Slaughterhouses Wastewater Treatment Plant - 584 Words

The influent, after screening and decanting is stored to the flow and organic load equalization tank and then inflows at a rate of QF = 80m3 d-1 to the SNdN activated sludge system. The SNdN system actually functions as an autonomous treatment plant where oxidation of organic pollutants, nitrification/denitrification and suspended solids sedimentation are taking place. Furthermore a sludge recycling from the secondary clarifier to the aeration tank is performed so as to ensure the required microbiological load (5000 Â ± 450 mg L-1). The aeration tank of the SNdN activated sludge system operates under low D.O. concentration (between 0,2 to 0,7 mg L-1). According to Mercalf and Eddy (2003), under low D.O. concentration conditions, low nitrification rates result, as the activated sludge floc will be partially aerobic. Denitrification occurs in the anoxic zones within the floc particles due to oxygen depletion. These conditions results nitrogen removal in a single aeration tank, referre d as simultaneous nitrification and denitrification (Mercalf and Eddy, 2003). In such systems, although usually both nitrification and denitrification are occurring at low rates, relative high SRT and HRT values achieves significant nitrogen removal (Mercalf and Eddy, 2003). The SRT and HRT values of the SNdN system studied are 29 and 0,75 days respectively. Subsequently the overflowing effluent of the SNdN system is then transferred for further treatment in the PCMAS part of the WWTP. The PCMAS is