Challenges, Traditional Solutions and Their Drawbacks in Treating Coal Chemical RO Concentrate

In the current booming coal chemical industry, wastewater treatment has become an important issue facing the industry, with the treatment of coal chemical RO concentrate being a particularly critical challenge.

During the coal chemical production process, a large amount of wastewater is generated, including gas washing wastewater, circulating water system discharge, and desalination system discharge. These wastewaters are complex in composition, containing various pollutants. In order to achieve water resource recycling and meet discharge standards, wastewater is usually pre-treated to remove suspended solids and colloids through flocculation and sedimentation, neutralize and adjust pH, and use sodium hypochlorite to inhibit microbial growth, among other methods, for initial purification. However, after pre-treatment, the wastewater entering reverse osmosis (RO) membrane treatment results in a high-concentration, saline wastewater with a high organic content, known as coal chemical industry RO concentrate.

Coal chemical industry RO concentrate has many characteristics that make it difficult to treat, thus becoming a pressing issue in the industry.

1. The high salinity not only affects the taste and usability of the water but also causes corrosion to subsequent treatment equipment.

2. Its high color, resulting from the complex organic components, poses another challenge.

3. Most of these organic materials are refractory to biodegradation, such as phenols, alcohols, benzene, aromatic hydrocarbons, fatty acids, etc., leading to high organic concentrations.

4. In addition, the composition of RO concentrate is complex, potentially containing heavy metals, ammonia nitrogen, etc., making treatment difficult and expensive.

The problems posed by coal chemical RO concentrate cannot be underestimated. Its high COD characteristics place significant stress on downstream wastewater treatment, severely affecting the stability of downstream processing units, making it difficult to achieve compliance with discharge standards. At the same time, this increases the operational difficulty and risks of wastewater treatment. In order to maintain the normal operation of the treatment system, companies are forced to invest more human and material resources, and the costs of treatment and labor also rise.

Although traditional coal chemical RO concentrate treatment processes can alleviate the problem to some extent, they all have obvious drawbacks. The reflux method increases the load on the membrane, accelerating membrane degradation and affecting its lifespan; coagulation adsorption mainly targets colloids and suspended solids, with treatment effectiveness closely related to water quality and pH, thus having limited applicability; activated carbon adsorption can reduce COD but requires regular activation, regeneration, or replacement, leading to high costs; advanced oxidation methods, although significantly improving COD, color, and biodegradability, are still insufficient when used alone.