No abstract

In situ toxicity tests were conducted to determine the toxicity of linear alkyl‐ (dodecyl‐) benzenesulfonate (LAS) on a natural periphyton community. Colonized periphyton were exposed to C11 9‐LAS in 21‐d continuous‐flow toxicity studies conducted in the Little Miami River (Ohio) above and below a wastewater treatment plant outfall. The lowest measured first‐effect levels were 3.3 and 16.6 mg/L, respectively, in the two locations, based on reductions in structural and functional community characteristics. The presence of 20 to 30% effluent did not increase the toxicity of LAS. The field‐derived effect levels confirmed the low phytotoxicity observed in most previously conducted laboratory toxicity studies with cultured algae. In addition, the field‐derived effect levels exceeded measured environmental concentrations, which supports the environmental safety of LAS to periphyton.

A pilot plant-scale composter using simulated solid waste was developed to test the fate of consumer products such as disposable diapers. The simulated waste consisted of a mixture of rabbit chow (which included alfalfa), shredded newspaper, sand, and composted cow manure. The compost mass self-heated from an ambient temperature of 27°C to about 55°C in the first 24 h. Dissolved ammonia levels, high in the early stages of the process, began to decrease after about 4 weeks as nitrate concentration began to increase. Both volatile solids and carbon:nitrogen ratios exhibited gradual decreases with time. Microbial biomass, esterase activity, cellulose mineralization, direct microscopic counts (AODC), and relative APIZYM enzyme activity increased significantly in the first several days, and maintained higher levels than initial measurements throughout the 22-week testing period. We concluded that the simulated solid waste underwent physical, chemical, and microbiological changes that would be expected to occur in municipal solid waste in a full-scale composting system. The pilot plant-scale composter should prove to be a valuable tool in assessing the fate of products and materials under simulated compost conditions.