Pioneering Decarbonization and Resiliency with Pile Cloth Media Filtration

[b]INTRODUCTION[/b] Wastewater utilities are facing increasing pressure from tighter nutrient regulations, more frequent extreme wet-weather events, rising energy costs, and limited site footprints, while also pursuing greater resource recovery and energy neutrality. Over the past 15 years, pile cloth media filtration (PCMF) has emerged as an effective alternative or complementary technology to conventional solutions for many of these issues. Initially developed for tertiary polishing, PCMF has demonstrated greater than 80% TSS removal and 45–65% BOD removal, while enabling carbon diversion, energy savings, and capacity expansion within a compact footprint. Today, early adopters are using PCMF for advanced primary treatment, dual-use wet- and dry-weather operation, and dedicated auxiliary wet-weather flow management. Figure 1 illustrates a typical layout of a PCMF replacing or supplementing primary clarifiers and managing peak wet weather flows with high-effluent quality. This presentation will showcase three full-scale WRRFs using PCMF in the following [b]innovative roles beyond traditional tertiary treatment[/b]: •Primary filtration, replacing conventional primary clarifiers; •Dual-use systems, providing treatment for both dry-weather flows and peak wet-weather events; and •Stormwater Adaptive Filtration Equipment (SAFE) system, managing peak stormwater/wet-weather flows in parallel with a biological treatment train. We will share data from these case studies and insights into the operation and performance of PCMF, highlighting how the technology enhances plant capacity, resiliency, and overall sustainability. [b]CASE STUDIES[/b] [b]Case Study 1: Cave Creek WRP (Phoenix, AZ) – Primary Filtration Ahead of MBR[/b] Increasing water demand, drought and climate uncertainty have driven the City of Phoenix to invest in Advanced Water Purification (AWP) and reuse to establish a sustainable, locally controlled water source to supplement its reliance on surface water from the Colorado, Salt, and Verde Rivers. As part of this effort, Phoenix is rehabilitating the Cave Creek Water Reclamation Plant (CCWRP), which was idled in 2008 due to a slowdown in projected demand. The upgraded CCWRP will initially produce Class A+ reclaimed water for non-potable reuse and groundwater recharge, with plans to deliver purified drinking water to more than 25,000 homes by 2028 (Harris, 2025). Key upgrades include installation of PCMF for advanced primary filtration (Figure 2), conversion of the BNR basin to a membrane bioreactor (MBR), and replacement of existing filters with reverse osmosis (RO) and UV advanced oxidation. Use of PCMF significantly reduces total suspended solids (TSS) and organic loading to the MBR, lowering aeration energy demand by an estimated 25%. The PCMF also eliminates the need for separate fine screening and is projected to increase biogas production by approximately 25%. Delivered through a CMAR approach with an estimated cost of $300 million, the project represents the first direct potable reuse (DPR) facility in Phoenix and only the second in Arizona. [b]Case Study 2: Adams Field WRF (Little Rock, AR) – Dual-use Filtration[/b] The Little Rock Water Reclamation Authority (LRWRA) began operating major improvements at its Adams Field WRF in 2021. Improvements included retrofits to the existing 36-MGD activated sludge process, construction of a 58-MGD PCMF multi-purpose filtration facility (Figure 3), expansion of UV disinfection, and new effluent pumping capacity. The multi-purpose filters provide high-rate auxiliary treatment during storm events and effluent polishing during dry-weather conditions. Data from March 2023 where the plant was in auxiliary treatment mode for 16 days of the month is shown in Figure 4 along with plant performance data. This dual-use strategy avoided expansion of the wet-weather equalization basin from 13 MG to 26 MG, saving more than $10 million in capital costs. The project was approved through an NPDES permit renewal with no objections from the USEPA, demonstrating regulatory acceptance of integrated, flexible treatment solutions (Fitzpatrick et al, 2018). [b]Case Study 3: Morro Bay, CA – SAFE Application[/b] The City of Morro Bay replaced its vulnerable coastal WWTP with a new advanced treatment facility to address flood risk and long-term water reliability. A design-build approach led to selection of a BNR-MBR process operating in parallel with a PCMF-based SAFE system for peak wet-weather flow management. Rather than constructing a 5-MG flow equalization basin, peak flows are directly treated through the SAFE system for marine discharge. This approach reduced the size of the BNR-MBR system by 30%, eliminated the equalization basin, and resulted in more than $7 million in construction savings. The facility is now the first MBR plant in California permitted for indirect potable reuse (Black & Veatch, 2025). [b]RELEVANCE[/b] These case studies demonstrate how PCMF has transitioned from a niche tertiary technology to a flexible platform capable of addressing multiple treatment objectives within a compact footprint. As utilities face increasing regulatory, climate, and financial pressures, technologies that provide primary treatment, wet-weather resiliency, and dual-use application offer significant value. The projects highlight how PCMF can support advanced water reuse, reduce capital costs, and enhance operational flexibility.