Basic Features of Metrochem's Environmental Management System

1. Integration of cleaner technologies/practices with plant operations by using ultrafiltration for desalting and concentration dye solutions and spray dryers to
eliminate generation of waste water.

2. Recovery of waste compounds as by-products, their inter-plant exchange and
use as raw materials. They include spent sulphuric acid, hydrochloric acid, acetic
acid, glauber salt, sulphanilic acid and sodium bisulphite.

3. Comprehensive treatment and disposal of effluent streams using state-of-the-art technologies.

Waste Treatment Systems

A. Waste Water Treatment and Disposal

The procedure employed for treatment of waste water includes segregation into biodegradable, weakly biodegradable and non-biodegradable streams. Each stream is heated separately prior to combined treatment/disposal.

Biodegradable stream passes through primary treatment involving equalization, neutralization, coagulation, floculation and clarification for the removal of suspended solids and organics. It is then subjected to two-stage activated sludge type secondary treatment for removal of dissolved organics and other pollutants. Finally, tertiary treatment is imparted in the sand filter and granular activated carbon (GAC) filters. The treated effluent conforming to the norms specified by regulatory agencies is discharged into common effluent disposal system for safe disposal as prescribed by the authorities.

The weakly biodegradable stream is subjected to rigorous physico-chemical treatment for substantial removal of suspended, colloidal and dissolved substances. This treatment transforms some of the substances into biodegradable organics.
This pre-treated stream is combined with the bio-degradable stream for further treatment and disposal.

The non-biodegradable stream is treated in the zero effluent discharge plant consisting of various operations like chilling, crystallization and separation of
glauber salt, neutralization, filtration and separation of gypsum, concentration in multiple effect evaporators and fluidized-bed type incineration.

B. Treatment of Gaseous Effluent

The gaseous streams containing high concentration of SO2 is liquefied for its recovery in the form of liquid sulphur dioxide. NO2 is recovered in the form of dil. HNO3 acid by absorption in chilled water. The tail gases are scrubbed with caustic solution before emission.

Dilute streams are scrubbed with water and/or caustic solution for removal and recovery of waste gases as by-products.

Products entrapped in gaseous stream in the form of particulate matter are recovered in bag filters and clean air is let out. The flue gases and other gaseous streams are let out through stacks of right height to ensure efficient dispersion to protect ambient air quality.

C. Waste Solids

Gypsum generated in neutralisation of acidic streams is dewatered and sold to cement manufacturers.

Sludges resulting from primary and secondary treatment of waste water are dewatered and solids are disposed of into secured landfill sites in conformity with approved practice/ procedures.

Filter cakes from clarification of liquid products are also disposed of into secured landfill sites.

Monitoring

The quality of all effluent streams is monitored to ensure compliance with applicable norms specified by the authorities. Development of Green Cover Extensive plantation is carried out and maintained for enhancement in environmental quality and aesthetics. Investment & Operating Cost The total investment involved in setting up the effluent treatment systems is over Rs 281 million (25% of total project cost). Operating and maintenance cost works out to be around Rs 7.9 million-- Rs 7.9 per kg of product.