Effect of pH, temperature and air flow rate on the continuous ammonia stripping of the anaerobic digestion effluent

A stable continuous stripping of ammonia from the anaerobic wastewater treatment plant effluent was obtained in the ammonia stripping bench plant. The effects of temperature, amount of air and pH level on the removal of ammonium from the effluent were examined in the experiments. The operating parameters in the trials were chosen in respect of the economically feasible operating conditions in a biogas plant. The results of ammonium removal were compared with theoretically calculated values of free ammonia in these conditions. Ammonia stripping bench plant continuously removed up to 92.8% of ammonium and 88.3% of total nitrogen from the anaerobic digestion effluent. High pH had the most significant effect on stripping, causing the change of the ammonia/ammonium ratio in favour of ammonia. The second important factor was the amount of air passing through the stripping bench plant promoting the transition of ammonia from the liquid phase to the gas phase. The temperature within the examined range had the least significant effect on ammonia stripping. Continuous stripping of nitrogen from the anaerobic digestion effluent could considerably reduce the area required for the application of nitrogen-rich digestate after the biogas production and enable the treatment of the anaerobically digested effluent in the wastewater treatment plant.

Research highlights▶ A stable stripping of ammonia from the anaerobic wastewater treatment plant effluent was obtained. ▶ Stripping of ammonia was continuous, with removal rate up to 92.8%. ▶ The most influence on stripping had high pH level, then air flow rate and finally temperature. ▶ High removal of ammonia nitrogen enables the final treatment of the anaerobic centrate in the municipal wastewater treatment plant.