Sludge Reduction Performance of Aerobic Digestion Reactors for Johkasou System

Abstract

In the Johkasou system ῍an on῍site domestic wastewater treatment system῎, excess sludge is withdrawn and transported to a human excrement treatment facility. The operation of this system occupies a large part of the total treatment cost. Therefore, it is beneficial for reducing the production of excess in the system. The work presented in this paper focuses on the development of aerobic digesters for this purpose. Two types of reactors were set῍up : Reactor῍A was equipped with a filter unit for sludge separation and Reactor῍B was a kind of submerged bio῍filter process.The sludge obtained from an anaerobic tank in a Johkasou system was fed once a day into the reactors at HRTῐ ῏῎ days. Both reactors retained about ῏῎῎῎῎ mgῌL ῏῏ of MLSS. Effective solid separation performance was obtained, and the effluent contained about ῏ῒῑ of the fed SS. After approximately ῏῎῎ days of operation from start῍up, the SS reduction ratios ranged from ῐ῎ to ῑ῎ῑ. However, the SS reduction ratios in the first half of the period were lower due to the acclimation of biomass in the reactors. CODMn was effectively removed at ΐ ῍ ῑ and the CODMn level of the effluent was similar to, or lower than, that of raw domestic wastewater.