The objective of this joint project between Dr. Gene F. Parkin at the University of Iowa and Dr. Bruce E. Rittmann at the University of Illinois include evaluation of the rate at which soluble metabolic products are produced during anaerobic processes for wastewater treatment, determination of their chelation properties and role in reducing metal toxicity during the respiratory process. A unified conceptual model will be developed and utilized as a basis for evaluation of more rational approaches to design of treatment processes than are now possible be based on effects of solids retention time, metal and substrate loading on metal toxicity to the reaction and nutritional requirements of the methanogenic organisms involved in the treatment process. This is a project that is responsive to recent findings regarding the role played by residual metabolic products and trace metals in anaerobic wastewater treatment. Through this cooperative project, the investigators will coordinate their work utilizing intermediate results to relate results of chemostat research to comparable reactions on fixed biofilms reactors. Results are expected to result in improvements in engineering design of biotreatment processes used for industrial and municipal treatment practice.