COMPREHENSIVE ONSITE WASTEWATER TREATMENT: WHAT WORKS AND WHAT DOESN’T Steven I. Safferman*, Bennette D. Burks 1 , Robert A. Parker 1 *Dept. of Civil and Environmental Engineering, University of Dayton, Dayton, OH 45469-0243 1 Consolidated Treatment Systems, Inc. ABSTRACT Four wastewater treatment systems were developed, each unique in its approach, to comprehensively treat onsite generated wastewater. The system’s reliability, operational requirements, and effectiveness to remove 5-day biochemical oxygen demand (BOD), total suspended solids (TSS), and total nitrogen were compared. Each system is briefly described below. • Suspended growth aeration unit preceded by an anoxic tank that received recirculated aeration unit effluent and influent. A splitter box and sump allowed for both the discharge and controlled recirculation of the effluent. • Suspended growth oxidation system with filter socks for solid/liquid separation preceded by an equalization tank equipped with dose controlled loading. • Fabric fixed-film system integrated with an anoxic tank and controlled effluent recirculation, preceded by an equalization tank with dose controlled loading. • Granular peat fixed-film system integrated with an anoxic tank and controlled effluent recirculation, preceded by an equalization tank, with dose controlled loading. The systems with suspended growth components proved to be reliable and required only minimum maintenance. The fixed-film systems were more simplistic but their novel and unproven design, in part, required much attention to maintain continuous operation. They also exhibited a fly and odor problem. BOD and TSS removal were excellent for the systems with suspended growth components. Excellent total nitrogen removal was achieved with both of these systems using low instantaneous loading. This operating strategy allowed the influent nitrogen to match the removal capacity of the systems. Control of the instantaneous flow was possible by using equalization and controlled dosing resulting in the distribution of pollutants over an increased amount of time. The inherent intermittent hydraulic loading of onsite generated wastewater made this strategy very practical. Neither fixed-film system supported an environment that substantially oxidized BOD. Consequently nitrification did not proceed and very little total nitrogen was removed. The further reduction of hydraulic loading to try to obtain comparable pollutant removal results as observed from the suspended growth systems was not attempted as this would make the size and cost of the fixed-film units uncompetitive. KEYWORDS Onsite Generated Wastewater, Fabric Media, Peat Media, Aeration, Nitrification, Denitrification, Biological Nutrient Removal 1632