Volume No. 6 Issue No.: 3 Page No.: 554-561 Jan-Mar 2012

 

EFFECT OF EFFLUENT RECYCLING AND SHOCK LOAD ON THE BIODEGRADATION OF ORGANIC SOLVENTS IN UASB REACTORS

 

U. G. Sawaiker*, K. G. Guptha1 and S. R. Asolekar2

1. Department of Civil Engineering, Goa College of Engineering, Farmagudi, Goa (INDIA)
2. Centre for Environmental Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai (INDIA)

 

Received on : September 25, 2011

 

ABSTRACT

 

This study describes the feasibility of anaerobic treatment of synthetic pharmaceutical wastewater using three identical 12.5 l (effective volume) bench scale up flow anaerobic sludge blanket (UASB) reactors (R1, R2 and R3) under mesophilic (27 ± 5 °C) conditions. Synthetic pharmaceutical wastewater with an average Chemical Oxygen Demand (COD) of 9000 mg/l using substrate as sodium acetate and solvents concentration of acetone 1000 mg/l and methanol 750 mg/l as co-substrate was used as feed. Effluent recirculation was employed at four different effluents to feed recirculation ratios (R/F) of 0.25, 0.5, 1.0 and 1.5 for 100 days to study the effect of recirculation on the performance of the reactors. Performance of the reactors improved with increase in effluent recycles. Recycling of 60% of the effluent (recycle ratio 1.5) has completely degraded acetone and methanol. COD removal improved from 96.19 to 98.44 % and 96.60 to 98.49% for acetone and methanol fed reactors respectively. The concentration of volatile fatty acids in the effluent was lower than the influent when effluent to feed recirculation was employed. A clear increase in alkalinity was also observed with increase in recirculation. Effect of shock load on the reactors revealed that solvents shock load up to 3.0 times increase in the normal input of solvents concentration did not affect the reactors performance irreversibly. The reactor could tolerate a continuous shock load of 3000 mg/l of acetone and 2250 mg/l of methanol for four days without failure.

 

Keywords : Pharmaceutical wastewater, Anaerobic reactor, Solvents, Biodegradation, Effluent recycle, Shock loading

 

 

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