| Sewage treatment belongs to the energy intensive industry, and the problems of high energy consumption and operating cost hinder the construction and operation of wastewater treatment plant in China, The electricity consumption of aeration system accounts for 50%-60% of wastewater treatment plant total electricity consumption, which is the key to energy saving of the whole plant. AOSD (automatic oxygen supply device) is a new kind of intelligent aeration control system, which is based on the changes of dissolved oxygen and temperature to automatically control the aeration time, and to save energy consumption of aeration utterly. A/O process is a kind of mature wastewater treatment process, and applying AOSD to A/O process is a novel process. Studying the novel process has important practical significance for improving the efficiency of wastewater treatment and reducing the treatment cost.In this study, AOSD was applied to A/O process, investigating the operation characteristics of intelligent aeration controlled A/O process (I-A/O) and continuous aeration A/O process (C-A/O) in treating sewage during start-up period, also investigating nitrogen and phosphorus removal performance of I-A/O under different influent NH4+-N concentration, nitrated liquid reflux ratios and hydraulic retention time (HRT). Results showed that:(1)I-A/O system started quickly and the stable phase can be reached in 15 d, the removal efficiencies of CODCr, NH4+-N and TN were 90.44%,94.10% and 89.80%, respectively, in I-A/O. The TP removal efficiency in I-A/O was 92.08%, while there is no significant removal for TP in C-A/O.(2)Different influent NH4+-N concentrations (35 mg/L,55 mg/L and 80 mg/L) had little effect on the CODCr removal but significant effect on TN removal in I-A/O system and C-A/O system. Especially when the influent NHl-N concentration was 55 mg/L and 80 mg/L, TN removal efficiencies in I-A/O system were 15.15% and 22.87% higher than those of C-A/O system, and short-cut nitrification and denitrification occurred in I-A/O system. The influent NH4+-N concentration had significant effect on NH4+-N removal in I-A/O system, but no obvious effect on NH4+-N removal in C-A/O system. Compared with C-A/O, I-A/O saved about 38%～55%daily power consumption of the aeration system.(3) The influent NH4+-N concentration had appreciable impact on TP removal in I-A/O system. When influent NH4+-N concentration rose from 35 mg/L to 80 mg/L, TP removal efficiency dropped from 92.47%to 69.44%. The mechanism of phosphorus removal in I-A/O system was as follows, anaerobic phosphorus release and the external carbon had been transformed into4 intracelluar carbon polymers (pory-β-hydroxybutyrate, PHB) in anoxic tank, in aerobic tank TP was removed through aerobic phosphorus uptake during aeration stage and denitrifying phosphorus removal during no aeration stage. The rising of influent NH4+-N concentration caused the concentration of NO3-increased and anaerobic phosphorus release was inhibited. As a result, the TP removal efficiency of I-A/O system decreased.(4)Through adjust the nitrated liquid reflux ratio and HRT, optimizing the operation of I-A/O system in treating sewage. Nitrated liquid reflux ratio was set three kinds of conditions:200%,300% and 400%, HRT was set three kinds of conditions:10 h,12 h and 14 h. The results showed that, when nitrated liquid reflux ratio was 200% and HRT was 12 h, the energy consumption of I-A/O system was reasonable and I-A/O system had good removal efficiencies on CODCr, NH4+-N, TN and TP. |
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