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The distribution and transformation of a quaternary ammonium surfactant, octadecyltrimethylammonium chloride (OTAC) , were studied in laboratory-scale activated-sludge systems a t various initial concentrations. OTAC was removed and extensively biodegraded when tested at concentrations ranging from 0.1 to 20 mg/L. Quantitative adsorption data indicated that greater than 99% of OTAC was adsorbed to wastewater solids within 30 min of initial exposure. Biodegradation of sorbed OTAC was slower than adsorption and followed apparent first-order kinetics. The half-life for OTAC primary biodegradation was about 2.5 h, based on the first-order rate constant. Mineralization of 14C-labeled methyl and C1-alkyl carbons occurred at somewhat slower rates, with half-lives of 28 and 40 h, respectively.

Extraction of the organic compounds from a dye manufacturlng plant wastewater with methylene chloride revealed the presence of several chemicals, some of whlch may be potentially toxic. Qualitative results of composlte sampling over a 2.5-month period indicated that grab sampling techniques would have been misleading In assesslng envlronmental Impact. Semiquanttlatlon of the compostles from both treated and untreated effluents Indicated that some compounds, 1,3,3-trimethyloxlndole for example, were actually /ncreas/ng in concentratlon as a result of reactions occurrlng during treatment. One of the compounds identified, 5-chloro-3-phenyl-l,2,4-thiadiarole, has been patented as a nematoclde and seems to result from an impurity in a raw material. The lack of relevant toxicity data about most of the compounds found in thls study emphaslres the need for methods of determlnlng the effects of chronic low level exposures to water pollutants.

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