| Water quality improvement and water restoration in the canal basin play an important role in building a better Tianjin.At present,the remediation technology of polluted water mainly includes chemical remediation,physical remediation and biological ecological remediation.This paper studies the bio ecological combined purification technology,and designs the construction scheme and process of the demonstration project to make the water quality of the demonstration river reach the standard.The research results have important practical application value for the improvement of water quality in Beiyun river system.In the non flood season,the river flow velocity in the urban section is slow,and the rainfall runoff composed of the first branch canal,the second branch canal,the third branch canal,the fourth branch canal,the fifth branch canal,the sixth branch canal and the seventh branch canal in the upstream dongpuwa village converges,resulting in the poor purification capacity of the water body.The following research is carried out:(1)The temporal and spatial variation laws and pollution sources of NH3-N,TP and COD concentrations in Wuqing section of the north canal were analyzed.Spatially,on the whole,the concentrations of NH3-N,TP and COD at the downstream laomidian gate are higher than those of the upstream eight hole gate bridge;In terms of time,the concentrations of NH3-N,TP and COD at the six sampling points in the flood season are significantly increased,and the concentrations in the non flood season are low.The non-point source pollution in dongpuwa and the tail water discharged from the sewage treatment plant are the main pollution sources in the Wuqing urban section of the North Canal.At the same time,the rainfall runoff will lead to the deterioration of the water quality of the river,which is the main factor for the non-compliance of the river water quality in the flood season.(2)Carried out the purification test of four aquatic plants in different seasons on the water body of the study river section,and analyzed the removal effects of four aquatic plants on three pollutants of NH3-N,TP and COD in the water quality of the study river section and the corresponding hydraulic load parameters in different seasons.The results show that under the condition of hydraulic retention time of 7 days and coverage ratio of 50%,the removal rates of NH3-N,TP and COD by Allium,iris,Canna and Chelidonium were 43%,81% and20% respectively in summer;46%,16% and 16% respectively in winter;Shallot is the dominant plant species.When the plant coverage ratio is 25%,the removal rates of NH3-N,TP and COD reach 53%,75% and 47% respectively.The corresponding hydraulic load parameters are 0.66 mg /(L · HR),0.18 mg /(L · HR)and 18 mg /(L · HR)respectively.(3)Carried out the experimental study on the purification of the raw water of the North Canal by the ultra-fine carbon fiber artificial water grass with natural film hanging in the river in different seasons and different aeration,analyzed the removal effect of NH3-N,TP and COD pollutants and the corresponding hydraulic load parameters,and sequence the biofilm microorganisms.The results show that when the hydraulic retention time is 7 days,the removal rates of NH3-N,TP and COD by artificial aquatic plants in summer are 66.67%,28.2% and 63.6% respectively;In the winter experiment,the removal rates of NH3-N,TP and COD by artificial aquatic plants under high dissolved oxygen environment reached 73.17%,30.6% and 86.6%.Microbial DNA sequencing of artificial aquatic grass biofilm contains a large number of microbial bacteria,which can adsorb and degrade nitrogen,phosphorus and organic matter in water,absorb heavy metals,and have strong ability to purify ammonia nitrogen and other pollutants.(4)According to the characteristics of the river channel in the urban section,research and develop the bio ecological combined purification technology,carried out the combined purification test of aeration aquatic plant artificial water and grass in different seasons indoors,and analyzed the removal effect of the combined technology on NH3-N,TP and COD pollutants in the water quality of the studied river section and the corresponding hydraulic load parameters.The results show that in the most unfavorable winter,when the hydraulic retention time is 7 days,the removal efficiencies of NH3-N,TP and COD by artificial aquatic plants and aquatic plants are 96.44%,56.52% and 65% respectively,and the corresponding hydraulic load parameters are 0.94 mg /(L · HR),0.04 mg /(L · HR)and 5 mg /(L · HR)respectively.The purification effect of bio ecological combination technology is obviously better than that of single technology such as aquatic plants and artificial aquatic plants.(5)Analysis of purification effect of demonstration project.According to the river conditions,improve the purification process of the river section of the demonstration project,and analyze the concentration changes of NH3-N,TP and COD pollutants at the inlet and outlet section of the river.It is concluded that after the construction and operation of the demonstration project,the water quality at the inlet and outlet of the river has been significantly improved,and the application of bio ecological combination technology makes the NH3-N,TP and COD of the outlet section of the demonstration river section The concentration of TP and COD can stably meet the class V water standard of surface water.It is calculated that after the completion of the demonstration project,the total absorption of total nitrogen by the four aquatic plants is about 538.61 kg and the total absorption of total phosphorus is about 45.74 kg. |
