Effluent quality of enhanced Modified Ludzack Ettinger - Oxic Settling Anaerobic Process (E- MLE-OSA) for treating real municipal wastewater

The purpose of this study was to investigated the performance of enhanced Modified Ludzack Ettinger Process - Oxic Settling Anaerobic Process (MLE-OSA) for treating real municipal wastewater in Sari Wastewater Treatment .To combine Oxic Settling Anaerobic Process technique with MLE system, the sludge holding tanks (SHT) were implemented in the return sludge line of designed pilot studies which comprise: 1) MLE which was regarded as the control system similar; 2) MLE-OSA4 with a 70-liter SHT operated at four-hour hydraulic retention time (HRT); 3) MLE-OSA6 with a 107-liter SHT operated at six-hour HRT. To start up the process, the overflow effluent of the primary settling tank of Sari Wastewater treatment plant was used. After a period of 45-60 days, the reactors reached a steady state. "Parameters including Dissolved oxygen (DO), Oxidation-reduction potential (ORP), Temperature, pH, Chemical oxygen demand (COD), Biochemical oxygen demand (BOD5), Total suspended solids (TSS), and nutrients were analyzed." The results revealed that the average TSS, COD, BOD, phosphorus, nitrite, nitrate, and total nitrogen in MLE-OSA4 effluent decreased 20.1, 14.6, 2.97, 10, 51.1, 19.3, and 20,7% in comparison to MLE, respectively. Similarly, in MLE-OSA6, the values decreased 34.2, 16.1, 14.6, 16.7, 69.6, 31.3, and 25.8 %, respectively with regard to the control process. Therefore, by using real wastewater, the enhanced MLE-OSA process showed a better performance on removal of the study parameters and better quality for the effluent. Furthermore, the quality of effluent is in accordance with the standards of Iran Department of Environment (IDE).