Study On Analysis,Prediction And Recovery Of Fouling Of RO Membrane

Reverse Osmosis (RO) technology has been widely used in the fields of water-treatment with its highly effieient, stable and high degree of automation. However, the key limited factor in varieties application of reverse osmosis is membrane fouling which increases the operating costs as well as shortens the life of membrane,and directly influences the efficient and continuous running.In view of this issue,this paper carried out a systematic study on fouling of RO membrane, including analysis,prediction and recovery of fouling on RO membrane.In the part of analysis of fouling membrane,the membrane module was dissected, and the pollutants and their distribution on membrane was analysised through the methods of apparent observation,SEM-EDX,LOI,FT-IR,GC-MS and static cleaning experiments.Results show that organic contaminations,including hydrocarbons,fatty acid,benzene ring and so on,are the main pollutants,except that there is also some inorganic contamination which is basically SiO2;The total pollutants are increased from the inlet side to the outlet side of the membrane module,the variation of the inorganic contaminations is the same as this,but that of the organic contaminations is opposite; analysis by synthesis the result of SEM-EDX and static cleaning experiments,the process of membrane fouling in this module can be guessed,which is that organic contaminations sedimentated on the membrane at first, then inorganic contaminations which is gradually covered by organic contaminations in the end,are sedimentated together with inorganic contaminations. For further study of organic pollution, molecular weight distribution of organic matter in the RO inflow,concentrated water and producing water is determined and compared,the result show that the molecular weight of the most of the organic matter in RO inflow is below 5kD,and most organic whose molecular weight is between 30kD and 100kD is sedimentated on the membrane in the process of RO.A study on the influence of cleaning conditions including temperature,pH,concentration,cleaning time,etc, to the effect of chemical cleaning is carried out,combined with the results of membrane fouling,eight cleaning solutions are put forward and compared through experiments,and finally the best solution is selected,which is 0.1%NaOH+0.025%Na-SDS→0.2%HCl→1.0%Na2S2O4.The best solution is used in the cleaning of membrane module,and get a good effect.A forecasting model of undissolved salt precipitation and a evaluation model of concentration polarization are made, in which the temperature,ionic strength,pH,concentrating of inflow are took into account.A method to forecasting undissolved salt precipitation on membrane is put forward by combining the forecasting model of undissolved salt precipitation and the evaluation model of concentration polarization.