A cost-effective modular recirculating filter for on-site wastewater systems

Failures of conventional on-site wastewater treatment systems have five common causes: hydraulic overloading, excessive biomat formation, poor design or installation, compaction, and soil-mineral bonding. Solutions generally involve pretreatment of septic-tank effluent, before it is discharged, by one of the following methods: aerobic treatment units, attached-growth media filters, or constructed wetlands. Many consulting firms, however, are not interested in designing on-site wastewater treatment systems for individual residential or small commercial users. Therefore, the author and his associates have developed a modular, multilayer, pre-engineered, prepackaged recirculating media filter system (patents pending) to provide pretreatment of septic-tank effluent for residential and small commercial users. The system is contained in a single precast concrete tank and includes an integral anoxic recirculation basin, dual attached growth media filters, a dosing basin for storage of treated effluent, pumps, valves, piping, and a digital control system. The unit is designed to reduce biochemical oxygen demand, total suspended solids, total nitrogen, and pathogen levels in septic-tank effluent before final disposal by conventional absorption systems, subsurface drip irrigation, or surface discharge as approved by regulatory agencies.