A Study on Zero Liquid Discharge Plant for Dyeing Industry

Abstract- Dyeing industry is one of the most and second largest polluting industries in India. Generally dyeing process produces mixed waste water in large quantities up to 600m3 per kg of fabric characterized by high organic load up to 1000mg/l COD, 7000 mg/l TDS, 2400 mg/l alkalinity. The release of coloured compounds and salt into the environment is undesirable not only because their colour, which may affect the photosynthesis of aquatic plants, but also because many dyes and their breakdown products may be toxic and/or mutagenic to life. The Zero liquid Discharge (ZLD) system removes dissolved solids from the wastewater and returns distilled water to the process (source). Reverse osmosis (membrane filtration) may be used to concentrate a portion of the waste stream and return the clean permeate to the process. This process may include pre-treatment, membrane filtration, evaporation, crystallization and solids recovery. Each module can be executed in parallel to expedite the design and implementation process. In this paper the effluent parameters should be analyzed and reduce the colour using oxidation reduction reactor. The treated water is recovered from the Reverse Osmosis Plant (RO) process during tertiary treatment phase and Salt is then recovered by Multiple Effect Evaporation (MEE) with Crystallization during reject management phase. In this process TDS removal efficiency of greater than90% resulted in permeate having average TDS of 20 mg/l. This coupled with the high water recovery of 80 to 90% made the RO process and reject management both technically and economically viable for recovery and reuse of the waste water. 80- 85% of the water can be recovered and re-used back in the process.