The locally designed water treatment technology for a vehicle washing bay’s effluent in Wakiso district, Uganda

Abstract

Vehicle washing is a very lucrative industry that is rapidly growing in Uganda due to the increased demand for transport services. In an event of washing vehicles, a lot of water is used that transform into waste water. Therefore, the study focused mainly on quantifying the daily volume of water used, characterizing the pollutants, designing waste water treatment technology and quantifying volume of water recovered. The study used a jerrycan model, Auto card to implement and design the technology, and used Microsoft Excel and R data analysis to organize and analyze data. Daily, 29.3±6 saloon vehicles of weight less than 3.5 tons and 9.4±3.3 heavy truck vehicles of weight at least 3.5 tons and more were washed. However, 4,841±314 litres of water were used daily 97.2±26 litres of water for each saloon vehicle and 212±48 litres for each heavy truck. The designed technology was effective in treatment of the vehicle washing bay waste water for turbidity from (1139±13.4 NTU to 57.5±24.1 NTU), TSS (2878±2.5 mg/l to 46±25.8 mg/l), COD (458±2.5 mg/l to 46±7.3 mg/l), orthophosphates (5±0.5 mg/l to 1.86±0.375±0.5 mg/l) and TDS (107±18.8 mg/l to 96.7±4.33), EC (413±24.3 μS/cm to 372±16) and pH (7 ±0.3 to 7.58±0.21) conforming to the recommended waste water discharge standards at 100% (NEMA, 2014). However, pH, EC and TDS values were within the recommended waste water discharge standards before treatment. In summary, 80% of the waste water was recovered as treated water and 20% of waste water lost by the treatment system. In conclusions, the waste water from Vehicle washing bays is polluted with pollutants levels that do not qualify it to be discharged into the environment without treatment. Therefore, there is a need to adopt a locally designed constructed wetland technology in the treatment and recycling of waste water from the vehicle washing bays, for both environmental protection and reuse.