282 36 87.2 95 289 23 92

Table 10 shows the COD removal rates at various VLR. The COD removal was found to be maximum at a volumetric loading rate of 95%. With the increase in VLR, the substrate utilization also increases. The removal efficiency was maximum when the fill volume was 4.75L.

4 6 8BOD -Removal Efficiency

in % 78.9 83.2 89.9

SS-Removal Efficiency in% 64.6 79.7 89.7

0102030405060708090

100

Rem

oval

Eff

icie

ncy

in %

Effect of Residence Time on BOD Removal & SS Removal



Table 11 Effect of VLR on Removal BOD

Volumetric Loading Rate

in %


Removal Efficiency

65 291 61 79.2 75 279 43 84.7 85 282 36 87.2 95 289 23 92

Table 11 shows the BOD removal rates for varying VLR. Maximum removal of 92% was

observed at VLR of 95%.Table 12 shows the suspended solids removal rates for varying VLR.

Table 12 Effect of VLR on SS Removal Volumetric

Loading Rate in %

Influent (mg/L)

Effluent(mg/l) Removal Efficiency

65 707 251 64.5 75 702 194 72.4 85 693 144 79.2 95 699 126 82

Maximum removal of 87.2% was observed at VLR of 95%. When the volume of fill increases, the OLR decreases. Substrate utilization was found to increase with increase in

OLR. Hence, an optimum VLR of 95% can be considered for effective removal with COD removal efficiency of 82%. Figure 8 represents the removal efficiencies of COD, BOD and suspended solids removal efficiencies for varying volumetric loading rates.

Figure 8 Effect of Voulmetric Loading Rate

Many treatment processes were made for treating the wastewater viz., chemical oxidation, adsorption, ultra-filtration, reverse osmosis, and biological treatment. Biological degradation can be adopted when the BOD/COD ratio is greater than 0.4, these methods are easier and

cost effective. Concerning the biological processes, the adoption of fill-and-draw systems known as SBR can be a reasonable solution to solve the operational problems of conventional activated sludge process. SBR are known to be highly flexible in terms of operation and the operational parameters can be varied with the reactor.

0

10

20

30

40

50

60

70

80

90

100

65 75 85 95

Rem

oval

Eff

icie

ncy

in %

Volumetric Loading Rate in %

Effect of Voulmetric Loading Rate

COD-Removal Efficiency

BOD-Removal Efficiency

SS-Removal Efficiency



Table 13 Summary of the studies are tabulated below

Operating Variables Optimized Conditions

Results in Removal (%)

Residence Time 8 Hours COD-79.4% BOD- 90.4 Suspended Soilds: 86.8

Organic Loading Rate 3.40kg COD/m3/day

COD 79.4% BOD -89.6 Suspended Soilds 85.2%

Volumetric Loading Rate 95%

COD 79% BOD -92% Suspended Soilds 82.3%

The following conclusions are drawn from the study:

1) Acclimatization improves the degradation process by increasing the MLSS concentration 2) SBR proves to be a flexible technology for treatment of wastewater 3) The removal efficiencies are maximum at VLR of 95% for a HRT of 8 hours and optimum organic loading rate is 3.24kgs COD/m3/day 4) BOD and suspended solids for discharge standards can be met using SBR and it proves to be a promising technology

4 CONCLUSION . The results obtained from the biological treatment indicates the high effectiveness of the

process to reduce mainly TSS, COD and BOD besides appreciable reduction of other parameters mainly sulfides and nitrogen. The overall results of the treatability study indicate that the suspended solids are removed with almost 99% efficiency while the removal of COD

& BOD levels reaches 93-95%. The quality of the treated effluent is incompliance with regulatory limits for discharging industrial effluent to public sewer and these levels sustained

for consecutive four weeks of feeding the reactor with chemically treated effluent. As a conclusion, from the study, it is concluded that the physico-chemical treatment followed by

biological treatment process using SBR system is the most reliable alternative treatment method for this kind of industry.

5. FUTURE STUDY The study can be further extended to Optimize Solids retention time and number of

operational cycles per day, study degradation rate using packing media as carrier elements in SBR and sulphate, nitrogen removal can also be studied.

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