Disinfecting Contaminated Water with Natural Solar Radiation Utilizing a Disinfection Solar Reactor in a Semi-arid Region

The present investigation was carried out to assess the efficiency of solar energy in disinfecting contaminated drinking water in a semi-arid region. Distilled water was inoculated with coliform bacteria and exposed to up to 6 hours of ultraviolet radiation using natural solar radiation and UV lamps of 365 nm wavelengths with varying intensities. Total coliform counts were enumerated at intervals to determine percentage inactivation against time. Other factors such as water turbidity, total hardness, chlorine level, pH and temperature were also monitored. The results showed a rapid decrease in microbial counts upon exposure to solar radiation. More than 99.99% reductions were achieved after 6 hours for the bacterial communities tested under different conditions. The rate of inactivation, however, varied and was mainly affected by water turbidity and temperature during the experiments. In addition, a solar flow through reactor for irradiating contaminated water was constructed and tested. The reactor consisted mainly of a disinfection reactor, storage tanks, a submersible pump, and a light activated switching unit. Flow regulation was achieved by a light activated switching unit which controlled the submersible pump. The flow rate was adjusted so that the time it took the water to pass the reactor was sufficient to inactivate the bacteria. The reactor was tested under varying levels of turbidity using coliform bacteria as the source of water contamination and selected bacterial species. The results indicated that turbidity affected the efficiency of water disinfection, and the reactor can be a valuable tool in solar water disinfection technology, especially, for remote and rural areas. Further work is still needed before it can be concluded that solar radiation can be an effective, costfree, technique for drinking water disinfection.