Batch Biodegradation Experiments Research Articles

Use of Biofiltration for Removal of Natural Organic Matter to Achieve Biologically Stable Drinking Water

The presence of organic carbon in raw drinking waters can cause problems such as trihalomethane formation during disinfection with chlorine, regrowth of bacteria in the distribution system and reduced GAC adsorber bed life. This research concerns biofiltration for the removal of organic matter from drinking water sources. A major objective of this research is to examine how differences in the source and composition of the natural organic matter relate to the biodegradability of the natural organic matter and influence biofiltration effectiveness. Most of the organic matter in Dismal Swamp water, one of the four sources of organic matter to be evaluated in this study, has an apparent molecular weight in the 3-10 K range and the < 0.5 K range as shown by an apparent molecular weight analysis using ultrafiltration. Aerobic batch biodegradation experiments were performed using Dismal Swamp water ozonated at a dose of 1 mg O3/mg TOC. A 30 % reduction in total organic carbon over an 11-day incubation period was observed.

Sequential Chemical/Biological Oxidation of 2-Chlorophenol

The feasibility of preozonation with subsequent biodegradation as an alternative treatment of 2-chlorophenol was investigated. The major ozonation byproduct of 2-chlorophenol was chlorosuccinic acid which was oxidized to oxalic acid upon further ozonation. Only chlorosuccinic acid sustained substantial growth of Pseudomonas putida during batch biodegradation experiments compared with a blank, 2-chlorophenol, and oxalic acid. Accordingly, based on the results obtained with this model system, preozonation of persistent compounds can result in an increased extent of mineralization. However, care must be exercised in the chemical oxidation process to prevent formation of secondary refractory intermediates.

Chlorinated Solvent Biodegradation by Methanotrophs in Unsaturated Soils

Chlorinated aliphatic solvents are common contaminants of unsaturated soils. This research focuses on the feasibility of treatment by \Iin situ\N bioremediation with indigenous methanotrophs. Batch biodegradation experiments are conducted with three unsaturated soils in which indigenous methanotrophs are stimulated by exposure to a methane/air atmosphere. Of the three chlorinated solvents tested, 1,2-dichloroethane is degraded the fastest, followed by trichloroethylene, and finally chloroform. Zero-order rate constants for conversion to CO\d2 range from 0.05 to 1.4 μ\Ng solvent/g dry soil-day. Assuming contaminant concentrations on the order of 100 μ\Ng/soil, these rates imply that \Iin situ\N bioremediation would require several months to several years for completion. Depending upon the particular chlorinated solvent and soil, microbial activity produces, in addition to CO\d2, significant quantities of nonvolatile products. The products represent disappearance of the parent chlorinated solvent, but may or may not represent acceptable bioremediation depending upon the nature of the products and the treatment goals. Availability of nutrients also significantly affects degradation rates.

Aerobic Biodegradation of Aromatic and Chlorinated Hydrocarbons Commonly Detected in Landfill Leachates

Abstract Aromatic and chlorinated hydrocarbons are hazardous organics which persist in groundwater impacted by landfill leachate. Recent studies have indicated that the aromatics biodegrade readily under aerobic conditions. Similarly, methane-oxidizers are reported to metabolize trichloroethylene. This study investigates an in-situ biorestoration scheme involving stimulating aerobic biodegradation in a contaminated anaerobic, methane-saturated groundwater using hydrogen peroxide as an oxygen source. Batch biodegradation experiments were conducted with groundwater and core obtained from the Gloucester Landfill, Ottawa, Canada. Hydrogen peroxide, added at a non-toxic level, provided oxygen which promoted the rapid biodegradation of benzene, toluene, ethyl benzene, o-, m-, and p-xylene. Morphologically different methane-oxidizing cultures were obtained from Gloucester groundwater and a surface sediment. Both cultures degraded trichloroethylene in microcosms containing a mineral media and Gloucester core. Degradation was not observed when the mineral madia was replaced with Gloucester groundwater, or when other chlorinated hydrocarbons were added. Additional research is required to identify and overcome this inhibition to trichloroethylene biodegradation, before this remedial strategy can be employed.