Research Of Wavy-Subsurface-Flow-Constructed-Wetland In Treating Simulated Domestic Wastewater

The constructed wetlands wastewater treatment technology is increasingly used in sewage treatment because of low-carbon environment,low cost,easy maintenance landscaping,etc.In this experiment,the horizontal subsurface flow constructed wetlands(Horizontal Subsurface Flow Constructed Wetlands,referred to as SFCW)served as controls and waveform subsurface flow constructed wetland (Wave Subsurface Flow Constructed Wetland, referred to as W-SFCW) was studied at the removal efficiency of organic compound, nitrogen and phosphorus in low concentration simulated domestic sewage at different hydraulic retention time and different water levels without aeration systems and also was studied at their removal efficiency further at different aeration locations, different aeration intensity and intermittent aeration with aeration systems.The results showed that:(1)The removal efficiency of nitrogen pollutants under the hydraulic load of 15cm3·cm-2·d-1,the hydraulic retention time of 1d and the water level of 40cm is good and the average removal rate of NH4+-N reaches 90.5%, and TN removal rate reaches 86.6% early in the experiment.That is because filler adsorption and microbial nitrification and de-nitrification are more thorough. Because of the adsorption mainly through the matrix, the removal efficiency of TP under the hydraulic load of 7.5cm3·cm-2·d-1,the hydraulic retention time of 2d and the water level of 40cm is good and the removal rate is up to 86.6% at this time.When the water level is maintained at 40cm, the residence time has little effect on COD removal,even in the residence time of 0.6d, the CODCr removal can still be reached 67.1%.(2) Because the oxygenation of W-SFCW is so low that that can not meet the necessary oxygen to microbial degradation, we use artificial aeration to improve DO. The ammonia nitrogen removal rate reaches 93.2% and CODCr removal rate reaches 85.4%,and the total nitrogen removal rate does not increase correspondingly when 2# and 4# wave intervals of W-SFCW are aerated at the aeration intensity of 300-350 mL·min-1.The reason may be that the higher level of DO cause some anaerobic zone to become aerobic in wetland, thus the nitrifying bacteria activities increase substantially. However, the total nitrogen removal rate could be raised to 70% when the intermittent aeration is used, owing to the formation of alternating aerobic and anaerobic environment within the wetland. The removal of TP relies mainly on the adsorption of substrate and is less affected by aeration. Thus, continuous aeration of measures can be taken if removal of CODCr-and NH4+-N as the main purpose is expected and intermittent aeration measures can be taken if removal of TN as the main purpose is expected.