自热式高温好氧消化工艺的氧化还原电位研究

Study of Oxidation-Reduction Potential ORP on Autothermal Thermophilic Aerobic Digestion Process

采用自热式高温好氧消化(ATAD)中试工艺系统,通过间歇式运行,改变进泥初始ρ(VSS)和曝气强度,考察了系统中氧化还原电位(ORP)的变化情况.对进泥初始ρ(VSS)为45.4和34.2 g/L的曝气强度恒定在1.0 m3/h,搅拌转速为95 r/min,停留时间为25 d;初始ρ(VSS)为40.7 g/L污泥的曝气强度在0.4～1.0 m3/h间由大到小进行调节,搅拌转速为95 r/min,停留时间为44 d.结果表明,初始ρ(VSS)与曝气强度对ORP有影响,当曝气强度充足时,ORP呈先下降再回升趋势,最终ORP能达到0mV以上.对于pH的变化,初始ρ(VSS)为45.4和34.2 g/L的污泥规律相似,均呈先上升后下降趋势,初始ρ(VSS)为34.2 g/L的污泥pH从开始的6.01上升到8.11,然后下降到5.60～6.03.但初始ρ(VSS)为40.7 g/L的污泥pH的变化规律有所不同,pH一直呈上升趋势,从开始的7.33到最终的9.16.表明由于溶胞作用,系统中ρ(总氮),ρ(氨氮),ρ(总磷)较高,pH上升,若曝气强度充足,pH随后下降,ORP回升;若曝气强度较低,pH则一直呈上升趋势,ORP则处于较低值.因此ORP与进泥初始ρ(VSS),曝气强度,反应温度,ρ(氨氮)和pH等因素有关.从ORP的测试结果看,ATAD系统处于厌氧到微好氧之间的状态.

Using an autothermal thermophilic aerobic digestion pilot-scale process, oxidation-reduction potential （ORP） was investigated by way of varying VSS concentration of feed sludge and aeration intensity with intermittent operation. VSS of feed sludge at mass concentrations of 45.4 and 34.2 g/L were operated with aeration intensity of 1.0 m^3/h, mixing velocity of 95 r/min, and retention time of 25 days, while VSS at mass concentration of 40.7 g/L were operated with aeration intensity from 1.0 to 0.4 m^3/h, mixing velocity of 95 r/min, and retention time of 44 days. The results showed that VSS concentration and aeration intensity had effects on ORP values. The ORP curves tended to decline at first and then rise progressively, and finally achieved above 0 mV under conditions of sufficient aeration strength. As for pH, similar curves were obtained for VSS of feed sludge at mass concentrations 45.4 and 34.2 g/L, firstly increasing, then a downward trend, pH of VSS at the concentration of 34.2 g/L rose from the initial 6.01 to 8.11, and then declined to a range between 5.60 and 6.03. However, the trend was different for pH of VSS at 40.7 g/L,rising continuously from the initial 7.33 to the final 9.16 .This indicated that high concentrations of total nitrogen, ammonia, and total phosphorus resulted in pH increases by virtue of cell lysis. The pH decreased and ORP rose subsequently under sufficient aeration intensity. The pH tended to rise all the time under short duration of aeration intensity, with ORP at a low value. In a conclusion, ORP is related to factors of VSS concentration of feed sludge, aeration intensity, reactor temperature, ammonia concentration and pH. ATAD process is the state between an anaerobic environment and a microaerophilic environment from ORP test results.