Evaluation of a single-residence biological wastewater treatment system with thermal biosolids destruction

An aerobic package residential wastewater treatment system was evaluated to determine process performance while connected to a single-family residence. Three components of the study were: 1) long-term (5-month) performance, 2) 24-hour performance track studies, and 3) enhanced loading study. For the long-term performance and enhanced loading study hourly influent and effluent samples were collected and composited on a flow-averaged basis. Short-term fluctuations in flow and mass loading rates were evaluated from the hourly discrete samples. The long-term average removals for CBOD5, TSS, and inorganic N were 97.3, 97.8 percent, and 89.6 percent, respectively, with average effluent concentrations of 5.7, 5.9, and 2.2 mg l(-1). To prevent biosolids buildup in the system and to eliminate the need for frequent sludge removal a thermal process is incorporated into the system for biosolid ash conversion. Periodic spikes of influent mass loading rates persisted in the treatment system at time scales of one hour or less. Treatment process peformance, evaluated from 24-hour composite samples, was not affected by the highly variable infuent concentrations and flow rates experienced in the study single-family household. Average monthly power consumption for aeration, thermal processing of accumulated biosolids, and biomass re-circulation was 132 kWh per month, or about 4.4 kWh per day.