Treatment of High Salt and High Concentration Organic Wastewater

Fine chemical wastewater is a typical recalcitrant industrial organic wastewater generated in industries such as dyes, pesticides, and pharmaceuticals. It exhibits high COD, high ammonia nitrogen, and high chromaticity characteristics. The pollutants in the wastewater are mostly complex, toxic, and difficult to biodegrade organic substances. The salt content in this wastewater is generally at least 5%, which has a high salt content and inhibits the growth of microorganisms in the biochemical system, making the treatment of this type of wastewater difficult. The following table provides a comprehensive comparison of the main governance methods used.

Table 1 Comparison of Main Governance Methods

Based on the characteristics of different organic compounds in wastewater, a series of adsorbents have been developed through specific functional group modification and pore size control techniques. By relying on van der Waals forces, hydrogen bonds, acid-base, coordination and other forces, as well as high specific surface area, the adsorbents can selectively adsorb organic compounds in wastewater without being affected by salt, separating organic compounds from salt. The adsorbents have high adsorption capacity and fast adsorption speed.

Adsorbents that are saturated with adsorption can be desorbed using relevant regenerants, and the desorbed organic matter can be further recovered based on specific conditions. After detachment, the adsorbent regains its adsorption capacity, with high strength and long service life.

The adsorbed water can be directly discharged or connected to the pipeline network according to the situation. Alternatively, it can be further treated with physical and chemical technologies such as oxidation, and then discharged or connected to the pipeline network to meet the standards. Or sodium chloride brine can be used as brine for chlor alkali production. Alternatively, the salt content can be recovered through evaporation crystallization and sold as a byproduct.

Case

A chemical plant in Shandong province produces wastewater containing phenols and halogenated hydrocarbons, with a COD of around 5500mg/L. Treatment requirements: COD should be reduced to below 2000mg/L, and the appearance should be colorless. Adopting adsorption technology, the effluent COD is below 1000mg/L, and the effluent enters the evaporation system to recover salt.

Table 2 Water Quality Status

Figure 2 Treatment effect (raw water, effluent)