Treating landfill leachate using passive aeration trickling filters; effects of leachate characteristics and temperature on rates and process dynamics

Biological ammoniacal-nitrogen (NH4+-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 °C. Comparing leachates, rates of NH4+-N reduction (0.126–0.159 g m− 2 d− 1) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072–0.194 g m− 2 d− 1) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012–0.144 g m− 2 d− 1) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029–0.319 g NH4+-N m− 2 d− 1 and 0.033–0.251 g C m− 2 d− 1 generally increasing with rising temperatures; rates at 3 °C were 9 and 13% of those at 30 °C for NH4+-N and TOC respectively. For the weak leachates (NH4+-N < 140 mg l− 1) complete oxidation of NH4+-N was achieved. For the strong leachates (NH4+-N 883–1150 mg l− 1) a biphasic treatment response resulted in NH4+-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH4+-N to TON in bulk leachate. The temporal decoupling of NH4+-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH4+-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH4+-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors.