· The whole system is designed to keep bacteria healthy and busy. Some live in the tank, but most do their work in the drain field. 1. All waste flows to the septic tank. 2. Watery waste, called "effluent," fills most of the tank. Anaerobic bacteria begin breaking down the organic material in the effluent. 3.
The reason that riffles work is two fold. First, there is an eddy created behind each riffle, causing a temporary lull in the water flow. The material that is flowing is in a liquid state. This causes the heavies to be at the very bottom of the flow. As the flow passes over a riffle, the heavies will fall to the bottom behind a riffle.