Study On Microbial Inhibition And Scale Inhibition Of Sea-salt Water Treatment By Double Membrane Process

In order to improve the safety and stability of the double-membrane desalination process,it is of great practical significance to find efficient and low-cost bacteriostatic and scale inhibitor for the pretreatment of raw water.In this study,HEDP,PASP,PESA and the combination of three agents were selected as the target scale inhibitors for comparison,and two concentration gradients of 5 mg/L and 10mg/L were designed to investigate the improvement of membrane flux,reversibility of transmembrane resistance,divalent ion interception effect and Zeta potential.The experimental results show that for the improvement of membrane flux,the mitigation of membrane resistance and the interception effect of divalent ions,the effect of 10mg/L PASP is the best group among all the scale inhibitor combinations.When investigating the electrostatic interaction between pollutants,the group adding 10mg/L PASP has a higher Zeta potential on the surface of pollutants,which is lower only to the mixed group of 10 mg/L HEDP and PESA and the mixed group of 10 mg/L three scale inhibitors.It shows that the addition of PASP can effectively increase the electrostatic repulsion between ions and reduce the electrodeless crystal precipitation on the membrane surface.Finally,10 mg/L PASP was selected as the optimal group among all scale inhibitors.Then,hydrogen peroxide,ozone,sodium hypochlorite and potassium permanganate were selected for comparison,and two concentration gradients of 4mg/L and 8 mg/L were set to investigate the improvement of membrane flux and the inhibition effect on microorganisms respectively.The common gram-negative bacterium in the ocean,Bacillus halophilus,was selected as the target to remove bacteria.The experimental results show that H₂O₂ and O₃ are better than the other two antimicrobial agents for the improvement of membrane pollution.The specific flux of4 mg/L H₂O₂ and 8 mg/L O₃ fluctuate around 0.52.In terms of microbial inhibition,H₂O₂ and Na Cl O have the best effect.When they are 4 mg/L or 8 mg/L,the removal rates of bacteria are both close to 100%,while the effect of O₃ is significantly lower than that of H₂O₂.Considering the improvement of membrane pollution and microbial inhibition,4 mg/L H₂O₂ was finally selected as the optimal antibacterial agent group.After determining the optimal type and dosage of bacteriostatic agent,it is combined with the optimal scale inhibitor group at the same time.In this study,the parameters such as membrane surface morphology,membrane flux improvement and effluent quality are comprehensively characterized,mainly including the improvement of membrane flux,fluorescent organics in effluent,membrane surface morphology,residual elements and disinfection by-products of effluent,The experimental results show that when 10 mg/L PASP is combined with 4 mg/L H₂O₂,not only the membrane flux and membrane pollution are significantly improved,but also the ion interception rate is significantly improved.However,the contents of humic organic matter and disinfection by-products in the filtered water after combined use are significantly increased,which indicates that there is an interaction between microbial inhibition module and scale inhibition dispersion module.In practical application,it is necessary to give sufficient reaction time to the bacteriostatic agent to ensure that the bacteriostatic agent can react completely after sterilization and does not react with subsequent scale inhibitors.If necessary,an appropriate amount of reducing agent shall be added.This study shows that when the sea-salt water is treated by double membrane process,the membrane flux can be increased,the membrane fouling can be slowed down and the ion retention rate can be increased if the bacteria inhibitor and scale inhibitor are added to the pretreatment of the raw water..This provides a theoretical basis for developing sea-salt water desalination equipment suitable,forming a targeted water supply process and water quality security scheme for coastal areas.At the same time,it is also of great significance in ensuring the safety of drinking water for residents in coastal areas.