Study On Nanofiltration Technology With High Recovery Of Drinking Water

With the continuous development of China’s national economy and the continuous improvement of industrial level,the exploitation of groundwater in China has increased year by year.However,in view of China’s natural environment,the supply capacity of groundwater is constrained,and the situation of groundwater pollution is not optimistic.Especially in the industrial agglomeration area,River coast,urban surrounding groundwater,there are varying degrees of pollution,nitrate,nitrite,ammonia nitrogen,phenolic organic matter,heavy metal ions in varying degrees exceed the standard,into 80% of the groundwater can not reach category III,the production costs of industrial enterprises,the people Health and safety pose a threat.In view of this kind of polluted groundwater,the traditional groundwater treatment process can not work very well.At present,the common small-scale water treatment station often uses the "quartz sand + melt blown filter core + reverse osmosis membrane" process.This process is simple,widely applicable,mature use.However,the system suffer from inherent limitations in various aspects,including inefficiency and easy scaling.Thus,it is essential to develop a more economically process to treat groundwater.Ion exchange softening and nanofiltration membranes are common water treatment processes in the industry,and are mainly used for boiler feed water and sewage treatment.The purpose of this paper is to study the operation of the nanofiltration membrane in the "ion exchange + nanofiltration" process under the condition of excellent groundwater quality and certain water production rate.There are two main types of water quality: high-hardness groundwater and high-salt groundwater.The operating cost of the process was discussed,and the application value of the "ion exchange + nanofiltration" high recovery process was also analyzed.This paper mainly compared the effects of two nanofiltration membranes in series and ion exchange + nanofiltration membrane on recovery rate and water quality.The dynamic experiment mainly analyzed the ability of the process to treat polluted groundwater from the comparison of pH value,flow rate,hardness,conductivity of raw water and concentrated water recovery of nanofiltration membrane,ion exchange + nanofiltration membrane,ion exchange + nanofiltration membrane.The results obtained through research are as following:(1)If the nanofiltration membrane is not subjected to concentrated water recovery,the recovery rate is only 15%,and it is greatly affected by the hardness of the water.As the water hardness increases,the recovery rate gradually reduces.(2)Dynamic experiments show that the increase of softening process has a certain effect on the recovery of nanofiltration membrane.When the water hardness is 200,after the softening process is increased,the recovery rate of nanofiltration membrane increases from the original to 40%;(3)The dynamic experiment proves that the concentrated water recovery is the way to increase the recovery rate of the nanofiltration membrane when the nanofiltration membrane is connected in series.After recovery with concentrated water,the recovery rate of the nanofiltration membrane can reach 80% or more.(4)From the current experimental conditions,the process is suitable for treating contaminated groundwater with a hardness below 800mg/L and a salt content exceeding the standard under high recovery rate.