Removal of Colour from the Wastewater of Pigment Manufacturing Unit

The paint and pigment manufacturing requires several tanks and mixers during the production process. When these tanks are washed, the resulting wastewater is loaded with coloured pigments. Besides this, the wastewater generated during pigment manufacture also contains various types of resins and solvents. Removal of colour in the effluent from the pigment manufacturing unit is one of the key goals of the ETP.

Chemically, most of the pigment industry wastewater contains high levels of organic acids, ammonia, phenol-based compounds, and derivatives of aniline and benzene-based compounds. The BOD levels are usually around 500 to 800 PPM while the COD is around 10000 to 15000 PPM. Due to the recalcitrant nature of most compounds found in the effluent the biological treatment is not easy. Generic bacteria struggle to survive in such effluent leading to inefficient secondary treatment and a negligible colour reduction if any.

ETP managers often tend to use chemical coagulants to remove suspended solids. This leads to the generation of large volumes of sludge at the end. Also, this process leads to colour concentration rather than actual colour removal which can occur only by degrading the pigment molecules.

Here in this example, we partnered with a pigment manufacturing company in Calcutta, India, for biological wastewater treatment. The water had high ammonia levels of 5782 PPM and the COD was at 39420 PPM. By using our standard aerobic bioculture - Evobac, the company was able to degrade pigments and reduce colour in wastewater significantly. Evobac has active aerobic bacteria that can easily break complex aromatic ring compounds into simpler molecules. Bacteria in Evobac are evolved to use phenol, benzene and aniline-based compounds as their carbon source (as food). These bacteria were able to rapidly break down the chromophores and remove the colour from the effluent water while lowering the COD and BOD of wastewater. With a retention time of 24 hours, the bacteria were able to degrade more than 90 per cent of the colour pigment in the wastewater.