Study On The Modular Vertical-flow Constructed Wetland For The Advanced Treatment Of Simulated Municipal Sewage Plant Effluent

The research is designed to solve the low nitrogen removal efficiency and poor substrate clogging problems by study the form of matrix structure, the water level height and aeration intensity of three vertical-flow constructed wetland(VFCW)respectively, to determine the appropriate parameters of high efficiency and energy saving of VFCW process; Under the optimal operating conditions, study the efficiency of three sets of modular VFCW during the summer and autumn.The main conclusions are as follows:(1)With the increase of outlet position, the removal rate of three sets VFCW systems on COD, TN and NO3--N showed varying degrees of improved removal rates;The removal of TP and NH4+-N show the opposite trend.The water concentration of COD, TP, NH4+-N in accordance with the class II water quality standards of environmental quality standards for surface water(GB3838-2002), while the concentration of TN shows poor water quality, has not reach grade v water quality standards yet, needs to be further improved.(2)As the aeration intensity increases, the removal of three sets of VFCW system on COD, TN, TP, NH4+-N and NO3--N showed increased signs of trends.When the gas-water ratio is 3:1, the removal of three sets of wetland systems on COD,TN, NH4+-N and NO3--N achieve to the best; When the gas-water ratio is 4:1,the maximum removal rate for TP can reach to 99.78%.Under the best aeration intensity,the best effluent concentration of COD, TN, TP, NH4+-N and NO3--N is in accordance with the class II water quality standards of environmental quality standards for surface water(GB3838-2002).(3) Under the best working conditions, the highest water level 75 cm and air/water ratio 3:1, three sets of VFCW system showed a strong purification effect on city water both spring and fall.The water concentrations of COD, NH4+-N and NO3--N are in line with the class II water quality standards of environmental quality standards for surface water(GB3838-2002); The average effluent concentration of TPin the three wetlands systems is in line with class III, class II and class IV water quality standards of environmental quality standards for surface water(GB3838-2002)respectively.(4) During the experiment, the pollutant removal of wetland was positively correlated with temperature, the purifying effect improved with the temperature increasing.(5) In the vertical-flow constructed wetland system, The removal of nitrogen and phosphorus by plant play a very important role. The distribution of nitrogen and phosphorus in plant was stem > blade; The maximum adsorption of VFCWS for nitrogen and phosphorus was VFCW2> VFCW1 >VFCW3.