Water Treatment Using Renewable Energy Technologies—A Pilot Plant Study

Disinfection of water by exposure to sunlight is an age-old concept. Historically, as a religious practice, copper containers filled with water were left in sunlight for hours to make it potable. In the last century, a renewed interest to develop sustainable water disinfection concepts for under developed communities has been revived. Many research studies incorporate water treatment systems involving both thermal and optical inactivation of bacteria. Progress focuses on increasing the effectiveness of systems by adopting improved reflector surface materials and shapes. Water depth and suspended solids are primary factors which impact the penetration of sunlight. Reduction of suspended solids can be achieved either by sedimentation or filtration. Filters comprised of natural material can make the system sustainable and reduce costs. To investigate the performance of such a water treatment system, a pilot water treatment plant using no fossil fuels was designed and tested. The plant consists of filters using natural materials, solar panels to operate a pump for moving water from the source, a natural stream in a highly urbanized area to the plant, and reflector basins to gather and focus natural sunlight for disinfection (SODIS). A reflective circular-section open channel was adopted for optical disinfection by sunlight. The study indicates an inverse relation between flow rate and disinfection rates. The pre-disinfection filters contributed to a reduction in bacterial concentration of the resulting water, and this form of SODIS was successful in achieving the minimum 30-day average E. coli concentrations necessary for recreational water access.