| The shortage of water resources has become a global problem,and the development and utilization of unconventional water resources has become an important way and method to solve the shortage of water resources.Among them,wastewater recycling is one of the main sources of unconventional water resources.At this stage,dual-membrane desalination treatment technology with ultrafiltration(UF)and reverse osmosis(RO)as the main body has carried out a lot of research work in the field of seawater desalination and industrial water treatment and has been applied in practical engineering.However,there are few researches on the application of UF-RO double membrane technology in the advanced treatment of sewage in specific cities and low temperature conditions,especially the lack of systematic research on the treatment efficiency of double membrane systems and the formation and optimization of RO membrane pollution under high pollution load conditions..In this paper,the secondary sewage treatment effluent of a municipal wastewater treatment plant in Qingdao and Zhangjiakou Chongli Miyuan Ski Resort under low temperature conditions was used as the treatment object.The pilot-scale UF-RO double membrane system device was used to carry out high-pollution load conditions.The treatment efficiency of the double membrane system and the formation and optimization of RO membrane pollution control methods and the research on the system operating effect under low temperature conditions,the operation stability of the double membrane system under different water quality fluctuations and operating conditions was investigated,and the composition characteristics of the RO membrane surface pollutants were analyzed,so An enhanced pretreatment and online membrane pollution control method to reduce membrane pollution are proposed to provide technical support for the application of UF-RO dual membrane technology.The main research results of this pilot test study are as follows(1)The UF-RO pilot test system was used to remove pollutants from the effluent of an urban sewage treatment plant in Qingdao,and it was found that UF as a RO pretreatment unit had significant removal of suspended particles and colloids,and the average turbidity removal rate reached 95.4%,The probability that the SDI15 value of UF produced water is less than 2.5 reaches 98.21%,which meets the RO influent requirements.RO produced water conductivity is 30 ?s/cm?90 ?s/cm,TN is 0.12 mg/L?1.12 mg/L,TOC is 0.12 mg/L?1.25 mg/L,UV254<0.008 cm-1,total hardness 92.73%Of the time is distributed below 2.5 mg/L,and the effluent quality and quantity of the system are stable(2)Conduct research on microflocculation enhanced ultrafiltration operation effect and membrane fouling,and found that microflocculation enhanced ultrafiltration can delay the degree of membrane fouling and improve the removal rate of organic matter Compared with no added flocculant,TOC removal rate increased by 19.74%when the dosage of polyaluminum chloride(PAC)was 3 mg/L,and increased when the dosage of FeC13 was 2 mg/L.18.16%.Excessive addition of PAC and FeC13 will accelerate the overall growth of UF TMP,ATMP,TMP0.The dosage of PAC in this system cannot exceed 4 mg/L,and the dosage of FeC13 cannot exceed 3 mg/L.PAC can be used as the preferred flocculant Used for micro-flocculation and enhanced ultrafiltration.Through the ultrafiltration filtration-backwash optimization study,the optimal operating conditions of the UF system were determined to be:operating flux of 60 L/(m2·h),water production cycle of 35 min,and backwash flux of 230 L/(m2·h)(3)Carry out the RO system operation stability test,and study the RO membrane desalination rate,membrane flux and span under the conditions of high salinity and large fluctuations in water quality conditions such as operating pressure,recovery rate,conductivity and inlet temperature The influence law and significance of the membrane pressure difference,and establish the relevant relationship to guide the production practice.Among them,the influence of operating pressure,influent conductivity and temperature on the desalination rate can be used to guide the desalination rate of the system during normal operationy=A2+(A1-A2)/(1+(x/x0)^p)=0.98858-0.00032/(1+(x/1.30967)15.94)y=0.991814-0.000017 x y=A1*exp(-x/t1)+y0=-0.506×e(-x/21.08)+99.46(4)Anatomical analysis of the RO membrane module revealed that the type of pollution was mainly organic pollution.The organic pollutants were mainly microbial metabolites and humic acid humic substances,and the membrane surface of the inlet side was more polluted than the outlet side.Both the water inlet and the water outlet contain aromatics or unsaturated carbon bonds of organic matter,nucleic acid substances,sugars,sulfates,and lipid substances.Through the analysis of microbial community structure,it was found that the advantages of pollutants in water samples and membranes along the UF-RO system are basically the same.The main dominant bacterial genus belongs to the class of ?-proteobacteria and actinomycetes.Actinobacteria,Alphaproteobacteria,Bacteroidia.(5)Through running a low temperature test with a water temperature variation ranging from 9.5? to 12.9?,it is found that the average value of OF produced SDI15 is 3.11,and the effluent turbidity is less than 0.5 NTU,which meets the RO inlet requirements.The UF-RO double membrane system has a good effect of removing pollutants under low temperature conditions:the average removal rates of CODCr,UV254,TN,total hardness,conductivity,and TDS are:92.6%,96.9%,87.4%,94.2%,98.1%,97.6%.During the long-term operation of the UF-RO system,the UF water production flow rate is stable at 3 m3/h,and the average water production rate is higher than 90%.The average desalination rate,recovery rate and water production flow rate of the RO system are 98.3%,69.9%,2.1m3/h,UF-RO system is running stably. |
PDF Full Text Request