Study On Biogas Slurry Concentrated By Reverse Osmosis Membrane Technology And Membrane Cleaning

There are a lot of use value with biogas slurry,it was directly used to fertilizer with its high performance,however,the original nutrients concentration of biogas slurry is low,the volume is too big difficult to long distance transportation,so it is not conducive to the industrialization and commercialization.Concentrating biogas slurry by choosing reverse osmosis membrane technology to make volume the shrink sharply and enable achieve higher nutrient concentrations,at the same time,impurities are got to removed.In this paper,the concentration experiments of biogas slurry by reverse osmosis technology were studied.However,biggest problem encountered in the process of concentration was membrane fouling,membrane fouling increases the cost of operation,greatly reduce the efficiency of membrane performance.So according to the characteristics of the processed liquid,the study of the chemical cleaning on reverse osmosis membrane fouling was systematically carried.The conclusions of concentration biogas slurry and reverse osmosis membrane cleaning are as follows:(1)Ideal biogas slurry concentration process:settler(aeration treatment)?cartridge filter(5 micron filter bag)ultrafiltration membrane?reverse osmosis membrane;Over 5 microns solid impurity can be intercept by cartridge filter,over 500 molecular materials can be intercept by ultrafiltration membrane,Reverse osmosis membrane can remove over 1 nm materials.(2)The mode of the experimental process for concentrate is total reflux.In the ultrafiltration process with constant back flow and under the condition of constant temperature,water production of flux with gradually reduce with the running time,and the water conductivity rate,ammonia nitrogen and COD content is still high;the process of reverse osmosis membrane concentration is total reflux,water production is constant and under the condition of constant temperature,feed water pressure will remain the same in a certain period of time and after that the rapid increase trend,electrical conductivity of water and temperature over time gradually increased.NaC1O and NaOH cleaning has good recovery effect on ultrafiltration membrane;Reverse osmosis membrane has good recovery effect with acid and alkali cleaning.(3)The best multiple is 3 times for biogas slurry concentration by the technology of reverse osmosis membrane.With the increase of concentration ratio,the pressure is gradually increased,and water production of COD and conductivity increases with the increase of concentration multiple.(4)Through the EDX-SEM,GC-MS and XPS analysis of pollutants at the membrane surface,According to the characteristics of the treatment fluid,contaminants on the surface of the membrane are mainly organic matter pollution,including materials such as hydrocarbons,fatty acids and aromatic hydrocarbons,also contain inorganic contaminants,mainly for calcium carbonate,silica and silicate scale.(5)According the biogas slurry composition and analysis method,pickling of membrane after caustic washing first order is better.Made the 12 sets of cleaning solution according to the results of analysis,By comparing the membrane performance recovery rate,ultimately determine the best recipe for cleaning:0.2%NaOH+0.1%EDTA+0.05%NaC1O+0.05%SDS+0.1%STPP?0.2%HC1,the desalting rate reached 98.2%,the flux recovery rate reached 57.0%,the best cleaning temperature is 25??35?.