Wastewater - Onsite Treatment


Michigan Environmental Education Curriculum
Wastewater Treatment

In many cases, homes are located too far from each other to make a community wastewater collection and treatment system economical. Here, wastewater is handled onsite using a "miniature treatment plant" consisting of a septic tank and drain field. Wastewater is delivered to the septic tank, a concrete box with a capacity of ~1000 gallons, where grease and large solids which would clog the drain field are trapped. Over time, much of the solid material is converted to a liquid form and passes to the drain field. Solids remaining in the septic tank must be removed by pumping every several years.

Septic Tank

Drain Field

The drain field consists of perforated plastic pipes placed in a layer of gravel. Organic matter is broken down by aerobic bacteria in the gravel and underlying soil and the treated water trickles into the groundwater. In constructing a home treatment system, it is important that water trickle or percolate through the soil at a rate which will not lead to formation of ponds of wastewater on the ground. Septic tanks are also located to avoid contamination of the home's well water.

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