studying the effluent quality of enhanced modified ludzack ettinger-oxic settling anaerobic process (e-mle-osa) for treating real municipal wastewater

Background: wastewater collection, treatment, discharge, additionally as reusing the treatedwastewater in urban are critical factors for maintaining public health preventing contamination ofwater resources. this study aimed to investigate the performance of enhanced modified ludzackettinger process-oxic settling anaerobic (mle-osa) process for treating real municipalwastewater in sari wastewater treatment, sari city, iran.methods: to combine the osa process technique with the mle system, the sludge holdingtanks (sht) were implemented in the return sludge line of designed pilot studies whichcomprised 1) mle, which was regarded as the control system similar; 2) mle-osa4 with a70-l sht operated at 4-h hydraulic retention time (hrt), and 3) mleosa6 with a 107-lsht operated at 6-h hrt. to start the process, the overflow effluent of the primary settlingtank of the sari wastewater treatment plant was used. after 45-60 days, the reactors reached asteady state. the parameters of 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.results: the results revealed that the average tss, cod, bod, phosphorus, nitrite, nitrate,and total nitrogen in mleosa4 effluent decreased 20.1, 14.6, 2.97, 10, 51.1, 19.3, and 20.7%,respectively compared to mle. similarly, in mle-osa6, the values decreased 34.2, 16.1, 14.6,16.7, 69.6, 31.3, and 25.8%, respectively compared to the control process.conclusion: therefore, using natural wastewater, the enhanced mle-osa process showedbetter performance in removing the study parameters and better quality for the effluent.furthermore, the quality of effluent is following the iran department of environment (ide).