[Temperature effects on DO and ORP in the wastewater treatment]

At present, there are some problems in the study of DO and ORP as control parameters, because the researches are usually developed in the invariable temperature. However, environmental temperature is changing in the wastewater treatment. The effect of environmental temperature on DO and ORP as control parameter was studied specially in some experiments carried on a sequencing batch reactor (SBR) fed with soybean wastewater in this paper. Results show that the law of variation in DO during organism removal were influenced with the environmental temperature, at different experiment condition of aeration intensity, MLSS concentration or inflow nutrition concentration, but the variation in ORP were not influenced with it. The reason that the DO was influenced was also discussed. This paper brought forward that the control parameter using ORP was accurate and reliable when environmental temperature changed. In addition, inflow COD concentration and the time that ORP concave value appeared was connected, and the speed that ORP in curve ascended related with the COD concentration during the degradation. So the end point of degradation may be estimated by applying ORP derivative. United ORP concave value and its derivative, it can be made on-line control of aeration intensity and aeration time.