Upgrading Reconstruction Of A Industrial Wastewater Centralized Treatment Plant In The Island Area

As a special zone for the transition from land to sea,island has its special industrial types,including marine fishery processing industry,ship building and repairing industry,petrochemical industry,marine biological pharmaceutical industry and so on.Based on the actual engineering design,this paper analyzed the operation status and existing problems of the industrial wastewater treatment plant in the island area,and proposed the upgrading plan to impro-ve the running performance and ensure the water quality.(1)As for the source of wastewater,there were 56 enterprises emitting wastewater into the industrial wastewater centralized treatment plant,the main types of which were aquatic products processing plants.The main pollutants involved COD,BOD5,SS,ammonia nitrogen(NH3-N)and total phosphorus(TP).In order to satisfy class 2 of the "Integrated Wastewater Discharge Standard(GB8978-1996)"’ the original system designed three-stage treatment process,including coagulation flotation-anaerobic-MSBR-coagulation sedimentation.Analysis of the previous two years of operation data showed that COD,BOD5,SS and NH3-N could be stable to meet the emission standards,but the effluent total phosphorus exceeded.(2)The reasons of phosphorus exceeded in the original system wastewater treatment plant effluent included:the deficiency performance of coagulation flotation,MSBR and coagulation process;the sludge dewatering liquid was directly returned to the regulating tank,and no phosphorus removal pretreatment was carried out.In addition,the other problems existed:biochemical system did not discharge sludge in time due to the deficiency of sludge dewatering capacity;there was no process designed to removal odor which resulting in excessive odor emission in the plant;the main equipment and materials did not have efficient performance due to many years’operation.(3)The upgrading project of this engineering belonged to partial reconstruction,which utilized the existing planes,structures,buildings,equipment,supporting pipelines and ancillary facilities.The upgrading plant mainly involved the adjustment of core wastewater treatment process,creating the new odor treatment process(mainly biofilter-alkali absorption)and the equipments updation.Among them,the adjustment of core wastewater treatment process,contained the addition of phosphorus removal agent lime in the coagulation floating and coagulation sedimentation stage,the timely sludge discharge,optimization of aeration and equipments in biological treatment unit for enhancing biological phosphorus removal.In addition,after collecting the supernatant of sludge thickener and filtered fluid of dehydrator,added agent lime to remove phosphorus.According to the performance of the upgrading plant during a year,the main pollutants of COD,BOD5,SS,NH3-N and TP all satisfied class 2 of the "Integrated Wastewater Discharge Standard(GB8978-1996)",and COD as well as NH3-N could reach class 1.