Wastewater Disinfection Using Artificial Ultraviolet Rays Technology

Despite technological advances in water and wastewater treatments, contaminated water is still an important vehicle of transmission for enteric pathogens of humans and animals. Untreated waters are normally discharged into surface waters. Proper disinfection treatment is extremely vital for reducing a large number of microorganisms present in wastewater. With proper disinfection, microorganism level in wastewater can be reduced to a safe level, allowing for wastewater to be reused in applications such as agricultural and urban irrigation without compromising on human health. Therefore, this study was developed to investigate the UV (ultraviolet) disinfection performance toward different microbial pathogens and evaluate the effectiveness of UV reactor in wastewater disinfection in Egypt. Low-intensity UV light was tested with different wastewater qualities to determine the variability of factors governing UV disinfection process in relation to bacterial types; also, compare the UV sensitivity of different microbial pathogens and fecal indicators to achieve the safe dose for wastewater disinfection, which could prevent the extent of (dark photo) repair in fecal indicators and pathogens after UV exposure; and investigate the suitable water characteristics for UV application to meet the allowable limits. It could be concluded that principal component analysis (PCA) indicated that each bacterial group has specific sensitivity and its inactivation is governed by different water characteristics in the UV reactor. VSS, TSS, and TDS of the wastewater were found to have the greatest effect on UV disinfection efficiency. UV dose was 5,305.2 mw/cm² s. Streptococci showed no repair for both dark and light, but fecal coliform and Vibrio cholerae showed little repair for dark and light. Salmonella and Shigella displayed more increase in dark and light than control samples. Photoreactivation was higher than dark repair. In relation to Salmonella and Shigella, a significant increase in the bacterial count in light repair is observed, that every cell (colony-forming unit) remained after UV exposure multiplied to 122 cfu in light repair.