Design of a car wash wastewater treatment and recycling system : case study : Clock tower car wash

Abstract

Uganda is a highly motorized society. Kampala as a city, has a high number of vehicles as the seat of power in Uganda. Most of the vehicle washing activities in Kampala city are carried out in streets. Cars that are washed in streets pollute streams, rivers, bays and estuaries (Huybrechts et al.,2002). Wastewater from car washing stations contains a number of impurities that include; sand and, dust, free oil, grease, detergents, phosphates" paint residues, rubber, volatile organic compounds (VOCs), and rubbish. The main objective of this project was to design a car wash wastewater treatment and recycling system and the case-study area being Clock Tower Car Wash Kampala. The project involved-a review of several literature pertaining, to car wash effluent treatment and recycling systems, characterizing and quantifying the waste water composition, designing the various components of the car wash wastewater treatment and recycling system and finally economic analysis of the project was done. Relevant equations were used, in the design of various components of the Car wash wastewater treatment and recycling system. From the research carried out wastewater generated from Clock Tower Car Wash was 16,800 Litres per day and the highest number of vehicles that could be washed in a particular day being too vehicles, with 5 heavy vehicles and 95 light vehicles. The wastewater being discharged showed poor physical chemical characteristics and thus needs treatment before discharge or reuse. Conveyance pipes were sized, then treatment units 2 oil water separator tanks, 2 slow and sand filters; clear water well plus water pump, and overhead tank were sized. An economic analysis of the system was done using benefit cost ratio approach and it was found to be 2.0. This means that the project is viable and thus should be, implemented to curb down environmental degradation and reduce on the cost of fresh water from National Water and Sewerage Corporation (NWSC).