Date of Award

Spring 1991

Document Type

Thesis

Degree Name

Master of Science in Environmental Science - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Samir S. Sofer

Second Advisor

Richard B. Trattner

Third Advisor

Issac Gotleib

Abstract

Biological removal of methylene chloride was studied under aerobic and anaerobic conditions using activated sludge cultures. Shaker flask experiments were conducted to test the ability of the microorganisms to degrade methylene chloride under aerobic conditions. Hydrogen peroxide was used a as source of dissolved oxygen to minimize physical removal of methylene chloride due to aeration. The effect of secondary substrates like glucose, cellulose acetate, ammonium acetate and nutrient broth on biodegradation of methylene chloride was studied. Biodegradation in the presence of surfactant and alkaline stress was also investigated.

No significant degradation was observed in all aerobic experiments.

Anaerobic sludge was obtained from a secondary wastewater treatment plant, and after digestion at 35 °C it was used for anaerobic experiments. Preliminary experiments were conducted in serum bottles to test the ability of the mixed cultures to biodegrade methylene chloride under anaerobic conditions. The effect on biodegradation due to the presence of glucose and sodium acetate was also studied. Very low methylene chloride removal rates were obtained in the serum bottles ( 0.0021 mg methylene chloride /day.mg biomass).

An effort was made to increase the degradation rates by immobilization. Two immobilized cell bioreactors namely, the Membrane Bioreactor and the Celite Carrier Packed Bed Reactor were developed and studied. Glucose was used to test the viability of the immobilized microorganisms in these reactors. The entrapped microorganisms in the membrane reactor did not display activity; however, the attached microorganisms on the Celite carrier remained viable. Two hundred and fifty ppm methylene chloride was treated completely in the Packed Bed reactor in 8 days. A tenfold increase in the removal rate was observed (0.021 mg methylene chloride/day.mg biomass) in the Celite Carrier Packed Bed Reactor compared to that obtained in the serum bottles (0.0021 mg methylene chloride /day.mg biomass).

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