Removal of organics and nutrients from tannery effluent by advanced integrated wastewater pond systems (R) technology

摘要

In this study, a pilot-scale experiment was carried out on a pre-settled combined tannery effluent from Modjo tannery, Ethiopia, to evaluate the feasibility of the Advanced Integrated Wastewater Pond Systems(R) or AIWPS(R) Technology, for the treatment of tannery effluent. The pilot-scale AIWPS(R) Facility was comprised of an Advanced Facultative Pond (AFP), Secondary Facultative Pond (SFP) and Maturation Pond (MP) all arranged in series. Three feed phases with low, moderate and overloading organic loading rates were applied to assess the organics and nutrients removal performances of the AlWPS(R) reactors. The overall organics removal performance of the AIWPS(R) Process was high, with removal efficiencies in the range of 90-98% for BOD5 and 86-92% for COD. Among the AIWPS(R) reactors, the AFP attained the highest organics removal efficiency with a BOD5 removal of 70-89%. BOD5 removal efficiencies of the SFP and MP were 34-65% and 30-40%, respectively. The AFP was also able to withstand a much higher volumetric organic loading rate (70% more) than the conventional open anaerobic ponds. The drop in BOD5 removal efficiency of the AFP at the overloading condition was only 7%, while the corresponding drop in the SFP was 29%. AIWPS(R) reactors achieved a cumulative ammonia removal efficiency of 85%. The highest ammonia removal (50-60%) occurred in the SFP, followed by the MP with removal efficiency of 20-26%. At the overloading condition the overall ammonia removal efficiency of the AIWPS(R) Facility decreased by 50%, while the BOD5, organics removal dropped by only 6%, signifying the higher vulnerability of ammonia removal mechanism to high loading conditions than the organics removal. The phosphorus removal in the AIWPS(R) Facility was erratic, with highest removal (up to 75%) occurring in the AFP. The lack of H2S odour nuisance from the AFP was mainly due to the proliferation of sulphide oxidizing anoxygenic photosynthetic pink bacteria of the genera: Thiocystis, Rhodobacter, Rhodospirillum and Rhodopseudomonas in the upper solar illuminated water layers of the AFP. [References: 37]