PRIVATE SEWAGE TREATMENT TANK

PROBLEM TO BE SOLVED: To provide a small-size private sewage treatment tank having enhanced performance. SOLUTION: This private sewage treatment tank is provided with: an anaerobic vessel impurity removal chamber N1 in which an inflow baffle B for allowing inflow water to be treated that is passed through a raw water inflow port 1, to flow into the chamber N1 along a peripheral wall W of the chamber N1, is placed; and also an anaerobic preliminary filtration chamber N2 which is placed adjacently to the anaerobic vessel impurity removal chamber N1 and has a high porosity filter medium F2 within and in which a water-to-be- treated transfer pump A for transferring the water to be treated to the downstream side is placed; wherein a partition wall W0 is formed between the anaerobic vessel impurity removal chamber N1 and the anaerobic preliminary filtration chamber N2 so that the wall height is lower than a set lower water level LWL of the anaerobic preliminary filtration chamber N2, and also, above the partition wall W0, a sludge storage space G for storing sludge as scum is formed.