Enhancing nitrogen removal performance of anammox process after short-term pH and temperature shocks by coupling with iron-carbon micro-electrolysis

Abstract

Abstract Nitrogen contamination is regarded as a major threat to terrestrial net productivity and environmental sustainability. Anaerobic ammonium oxidation (anammox) is a cost-effective and promising technology in wastewater treatment. In this study, the effects of pH/temperature and their short-term shocks on a hybrid system of anammox coupled with iron-carbon micro-electrolysis (IC-ME) were investigated. Results indicated that the hybrid system significantly enhanced the total nitrogen (TN) removal and expanded the stable pH operating range (TN removal efficiencies over 50%) from pH 6.5–8 to pH 5.5–8.5. Free nitrous acid (FNA) in acid environment, when its concentration was higher than 396.36 ± 5.51 μg/L, was thought to be one critical degradation inhibitor. After suffering a short-term (one day) pH shock, the hybrid system exhibited the improved performance of both stability and nitrogen removal, mainly because Fe corrosion maintained the pH value by IC-ME. More diverse nitrogen removal processes promoted by IC-ME enhanced the TN removal of hybrid after high temperature shocks. However, the susceptibility and inferior adaptability of anammox bacteria were considered to inhibit the nitrogen removal performance of the hybrid and individual anammox system. Microbial analysis identified Candidatus Kuenenia as the major anammox genus, accounting for 3.61% of the microbial community biomass, and the genus of SM1A02 might be one novel potential strain that help the anammox process.