Experimental Study On Membrane Distillation Treatment Of Reverse Osmosis Concentrated Water From Deep Treatment Of Coking Wastewater

Coking wastewater is the waste water produced in the process of coal chemical production.The double membrane process?microfiltration/ultrafiltration-reverse osmosis?is widely used in the deep treatment of coking wastewater.However,the yield of reverse osmosis is only70% 75% Produce25% 30%of the reverse osmosis concentrated water.With the industrial wastewater "zero liquid discharge" requirements proposed to seek better treatment,more stable process,lower operating costs of reverse osmosis concentrated water treatment process to achieve zero waste discharge targets,coal chemical industry has become the development of their own needs And external requirements.In this paper,the reverse osmosis concentrated water of a coking enterprise in North China was taken as the research object,and the experimental study on the membrane distillation of coking and reverse osmosis was carried out.The combined treatment process of pretreatment and membrane distillation was explored.The main conclusions are as follows:The softening treatment of coking and reverse osmosis concentrated water by lime/soda ash softening method can effectively reduce the hardness of raw water.When the hardness of raw water is 763.4mg/L,the dosage of Ca?OH?₂ is 400mg/L,the dosage of Na₂CO₃ is 720mg/L,the total hardness is 68.3%,the total hardness is 242.0mg/L,The cost of treatment of pharmaceuticals is 1.17 yuan.Fenton oxidation method has the advantages of high removal efficiency and low cost of pharmaceuticals compared with powdered activated carbon adsorption method,which can effectively reduce the content of organic matter in coking reverse osmosis concentrated water.When the CODcr of raw water was 308.3mg/L,the CODcr removal rate was 53.73% at pH 4,the ratio of H₂O₂ / CODcr was 1: 1,the molar ratio of H₂O₂ / Fe²⁺ was 20: 1,and the cost of water treatment was about 1.4 yuan.VMD method can effectively deal with coking and reverse osmosis concentrated water,the appropriate process operating parameters for the feed temperature of 60?,cold side vacuum 0.095 Mpa,feed flow 1.5L/min;test membrane distillation TDS removal rate>99.9 %,CODcr removal rate>90%,the conductivity stabilized at 10 us / cm below.The results showed that the combination of softening+Fenton oxidation+VMD had a good effect,and the decay of water flux decreased during the process of membrane distillation.CODcr <20mg / L,TDS < 10 mg / L,conductivity <10us/cm,excellent water quality,is feasible coking reverse osmosis concentrated water treatment process.Membrane cleaning results show that the use of hydrochloric acid,EDTA,sodium hypochlorite on the membrane components were combined to clean up to 93% of the membrane flux.