Impact of dissolved oxygen on hospital wastewater quality treated by SBBR in Basrah city, Iraq

The hospitals close to the residences can make problems for the environment as a consequence of sewage drained into the water stream. Sequencing batch biofilm reactor (SBBR) offers advantages for treating sewage; such as simple operation, flexible process, and cost-effective. The laboratory bench-scale experiments were carried out treating hospital wastewater (HWW) of one of Basrah hospital city by a fabricated SBBR reactor of 26 l working volume. The hospital wastewater has the following characteristics (average values): pH 7.3, BOD equal to 280 mg·l–1, COD equal to 550 mg·l–1, total phosphorus (TP) equal to 6.4 mg·l–1, ammonia (NH3-N) equal to 44 mg·l–1 and total suspended solid (TSS) equal to 272 mg·l–1. This research aims to estimate the performance of the SBBR system for treating hospital wastewater to enhance different effluent parameters such as COD, total nitrogen (TN), ammonia, and total phosphorous (TP) with various dissolved oxygen (DO) with range of 2.15–6.55 mg·l–1, the best DO values give these removal efficiencies for COD equal to 84.55%, NH3-N equal to 65.91% and TN between 78 and 18% for DO equal to 3.67 mg·l–1, while TP removal efficiency was 79.70% for DO equal to 6.55 mg·l–1. By comparison of the SBBR effluent with international standards for effluent sewage, it noticed COD concentration 85 mg·l–1, TN 12 mg·l–1 and TP 1.3 mg·l–1 met all standards (European, WHO, and China), while NH3-N 15 mg·l–1 was outside WHO and European standards, while satisfies only Chinese standard.