Determining the effects of Class I landfill leachate on biological nutrient removal in wastewater treatment

The disposal of landfill leachate is a chronic problem facing the municipal solid waste industry. The composition of landfill leachate is highly variable and often dependent on site-specific conditions. Due to the potentially disruptive impact on wastewater treatment processes, wastewater treatment plants (WWTP) are reluctant to accept landfill leachate for co-treatment. To improve the ability of WWTPs to screen the impact of landfill leachate and reduce landfill owners’ cost of disposal, two bench scale methods were evaluated. First, six landfill leachates were screened with the specific oxygen uptake rate (SOUR) test, and second, the effect of leachate on the efficacy of activated sludge processes using lab scale sequencing batch reactors (SBRs) was determined with volumetric loading rates ranging from 5% to 20%. Results suggested that these tools can be used to estimate the impacts of leachate loading on biological processes. Both tools were able to identify loadings where biological activity was increased and inhibition of biological processes was minimized. The loading that maximized microbial activity was leachate specific and typically ranged from 5% to 10%. Taken together, these results suggest that improved landfill leachate screening and testing may improve outcomes at WWTPs by identifying a “Goldilocks” loading rate that increases biological activity. Nevertheless, our results also demonstrated that the effluent quality was degraded even at loading rates that increased biological activity. It is uncertain at this time if biological acclimation can remedy increased effluent nutrient mass loadings, suggesting further research is needed.