Pollutant Removal Performance And Membrane Fouling Characteristics In Marine Aquaculture Wastewater Treatment By A Microalgae Biofilm MBR

In recent years,the rapid development of the marine aquaculture industry has led to the discharge of a large amount of marine aquaculture wastewater,which poses a serious threat to the coastal ecology.Marine aquaculture wastewater is usually rich in organic matter,nitrogen and phosphorus.In addition,the problem of high salinity in marine aquaculture wastewater also brings huge challenges to the treatment process.The microalgae biofilm MBR uses a combination of immobilized microalgae and membrane bioreactor.Compared with traditional physical and chemical methods,wastewater is treated efficiently while microalgae biomass is enriched by the process,which greatly reduces the harvesting cost,and the microalgae harvested can be used in food and other industries widely,economic benefits is bright.In this experiment,a three-stage fluidized bed microalgae biofilm reactor(microalgae biofilm MBR)was built.Polyurethane fillers were used as biological carriers,marine aquaculture wastewater was used as the research object,mixed algae was used as algae specie.In the following discussion,the three compartments are represented by M1,M2,and M3.A suspended microalgae membrane reactor was used as a control group to investigate the efficiency of the microalgae biofilm reactor in treating marine aquaculture wastewater and the characteristics of membrane fouling during the operation of the reactor.At the same time,the operating conditions were improved to strengthen the efficiency of the wastewater treatment.The results showed that the process had good efficiency in removing ammonia nitrogen and organic matter.Removal efficiency of organic matter,phosphate,and ammonia nitrogen were taken as indicators,the experiment explored the effects of different HRT(8 h,16 h,24 h),and different concentration of organic matter in influent(TOC=50 mg/L,TOC=70 mg/L,TOC=90 mg/L)on removal of pollutant,microalgae growth,and membrane fouling.The results showed that the growth efficiency of microalgae,and the removal efficiency of ammonia nitrogen increased with the extension of HRT,and the removal efficiency of phosphate decreased with the increase of HRT.the removal efficiency of TOC increased slightly with the increase of HRT and concentration of influent organic matter.The growth efficiency of microalgae and the removal efficiency of phosphate increased with the increase of the concentration of the organic matter,and the removal efficiency of ammonia nitrogen did not change much.During the experiment,the removal of ammonia nitrogen,and organic matter was mainly carried out in the first compartment.Combined with the analysis results of membrane fouling characteristics,removal efficiency of the pollutant and membrane fouling of the experimental group were better than those in the control group.During the 90-day operation of the microalgae biofilm MBR,the treatment performance for wastewater and membrane fouling characteristics were monitored.The results showed that the removal efficiency of ammonia nitrogen was at about95%,50% was removed in M1,and 40% was removed in M2.The removal efficiency of TOC was at around 90%,70% was removed in M1,and 15% was removed in M2.The removal efficiency of phosphate was at around 30%.The treatment efficiency of the reactor was enhanced by changing the aeration rate.The results showed that the nitrification reaction in the system was strengthened under intensified conditions,removal efficiency of the total nitrogen and the phosphate increased by about 10%.The analysis of the pollution characteristics of the microalgae biofilm MBR showed that the main components of SMP and EPS were protein and polysaccharides the polysaccharide content in SMP was higher,and the protein content in EPS was higher.Protein-based macromolecular substances were the main cause of membrane pollution.The content of biological macromolecular substances in the microalgae biofilm MBR was gradually reduced in the three-stage fluidized bed,which indicated that the microalgae biofilm MBR process can alleviate membrane pollution effectively.The research results showed that the microalgae biofilm coupled MBR process had obvious advantages in terms of purification of wastewater and laxation of membrane pollution.This process provided a new idea for the purification and treatment of marine aquaculture wastewater.