Abstract
A simplified phosphorus removal method for the small-scale on-site domestic wastewater treatment systems, which have been used for disposal of domestic wastewater, was examined.
This method consisted of submerging the iron media in an anaerobic chamber. Phosphorus could be effectively removed even at a low oxygen concentration in the anaerobic chamber.
The phosphorus removing effect in the anaerobic environment was examined in different iron media. Iron cations were dissolved from steel wool more than from other media, because of the relatively large surface area.
The phosphorus removal method was examined using a continuous experimental apparatus. To obtain 90% phosphorus removal, it was necessary to submerge the iron media of 6.6kg·m-3 or more, and to maintain phosphorus-iron surface area loading to be 0.05g·m-2·d-1 or less.
The iron surface was covered gradually with reaction products and captured SS, and the weight of iron increased. After 2 months of submersion of iron media, dissolution of iron cations was hindered, and phosphorus removal decreased markedly. Therefore, periodic back-wash at least every 2 months was considered necessary.
Phosphorus removal cost was calculated. This method was considered to be expensive about 30-160%. However, it is possible to reduce the cost further by periodic maintenance.
