Many US water utilities have switched from chlorine to chloramine as a primary disinfectant to reduce disinfection byproduct (DBP) formation. This shift affects water treatment strategy for households concerned about both PFAS and disinfectant chemical management, as chloramine behaves differently from chlorine in filtration systems.
Why Chloramine Matters for PFAS Filtration
Reverse osmosis membranes are susceptible to degradation by chlorine but are generally more resistant to chloramine. Standard carbon pre-filters remove chlorine readily but require different carbon formulations or longer contact time to effectively remove chloramine. If a carbon pre-filter does not adequately remove chloramine before the RO membrane, membrane degradation can reduce both water production rate and PFAS rejection over time.
Carbon Selection for Chloramine Removal
Catalytic activated carbon — carbon processed to enhance its catalytic activity — is significantly more effective at chloramine removal than standard activated carbon. Households on chloraminated water supplies should verify that their carbon pre-filter uses catalytic carbon or is specifically certified for chloramine reduction, not only chlorine reduction. Neglecting this distinction accelerates RO membrane degradation and can shorten membrane replacement intervals substantially.
Impact on PFAS Treatment
Chloramine itself does not affect PFAS removal performance. The concern is indirect: inadequate chloramine removal in the pre-filter stage allows chloramine to reach and degrade RO membranes, reducing overall system performance including PFAS rejection. Proper pre-filter selection for chloraminated water protects membrane integrity and ensures sustained PFAS removal throughout the rated membrane service life.