Simultaneous biological nitrogen removal and electrochemical phosphorus recovery from municipal wastewater
Kruk, Damian Jakub
The main objective of the study was to develop a partial nitrification/anammox electrically assisted struvite yield membrane bioreactor (PN/A EASY MBR) with simultaneous phosphorus recovery for treatment of municipal wastewater. The research was conducted in four separate experiments evaluating the feasibility of electrochemical phosphorus recovery, impact of electric current on nitrifying and anammox bacteria, and long term anammox performance at low temperature. The EASY method based on the magnesium dissolution from a sacrificial anode was found to be very effective in recovery of high-quality struvite even from fermented waste activated sludge from a wastewater treatment plant that does not practice enhanced biological phosphorus removal. Effects of short and long term exposure of nitrifying biomass to direct current were investigated using inert graphite electrodes. Both short and long term exposure kinetic tests indicated that the activity of ammonia oxidizing bacteria was slightly inhibited with almost linear decline, whereas the activity of nitrite oxidizing bacteria was stimulated. The trends of relative activity changes exhibit a high correlation to the electric current applied per mass of volatile suspended solids. Low temperatures are one of the main obstacles to implementation in the main stream. In this study the impact of long-term exposure to a temperature of 10°C on the anammox process was investigated. Quantitative PCR was used to follow the population dynamics of different strains of anammox bacteria. Results of the investigation of the electric current impact on anammox activity provided evidence that simultaneous anammox and electrochemical processes is not a feasible approach. However, the study provided a novel method of phosphorus recovery available also for non-EBPR plants, which can be applied in the mainstream process simultaneously with conventional nitrification. The study of anammox at low temperature generated valuable insights for development of mainstream anammox treatment.
Wastewater treatment, Nutrient recovery, Nutrient removal, Struvite, Anammox, Nitrification