Activated carbon adsorption systems represent a substantial installed base in water treatment—thousands of vessels operating at utilities and industrial facilities worldwide, representing significant capital investment in vessels, piping, controls, and operator training. When these systems are found to be inadequate for short-chain PFAS removal, the question is rarely ‘should we replace the infrastructure?’ but rather ‘how do we upgrade performance within existing infrastructure?’ MARISORB™ was designed as a direct replacement for GAC in adsorption columns, and the retrofit process is straightforward when approached systematically.
Pre-Retrofit Assessment and System Documentation
Begin with a complete documentation review of the existing GAC system: vessel dimensions, rated flow rate, design EBCT, underdrain type (hub-and-lateral, header-lateral, or plate underdrain), and current media specification. This information, typically available in the original engineering drawings and O&M manuals, establishes the hydraulic envelope within which MARISORB™ must operate. In most cases, granular MARISORB™ has comparable particle size distribution and bulk density to coal-based GAC, meaning hydraulic calculations and backwash specifications require only minor adjustment.
Collect a representative influent water sample for PFAS compound characterization using EPA Method 533 or 537.1. This provides the compound-specific concentration data needed to predict MARISORB™ service life using site-specific RSSCT or isotherm models. If short-chain PFAS (PFBS, PFHxA) are present at significant concentrations, document their levels carefully—this baseline establishes the technical case for the retrofit and the performance improvement expected post-changeout.
Media Changeout Procedure and Startup Commissioning
Drain the vessel to be retrofitted and sluice out the spent GAC using the existing backwash and drain connections. Inspect the underdrain laterals and distribution header for scaling, fouling, or mechanical damage. Replace or repair any compromised underdrain components before loading new media—underdrain integrity is critical for preventing media bypass and ensuring uniform flow distribution. Refill the vessel with granular MARISORB™ to the same bed depth used for GAC, compact gently during filling to minimize void spaces, and install the top distribution gravel layer if used.
Commissioning begins with a slow-rate flush at 10–20% of design flow for the first two hours to classify any fines and achieve hydraulic stability. Collect effluent samples at 30-minute intervals during startup commissioning for PFAS analysis—any fine particles that elute during this period are expected and do not indicate a media performance issue. Once effluent turbidity stabilizes below 0.1 NTU, ramp to full design flow and collect baseline performance samples at 1, 24, 72, and 168 hours post-startup.
Operators familiar with GAC systems will find MARISORB™ operations essentially identical: same backwash procedures, same vessel pressure monitoring, same effluent sampling protocols. The difference becomes apparent in effluent quality data: where GAC systems show short-chain PFAS breaking through within weeks, MARISORB™ maintains >95% removal across the full compound spectrum for significantly longer operational periods. For water treatment managers responsible for regulatory compliance, this performance advantage translates directly into reduced regulatory risk and more predictable operating cost.