Stabilisation of urine by nitrification in a moving-bed biofilm reactor
The urban population is an important point source of recycled crop nutrients in a sustainable society. In conventional wastewater treatment plants with enhanced nutrient removal more than 95% of the phosphorus ends up in the wastewater sludge, while only up 25% of the nitrogen is bound to the sludge. The availability of the phosphorus in the sludge is, however, questionable, and sludge spreading on farmland is also under debate due to the content of micropollutants. Moreover, the amount of reactive nitrogen in the environment is exceeding the earth’s planetary boundaries causing eutrophication, acidification, ozone destruction and global warming. There is a need for closing and shortening the urban nitrogen cycle loop. Urine contains most of the crop nutrients in the toilet waste (e.g. 80 % of the nitrogen). Urine has also very low cadmium content and is easily and quickly sanitised. In large cities, there is a need of volume reduction of urine to decrease the storage volume. Nitrification with following distillation is a promising volume reduction method (Udert & Wächter, 2012).
SuNha (Sustainable urban Nitrogen handling) is a project exploring different methods for recycling a larger part of the urban nitrogen flows in Sweden. The main aim of the project is to install a urine separation system in full-scale in the Malmö/Lund region, Sweden, that also can be studied in detail during its life-time.
The main aim of the master´s thesis is to investigate the process stability of the operation of a moving-bed biofilm reactor (MBBR) for nitrification of urine. Also, different operational strategies should be tested and a design of a future pilot plant should be performed.
An MBBR for nitrification of urine will be operated at lab-scale in a laboratory at Lund University. The lab reactor will be subjected to different loads, dissolved oxygen and pH levels and nitrate:ammonium ratios.
David Gustavsson, research leader at VA SYD/Sweden Water Research
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