Nitrogen and phosphorus are essential elements needed for agricultural crop fertilization, used in increasing quantities in order to feed an ever-growing population. Agricultural wastewater from livestock (AWL) farms contains high concentrations of nitrogen and phosphorus in addition to organic loads. AWL runoff to aquatic ecosystems leads to severe environmental impacts such as eutrophication of rivers, lakes, and coastal oceans. Currently, conventional wastewater treatment plants are unable to remove such high concentrations, which require complex anaerobic/anoxic treatment stages and reduce the efficiency of the treatment. Consequently, use of primary-treated agricultural wastewater effluents for agricultural irrigation gradually deteriorates the quality of soil, ground, and surface-water resources through loading of nitrate, nitrite, pharmaceutical byproducts, and/or antibiotics. An important strategy to mitigate phosphorus and nitrogen scarcity is to recycle them from waste streams back into agricultural production. Our research shows the ability of P and N recovery from concentrated and diluted solutions (1-100 mg L<sup>-1</sup>) of synthetic AWL. The recovered P and N are in the form of Struvite which is considered an “eco-friendly” fertilizer. The recovery is based on an electrochemical reaction near an electrically conducting ultrafiltration membranes (ECM). The electrochemical reduction of dissolved oxygen and water molecules generate a local pH gradient in the close vicinity of the electrode. The pH near the cathode increases, leading to nucleation and growth of Struvite (Figure 1) and, importantly, high yield with no chemical additives. As the recovery process utilizes permeate to control mass transfer, diffusion limitations are eliminated, leading to a significant increase in reaction rates and removal ratio. In terms of collecting the recovered Struvite, our ECMs have pores in the range of 10-100 nm which are significantly smaller than the size of Struvite particles, therefore, Struvite solid particles which are filtered by the ECM accumulate on the membrane’s surface, to be collected by a pressurized backwashing process or by simply blocking the permeate flux.

Nitrogen and phosphorus recovery and separation from agricultural wastewater effluents: The role of electrically conductive membranes

256th National Meeting (2018)

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