Selection of Suitable Techniques for Treatment of Wastewater in Karachi

Karachi is a metropolitan city divided into eighteen towns. The increase in the town population results in the rise of domestic waste generation. Five treatment plants were to be set up but only three are working and unable to meet the treatment requirements, so there is a need to construct a sewage treatment plant town-wise. Sewage water contains domestic household and industrial waste, which should be treated to remove harmful materials for a safe environment. This research has collected the data (contamination in sewage water) from KWSB (Karachi Water and Sewage Board) and reviewed different researches. To study preliminary, primary and secondary treatment and carried out detailed research and literature review to comprehend all aspects of existing mechanisms and concluded the most efficient mechanism to use in our design. This study has also designed the equipment used to purify water and the modeling of the purification process. The activated sludge process has been selected for the purification of sewage water. It is an economically feasible process for treating sewage water as easy to maintain and can handle a large amount of sewage water. The sludge generated by this process can be used as fertilizers or land fillers. Treated water can be used for irrigation purposes as the effluent characteristics are maintained according to standards of the irrigation water provided by environmental protection agencies, such as invigorating groundwater. Keywords: wastewater, purification, activated sludge, recycling, fertilizers