Abstract: A multistage residential wastewater treatment system. The preferred system has three chambers. Wastewater flows into the first chamber via an inflow line. Primarily anaerobic treatment occurs in the first chamber. From the first chamber, wastewater flows into a second chamber. The second chamber is aerated, and primarily aerobic treatment occurs there. Substantially fully treated wastewater flows from the second chamber to the third chamber. The third chamber is substantially quiescent and anaerobic. Most remaining solids settle out in the third chamber. A bactericide pump is configured to introduce batch doses of bactericide in the desired volume to the third chamber at set intervals. After sufficient delay following introduction of the bactericide to allow for substantially complete toxicity to the bacteria in third chamber, effluent is pumped out of the tank by an effluent pump via an effluent line. The effluent pump preferably powers the bactericide pump.

Abstract: The wastewater treatment unit includes a tank which in cross-section has a trapezoidal shaped lower portion and a rectangular upper portion. The tank has an opening into a hollow interior defined by a horizontal bottom wall and an upright peripheral wall extending from the bottom wall. A divider wall and a baffle are disposed vertically across the interior for subdividing the tank into a first aeration chamber, a second aeration chamber, and a clarification chamber. Wastewater flows from the first chamber into the second chamber through a conical shaped opening in the divider wall. The wastewater then flows into the clarification chamber in which solid matter is permitted to settle. The clarification chamber has a sloped floor and guiding wedges to return settled matter, or activated sludge, back to the center of the second chamber where turbulence is greatest.