Decolourisation of leather dye by ozonation

Sewage and industrial effluent treatment plants are installed with primary and secondary biological treatment units to reduce the discharge of pollution load into the environment. These treatment plants normally reduce the organic load in terms of BOD but not the pollution load in terms of inorganic salts (total dissolved solids—TDS) and colour in the effluent. To eliminate the contamination of ground and surface water bodies and to conserve water sources, the regulatory authorities have taken very stringent regulations to implement zero liquid discharge (ZLD) for industrial effluents, i.e., water recovery from wastewater and reuse. It is difficult to recover water from secondary treated wastewater directly, as it does not meet the reverse osmosis feed requirements. In order to achieve the feed requirements, different tertiary treatment methods are being tried. In this study, removal of colour due to residual dyes has been attempted using ozone. The main purpose of this study is to decolourise the dye used in leather processing. Also, the effect of pH and dye concentration on dye decolourisation has been investigated. From the study it has been observed that maximum decolourisation efficiency up to 97% could be achieved for the pH values (4,7, 9 and 11) and dye concentrations (30, 65, 180 and 360 mg/L) studied.     

Enhancing methane production by anaerobic co-digestion of extruded organic wastes from slaughterhouse and vegetable market in batch and continuous processes

Clean Technologies and Environmental Policy - The organic wastes generated from centralized wholesale markets from urban centres are predominantly disposed in dumpsites/landfills. Although...     

Combined advanced oxidation and biological treatment of tannery effluent

During leather processing in tanneries, considerable amount of wastes with organic and inorganic pollutants are generated. For removal of these pollutants and recovery of water, biological treatment methods and reverse osmosis (RO) based membrane technologies are adopted. While recovering water from treated tannery effluent using RO membranes, presence of residual organics, dye molecules, and other impurities in the effluent have been reported as the major drawback which leads to membrane fouling and failure. In this study, an attempt was made to improve the quality of the treated tannery effluent by subjecting the secondary treated tannery effluent by ozonation alone and ozonation of primary and secondary treated tannery effluent followed by aerobic biological Sequential Batch Reactor (SBR). Maximum color reduction of 98% at pH value of 12 with ozonation alone was observed for secondary treated tannery effluent. Ozonation of secondary treated tannery effluent followed by further biological treatment in aerobic SBR increased the chemical oxygen demand (COD) removal rate and resulted in COD values less than 300 mg/L. In case of primary treated tannery effluent, maximum COD reduction of 64% was achieved in SBR.