Phosphate Removal from Wastewaters by Combining Different Electrochemical Processes

Water is essential to life, but during its use it becomes contaminated with many different materials that need cleaning up before it can be safely discharged to the environment. One of these pollutants is phosphorous which is a major constituent in detergents. Increasing standards of living and population growth are resulting in increasing concentrations in sewage. Phosphorous is an essential yet limited resource that cannot be replaced by any other element, resulting in increasing efforts to recycle the phosphorous contained in the wastewater. Phosphorous is a vital component of DNA and the key element of ATP (adenosine triphosphate). Additionally, phosphate is a mined material that is becoming depleted. Recycling this phosphorous is important as the phosphate is used as a nutrient in fertiliser and will be essential to maintaining food production to meet the needs of a growing population. The proposed process aims to recover the phosphorous for reuse, providing a valuable resource from the treatment of sewage.

Phosphate (and nitrates) are nutrients in water and too high a concentration can result in algal blooms (Eutrophication). Phosphate is often the rate limiting nutrient and removal of this contaminant will reduce eutrophication. This is significant as the blue green algae can release toxins that can be lethal to wildlife and domesticated animals (eg lifestock), as well as preventing sunlight penetrating the water, limiting photosynthesis. When these algae die, they settle to the bottom and their decomposition uses up the oxygen in the water, which causes difficulties for fish and other organisms that need oxygen to breath. It can result in the water becoming coloured and cloudy. Reduction in water quality affects the aesthetic and recreational value of the water and results in increased treatment costs.

In addition to fresh water algal blooms, large costal blooms have been detected in a number of locations where rivers discharge their waters. The World Resources Institute has identified hundreds of costal areas that are susceptible to algal blooms.

Traditional biological sewage treatment removes around 20% of phosphorous (significant as humans excrete 3.3 million tonnes of phosphorous annually), but current standards require the removal of 90%. Chemical processes are able to achieve phosphorous removals down to these levels but require significant quantities of chemicals. Sewage works are believed to contribute 70% of the phosphorous in water, leading to increased regulation to reduce this source.

Arvia have a patented, award winning technology (NyexTM) which is used for the removal and destruction of toxic and hazardous organic chemicals in water, eg pesticides and industrial chemicals. This innovative process concentrates the organics onto the surface of the Nyex particles through adsorption with the Nyex being electrochemically regenerated by passing electricity through the particles. This destroys the organics to carbon dioxide and water. However, by combining Arvia's Nyex system with other electrochemical processes, a chemical free process for the removal of phosphorous can be delivered.

This short, intensive project aims to demonstrate that the combination of processes can achieve the necessary water quality and provide data of the treatment costs.