ONSITE AEROBIC PACKAGE TREATMENT SYSTEMS

Several studies were conducted to evaluate the performance of onsite a erobic package treatment systems (APTS), and to suggest operational an d design modifications. In the first phase, five APTS in southwest Vir ginia were found to be operating poorly (average BODs = 69.4 mg/l, TSS = 99 mg/l, TKN = 18.6 mg/l), often violating Virginia effluent standa rds. Mechanical failures, improper maintenance and design were identif ied as causing the poor performance. In the second phase, excessive hy draulic retention time (HRT) in held systems (over 3 days) was identif ied as a significant design problem. Laboratory systems operating with aeration basin HRTs of 0.5 to 2 days produced better effluent quality (average BODs = 19 mg/l, TSS = 29 mg/l, TKN = 0.7 mg/l). In a separat e experiment relatively high levels of laundry detergent did not signi ficantly affect laboratory system performance. Finally, a field experi ment was conducted to determine the effect of equalizing washing machi ne how on the operation of an APTS. An improvement in system performan ce and stability was observed. Based on these studies, potential desig n and operational modifications are suggested, including improved main tenance, reduction of aeration basin HRT, and equalization of wastewat er flow.