CS#4: Innovative landfill leachate treatment to enable resource recovery from wastewater treatment plants, Ancona & Sofia

Partners: UNI VPM, UNI Sofia, KWB

 

Our aim: Developing an innovative approach to treat landfill leachate

 

If landfill leachate with high PFAS loading reaches municipal wastewater treatment plants (WWTPs), no proper treatment is possible, which prevents a zero pollution discharge and thus further water reuse. Therefore, PFAS contaminated sewage sludge and reverse osmosis (RO) concentrate are currently transported to incineration plants or hazardous waste landfills for disposal.

However, these practices are not sustainable, do not avoid the spreading of PFAS into the environment and do not aim to recover resources.

Case Study 4 aims to obtain a near zero pollution discharge from landfill leachate and to enable a safe resource recovery. For this purpose, membrane filtration, co-pyrolysis, and plasma treatments will be tested in existing full-scale landfill leachate treatment plants in Italy and Bulgaria.

The investigation of the fate of PFAS in conventional landfill leachate treatment plants will help to identify potential contamination pathways to the environment and to plan corrective actions.

To provide effective and sustainable barriers for the spread of PFAS, innovative and advanced technological solutions will be tested in particular. Landfill leachate will be treated by RO and nanofiltration (NF) at pilot scale to assess the environmental and economic sustainability of membrane technologies to remove PFAS. To treat sewage sludge and leachate concentrate, pyrolysis and plasma processes will be tested.

Thus, the possibility for resource recovery will be evaluated. 

What we have done so far...

 

In Bulgaria, laboratory scale experiments for plasma treatment of model solutions containing PFAS compounds (PFOA, PFBA, PFDA, PFHxA, PFPeA) were conducted. Four different plasma sources are used: Microwave (MV) plasma torch (in batch and flow configurations), dielectric barrier discharge (DBD), underwater diaphragm discharge and the newly constructed Beta device (in flow and batch configurations - above the liquid surface and inside the liquid).

After the plasma treatment, a significant toxicity reduction is obtained. The toxicity is assessed by applying the fluorescence-based assay.

In Italy, we conducted several mass flow studies for PFAS compounds in three full-scale leachate treatment plants (LTPs), which showed that almost the entire load of PFAS measured in the influent landfill leachate remained in the liquid phase after conventional treatments (i.e., coagulation/flocculation, ultrafiltration, biological treatment). Advanced treatment such as RO was able to remove PFAS from the liquid stream and to produce a PFAS free permeate. Nevertheless, appropriate technologies for treating RO concentrates need to be implemented to remove PFAS from this waste stream.

At the LTP of Jesi (Ancona, Italy), we installed a membrane pilot system, which is being operated in the NF/RO double stage configuration (Figure 1). Preliminary data on PFAS removal and on economical/environmental costs to treat leachate were obtained. Pilot tests are still ongoing to collect further data for a Life Cycle Assessment study.

Finally, we have performed some pyrolysis test to remove PFAS from the wastes produced at Jesi LTP, which are sludge and RO concentrate. A stack-emission treatment line was installed to recover bio-oil and to characterize syngas (Figure 2). Promising data are being collected about PFAS destruction and the possibility for energy recovery.