ABSTRACT: Objectives: This research aimed to investigate the influence and possibility of operating an AnA2/O2 SBR process with a shortened operating cycle time and SRT on biological nutrients removal. Materials and methods: Slaughterhouse wastewater was treated with AnA2/O2 SBR, varying the SRTs (10, 20 and 30 days) at a cycle time of 12 hours, and performed under an anaerobic static fill (0.5 hours), reaction, consisting of Anoxic/Oxic/Anoxic/Oxic (1.5/2.5/2.5/1.5 hours) and settle phases (0.5 hours). Results and discussions: The results showed that SRTs had slight influence on the organic matter removal; the COD removal efficiencies of each SRT were above 90%. Moreover, too high or low SRT removed lower nitrogen and phosphorus levels. Nitrogen removal was increased with SRT but with an extremely prolonged SRT and also under lower SRT conditions, resulting in reduced nitrogen removal due to the detection of NO2-N in the effluent. For phosphorus removal, PAOs were predominant in the systems with a long SRT, resulting in retaining more phosphorus than that of common bacteria. However, a prolonged SRT produced poor phosphorus removal performance resulting from the depletion of excess sludge wasting. Conclusion: The removal of COD and TP were similar under SRTs of 10-30 days, but the impact mostly involved nitrogen removal and the optimal operation was obtained at SRT 20 days, with an average removal efficiency of TCOD, SCOD, TKN, TP and NH3-N at 94.1%, 95.5%, 97.3%, 84.8% and 99.2%, respectively.
*Department of Sanitary Engineering, Faculty of Public Health, Mahidol University
** Department of Environmental Health Sciences, Faculty of Public Health, Mahidol University
Center of Excellence on Environmental Health and Toxicology (EHT)
Science & Technology Postgraduate Education and Research Development Office (PERDO)