Study On Characteristics And Performance Of Short-Cut Denitrifying Dephosphatation

To resolve the problems encountered in conventional biological nutrient removal (BNR) processes, two novel technologies of short-cut nitrification and denitrifying dephosphatation were investigated, respectively. Based on it, an innovative hybrid system combining the above technologies was proposed and set up for the advanced treatment of domestic wastewater.Intermittent aeration was proved an efficient way to achieve short-cut nitrification with easy operation. In the intermittent-aeration system, ammonia-oxidizing bacteria (AOB) was capable of increasing its biomass in the reactor by an elevation in growth yield (YAOB), which as a result compensated the decreased specific substrate utilization rate at low DO level and further led to the unchangedμm value and NH4+ oxidation rate. On the contrary, nitrite-oxidizing bacteria (NOB) was lack of the function of compensability, and it hence lowered theμm value and NO2- oxidation rate, accompanied with the accumulation of NO2- in the effluent. Under the SRT of 5d, rather higher nitrification rate of 8.8mg NH4+-N/L.h and NO2- accumulation ratio of 84.6% were obtained in the intermittent-aeration system as compared to the continuous-areation system, where the corresponding values were 6.0mg NH4+-N/L.h and 21.2%, respectively.With the aid of a stepwise elevation of NO2- added in influent, denitrifying Poly-P accumulating organisms (DPAO) were gradually accommondated to resist and utilize NO2- as electron acceptor. However, glycogen accumulating organisms (GAO) that deteriorates the phosphorus removal was found enriched more in the reactor concurrently. After an increase in pH from 7.0±0.5 to 7.8±0.5 in anaerobic phase, the growth of GAO could be inhibited to some extent and was attributed to the reduced competition for acetate by the GAO in relation to the DPAO, as illustrated by the DPAO/GAO acetate-competition model. Moreover, a good correlativity existed between sludge glycogen content and phosphorus removal capacity; and the more phosphorus removed, the lower sludge glycogen content was, vice versa. Both low DO and anoxic phosphorus uptake could restrain the amount of glycogen replenished when phosphorus was taking up by the PAO.All the coefficients in terms of stoichiometry for anaerobic phosphorus release,...