7 Common Challenges in Treating High-Salinity Wastewater from Chemical Plants

The following are seven common challenges in treating high-salinity wastewater from chemical plants, compiled based on industry experience and technical literature, to facilitate comprehensive understanding and targeted solutions:

1.High salinity inhibits microorganisms and hinders biochemical treatment. High concentrations of salt (such as sodium chloride and sodium sulfate) alter the osmotic pressure of microbial cells, leading to the inactivation and death of microorganisms in activated sludge systems, and a sharp drop in biochemical degradation efficiency.

This manifests as low COD removal rates, unstable system operation, and in severe cases, system collapse.

2.Salt accumulation leads to equipment scaling and corrosion. Salt in wastewater crystallizes and precipitates on the surfaces of evaporation and heat exchange equipment, forming hard scale, reducing heat transfer efficiency, and clogging pipes.

Some ions (such as chloride ions) exacerbate equipment corrosion, shorten equipment lifespan, and increase maintenance costs.

3.Coexistence of recalcitrant organic matter increases treatment difficulty. High-salt chemical wastewater often contains recalcitrant organic matter such as dyes, pesticides, and pharmaceutical intermediates. These substances are highly toxic, structurally stable, and difficult to remove completely using conventional biochemical or physicochemical methods.

This results in effluent COD and toxicity indicators failing to meet standards.

4.Complex and fluctuating wastewater composition, resulting in poor process adaptability: Significant fluctuations in salinity, organic matter, pH, and suspended solids between different batches of wastewater lead to frequent adjustments to treatment process parameters, weakening the system's shock resistance and causing unstable effluent quality.

5.Difficulty in disposing of mixed salts and low resource utilization: The mixed salts produced after evaporation and crystallization have complex compositions and are often classified as hazardous waste, resulting in high disposal difficulty and costs.

Immature salt separation technology makes it difficult to recover and reuse valuable salts, leading to low resource utilization rates.

6.High energy consumption and high operating costs: Evaporation, concentration, and crystallization of high-salinity wastewater are extremely energy-intensive, especially traditional evaporation processes, which consume large amounts of steam, resulting in high electricity and reagent costs, placing a heavy burden on enterprises.

Equipment investment and maintenance costs are also high.

7.Difficulty in achieving water reuse rates and zero discharge: Achieving near-zero discharge of wastewater requires extremely high standards for treatment processes, system integration, and automation.

Water reuse rates are limited by water quality, technology, and economics. Some concentrated water and mother liquor are difficult to treat completely and ultimately require safe disposal.

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