Utilisation of Solar Energy Driven Photochemical Processes for River Water Purification

Abstract

More than two billion people across the world do not have access to potable water. Communities globally are struggling with epidemic level disease outbreaks, limited water supply among other large-scale public health risks. Water is essential for life and several regions across the world have poor infrastructure for the management of potable water resources and lack critical wastewater treatment facilities. As the population of the Earth grows rampantly, the demand for water resources is increasing exponentially. Large-scale critical infrastructure chains are required to produce potable water from raw water sources, and developing countries continue to struggle economically and cannot afford the same treatment chains as the developed world. This research project evaluated the feasibility of two photocatalytic / photo-Fenton solar reactors on their capabilities to breakdown water contaminants present in natural hydro-systems and freshwater resources namely rivers in Chatham, Kent, England between September 2015 and August 2017. The photo-Fenton reaction and solar-photochemical reactors were designed, constructed, and tested for the removal efficiencies of Chemical Oxygen Demand (COD), ammonia, nitrates, nitrites, and phosphates via LCK curvetted tests, in addition to turbidity and colour. The water quality analysis and results showed that oversaturation of the photo-Fenton reagents reduces the effectiveness of the reaction, and that finding the correct chemical balance has a greater impact on the removal efficiencies of the five pollutants than the use of ultraviolet (UV) light catalyst. Under the conditions set by this research project, a smaller diameter of piping yields the best removal efficiencies of pollutants. The optimal photochemical balance of H₂O₂: Fe²⁺ has more of an impact on the effectiveness of treatment than the use of UV radiation. The ideal H₂O₂: Fe²⁺ ratio for the treatment of river water is close to 100:1 mg/L. The impact of semi-variables such as diameter of pipe and UV influx on the effectiveness of treatment are not noticeable compared to the effect of changing the photo-Fenton chemical ratio. Moreover, the photo-Fenton process’ removal efficiency is directly proportional to the remaining H₂O₂ concentration, as the photochemical reaction proceeds.