Methodology, preliminary results and future plans for an on-going Water Environment Research Foundation (WERF) funded research project, WERF project number 04-DEC-7, are presented. The objective of this project is to identify, compile, analyze, and report on the existing body of literature and other data sources addressing the performance of primary treatment units (septic tanks and grease traps) in onsite wastewater systems and the factors impacting performance.To date, a bibliographic database has been developed and approximately 470 relevant references have been identified and/or collected. The database is being used to manage information for the project, including review input from a team of four leading practitioners and researchers in the field. The references, which include texts, guidance manuals, journal articles, conference proceedings, demonstration system reports and as-yet unpublished data, cover a wide range of factors influencing primary treatment performance in onsite systems. Factors which have been studied in the past and will be closely examined for this project include: sizing, compartmentalization, effluent filtration, baffling, hydraulic loading, water conservation, additives, nutrient removal, temperature effects, solids accumulation rate, removal of trace organics, settling theory and many others.The results of this extensive literature/data review will be compiled in a comprehensive white paper supplemented by the bibliographic database. Additionally, an extension-style communications piece will be developed to communicate the results of the project to practitioners and other stakeholders in a practical way that facilitates their decision-making regarding primary treatment units in onsite systems.
