| Summary: | Deammonification is a well-established process for sludge liquor treatment and promising for wastewaters with high nitrogen loads because of its low energy demand compared to nitrification/denitrification. Two wastewaters with high NH<sub>4</sub>-N concentrations and a rising significance in Germany—pig slurry (12 samples) and condensates from sewage sludge drying (6 samples)—were studied for their deammonification potential. Furthermore, a comprehensive quality assessment is presented. Both wastewaters show a wide range in terms of COD<sub>t</sub>, COD<sub>s</sub>, TN and NH<sub>4</sub>-N, whereby condensates show a greater variability with no direct relation to dryer type or temperature. In the slurries, COD<sub>t</sub> shows a relative standard deviation of 106% (mean 21.1 g/L) and NH<sub>4</sub>-N of 33% (mean 2.29 g/L), while in condensates it reaches 148% for COD<sub>t</sub> (mean 2.0 g/L) and 122% for NH<sub>4</sub>-N (mean 0.7 g/L). No inhibition of ammonium-oxidizing-bacteria was detected in the slurries, while two out of five condensates showed an inhibition of >40%, one of >10% and two showed no inhibition at all. Since the inhibition could be avoided by mixing, deammonification can be recommended for condensate treatment. For slurry treatment, the importance of employing some form of solid-liquid-separation as a pretreatment was noted due to the associated COD.
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