Effect of low temperature on the performance of a gravity flow CANON-like pilot plant MBR treating surface water

A gravity flow completely autotrophic nitrogen removal over nitrite (CANON)-like pilot plant Membrane bio-reactor was designed to treat surface water for indirect potable reuse and was operated for over seven months with a constant Trans-membrane pressure of 100 mbar after the start-up phase. The effect of low temperature on the performance of autotrophic nitrogen removal over nitrite was investigated over a seven-month period during which the feed water temperature changed from 29°C to 1°C and the viscosity of the permeate more than doubled. The process showed good biostability and sustainability across the different seasons. Initially when the temperature fell below 10°C (which seems like a turning point for the activity of ANAMMOX bacteria) high fluctuations happened, but the activity of ANAMMOX bacteria recovered in 18 d. Increasing Hydrogen retention time during this period was the means by which one can successfully compensate for low temperature. The dissolved oxygen (DO) (7.12–10.9 mg/L) in the raw water supported the partial nitrification and anaerobic ammonium oxidation (ANAMMOX) process without the use of aeration. There was high ammonium (up to 5 mg/L) removal even at extremely low temperatures of 1°C.