Analysis of High-Salt Wastewater Treatment Processes

In recent years, with the continuous improvement of people's material living standards, their environmental awareness has been continuously enhanced, and they have paid great attention to things that can aggravate environmental pollution in social development. The gradual increase in the discharge of industrial wastewater has increasingly aggravated the problem of environmental pollution, and it has also posed a great threat to human life and health, especially the discharge of salt chemical wastewater, which is not only toxic but also difficult to treat, making it difficult to solve China's environmental pollution problems. Therefore, it is necessary to optimize and improve the existing wastewater treatment processes of salt chemical industry. This article elaborates on the main sources of high-salt chemical wastewater and studies the treatment processes of high-salt chemical wastewater, so as to provide good help for relevant personnel in choosing the correct process. High-Salt Wastewater Treatment Process

1 Overview

1.1 Definition of High-Salt Chemical Wastewater

High-salt wastewater refers to a mixture with a total salt mass fraction of at least 1%. In terms of NaCl content, it is considered high-salt water with a concentration of 10 g/L or more. High-salt wastewater usually contains a variety of ionic components and a high content of organic matter, which is currently difficult to treat.

1.2 Sources of High-Salt Chemical Wastewater

At present, the wastewater discharged by dyeing, papermaking, chemical, food and pharmaceutical industries has a large volume and high salinity. Wastewater from petroleum, natural gas processing and recovery industries, and coal chemical industries is also saline wastewater. These wastewaters generally have high salinity and high organic load, and some even contain toxic and refractory organic substances such as benzene ring compounds and hydrocarbons, which are high-salt toxic industrial wastewaters. If their discharge is not strictly treated and they are discharged without reaching the relevant discharge standards, they are likely to cause serious pollution to the surrounding ecological environment.

For relevant sewage treatment, overall design and arrangement are needed to comprehensively improve the comprehensive pollution treatment effect.

2 Process Analysis

2.1 Pretreatment Process Analysis

2.1.1 Coagulation-Sedimentation Process

For high-salt wastewater with CODcr <5000mg/L, the "adjustment-chemical addition flocculation-flotation, sedimentation" process is used for pretreatment. This process has low investment and operating costs, but the crystalline salt quality of the subsequent evaporation concentration crystallization desalination system is poor.

2.1.2 Fenton or Electro-Fenton Catalytic Oxidation Process

Fenton's reagent has a strong oxidation capacity for organic pollutants in wastewater, and the reaction is fast and the investment is low. After sedimentation purification, the effluent can achieve pretreatment purposes. The Fenton or electro-Fenton catalytic oxidation process requires adjusting the wastewater pH to 2~4, and will produce a lot of iron-containing sludge, and the effluent will have color. When the wastewater pH is low or the enterprise has usable waste acid, the Fenton method is more economical. When the wastewater CODcr>10000mg/L, multi-stage oxidation purification treatment is required, and the Fenton method has no obvious advantages.

2.1.3 Dual Membrane Process

The dual membrane method is one of the more important wastewater treatment methods. First, in the overall use process, it is necessary to comprehensively use relevant semi-permeable membranes for ultrafiltration treatment, and the overall treatment of pollutants needs to be arranged in a diversified manner. Proteins and various enzymes have good effects. It has a good treatment effect on large substances. Secondly, in the treatment of high-salt wastewater, it is necessary to comprehensively improve the comprehensive treatment effect of the relevant water volume, reasonably treat the relevant pollutants, ensure the overall effect of sewage treatment, and the dual membrane method has great advantages in practical use, reducing the flow rate of evaporation crystallization, and comprehensively reducing operating costs and investment.

2.1.4 Ozone/Catalysis/Coagulation Composite Pretreatment Process

Ozone can be used as a catalyst and flocculant, and can complete the relevant synergistic reaction under specific environment and time. In the whole treatment process, it can break the ring chain and long chain of wastewater, ensuring that the biodegradability of wastewater can be improved. Therefore, in the current specific treatment process, it is necessary to reasonably complete the use of ozone to improve the overall treatment effect of wastewater. In the current environmental pollution process, the use of ozone can treat organic matter in wastewater, and for relevant organic matter, the colloid in wastewater can be comprehensively treated to ensure the overall effect of wastewater treatment. However, there are still some problems in the overall wastewater treatment process. Relevant salts and ammonia nitrogen cannot be treated, so in the current overall treatment process, it is necessary to improve the overall technology and reasonably use various treatment methods to comprehensively improve the water treatment quality.

2.2 Thermal Evaporation Crystallization Desalination Process Analysis

2.2.1 Multiple Effect Evaporation (MEE) Technology

In a multiple-effect evaporation device, the secondary steam produced by heating the first effect with new steam does not enter the condenser, but is reused as the heating medium for the second effect. This can effectively reduce new steam consumption. Repeating this principle can further reduce new steam consumption. The high heating temperature of the first effect and the low boiling point temperature of the next effect form a total temperature difference, distributed in each effect, as the driving force for evaporation. The secondary steam of the last effect needs to enter the condenser to be condensed using circulating cooling water.

2.2.2 Mechanical Vapor Recompression (MVR) Technology

MVR is the most energy-saving among all evaporation crystallization processes. Its basic principle is to compress the secondary steam that would originally need to be condensed with cooling water in the evaporator by a compressor to increase its pressure and saturation temperature, and then send it to the evaporator heater as a heat source to heat the liquid material. Because the latent heat of the secondary steam is fully utilized, energy saving is achieved.

3 Conclusion

In summary, although China is a country with relatively abundant water resources, there is an uneven distribution of water resources between the north and the south, and the usable water resources are also limited. Therefore, the reasonable treatment and reuse of high-salt chemical wastewater is of great practical significance. The selection of high-salt wastewater treatment technology needs to be based on the actual salt chemical production situation to select a mature and economically reasonable treatment process, so as to achieve efficient wastewater recovery, ensure the improvement of crystal salt purity, and promote the efficient use of resources by salt chemical enterprises.