Study On Phosphorus Removal From Wastewater In High Speed Service Area By Constructed Wetland System

In recent years,with the rapid construction and development of expressway service area,there are few researches on efficient,environmental protection and resource-based treatment of phosphorus in the wastewater of expressway service area.The application of constructed wetland treatment technology in the wastewater dephosphorization of expressway service area is only in the primary research stage,and the operation data of relevant constructed wetland technology in the service area is still in the initial stage of exploration,and the selection of technology is contradictory.In order to improve the efficiency of the process for the treatment of phosphorus in the sewage in the service area of the expressway,realize the sewage resource treatment,and achieve the treatment goal of high efficiency,energy saving and environmental protection,this paper makes an in-depth study on the enhanced method of the constructed wetland treatment process for the sewage phosphorus treatment in the service area of the expressway.This paper studies the best operation state of constructed wetland system in the test process,and adopts the method of combination of small-scale test and small-scale test to design and test the influencing factors such as p H value of water environment,water temperature,dissolved oxygen of water body,hydraulic retention time,variable hydraulic load,etc.,using the sewage of low load expressway service area as the research object,through the preparation and pretreatment of raw water,dilute The related tests were carried out after release.Taking the adsorption capacity and removal rate of phosphorus in sewage as the water quality treatment standard,the optimal operation conditions of phosphorus removal can be obtained by changing the operation conditions of the constructed wetland system,which provides the test data support for the practical engineering application of the expressway service area in the future.The main results are as follows:（1）The comprehensive evaluation and Analysis on the technical and economic aspects of the common wastewater treatment processes of the expressway service area,such as Anaerobic constructed wetland treatment process,the underground soil capillary filtration wastewater treatment process,the sequencing batch activated sludge treatment process,and the biological aerated filter treatment process,are carried out.The results show that the anaerobic hydrolysis constructed wetland treatment process has a score of 3.374,which is suitable for use It is used for sewage treatment in expressway service area.（2）Study on the factors influencing the adsorption capacity of matrix particles in the service area,including the size of matrix particles,p H value of water environment,organic matter of water body,total phosphorus concentration of influent water,etc.The influence of matrix particle size on phosphorus adsorption capacity of constructed wetland system in service area is mainly affected by the particle radius.The smaller the particle size is,the larger the mesh number is,the easier it is to adsorb phosphorus in water body,making the water purification effect better;the influence of p H value of water body on phosphorus adsorption capacity of matrix is more obvious,the adsorption capacity of matrix particles on total phosphorus in alkaline and acid conditions is increased,and the neutral water sample is increased The results show that the adsorption capacity of different organic matter is different,oxalic acid solution makes the adsorption capacity of matrix particles increase,tartaric acid solution makes the adsorption capacity of matrix particles decrease,glucose has the effect on the adsorption capacity of matrix particles The results show that the increase of initial phosphorus concentration can increase the adsorption capacity of matrix particles.（3）Study the influence of various factors on the total phosphorus in the whole operation process of the constructed wetland system,explore the optimal external conditions for the operation of the constructed wetland process in the sewage treatment of the expressway service area,and achieve the efficient phosphorus removal effect in the operation process of the system.The effects of p H value of water environment,water temperature,dissolved oxygen,hydraulic retention time and variable hydraulic load on phosphorus removal capacity of the system were studied.The p H value of water body has a certain influence on the phosphorus removal performance of the system.The phosphorus removal rate is the highest when the p H value is between 7 and 8.The experimental device can perform better phosphorus removal performance,and the system can perform better phosphorus removal rate when the alkaline condition is better than the acid condition.When the temperature of the system is 26℃～28℃,the phosphorus adsorption capacity of the system is 3.76mg/l～3.84mg/l,and the removal rate is 87%～89.0%,which is at the highest level of the curve.The decrease of temperature and The increase of phosphorus in the water body will weaken the resistance of the liquid membrane on the surface of the particles,weaken the diffusion effect and reduce the phosphorus adsorption capacity;under different do values of the influent water,the phosphorus removal effect is not different,indicating that the different do values of the influent water have little influence on the phosphorus removal of the constructed wetland system in the service area;the increase of the hydraulic retention time of the system is conducive to the interception and filtration of the matrix particles and plant roots With,it can filter out more suspended phosphorus,increase hydraulic retention time,enhance the mineralization and decomposition of total phosphorus by microorganisms in water body and the adsorption of H₂PO₄-by matrix particles.The change of hydraulic retention time has many effects on the constructed wetland system,which can increase the removal rate of total phosphorus,and the reasonable hydraulic load in the system is conducive to the removal effect of phosphorus Strong hydraulic load will destroy the stability of the system,so that the effect of phosphorus removal is not obvious.（4）In order to verify the engineering practicability of the constructed wetland system in the sewage treatment process of the high-speed service area,and to verify the cooperative role of matrix particles and wetland plants in the wetland system,a small-scale pilot system test of the constructed wetland was carried out.The phosphorus concentration in the effluent water was 0.88mg/l～1.56mg/l,which was 22%～38%lower than that in the influent water,achieving a certain treatment effect.The results of the pilot system show that the constructed wetland system is feasible in the sewage treatment process of the high-speed service area.