Alachlor, metolachlor, and propachlor are detoxified in biological systems by the formation of glutathione-acetanilide conjugates. This conjugation is mediated by glutathione-S-transferase, which is present in microorganisms, plants, and mammals. Other organic sulfides and inorganic sulfide also react through a nucleophilic attack on the 2-chloro group of acetanilide herbicides, but the products are only partially characterized. Sorption in soils and sediments is an important factor controlling the migration and bioavailability of these herbicides, while microbial degradation is the most important factor in determining their overall fate in the environment. The biodegradation of alachlor and metolachlor is proposed to be only partial and primarily cometabolic, and the ring cleavage seems to be slow or insignificant. Propachlor biodegradation has been reported to proceed to substantial (> 50%) mineralization of the ring structure. Reductive dechlorination may be one of the initial breakdown mechanisms under anaerobic conditions. Aerobic and anaerobic transformation products vary in their polarity and therefore in soil binding coefficient. A catabolic pathway for chloroacetanilide herbicides has not been presented in the literature because of the lack of mineralization data under defined cultural conditions.

The bacterial population of a graywater treatment system was monitored over the course of 100 days, along with several wastewater biochemical parameters. The graywater treatment system employed an 1,800-liter membrane bioreactor (MBR) to process the waste, with essentially 100% recycling of the biomass. Graywater feed consisting of 10% galley water and 90% laundry water, selected to approximate the graywater composition on board U.S. Navy ships, was collected offsite. Five-day biological oxygen demand (BOD(5)), oils and greases (O/G), nitrogen, and phosphorus were monitored in the feed and were found to vary greatly day to day. Changes in the bacterial population were monitored by PCR amplification of region 332 to 518 (Escherichia coli numbering) of the 16S rRNA gene and denaturing gradient gel electrophoresis (DGGE) analysis of the resultant PCR products. DGGE analysis indicated a diverse and unstable bacterial population throughout the 100-day period, with spikes in feed strength causing significant changes in community structure. Long-term similarity between the communities was 0 to 25%, depending on the method of analysis. In spite of the unstable bacterial population, the MBR system was able to meet effluent quality parameters approximately 90% of the time.

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The purpose of this work was to elucidate microbiological and abiotic transformations relevant to the environmental fate of the acetanilide herbicides alachlor [2‐chloro‐2′,6′‐diethyl‐N‐methoxymethyl)acetanilide], propachlor (2‐chloro‐N‐isopropyl‐acetanilide), and metolachlor [2‐chloro‐2′‐ethyl‐6′‐methyl‐N‐(1‐methyl‐2‐methoxyethyl)‐acetanilide]. Several attempts to retrieve aerobic and anaerobic microbial cultures capable of degrading alachlor from agricultural soils and pond sediments were unsuccessful with the exception of sulfate‐reducing bacteria that partially transformed acetanilide herbicides during active sulfate reduction. The transformation products of alachlor and propachlor were more hydrophobic than the parent compounds. The transformations were associated with the activity of sulfate‐reducing bacteria because the reactive species was sulfide and possibly other reduced S species produced during the bacterial reduction of sulfate. Transformation could be duplicated under abiotic conditions by reacting Na2S with alachlor, propachlor, and metolachlor. One of the reaction products of the abiotic reaction between alachlor and sulfide was identified by mass spectroscopy as a S‐substituted dimer of alachlor. This compound was formed by the nucleophilic substitution of chloride by reduced S, with the subsequent oxidation to a disulfide.

This study investigates the effect of surface immobilization on the bactericidal function of a quaternary ammonium compound. Quaternary ammonium silane (QAS) coated planar surfaces did not produce any measurable mortality of Staphylococcus aureus, while 1 µm QAS-coated microparticles did produce S. aureus mortality. The experiments using QAS-coated microparticles indicate that the ability of QAS molecules to disrupt the cell wall is not hindered by covalent immobilization of QAS to a surface. These results provide evidence that S. aureus cells on a QAS-coated planar surface are not exposed to a sufficient number of QAS molecules to produce significant mortality. This result has important implications for the development of self-decontaminating coatings. Covalent immobilization is used to prevent leaching of the bactericidal compound. However, covalent immobilization may result in a significant tradeoff in bactericidal performance.