Technological Development For Nitrogen And Phosphorus Removal In Wastewater Treatment By CIBR/Enzymatic Wetland

At present, the problem of municipal wastewater treatment in China is"Three high and one more". Focusing on this problem and the front field research of the current water pollution control, a new practical biological/ecological combined process has been developed to treat municipal wastewater with"Three low and one less"-named continuous-flow integrated biological reactor (CIBR)/enzymatic wetland, technology for nitrogen and phosphorus removal in municipal wastewater. Two basic technical principle models of facultative biological process in CIBR and nitrogen and phosphorus removal by AAA, as well as enzymatic wetlands co-purification are analyzed, and a control principle by nitrogen and phosphorus in biological and ecological system is established. The main results are as follows:①facultative biological technology in CIBRThe technology is based on mass transfer theory within biological flocculation, basic theory of concentric flocculation and flocculation settling. Biochemical reaction in facultative biomass, mass transfer promoted by fluid cutting flocculation, as well as turbulence mass transfer in the reactor are studied. Model on transfer theory within biological flocculation, facultative biological dynamics, flocculation dynamics within facultative biomass, and precipitation dynamics in mixing are constructed which lay a foundation for facultative biological technology in CIBR.Facultative biological model is adopted in municipal wastewater treatment of low nitrogen and phosphorus concentration at higher temperature. Lower energy is consumed to degrade organic matters at higher temperature. However, the nitrogen removal efficiency is weak, and the model should be changed to adjust higher nitrogen concentration. The range of original water suitable for facultative biological process is: COD≤300mg/L, NH3-N≤15mg/L, TN≤30mg/L and TP≤2mg/L. The temperature has great effect on the facultative biological technology, tests has been done under different seasons, through calculation by COD removal rate and the extreme value point from water temperature changing cure, The critical temperature 12.38℃is obtained as the model change from facultative biological to AAA.Under low temperature, the combination of enhanced flocculation and facultative biological reaction has cooperative and accelerating effect on removal of COD, TP and turbidity, and the average COD removal efficiency is 15% more than that of single wastewater coagulation or single biological reaction,the cooperatives of coagulant and microorganism can improve TP removal efficiency by 20%, while there is no significant change in the nitrogen removal. For the flocculent PAC, the optimum dosage and retention time for the facultative biological system is 20mg/L and 8h, respectively.②Removal of nitrogen and phosphorus by CIBRAiming at low C/N ratio and low C/P ratio in municipal wastewater, short-cut nitrification and denitrification, as well as denitrification and phosphorus removal using nitrite are studied to realize"diplex utilization of the carbon source", also to relieve carbon shortage and to increase nitrogen and phosphorus removal efficiency.Low oxygen and timed alternating aerobic/anoxic operation modes are used in the CIBR to achieve stable short-cut nitrogen removal under normal temperature successfully. The notarization rate is between 80% and 85%. While when the on-time control is adopted, the short-cut nitrogen removal can be achieved stably under normal temperature, normal dissolved oxygen and neutral pH value, and the nitrite accumulation rate is beyond 95%. Denitrifying phosphorus removal bacteria is cultured by the special alternating aerobic/anoxic operation of CIBR, and continuous strengthen"aerobic/anoxic"environment. Under normal temperature, normal dissolved oxygen and practical domestic wastewater, denitrifying phosphorus removal is obtained by on-time control, and the phosphorus removal efficiency is beyond 90%, while the effluent phosphorus concentration is below 1mg/L.Pilot research has been done on the basis of the results of laboratory study, and the optimum condition is 2:2:2. Under this condition, the removal efficiency of COD, NH3-N, TN and TP are 76.60%,81.73%,60.19% and 66.76%, respectively, which can well meet the following ecological treatment.The changing model rule of CIBR is determined through the above test results, and the energy saving efficiency is accounted. Research shows that the special power consumption for wastewater treatment by CIBR is 0.15 kWh/m3 in the whole year, compared with A2/O and oxidation ditch, the energy consumption is less than 24.27% and 28.96%, respectively.③Co-purification with enzyme wetlandsThrough pilot research,multi-niche optimize structure for enzymatic wetlands has been studied. Four types and six kinds of enzymatic wetlands are constructed based on researches include comparison and chooses between wetland fillers and wetland plants, structure and types of the wetland, stage influents and law of wetland block. The best wetland type and better co-purification effects are attained through different run operation.Different fillers for wetlands are chosen by comparison and then matched, the following filler matching is achieved aiming at different influent: for wastewater with low nitrogen concentration and medium or high organic matter concentration, better removal efficiency is attained by combined fillers of coal cinder + pebble stone + gravel; for wastewater with high nitrogen concentration and low organic matter concentration, the optimum combination is fly ash brick crumbs + gravel. For wastewater with high phosphorus concentration, each combination achieved good removal efficiency.Four wetland plants of different seasons and their function matching are selected and cultured. Under normal growth period, there is no significant difference among cannas, typhus, juncos and water bamboo. But cannas and water bamboo has longer growth period, as well as larger biomass and amount of fine roots. Their purifying efficiency is better than that of typhus and juncos.The construct and type among four types and six kinds of wetlands are compared, and the process optimization and pollutants degrading test has been done. Contractive wavy-flow wetland with stage influents has more stable pollutants removal efficiency, and its hydraulic flow pattern is more suitable, as well as even distribution pollutants loadings. The block can be avoided through ratio in three stages, and the treatment efficiency and use age can be improved.The pollutants degradation dynamic of wavy-flow and horizontal-flow enzymatic wetlands are discussed, which are good for further research and application of the enzymatic wetlands.④To establish control principle of the nitrogen and phosphorus between CIBR and enzymatic wetlandsThrough cell technology integration and optimize allocation, the optimization combined process between CIBR and enzymatic wetlands are formed, nitrogen and phosphorus concentration are the main control factors, by making full use of enzymatic wetlands to remove nitrogen and phosphorus, we take pH value and ORP as control factors to control CIBR operation condition to realize the best nitrogen and phosphorus removal efficiency in the CIBR and enzymatic wetlands system. On this basis, the interface optimization control strategy of nitrogen and phosphorus loading in CIBR and enzymatic wetlands system has been established, and a control system with energy-saving and multi-model in the process of CIBR and enzymatic wetlands has been formed, which takes efficient nitrogen and phosphorus removal as well as energy-saving to the system.