This article describes an innovative , multi-stage process in which the benefits of selective anion exchange resins play a vital role in final polishing and reduce the level of PFAS , including the removal of perfluorobutanoic acid ( PFBA ) to non-detectable levels and with high capacity utilisation , too . The efficient removal of PFBA will be among the biggest challenges in the water treatment processes of tomorrow .

Australia is playing a pioneering role in the detection and removal of PFAS from groundwater . In 2018 , an intergovernmental agreement between the Commonwealth and federal states and territories entered into force as a concerted response to the problem of PFAS contamination in order to protect the environment and , as a precautionary measure , human health .

The effectiveness of this standardised approach is demonstrated in our case study from the state of Victoria in southeast Australia , where levels of PFAS as high as 200 ppb were removed from the wastewater of the former fire service training facility of the Country Fire Authority . An aqueous , PFAS- containing fire-extinguishing foam was used for many years at this location , causing persistent chemicals to pollute the groundwater .

Currently no standardised standard flow sheet has been established , because the water composition of each PFAS treatment project is unique and comes with its own set of challenges and variables . These include :

• Molecular composition of PFAS compounds ( long chain vs . short chain , carboxylates vs . sulfonates )

• Presence of co-contaminants

• Receiving environment

• Regulatory compliance

• Waste disposal

• Client ’ s budget

• Time constraints

Haldon Industries , an Australian provider of water treatment plants , developed a treatment plant that used a selective , multi-stage ion exchange process . It used a mobile waste processing plant specially designed for the on-site treatment of waste contaminated with PFAS , employing a strategy centred around the utilisation of various adsorptive and anion exchange media in a sequence tailored to each project ’ s unique characteristics and treatment objectives .

The mobile plant , which is capable of processing 125,000 L water / day , was put into operation on the site of the old fire service training facility and successfully removed high concentrations of PFAS in compliance with the EPA standards that apply in Australia .

The IER configuration encompassed the regenerable , weak base anion exchange resin Lewatit MP 62 WS , followed by the highly selective , singleuse anion exchange resin Lewatit TP 108 in a lead / lag configuration . The filter , which was filled with Lewatit MP 62 WS , reduced the majority of all the PFAS ( Figure 1 , grey ).

The remaining leakage , which was mostly PFBA , was effectively reduced to non-detectable levels with the use of Lewatit TP 108 . This achieved a high throughput ( Figure 2 ) of 10,000 bed volumes ( BV ), which significantly reduced the opex costs associated with the disposal of the used resin .

Design & operating parameters

Figure 3 shows the process flow diagram , outlining the multi-stage process . The process includes oxidation , adjustment of the pH value , flocculation , the separation of solids , media filtration , the use of granulated activated carbon for removing dissolved organic carbon , and ion exchange using weak and strong base anion exchange resins .

The polyamide resin columns filled with Lewatit TP 108 were operated in a lead / lag polisher configuration . The

Figure 3 - Process flow diagram outlining the multi-stage process

52 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981