Study On Pollutant Migration For Highly Saline Organic Wastewater In Distillation Compression Process

High-salt organic wastewater discharges are large,and high salinity and high organic matter content make it difficult to handle,resulting in adverse effects such as soil compaction,eutrophication of natural water systems,and fresh water pollution,which are harmful to human living environment and human health.Based on increasingly stringent environmental standards,zero discharge of wastewater has become a trend.On the other hand,high-salt organic wastewater is also an invaluable resource,with inorganic salts and large amounts of energy having recycling value.The most effective way to treat high-salt organic wastewater is to realize its efficient resource utilization based on zero emission.To realize the final zero discharge of wastewater,distillation is an irreplaceable process.This method can simultaneously realize the recycling of salts.Currently,multi-effect evaporation and other technologies are widely used in wastewater treatment.Mechanical vapor compression(MVR)technology is based on vacuum distillation,making full use of the latent heat of vaporization,compressing the vapor and increasing the heat enthalpy for heating the wastewater.The steam itself condenses into water,eliminating the raw steam and the secondary steam cooling water system.Compared with multi-effect evaporation technology,it has become more energy-efficient and has attracted much attention in recent years.In this paper,high-salt organic wastewater was used as the research object.The migration characteristics of typical pollutants in the process of vacuum distillation compression were studied using vacuum distillation mechanism experimental device and MVR device.The evaporation temperature,evaporating pressure,cooling water temperature,evaporation time and pollutant types were emphatically expounded.Factors affecting the migration characteristics of pollutants such as inorganic salts,ethanol,toluene,and malachite green in wastewater are designed to provide basic experimental data for vacuum distillation to achieve zero discharge and resource utilization of high-salt organic wastewater.The control of pollutants provides the basis.After the high-salt organic wastewater is treated by vacuum distillation and mechanical vapor compression technology,the concentrated water is the main destination of Cl-,and the concentration in the condensed water is below 250 mg/L,which can meet the requirement of reuse water.Most of the ethanol migrates to the condensate,and subsequent treatment must be considered.Toluene migrates mainly to non-condensable gases,and most of the toluene has evaporated during the initial stage of evaporation.The interception rate of malachite green in concentrated water can reach 100%.The increase of the evaporation temperature and the decrease of the evaporation pressure both increase the evaporation rate ER,the Cl-concentration in the concentrated water,the toluene concentration in the non-condensable gas and the malachite green adsorption rate,and reduce the ethanol concentration in the condensed water.The increase of the cooling water temperature reduces the evaporation rate ER,the concentration of ethanol in the condensed water and the concentration of malachite green in the concentrated water,and the concentration of toluene in the non-condensable gas increases.The addition of NaCl,toluene and malachite green all reduced the evaporation rate ER;the presence of toluene inhibited the evaporation of Cl-and reduced the migration of ethanol to the condensate;the addition of malachite green led to a decrease in Cl-concentration in the concentrated water.Inhibition of the evaporation of ethanol.The presence of ethanol leads to an increase in the evaporation rate ER,the concentration of Cl" in the concentrated water and the concentration of toluene in the condensed water.The concentration of ethanol in the condensate water and the concentration of toluene in the non-condensable gas decreased significantly with the increase of the evaporation time.The concentration of malachite green in the concentrated water increased with the increase of evaporation time.Compared with vacuum distillation,the compression process of wastewater treated by MVR increases the concentration of Cl" and ethanol in the condensate,and the concentration of toluene decreases.The compression process has almost no effect on the migration of salts,and it still maintains a high salt rejection rate;the increase in the condensation temperature in the compression process leads to a reduction in the total migration of ethanol to the condensate,and the migration of ethanol in the condensed and non-condensable gases.Increase,while promoting the migration of toluene to non-condensable gases.Looking ahead,vacuum distillation is highly feasible for the treatment of high-salt organic wastewater.Not only can high-quality condensate water be recovered,but also the recycling of salts and organic materials can be realized,laying the foundation for zero emissions.As one of the key energy conservation and environmental protection technologies promoted by the country,the application of MVR in the treatment of high-salt organic wastewater will achieve the triple benefits of environmental pollution control,energy conservation,and maximum resource recycling.