The reliability of partial nitrification coupled with heterotrophic denitrification for the treatment of real anaerobic digester centrate produced in a wastewater treatment plant was technically and economically assessed in two sequencing batch reactors. Removal efficiencies above 90% were consistently achieved at N-ammonium loads above 1.2 g N L−1 d−1. Ethanol, affluent from a waste water treatment plant (biological treatment inlet) and a zero-cost liquid residue from a chemical industry containing polyethylene glycol and sorbitol were employed as carbon source for denitrification. In this last case, a total organic carbon (TOC) requirement of 4.5 g TOC g−1 NO2-N was calculated. The denitrification rate was 0.26 g NO2-N g VSS−1 d−1 (VSS: volatile suspended solids). These results show that a carbon-rich waste can serve as a no-cost feed for denitrifying bioreactors. An in-depth economic analysis considering the main investment and operating costs of the process was developed, showing that it can suppose yearly savings above 50% with respect to the most widely used alternative of returning anaerobic digester centrate untreated to the head of the facility.

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