Rapid start-up of the biofilter for simultaneous manganese and ammonia removal at low temperature: Effects of phosphate and copper

Abstract

In low-temperature environments, low nutrients such as inorganic salts limiting microbial proliferation further extended the start-up period of biofilters for drinking water treatment. This study explored the ammonia and manganese (Mn) removal performance and the relevant mechanisms under single and combined PO43− at 30 μg/L and Cu2+ at 10 μg/L. The start-up periods of R0 (control), R1 (Cu2+ single), R2 (PO43− single) and R3 (combined Cu2+ and PO43−) were 98, 82, 32 and 24 days, respectively. PO43− increased the concentration of extracellular polymeric substances (EPS) by stimulating cellular metabolism, which promoted the formation of biofilm. Additionally, the combined Cu2+ and PO43− significantly promoted the ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) activities, which further facilitated the removal of ammonia. The combined Cu2+ and PO43− accelerated the conversion of NH4+-N to NO2−-N and NO2−-N to NO3−-N processes thereby reducing the inhibition of Mn removal by NH4+-N and NO2−-N, and the kinetics of biological manganese oxidation showed that the combined Cu2+ and PO43− increased the rate of Mn removal, which both promoted the Mn removal in the biofilters. Furthermore, the combined Cu2+ and PO43− supported the proliferation of functional microorganisms. In summary, the synergistic effect of Cu2+ and PO43− enhanced the Mn and ammonia removal performance and achieved rapid start-up of the biofilter at low temperatures.