Abstract

Nutrients, phosphorus and nitrogen, from municipal and industrial water streams contribute to the pollution or reduce the ecological potential of receiving water bodies. Recovering or reducing the nutrient content of waste streams, thus reducing the amounts of phosphorous and nitrogen that ends up in the water bodies, will contribute to a better environment. The first part of this report describes two tests performed to treat the concentrate of the reverse osmosis process at the Torreele facility. The first test used a natural system based on willows; the second test was based on post-denitrification MBBR. The willows proved able to remove nutrients for more than 30%, resulting in a substantial cost benefit for discharge which could make it economical feasible when installed at full-scale to treat the total volume of RO concentrate. Contrary to the willows, that even remove part of the nitrogen in winter, the post-denitrification MBBR was only efficient when N-NO3- exceeded 30 mg/L. The variable N-NO3- N-NO3- concentration and salinity of RO concentrate seemed to be limiting factors for a good performance. The second part of this report summarizes the activities regarding the optimization of water and nutrient (nitrogen and phosphorus) management at the reuse site Braunschweig, Germany. A detailed analysis of supply and demand of both, water and nutrients, for the reuse site was conducted. The optimization potential is especially high for nitrogen management, since the simultaneous supply via the Braunschweig wastewater treatment plant and additional conventional nitrogen fertilizer application by farmers result in an oversupply of nitrogen, losses to environment and a low efficient reuse compared to the total potential of renewable nitrogen in wastewater or sludge. Following this analysis, two possible solutions are discussed (fertigation and technical nutrient recovery), which are practically relevant for the Braunschweig reuse scheme in mid- and long-term timescale. Results indicate a high potential to increase the efficiency of nitrogen recycling. Simultaneously irrigation adopted on water demand of plants can be achieved.

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