Control and nitrogen load estimation of aerobic stage in full-scale sequencing batch reactor to treat strong nitrogen swine wastewater

Three different control methods based on oxidation reduction potential (ORP) and dissolved oxygen (DO) for determining aeration time were evaluated for swine wastewater treatment at full-scale SBR. For determining theEnding Point of Ammonia Oxidation (EPAO), the plateau in ORP profile, the derivative of DO, and absolute DO were tested. Below 0.5 kg NH ₄ ⁺ -N/m³·day of influent loading rate, three control methods produced good results; however, above this loading rate, only absolute DO method was feasible. The volumetric ammonia nitrogen load at the sub-cycle (Kg NH ₄ ⁺ -N/m³/sub-cycle) had an effect on the period of aeration. To put it more concretely, the higher loading rate required a longer ammonia nitrogen oxidation period. To estimate nitrogen load, the length of low DO period, which was defined as the required time to reach 3 mg DO/l from the start of aeration, was the most proper parameter.