Study on the microaerobic EGSB reactor+chemical coagulation system treating domestic wastewater

A novel domestic wastewater treatment system for reuse was proposed, which consisted of a microaerobic EGSB reactor unit and the following chemical phosphorus removal unit, as a low-cost and highly efficient process. In order to confirm the feasibility of the domestic wastewater treating technique at ambient temperature for reuse through the combination of the micro-aerobic EGSB reactor and the chemical phosphorus removal process, the operation characteristic of the microaerobic EGSB reactor was analyzed. Moreover, the final chemical precipitations with aluminium sulphate, PAC, ferric trichloride and PES were employed to enhance the TP removal from the micro-aerobic EGSB system. Studies were focused on the influences of flocculation and settling time, coagulant dosage, pH and temperature on the effluent TP removal of the microaerobic EGSB reactor. The resulted showed that the microaerobic EGSB reactor treating domestic wastewater run well at 15–26°C. And at the conditions of 2.5-3.1L·h⁻¹ influent flow, 3.9–4.8h HRT, 2.2–2.9m·h⁻¹ Vup, with influent COD, NH3-N, TN and TP concentration of 213–1145, 26.5–72.1, 31.7–81.7 and 3.9–16.3mg·L⁻¹, the effluent COD, NH3-N, TN and TP concentratios were 26.3, 9.9, 14.0 and 4.7mg·L⁻¹, and which was up to the IA, IB, IA and III distinction standard of GB 18918–2002, respectively. Subsequently, it was essential to enhance the TP removal of the micro-aerobic EGSB reactor effluent through chemical precipitation. The optimal “β” (the mole ratio of Al³⁺: P or Fe³⁺:P) for aluminium sulphate, PAC, ferric trichloride and PES was 1.1, 6.9, 3.1and 2.1, and meanwhile 20, 10, 20 and 15min flocculation time were selected, respectively. And in succession, sedimentating with 20min, the minimum TP removal efficiency of 85%, 90.8%, 92% and 92% could attain, and the effluent TP was under the value of 0.71, 0.43, 0.38 and 0.38mg·L⁻¹, respectively, and which had accorded with the IA distinction standard of GB 18918-2002 except for the aluminium sulphate. It was compulsory for the 0.5mg·L⁻¹ TP distinction standard to adjust the pH. Consenquently, the domestic wastewater treating technique at ambient temperature for reuse through the combination of the micro-aerophilic EGSB reactor and the chemical phosphorus removal process is feasible.