This paper reviews the kinetics of biodegradation of linear alkylbenzene sulfonate (LAS) in engineered (wastewater treatment) and natural environment systems, focusing on work conducted in our environmental laboratories over the past 10-15 yr. Biodegradation studies were conducted in laboratory microcosms in which pure-chalnlength [14CIting-labeled LAS homologs were used to allow complete mineralization to be assessed. In general, biodegradation rates for a series of LAS homologs (C10-C14) were comparable to each other and to values for naturally occurring materials such as sugars and fatty acids. Half-lives for LAS mineralization ranged from 1-2 d in aerobic and anaerobic sewage sludges, river water and sediments, to 1-3 wk in surface and subsurface soils and estuarine environments. The half-life for LAS degradation in different environmental compartments, relative to its residence time in these compartments, makes biodegradation a practically significant removal mechanism in a broad range of aquatic, benthic and terrestrial habitats.

The influence of readily degradable, naturally occurring carbon substrates on the biodegradation of several monosubstitued phenols (m-cresol, m-aminophenol, p-chlorophenol) was examined. The natural substrate classes used were amino acids, carbohydrates, and fatty acids. Samples of the microbial community from Lake Michie, a mesotrophic reservoir, were adapted to different levels of representatives from each natural substrate class in chemostats. After an extended adaptation period, the ability of the microbial community to degrade the monosubstituted phenols was determined by using a radiolabeled substrate uptake and mineralization method. Several microbiological characteristics of the communities were also measured. Adaptation to increasing concentrations of amino acids, carbohydrates, or fatty acids enhanced the ability of the microbial community to degrade all three phenols. The stimulation was largest for m-cresol and m-aminophenol. The mechanism responsible for the enhancement of monosubstituted phenol metabolism was not clearly identified, but the observation that adaptation to amino acids also increased the biodegradation of glucose and, to a lesser extent, naphthalene suggests a general stimulation of microbial metabolism. This study demonstrates that prior exposure to labile, natural substrates can significantly enhance the ability of aquatic microbial communities to respond to xenobiotics.

The biodegradation of nitrilotriacetic acid (NTA) was examined in three estuarine ecosystems, one of which had been exposed previously to the chemical. Biodegradation was measured as the conversion of radiolabeled NTA to I4CO,, 14C-labeled cells and the amount of label remaining in solution. The relatively unpolluted Newport River estuary system in North Carolina metabolized NTA slowly, with no apparent increase in rate over time. Jamaica Bay in New York showed an adaptation response, with approximately 50 d required for the onset of relatively rapid rates of biodegradation. The Fraser River estuary in Canada, exposed to NTA for more than 10 years, showed rapid degradation with no lag period at a concentration of 10 pg/L. At 100 and 2,000 pg/L, short lag periods (2 to 4 d) were observed before rapid degradation rates were achieved. Measurements of NTA-degraders indicated that the Fraser River estuary contained 650/ml versus fewer than 10 in the Newport River and Jamaica Bay communities. The results demonstrate that NTA can be degraded by estuarine microorganisms. Estuarine bacteria will adapt to the presence of NTA in the environment and, after adaptation, can respond to increased levels of the compound after relatively short lag periods.

This study assessed the tretability of olestra, an edible oil and shortening replacement, during conventional wastewater treatment using laboratory and bench‐scale testing. Results showed removal efficiencies for primary treatment to be similar to suspended solids removal (typically ranging from 45 to 65%) and removal during secondary activated sludge treatment to be ∼84%. Overall removal for primary and secondary treatment was estimated to range from 91% to 94%. The removal during treatment occurred primarily by sorption onto wastewater solids and settling during clarification, although some olestra was removed by biodegradation. Olestra exhibited no adverse effects on total suspended solids (TSS) and chemical oxygen demand (COD) removal during primary or secondary treatment. In addition, olestra caused no adverse effects on sludge dewatering as determined by filtration or gas production during the anaerobic digestion process. Under expected worst‐case conditions (that is, assuming that all conventional fat in savory snacks will be replaced with olestra) predicted U.S. average wastewater influent, effluent and 90th percentile receiving water concentrations under mean flow conditions were 4.9, 0.7, and 0.2 mg/L, respectively. The concentration of olestra in anaerobically digested sludge under this worst‐case scenario was predicted to be 1 281 mg/L (32.0 g/kg), with a corresponding sludge‐amended soil concentration of olestra immediately after sludge application (37 mt/ha) estimated to be 656 mg/kg.

The colonization of granular activated carbon columns by bacteria can have both beneficial and potentially detrimental consequences. Bacterial growth on the carbon surface can remove adsorbed organics and thus partially regenerate the carbon bed. However, growth can also increase the levels of bacteria in the column effluents, which can adversely affect downstream uses of the treated water. This study of a sand column and several activated carbon columns demonstrated that considerable marine bacterial growth occurred in both sand and carbon columns and that this growth increased the number of bacteria in column effluents. Activated carbon supported approximately 50% more bacteria than did sand. Bacterial growth on activated carbon was reduced by increasing the flow rate through a carbon column and increasing the carbon particle size. Scanning electron micrographs showed that bacteria preferred to attach in the protected crevices on both the sand and carbon surface. The results of this study indicated that the colonization of activated carbon by marine bacteria was enhanced because of carbon's high surface area, its rough surface texture, and its ability to absorb organic materials.