2019 Volume 55 Issue 3 Pages 67-77
In the present study, the effect of phosphorus removal pellets containing alum as a main component on the phosphorus removal efficiency in various on-site treatment systems for domestic wastewater was evaluated. When 400 g/week or 800 g/week of phosphorus removal pellets were put into the aeration tank and the raw water tank of three types of Johkasous (Tandoku-shori Johkasou, conventional Johkasou and nitrogen removal type Johkasou), total phosphorus (T－P) and phosphate phosphorus (PO4－P) in the effluent water were decreased after one week. In addition, there was no adverse effect of phosphorus removal pellets on the removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total nitrogen (T－N) in the effluent water. Depending on the conditions of the Johkasou, the T－P concentration tended to be higher when the suspended solids (SS) concentrations were increased. When the phosphorus removal pellet was applied to the aeration tank and the raw water tank of the Tandoku-shori Johkasou and the conventional Johkasou, the ratio of T－P concentration in each effluent water after addition of pellets to that before the pellets addition (T－P ratio) ranged from 0.3 to 0.6. In contrast, the phosphorus removal effect was low in the nitrogen removal type Johkasou, despite that pellets were put into the aeration tank, whereas when the pellets were put into the raw water tank, the T－P ratio was around 0.6.
