Wastewater Treatment Project for the Leather Industry in India

Project Name: Wastewater Treatment Project for the Leather Industry in India

Pollution Type: Wastewater from the Textile Printing and Dyeing Industry

Treatment Scale: Daily treatment capacity of 3,000 tons

Treatment Technology and Process: Physicochemical + Biological

Case Introduction:

Located in Kolkata, India, a leather industrial park is primarily engaged in printing and dyeing of cotton knit fabrics. During the printing and dyeing process, a significant amount of wastewater is generated, mainly originating from production processes such as boiling, dyeing, soaping, and supplemented by a small amount of domestic sewage. The wastewater contains a large amount of residual dyes, auxiliaries, sizing agents, waste alkalis, fiber impurities, inorganic salts, etc., characterized by high organic content, high chroma, and high pH value. The water quality characteristics of this case are COD 1800 mg/l, BOD 350 mg/l, and SS 300 mg/l.

The wastewater is collected through a sewage collection pipeline network and enters a regulation tank, which homogenizes the water quality and quantity, reducing the impact on the biological treatment system.

Polyaluminium chloride is added to the flocculation and sedimentation system to remove suspended solids from the wastewater, reducing the load on subsequent systems.

The effluent flows naturally into the hydrolytic acidification tank, where large organic molecules are decomposed into small organic molecules, improving the treatment capacity of aerobic biodegradation. Simultaneously, effective nitrogen and phosphorus removal is achieved. Aerobic microorganisms in the aerobic tank utilize the organics in the wastewater for metabolism, reducing the organic content in the wastewater.

The microbial floc further flocculates and precipitates, with the upper clear water entering the filtration tank and the effluent entering the clear water tank, meeting discharge standards. The settled sludge enters the sludge thickening tank, where it is pumped into a filter press for dehydration by a sludge pump. The filtrate is returned to the regulation tank, and the mud cake is transported externally.

The wastewater treatment system for the textile printing and dyeing industry produces high-quality effluent, with major water quality indicators meeting discharge requirements. It effectively adapts to the reality of unstable effluent quality and unacceptable effluent chroma. Based on actual requirements and design processes, the "biological + physicochemical" combined treatment process is adopted to improve effluent quality, ensuring compliant discharge and long-term stable operation of the wastewater treatment system.