Mainstream partial nitritation-anammox as post-treatment of anaerobic effluents under warm climate regions: a critical review of the reported drawbacks

Abstract

ABSTRACT The anaerobic technology via UASB reactors is consolidated for mainstream sewage treatment in warm climate regions (i.e. Brazil and India). The need to improve the post-treatment step in terms of nitrogen removal has driven researchers and practitioners to assess different technological alternatives. Although the anammox (anaerobic ammonium oxidation) process has been already used in full-scale applications to remove nitrogen from ammonium-rich (> 1000 mgN L−1) wastewaters (sidestream), it is still a concern for mainstream application. Several studies have been performed aiming to solve existing drawbacks related to the implementation of mainstream partial nitritation-anammox (PN/A) for N removal from sewage, however, none of them addressed the particular conditions of anaerobically treated sewage under warm climate conditions. Therefore, this paper presents a critical review of the main limiting factors commonly reported for mainstream PN/A application, focusing on possible applications of single-stage partial nitritation-anammox for post-treatment of anaerobically treated sewage under warm climate conditions. Commonly reported constraints for achieving mainstream PN/A application such as temperature, COD/N ratio, sulfide toxicity and nitrite requirements were addressed. It was concluded that temperature and COD/N should not be concerns for mainstream anammox systems fed on anaerobically treated sewage under warm climate regions. Despite long-term exposure assessments should be still performed, sulfide toxicity seems to be of less relevance. Therefore, reaching reliable nitritation is the major challenge that remains among the typically reported limitations for mainstream PN/A application following anaerobic sewage treatment. GRAPHICAL ABSTRACT