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With onsite treatment replacing municipal sewers in nearly half of all new residential developments, precast concrete producers have an increasing opportunity to help landowners take responsibility for onsite wastewater treatment.

In many municipalities, code officials are giving producers no choice, and require both primary and secondary effluent treatment prior to discharge. Land capacity also plays a role.

Even where secondary treatment is not required, producers can establish concrete as the preferred wastewater-treatment containment material by diversifying their product lines with secondary treatment systems. Two systems help producers increase not only sales but also environmental goodwill.

An aerobic system like the HOOT Aerobic Treatment System, rather than using soil to organically break down sewage, relies on an aeration chamber that breeds bacteria for that purpose so the sewage is pure enough for discharge. The typical aerobic system, however, has two separate tanks: one for primary, the other for secondary, treatment. The HOOT system is said to be the only complete system in one tank, which is made exclusively of concrete.

According to a 1995 Baylor University research report, the system creates a 97.7% mean reduction of biochemical oxygen demand (BOD) and a 98.2% mean reduction of total suspended solids (TSS) in wastewater. (Class I aerobic treatment system requirements established by the National Sanitation Foundation (NSF) are 85% for both.) These reductions allow licensees to sell the system in areas where regulations are particularly strict.

Concrete is superior in durability and watertightness but costs 15% to 20% less than fiberglass. The licensor ships the producer ready-to-assemble kits consisting of controls, pumps, PVC pipe, and an internal PVC hopper, and all the contractor has to do is hook up the wiring and connect it to the house.

A newly patented secondary-treatment system, from Earthtek Environmental Systems, Batesville, Ind., uses a different purification method. It uses a sort of internal drip-irrigation method in which sewage that has been primarily treated in a separate septic tank flows downward through a bed of bacteria-rich filter media in a secondary tank before being discharged.

The secondary treatment reduces conventional septic-system failures and is the best reducer of nitrates in the effluent, according to inventor Kevin R. Chaffee, P.E. The system reportedly yields an average nitrate concentration of only 10 parts per million. It, too, meets NSF requirements. In addition, Earthtek Environmental Systems will provide producers with forms and technical assistance in setting up an optional drip-irrigation system.