Effectiveness Of Oxidation Ponds In Industrial Wastewater Treatment

This study was aimed at evaluating the efficiency of the oxidation ponds in industrialrn(Tannery) wastewater treatment. The analyses were carried out on selected tanneries ofrnModjo area, East Shewa, Oromia National regional State, Ethiopia and Mesaco GlobalrnTanneries. In order to evaluate the efficiency of oxidation ponds in treating industrialrnwastewater, a total of 27 samples from three sampling sites of the oxidation ponds ofrneach tannery were collected and analyzed for the major physico-chemical and biologicalrnparameters; E.C, pH, BOD, COD, Cr+3 , S-2, N-NH3, N-NO3, TKN, PO4, TSS, TS, TDS,rnSO4, Cl-, Mg+2, Ca+2, TC and FC.rnThe result of analyses revealed that MOP had the most BOD, TC and FC removal withrnthe value of 67.7%, 92% and 93% respectively to that of Chrome oxidation pond withrnBOD, TC and FC percentage removal of 52.5, 75.4 and 81.5 respectively, and sulfidernoxidation pond having BOD, TC and FC percentage removal of 64, 72.6 and 86.2rnrespectively. Similarly, the study showed that the highest percentage removal of TSS andrnS-2 were achieved in Sulfide oxidation pond with value of 93% and 89.8% respectively,rnand 65.7% of Chromium (Cr+3) removal was achieved in Chrome oxidation pond.rnHowever, the COD removal efficiency of the oxidation ponds; Chrome oxidation pond,rnSulfide oxidation pond and Mesaco global oxidation pond was 35%, 44.8% and 37%rnrespectively.rnIn addition, the study findings revealed that the concentrations of N-NH3 and TKN havernshown increasing trends in sulfide oxidation pond, while the concentration of N-NO3 hasrnbeen declined with percentage removal of 82.5%. Though the concentrations of N-NH3rnand TKN were not in increasing trends in the Chrome oxidation pond and Mesacornoxidation pond, their removal efficiencies were very low, 32.6% and 48.4% respectivelyrnin Chrome oxidation pond, and 47.2% and 54.6% respectively in Mesaco oxidation pond.rnIt was concluded from these results that the oxidation ponds were inefficient in removingrnnutrients, COD, BOD and Cr+3 due to absence of multiple ponds neither connected inrnseries nor in parallel, lack of uniformly mixing of the wastewater in the ponds, and prernscreening of coarse material prior to entering the oxidation ponds. Thus, effectivernremovals of these parameters need sequentially connected; anaerobic – facultative –rnmaturation ponds systems with reasonable organic loading and retention time.

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