Treatment of textile wastewater using calcium hypochlorite oxidation followed by waste iron rust aided rapid filtration for color and COD removal for application in resources challenged Bangladesh

The textile industry is the main revenue source of the foreign exchange of Bangladesh. Unfortunately, in recent times the industry is marred with bad operation practices such as the discharge of untreated textile wastewater into the water bodies. This is having a disastrous environmental impact on the rivers and streams in areas of Bangladesh where the industries are clustered. The high cost of treatment incurred due to the use of expensive imported treatment chemicals and the dependence on energy-intensive technologies leads to incompliance. In search of a sustainable option, a technology development project was undertaken at the bench-scale with the research goal of developing an appropriate method of pre-treating textile wastewater using locally available chemicals and materials. The process involved chemical oxidation using Calcium hypochlorite followed by waste iron filings aided rapid sand filtration to remove residual OCl- ions and suspended residue from reduced calcium hypochlorite. Complete removal of the color and over ninety-five percent removal of chemical oxygen demand was achieved. Reducing the chemical oxygen demand calls for reduced loading to the downstream biological treatment system thereby reducing aeration requirement and thus energy consumption. The developed process has the potentials as a sustainable wastewater pre-treatment option for the textile industries of Bangladesh as a bottom-up reliable supply chain technology using local chemicals and materials.