| As per the seven principles of “cutting-off,diversion,purification,reducing,transferring,conservation and monitoring” in the overall comprehensive water management method,at present the most feasible and economic solution is to transfer the secondary effluent of the municipal sewage plant to the landscape river course as the supplementary water resource.In this paper,experimental studies are carried out on technologies such as municipal sewage oxidation ditch secondary treatment,biological filter advanced treatment and chemistry flocculation & filter unit on basis of comprehensive summing-up of quality index analytical investigation of reclaimed water for landscape water body via combinative method of the small-scale test and pilot scale test;the main research contents are as below:1.Study on nitrogen & phosphorus control index in reclaimed water which is used as supplemental water for landscape water body;study on supplemental water,aiming at meeting the “Urban Wastewater Reclamation and Reuse,Water Quality of Water for Landscape Environment”(GB/T 18921-2002)standard;and study on landscape water body mobility control index.2.Study on wastewater treatment technology which aims at landscape use through analysis and evaluation on treatment degree of current urban sewage treatment plant and the effluent quality index,carrying out pilot scale experimental study mainly on oxidation ditch upgrading and reconstruction technology,biological filter advanced treatment technology and chemistry flocculation & filter unit etc.so as to determine key technological parameter.3.Analyze the conditions and existing problem to use treated urban sewage as main supplemental water for urban landscape water system;propose sewage regeneration treatment group technological process mainly for nitrogen and phosphorus content controland analyze its operation efficiency so as to determine the optimum technical performance parameter.Results:1.As phosphorus is the first restrictive nutrient element of algae population and density in water body,in order to prevent eutrophication,the concentration level of phosphorus shall be strictly controlled below 0.3mg/L The nitrous standard may be fixed at 15mg/L which is specified in the “ Standard of Reclaimed Water for Landscape Environment Use ”,however it is suggested to be controlled below 8mg/L.2.Hydraulic condition is another key factor for landscape water body eutrophication control,the minimum critical flow velocity determined by experiment is around 80cm/min,when the flow velocity is extremely low,other measures are needed to control excessive multiplication of algae.3.Addition of activated sludge/biological membrane compound technology in oxidationditch process can enhance nitrating capacity of the system and improve settling performance of sludge;addition of carbon source in oxidation ditch can remarkably enhance denitriding level remarkably to make effluent TN meet grade I-A standard,the middle ditch is recommended to be chosen as dosing point so as to save carbon source.4.Biological filter advanced treatment with glucose,methyl alcohol,ethyl alcohol,acetic acid and sodium acetate as carbon sources can get a perfect denitrification result,and the average removal rate of nitrate nitrogen is above 65%.Denitrification rates and nitrogen removal efficiencies of filter are different under different carbon sources;the filter has the highest removal rate when sodium acetate to be used as carbon source with the shortest contacting time and lower carbon nitrogen ratio,therefore sodium acetate is the priority option for anoxic biological filter denitrification.5.Utilization of ordinary biological aerated filter,denitrification filter or A/O integrated biological filter can achieve further removal of TN and ammonia nitrogen in effluent from common secondary treatment,and the effluent can meet grade I-A standard through control optimization of operating parameter.Different ammonia nitrogen and total nitrogen concentration need different biological filter type and operational mode.Denitrification biological filter can be used for advanced treatment when the ammonia nitrogen is low and the TN content is high in the secondary effluent;when both the ammonia nitrogen and the TN content in the secondary effluent are high,integrated biological filter with functions of deintrification and nitration can be used for advanced treatment.6.Urban sewage treatment plant secondary effluent after coagulation-sedimentation-sand leaching process,micro-flocculation-sand leaching process and coagulation-sedimentation-fiber bundle filtration process advanced treatment,the effluent TP can be controlled below 0.3mg/L.The coagulation-sedimentation-fiber bundle filtration process has its major advantage in the aspects of stability and economy,so it can be adopted with priority when the reclaimed water is expected to be used for landscape water body.7.The selection of reclaimed water treatment technological process shall meet the requirements of reclaimed water utilization standard and take full consideration of safety,rationality and economic efficiency of reclaimed water utilization.The technological process for the reclaimed water which will be used for landscape watercourse can be selected as per different inflow water quality condition,and the inflow pollutant concentration in each unit shall be controlled as per the actual condition of the inflow water to ensure the landscape recycling requirements are met. |
PDF Full Text Request