Research On The Efficiency And Mechanism Of Enhanced Ecological Filter Wall For Carbon,Nitrogen And Phosphorus Removal In Surface Water

In recent years,with the rapid development of urban economy,we pay more and more attention to water resources.However,a considerable part of the water quality of surface water resources in China can not meet the V water quality standard,and the water quality is in a fluctuating state.Compared with the conventional treatment process of urban domestic sewage,surface water has the characteristics of complex pollution components,large amount of water and wide distribution.So it is better to carry out in-situ treatment to treat surface water if conditions permit.Surface water pollution seriously affects people’s quality of life.We need to find an efficient,low-cost,low energy consumption and sustainable surface water treatment technology according to its water quality characteristics.This research proposes an"ecological filter wall treatment technology"to purify conventional pollutants carbon,nitrogen and phosphorus exceeding the standard surface water.The ecological filter wall is placed in the polluted water body,and the matrix material polyamide fiber is used to achieve the adsorption and sedimentation of the pollutants.In addition to physical effects such as filtration and filtration,it can also biodegrade pollutants through directional enrichment of microorganisms,which has high practical application value.When exploring the pollutant removal efficiency of the"ecological filter wall treatment technology",this paper found that the ecological filter wall has certain limitations in the removal of pollutants,and the removal effect of nitrogen and phosphorus is limited.After theoretical analysis,the ecological filter The wall treatment technology proposes three strengthening measures.One is to dope basalt fiber into the matrix material to increase the biomass;the other is to use plants to absorb and transform pollutants in the water to achieve the removal of nitrogen and phosphorus,and the third is to use aeration.Control the formation of dissolved oxygen concentration gradient.Through experiments,it is found that when the basalt fiber filling amount was 3mg/g,the ecological filter wall showed the best performance on the removal of pollutant.Compared with control group,the enhanced ecological filter walls,which doped with basalt fiber,planted plants and added aeration,presented the best treatment effect,achieving the purpose of enhanced removal of pollutants,and it is applied to the follow-up research After the control experiment reactor operated stably for 27 days,the removal rates of TOC,TN,ammonia nitrogen,nitrate nitrogen and TP by the enhanced ecological filter wall were87.03%,43.04%,99.16%,55.39%and 47.84%,respectively.The enhanced ecological filter wall has a significant improvement in the removal of ammonia nitrogen,and it also has a good potential for TP treatment.After the construction of the enhanced ecological filter wall system,the operation conditions of the enhanced ecological filter wall were optimized,including the concentration of dissolved oxygen,the ratio of carbon and nitrogen in the water and the hydraulic load.The optimized operation mode for dissolved oxygen concentration and influent carbon-nitrogen ratio is intermittent flow.At the same time,the peristaltic pump is used to realize the internal circulation of the water body outside the reactor.The optimized operation mode for hydraulic load is continuous flow,which is closer to the characteristics of the actual water body.The results of the test show that when the dissolved oxygen concentration is 3mg/L,the influent carbon-nitrogen ratio is 10:1,and the hydraulic load is 1.25 m³/（m²﹒d）,the pollutant removal effect in the water body is the best,with continuous outflow.The removal rates of TOC,TN,TP,ammonia nitrogen and nitrate nitrogen of water were 94.12%,93.08%,62%,89%and 96.4%,respectively.The removal rates of TOC,TN,TP,ammonia nitrogen and NO₃ nitrogen in continuous effluent were 94.12%,93.08%,62%,89%and 96.4%,respectively.Under the continuous flow operation mode,the effluent TOC,TN,NH3-N and NO₃^--N can reach the Class III surface water quality standard,and the effluent TP can reach the Class IV water quality standard,all of which achieve the expected treatment effect.efore and after the optimization of conditions,the plants in the enhanced ecological filter wall system were detected.It was found that the fresh weight of the plants with three dissolved oxygen gradients was reduced by more than 5%compared with that before the optimization,and the chlorophyll content was also generally reduced.After the optimization of the influent C/N ratio,the fresh weight of plants was reduced by more than 14%,but the chlorophyll content was increased,indicating that the low concentration of dissolved oxygen and the high concentration of pollutants in the water had an inhibitory effect on the growth of plants.This study further investigated the microbial community structure in different time and space on the matrix material,and combined it with the pollutant removal path in the water body.The results of microbial community analysis showed that after the optimization of dissolved oxygen and influent C/N ratio,the bacteria genus Dechloromonas and Zoogloea had the highest relative abundance in the anaerobic zone of the ecological filter wall.They can carry on the oxidation decomposition of organic matter and participate in the denitrification process to realize the effective removal of carbon and nitrogen pollutants.