Long-term treatment performance of innovative systems

Document Type

Conference Proceeding

Date of Original Version



Six full-scale innovative onsite wastewater treatment systems were installed in 1999 to replace failed septic systems. The systems installed consisted of two textile filters; one textile filter followed by a bottomless sand filter; one single pass sand filter; one modular peat filter followed by an ultraviolet (UV) light disinfection unit; and one fixed activated sludge treatment system followed by a UV disinfection unit. This paper reports results of long-term treatment performance monitored for BOD5, TSS, fecal coliform, TP, and TN collected for 33 sample events over a 48-month period. All packed bed filters operating in a single pass or recirculating mode produced mean BOD5 and TSS effluent concentrations between 2-9 mg/1, representing a 91-99% reduction. The fixed activated sludge treatment system produced BOD5 and TSS concentrations that averaged 15 and 10 mg/1, respectively. TN reductions averaged 15 and 21% for the single pass sand filter and single pass modular peat filter, respectively. TN reductions for the two recirculating textile filters averaged 44-47%. Mean TN concentrations for the one textile filter operating in a mixed effluent mode and the fixed activated sludge treatment system were 8 and 14 mg/1, respectively, and met the Rhode Island TN standard of ≤19 mg/1 on 100% and 77% of the sampling events, respectively. TP removal in the single pass sand filter was 40%, and minimal in all other systems. The single pass sand filter consistently achieved the highest level of fecal coliform reduction (3.9 logs) followed by the two recirculating textile filters (3.1-3.4 logs), and then the peat filter (3.3 logs). The two UV light disinfection units produced effluent with a geometric mean fecal coliform concentration between 2 and 6 counts / 100ml. Operational procedures/problems encountered for the systems are also briefly discussed.

Publication Title, e.g., Journal

Proceedings of the 10th National Symposium on Individual and Small Community Sewage Systems - On-Site Wastewater Treatment X