Septic tank outlet filters

The performance of post-primary treatment components of on-site wastewater management systems is critically dependent on the loads imposed upon them, in particular those of biochemical oxygen demand (BOD5) and total suspended solids (TSS). A potentially cost effective means of reducing solids carry-over and improving the quality of treated wastewater is by the fitting or retrofitting of a septic tank outlet filter. Currently, the fitting of septic tank outlet filters is not mandatory in many jurisdictions in Australia, but there is compelling evidence from both the USA and New Zealand that significant performance improvements can be gained by fitting such filters and that the service life of the components of the treatment system which follow can be considerably extended. This paper reviews the variety of septic tank outlet filters available in Australia and New Zealand, describes their design, construction, installation and performance expectations.