2025-09-29 – Weekly Water Treatment News : PFAS: GAC vs AIX debate

Last week’s discussions in the Water Treatment community centered around emerging technologies and pressing industry debates. Members shared insights on the latest job prospects, particularly focusing on remote roles for project managers. There was also a lively exchange regarding the treatment of PFAS, with differing opinions on the efficacy of GAC versus AIX methods. Additionally, community members reminisced about their first jobs and the skills they value most in this field.


This Week’s Hot Topics

Weekly Water Treatment Jobs: Remote roles for water project managers
This thread is buzzing with opportunities for those looking to manage projects from afar. It’s a great time to explore new roles in this evolving field.
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Would You Take This Job? – Water/Wastewater Operator in DE
Considering a new role? This discussion delves into the pros and cons of a specific operator position in Delaware.
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The loudest 10 mm in the room
An intriguing technical discussion that’s turning heads—explore what makes this 10 mm topic so crucial in the field.
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FAQ/Guidelines
For newcomers and veterans alike, this guide is a handy reference for forum rules and best practices.
Read more here

Admin Guide: Getting Started
Admins, this one’s for you—find everything you need to manage your community effectively.
Read more here

Interested in a Career in Water Treatment? Here’s What to Expect
An informative guide for those contemplating a career in water treatment, outlining what lies ahead.
Read more here

What Was Your First Job in Water Treatment?
A nostalgic thread where members share their first steps and experiences in the industry.
Read more here

What Skills Are Most Valuable in Water Treatment?
This discussion highlights the key competencies that can set you apart in the water treatment sector.
Read more here

PFAS and ‘Forever Chemicals’—What’s Your Take?
With ongoing concerns about PFAS, this thread offers a platform for members to voice their thoughts and solutions.
Read more here


Thank you for being an active part of our community. Your contributions make a real difference. Until next week, take care and keep sharing your knowledge and experiences.

Last fall we ran a 4‑week split‑stream pilot and found ‘GAC vs AIX’ hinged on TOC — AIX only beat GAC on PFHxA/PFBS once we got TOC under about [redacted]/L and held AIX EBCT near 3–5 minutes. Practical tip: if disposal costs are tight, start with lead‑lag GAC at about 12–15 min EBCT and only layer in AIX after a short pre‑GAC/MIEX polish to keep the resin from fouling so fast.

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But @Guide We’ve kept AIX happy by prefiltering to <1 NTU; otherwise GAC wins.

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Quick field note: AIX outperformed on short‑chains for us until sulfate crept past about [redacted]/L and the plant kept free chlorine ahead of the resin — adding upstream dechlorination and a chloride preflush brought capacity back. If you stick with GAC, we nudge EBCT from 12→15 min in winter because cold water makes kinetics move like molasses. @Guide, EPA’s tech brief is a handy sanity check: https://www.epa.gov/water-research/drinking-water-treatment-technologies-removing-per-and-polyfluoroalkyl-substances-pfas.

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In our midsize plant, the most practical lever was setting a UV254 threshold to flip the lead GAC early; it kept short‑chain PFAS in spec without waiting on lab results. AIX only edged GAC after we dechlorinated upstream — matches @Guide’s experience and this EPA brief: https://www.epa.gov/water-research/drinking-water-treatment-technologies-removing-per-and-polyfluoroalkyl-substances-pfas.

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Last week’s GAC vs AIX debate pushed us to try “AIX lead/GAC polish” only after a cheap sidestream softener knocked down alkalinity; before that, bicarbonate killed AIX capacity and GAC held its own. Quick win: we bumped EBCT with a repurposed 36‑in contactor and kept short‑chains in spec without a media swap. Caveat: when water temps drop, AIX tends to pull ahead, so plan for the seasonal swing.

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