Nitrogen removal by Anammox and Heterotrophic Denitrification (South Africa)

Anammox (anaerobic ammonium oxidation) bacteria have been proven to be a cost-effective biological nitrogen removal technique for sewage treatment, especially in warm climates, such as in South Africa. This study was carried out in order to assess the activity of anammox bacteria when treating the effluent from the Anaerobic Baffled Reactor (ABR) from Newlands Mashu DEWATS (decentralised wastewater treatment system) plant in Durban, South Africa. The anammox sludge was obtained from Dokhaven Wastewater Treatment Plant in Rotterdam, the Netherlands. One batch activity test per week was executed for three weeks to assess the effects of three different COD:N ratios. The highest nitrogen removal was achieved at COD:N ratio of 1.3 (93.35%) and the lowest at COD:N ratio of 4.0 (45.87%). In all the experiments nitrite was a limiting compound. Anammox process contribution for nitrogen removal was higher than heterotrophic denitrification in all the different settings and it presented the highest contribution (85.44%) at the lowest COD:N ratio (1.3). The results of this study indicated that anammox bacteria can be an alternative solution for nitrogen removal from the effluent of the ABR at Newlands Mashu DEWATS plant.