Simultaneous treatment of graywater and waste gas in a biotrickling filter
Abstract
A set of bench scale biotrickling filters were designed and operated for simultaneous treatment of graywater and waste containing elevated levels of ammonia (NH3) and hydrogen sulfide (H2S). Preliminary experiments were conducted to optimize graywater processing in the reactors. While surfactants have been considered to be readily biodegradable, removal of carbon from graywater was not as high as expected during preliminary experiments when no waste gas was supplied to the system. Removal efficiency was not improved after several modifications to reactor design and it was hypothesized that complete removal of surfactants and their relevant biodegradation metabolites was a challenge. Therefore, surfactant biodegradation was studied in detail. Experimental work showed that while all three surfactants exhibited rapid primary biodegradation, biodegradation of by secondary byproducts was very slow. In the case of the amphoteric surfactant, disodium cocoamphodiacetate, biodegradation byproducts seemed to be recalcitrant. A mathematical model was developed to describe the biotrickling filter processes and this model was used to conduct a sensitivity analysis so that governing processes within the biotrickling filter could be determined. Important design parameters were elucidated as well as parameters inherent to the system, or intrinsic parameters. Results showed that an increase in wetted area within the biotrickling filter could significantly improve process performance. Therefore, a set of tracer test experiments was conducted to examine the effects of packing material and hydraulic loading rate on hydrodynamics in the bench scale biotrickling filters. Of the packing materials tested, the use of Rings in the biotrickling filters resulted in improved hydrodynamics. Proof of Concept was established for simultaneous treatment of graywater and waste gas in the studied biotrickling filters. Complete removal of NH3 gas loaded at 150 mg/min and H 2S loaded at 0.83 mg/min was achieved while removal of carbonaceous compounds from graywater remained stable.
Degree
Ph.D.
Advisors
Banks, Purdue University.
Subject Area
Civil engineering|Environmental engineering
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