Treatment and Mitigation of PFAS in Drinking Water | AAAS EPI Center
cleanup (i.e., site remediation) upstream of the drinking water treatment plant (WTP), shut-down or mixing of contaminated drinking water sources, and in-home treatment. PFAS treatment produces waste that requires proper disposal to prevent it from cycling back into the water system. When sent to a landfill, PFAS-contaminated waste may leach into soil or water. Incineration is one of the main methods used to destroy PFAS. Incineration facilities discharge air emissions when incinerating materials such as media and resin used during the treatment of PFAS in drinking water facilities 23,24 . Without incineration temperatures above 1,400 degrees Fahrenheit and long enough contact times to destroy the PFAS, these incineration facilities have the potential to discharge PFAS-containing air emissions that deposit PFAS back into the environment through settling and precipitation 21,22 . Research is ongoing to characterize PFAS behavior in air emissions and determine the conditions required for the destruction of PFAS during high-temperature incineration. Effective PFAS Treatment Methods Several established water treatment technologies provide varying degrees of PFAS removal. The three most commonly used are activated carbon, ion exchange (IX), and certain semipermeable membranes . Each of these processes has benefits and limitations, including extent of treatability, secondary water quality benefits, ease of implementation, waste disposal challenges, and capital and operating costs. Additional information on these technologies can be found in the EPA Drinking Water Treatability Database 4 . Activated Carbon Treatment Methods Reduce PFAS Adsorption is a process where organic substances (e.g., PFAS) present in a liquid are adsorbed on a solid (e.g., activated carbon granules) and consequently removed from the liquid. Activated carbon can be used in WTPs in two forms: granular activated carbon (GAC) or powder activated carbon (PAC). There are major differences between these two applications, including carbon particle size, operational considerations, capital cost, and PFAS removal effectiveness. PAC Is a Quick Solution for PFAS Adsorption but Comes with Operational Challenges In PFAS treatment applications, PAC is typically utilized for short-term, rapid PFAS treatment as a temporary reduction method before a permanent treatment method is selected. PAC adsorption is a well-known process used in drinking water applications for reducing total organic carbon (TOC), and compounds causing color, taste and odor 5 . PAC is an activated carbon fine powder with a small particle size range (<0.18 mm) that is added to water and mixed. After the powder is in contact with the desired water, it is removed prior to drinking water distribution. The ability of PAC to reduce contaminants depends on the type of PAC product, the PAC dose applied and application point, the mixing efficiency, other constituents in water, and the contact time in water 5 . Figure 1 shows PAC system equipment. Figure 6 - PAC Feed System
22
Made with FlippingBook Online document