1. U.S. Environmental Protection Agency (USEPA) 2021. https://www.ozonetech.com/water-treatment/cod-bod-treatment-ozone accessed on 27/04/2020 2021.
2. How is water pollution treated? Prevention of water pollution 2021. https://www.water-pollution.org.uk/treating-water-pollution/accessed on 26/04/2020
3. OCHA, Policy Development and Studies Branch 2021. https://www.who.int/pmnch/media/news/2012/201205_africa_scorecard.pdf accessed on 02/05/2020 2021
4. Decolourization and cod reduction of textile wastewater by ozonation in combination with biological treatment;Abidin;Int. J. Autom. Mech. Eng. (IJAME),2016
5. Characteristic of COD and colour removal of azo dye in ozonation and biological treatment;Abidin,2011