Integrated Treatment of Landfill Leachate Treatment Plant Effluent and Sludge for PFAS Removal and Resource Recovery

If high PFAS loads from landfill leachates are reaching municipal Wastewater Treatment Plants (WWTPs), they prevent proper treatment and ultimately hinder zero pollution discharge and further water reuse due to higher PFAS discharges from WWTPs. Currently, PFAS-contaminated sewage sludge and Reverse Osmosis (RO) concentrate from landfill leachate treatment are transported to incineration plants or disposed of in waste landfills. However, these practices are not sustainable and do not aim to recover resources.

Our approach was designed to treat PFAS contamination in multiple stages. First, landfill leachate treatment plant (LLTP) effluent was treated using a pilot-scale filtration system containing Nanofiltration (NF) and Reverse Osmosis. The filtration system was able to remove PFAS and other contaminants by moving it to the concentrate, producing high quality permeate.

Then the concentrate was evaporated to recover the water and create dry salts, which were utilised as a catalyst in the thermochemical treatment (Pyrolysis) of LLTP sludge. Then by combining these salts (high in PFAS concentrations) with LLTP Sludge, a co-treatment process was created that not only breaks down PFAS contaminants, but also recovers some of the energy by producing syngas (and bio-oil). In addition, the amount of solids (biochar) is reduced, which lowers the cost for handling this waste.

By integrating these processes, environmental impacts could be minimized and circular economy opportunities for landfill leachate management could be created.

An extra addition to our work was the ability to check the stack emission (syngas) produced by Pyrolysis for PFAS contamination. This made it possible to close the cycle of PFAS in all expected pathways after treatment. The results were very promising showing almost no detectable PFAS at optimal conditions.

A Life Cycle Assessment (LCA) was conducted to evaluate and compare the environmental impacts of treating LLTP effluent using NF and RO systems, combined with either incineration or pyrolysis for the treatment of salts from the concentrates. According to obtained results, pyrolysis is a more sustainable solution than incineration to treat the waste resulting from landfill leachate treatment. Particularly, pyrolysis can be performed in compact reactors operable on-site, which can reduce significantly costs and environmental impacts.

Our work showcases how innovation can turn complex challenges into sustainable solutions. Stay updated as our research continues. Together, we can make a cleaner PFAS-free future.