Removal of nitrogen and emerging pollutants from anaerobically treated effluents from domestic wastewater, using nitritation/anammox: a state of art review

Since the discovery of anaerobic ammonium oxidation bacteria, commonly known as AnAOB in the early 1990s, more than a quarter century has passed and partial nitrification/anammox process for sewage treatment is still mainly in lab and pilot-scale research phase with few plants in operation. The main challenges for that are enrichment, grow and how to keep AnAOB in the reactor on low-strength wastewater treatment, such as in anaerobically treated domestic sewage. Another important aspect is need for continuous supply of nitrite and how to minimize nitrite consumption by others than anammox. In addition to that other minor control parameters play an important role, such as hydraulic and sludge retention time, dissolved oxygen, temperature, pH, etc. This paper presents a detailed review of essential process parameters and identifies gaps and solutions for effective implementation of the anammox process highlighting the different factors that suppress AnAOB growth, along with the aspects favouring activity and immobilization. Reactor start-up and operation, bacteria inhibition and conversion of emerging-pollutants is also investigated, with their effect on AnAOB and their removal. The main conclusions are the sustainability evaluation, which found that the process reduce the overall GHG emissions compared to conventional nitrogen removal processes; a possible microbial pathway that could be involved for simultaneous organics, nutrients and emerging-pollutants removal; and, finally, a novel concept of a three-stage treatment process in two up-flow anaerobic sludge blanket-based system is proposed.