Research On Optimization Of Subsurface Flow Constructed Wetlands In The Purification System With Four-pools

The experience which is optimizing of constructrd wetland wastewater treatment technology aimed to reduce investment and operation cost of domestic sewage treatment, give full play to ecology landscape benefit and economic benefit, and improve the performance and stability of sewage treatment by constructed wetland.The main result were as follows:1.The obvious positive correlation between the operation time and matter accumulation that caused blocking of subsurface flow constructed wetland. The rate of matter accumulation that caused blocking increased fast first before descend, and then increased slowly and gently.The obvious positive correlation between the rate of matter accumulation that caused blocking and substrate proportioning and water inlet line deepness. Four months after the operation, the matrix ratio is third, four respectively is10cm thick gravel (Φ5～10mm) and20cm thick gravel (Φ10～30mm) permeability of subsurface flow constructed wetland system decline rate was the lowest in the three group. The water permeable pipe depth from the subsurface flow constructed wetland system bottom10cm rate was significantly lower than the water inlet pipe from the bottom of the pool depth system20cm and30cm.2. Four months of artificial wetland system, the status of plant growth is good. The summer (7, August) the number of branches and leaves increased significantly, and the blade is basically no dead. The growth of the plant began to slowly into the fall, Lythrum salicaria no new branch formation, Alocasia basically no new leaf growth, but Lobelia could still be observed new leaf growth.Three species of plants in the summer and autumn have better removal effect on plant nutrients in sewage, wherein the Calla showed optimal effect of removing ammonia nitrogen (64.5%), optimal results of total nitrogen removal Arum (80.7%). Lythrum salicaria on phosphorus removal effect is best (62.9%). The removal rate of Chemical Oxygen Demand (COD), Lythrum salicaria optimal performance in summer (73.2%); Lobelia in autumn the best performance (76.5%). Three species of ammonia nitrogen, total nitrogen, total phosphorus removal efficiency was better than that of autumn in summer. No significant difference on COD removal effect, but with decreasing temperature, removal efficiency decreased.3. Planted vegetable mixed planting mode applied to the artificial wetland system treating rural life is feasible. But must pay attention to the rational allocation of landscape plants and aquatic vegetables.Lythrum salicaria and water spinach mixed planting on removal of plant nutrients are good. Lythrum salicaria and spinach mix of ammonia nitrogen and phosphorus removal rate was8%, increased by8.6%compared to a single Lythrum salicaria respectively. The total nitrogen and COD compared to plant Lythrum salicaria were decreased by4.8%,10.5%. Lobelia chinensis and Ipomoea aquatica Forsk combination of total nitrogen, total phosphorus and the average removal rate of COD compared to a single Lobelia decreased by3.5%,4.3%,6.9%. Calla and water spinach mixed planting, on nutrient removal rate is much lower than the single planting taro.4. Septic tank effluent by three formatting Lythrum salicaria, lobelia and Alocasia artificial wetland system treating, Concentrations of COD and ammonia nitrogen in water decreased by more than60%, total nitrogen concentration decreased more than55%, more than50%of total phosphorus concentration. Stable water quality of effluent. In addition to lobelia and Alocasia system total phosphorus concentrations exceed the standard, the other can reach the discharge standard for municipal sewage treatment plant (GB18918-2002) of a class B. Combination of Lythrum salicaria and water spinach on plant nutrients septic tank unit in water removal efficiency performance. Compared to single Lythrum salicaria system, removal efficiency of combination of Lythrum salicaria and water spinach on the ammonia nitrogen and phosphorus were increased by3.8%,10.4%. The removal efficiency of total nitrogen and COD were decreased by8%,14.6%. Stable water quality of effluent, can reach the discharge standard for municipal sewage treatment plant (GB18918-2002) of a class B.