Study On Operational Optimization Of Modified Carrousel Oxidation Ditch Process

This article studies on operation optimization of the modified Carrousel oxidation ditch process in a wastewater treatment plant, which is to solve the problems about the process operation and to achieve high-efficiency energy saving operation.The water quality analysis showed the average concentrations of CODCr, NH4+-N, TP and TN in effluent were 46 mg/L, 11.24 mg/L, 0.64 mg/L and 17.95 mg/L,while the corresponding removal efficiency were 89%, 73%, 88% and 65% respectively. It is showed that the average concentrations of NH4+-N and TN has exceeded the A standard of 《Discharge standard of pollutants for municipal wastewater treatment plant》(GB18918-2002). And then the flow velocity requirement could be ensured when the underwater driving devices were operated alone through flow pattern analysis when the separated operation and combined operation of underwater driving devices and aeration disks, which meant the main function of aeration disks was oxygenated to the mixed liquor in the oxidation ditch. The average section flow velocity of anoxic zone was 0.3 m/s and the bottom velocity was above 0.1 m/s; the average section flow velocity of aerobic zone was in the range of 0.41~0.56 m/s and the bottom velocity was above 0.15 m/s under the normal conditions. The flow velocity analysis results showed that the flow velocity requirement in the ditch could be achieved under the normal conditions.The operational parameters(such as SRT, HRT and DO concentration) were optimized due to the higher NH4+-N and TN concentrations in the effluent. The results showed that longer SRT, shorter HRT and lower DO concentration resulted in the nitrogen removal deterioration directly. The optimal nitrogen removal could be achieved in the case of SRT of 18 d, HRT of 16 h and DO concentration in the range of 2.0~2.5 mg/L, with the NH4+-N and TN concentrations of 3.17mg/L and 12.55 mg/L in the effluent steadily, while the corresponding removal efficiencies were 93% and 78% respectively.On the basis of process performance and energy consumption analyzed through adjusting operational parameters, the CODCr, NH4+-N, TP and TN concentration could be maintained at about 41.60mg/L, 2.70mg/L, 0.59mg/L and 12.23 mg/L in the effluent respectively, with the corresponding removal efficiencies of 83%, 93%, 87% and 75%under the condition of F/M in the range of 0.065~0.085 kg BOD5/(kg MLSS·d), SRT of 18 d, MLSS of 4000mg/L, R of 50%, HRT of 18 h and DO concentration in the range of 2.0~2.5 mg/L. In the meanwhile the operational energy consumption was kept in the range of 0.22~0.27kw·h/m3.