Addition of external organic carbon source for denitrification is generally used in wastewater treatment plants (WWTPs) to intensify nitrogen removal processes. The aim of the laboratory survey was to measure the composition of concentrated industrial wastewater, determine the possibilities of its use as an external denitrification substrate, and assess its overall impact on WWTP. The obtained results demonstrate that the analysed industrial wastewater is biodegradable, and can be used as a denitrification substrate without special adaptation of biomass. The denitrification rates with tested wastewater were in the range of 1.6 to 1.9 mgN/g·h. Negative influence of long-term dosing of industrial wastewater on activated sludge were not confirmed. The effect of imported wastewater on WWTP must be assessed comprehensively, including the impact of heavy metals from wastewater on the sludge quality. The instructions on how to calculate this balance are provided in the article.
Undissociated HNO2 (up to 2 mg dm−3) was confirmed as substrate inhibitor for granular biomass from a denitritation upflow sludge bed reactor used for biological removal of nitrite. On the contrary, total nitrite nitrogen (N-NO2 up to 500 mg dm−3) and methanol (COD up to 2000 mg dm−3) were not proven to be inhibitors. pH also affected the denitritation efficiency (optimal pH was 5.9). Reduction of HNO2 concentration in the reactor by effluent recycling is recommended.
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