Advanced wastewater treatment system comprising biological contact process and chemical phosphate exchange

Abstract

Approximately 64% of SCOD in the synthetic wastewater and 61% of SCOD in the sewage were reduced by or sorbed into the activated sludge in 30-min contact. While the SCOD of the diluted livestock wastewater was reduced by about 43% at the same contact time. Based on the result, the specific mass of organic matter uptaken was 55 mg SCOD/g MLSS in 30 min. In the same manner, 20.1 and 14.3 mg SCOD/g MLSS were calculated as the values in the sewage and livestock wastewater, respectively. During the contact reaction, the dissolved ammonium was ranged between 26 and 29 mg NH4+-N /L, while the extractable ammonium between 28 and 32 mg NH4+-N/L. Thus, the detachable ammonium was about 2.82 mg NH4+-N/l, that was 9.4% of the influent ammonium of 30 mg NH4+-N/l. The specific mass of ammonium adsorbed was 0.94 mg NH4+-N/g MLSS. An interesting observation was the amount of ammonium adsorbed was far less than that of organic matters uptaken in the same period. It indicated that the organic-rich sludge flow and the ammonia-rich supernatant stream were effectively separated through biological uptake reaction. Due to the low growth rate of nitrifying bacteria, immobilization of nitrifiers was tried in order to improve nitrification efficiency and to prevent washing-out of nitrifiers. The proposed separate-sludge system showed very stable nitrification efficiency. In this system, it is possible to control the streams individually in the nitrifying and denitrifying step. Moreover, the separation of an ammonium-rich stream from an organic-laden stream through the biological uptake reaction gave nitrifiers a favorable condition in growth as well as competition. It leads to the optimal control of the separate nitrification step in the proposed activated sludge system. In sequestered denitrification, it was found that 8.72 mg SCOD was consumed for denitrifying 1 mg nitrate. Thus, it means that the required organic matter for denitrification can be saved up to 63% in the proposed syste...