A review on the advances in nitrifying biofilm reactors and their removal rates in wastewater treatment

Abstract

AbstractGrowing demand for efficient wastewater treatment systems is spurring on the development of new technologies. Biofilm‐based reactors can be used for the treatment of a variety of wastewaters and these reactors are resistant to toxic environments. Bioreactors, such as sequencing batch biofilm and moving bed biofilm are advanced techniques to treat various types of wastewaters with diverse operating conditions. Ammonium oxidizing bacteria, nitrite oxidizing bacteria and Anammox (anaerobic ammonium oxidation) bacteria are reported to be responsible for nutrient removal. In recent decades, the performance of these systems has been studied widely and compared for a number of wastewater treatment applications. In general, they are particularly suitable for high‐rate nitrification and nitrogen removal. The efficiency of these reactors has been confirmed in the laboratory and large‐scale plants. Their efficiency depends on the surface area of the biocarrier, the filling percentage volume of biofilm carriers, organic loading and diffused aeration supply. Chemical oxygen demand removal of 50–98% was reported for <12 h hydraulic retention time, 0.2 to 6.5 mg L−1 dissolved oxygen concentration and temperature range 15–35 °C. Also, the ratio of nitrate to ammonium conversion was from 0.2 to 90 and N2 conversion was from 0 to 8.5 mg. This review studied each of these bioreactors in the removal of nutrients (nitrogen, phosphorus and oxygen) from different wastewaters and compared them to conventional treatment. The review also includes the relevant studies on laboratory and pilot‐scale bioreactors to enhance their performance and reduce their costs. © 2018 Society of Chemical Industry