A Closer Look at Advanced Filter Technology

The field of wastewater treatment has seen significant technological advancements over the years, particularly in filtration processes. Filtration plays a crucial role in removing contaminants from the wastewater stream before it is released back into the environment or reused for industrial and municipal applications. Over the past several decades, conventional tertiary filtration techniques like disc, fuzzy, sand and media filters have evolved to more advanced systems, improving efficiency, sustainability and compliance with environmental regulations.

The Evolution of Filtration Technology

Filtration technology in wastewater treatment has transformed from simple sand filters and sedimentation techniques to cutting-edge membrane processes, some of which can be directly combined with biological processes, known as membrane bioreactors (MBR). In recent years, the desire to find opportunities to reuse water and evolving environmental regulations have led to the development of new filtering solutions that offer higher contaminant removal efficiencies. The move to advanced filtration methods has resulted in more effective removal of dangerous pollutants such as heavy metals, pathogens, synthetic chemicals Per- and polyfluoroalkyl substances (PFAS), microplastics and pharmaceutical residuals.

Two of the most prominent filtration technologies in advanced wastewater treatment (AWT) are membrane-based filters and membrane bioreactors. While both technologies rely on membranes for filtration, they have distinct differences in their application and effectiveness.

Membrane-Based Filters

Membrane-based filters use semi-permeable membranes to remove contaminants from wastewater. These filters can be classified into different types based on pore size:

• Microfiltration (MF): Removes suspended solids, bacteria, and some large pathogens.
• Ultrafiltration (UF): Filters out bacteria, viruses, and macromolecules.
• Nanofiltration (NF): Targets dissolved solids, organic matter, and hardness-causing minerals.
• Reverse Osmosis (RO): Provides the highest level of filtration, removing nearly all dissolved substances, including salts and heavy metals.

Membrane-based filters are used to treat groundwater, surface water, wastewater and seawater treatment for potable and non-potable uses.

Membrane Bioreactors

Membrane bioreactors (MBR) integrate biological treatment with UF or MF membrane filtration, offering a more productive removal process for nutrients, organic matter and suspended solids. MBRs operate by combining activated sludge treatment with membrane filtration, which enhances the breakdown of organic pollutants while simultaneously filtering out solids and bacteria. More specifically, MBRs allow for significantly higher mixed liquor suspended solids (MLSS) concentrations, around three to four times more than conventional biological processes, which improves nutrient and organic removal of the effluent stream.  Additionally, the membrane removes almost all suspended solids or particulates. This method allows for high-quality effluent water within a small footprint, making it suitable for reuse in irrigation, industrial processes and even potable water applications.

Benefits of Advanced Filter Technology

The advancements in filtration technology provide numerous benefits, including:

• Improved Water Quality: Advanced filters remove a higher percentage of contaminants, resulting in cleaner and safer water for discharge or reuse.
• Energy Efficiency: Modern filtration systems are designed to operate with lower energy consumption, reducing overall treatment costs.
• Compact Design: Many advanced filters, such as MBRs, require less space compared to conventional treatment methods, making them ideal for urban and industrial settings.
• Regulatory Compliance: Enhanced filtration methods help facilities meet stringent environmental regulations, avoiding legal penalties and protecting public health.
• Sustainability: Many advanced filtration systems support water reuse and recycling, reducing the demand from traditional water treatment plants and minimizing wastewater discharge.

Municipal Water Planning with End Goals in Mind

Choosing the right combination of advanced water technology involves several unique non-economic and economic considerations. The technological feasibility of various options is often decided on using water source assessments and removal requirements, but equally as important for a municipal management team are brine management; the technical and social implications of distribution system connection locations; and source water blending and system stability. 

On top of these considerations, the selection of technologies and project scope can significantly impact project budgets. In AWT projects, factors like subcontractor and labor availability, supply-chain disruptions, escalation impacts, and federal funding requirements make budgeting complex. However, utilizing collaborative delivery methods to incorporate engineering and construction expertise can provide timely, accurate estimates. This approach allows the municipalities understand the cost of AWT technology treatment alternatives and project analysis – without the risk of wholesale redesign. 

Advanced Filters in Action

Multiple sources of surface water are treated at the Chandler Reclaimed Water Interconnect Facility in Chandler, Ariz. McCarthy Building Companies worked with the City of Chandler to install Veolia ZeeWeed ultrafiltration membranes, a membrane filtration technology used in advanced water purification processes. The complex system, capable of 10 MGD, was constructed in a small footprint and integrated into an existing SCADA system. Brought online in late October 2024, the system is fully operational and meets the specified filtration performance requirements.

Also in Chandler, Ariz., McCarthy Building Companies completed a significant expansion of the Ocotillo Water Reclamation Facility (OWRF) to address rapid growth and the City's need to provide adequate wastewater treatment capacity and produce high-quality reclaimed water. The project team selected submerged hollow fiber MBR technology, which combines activated sludge treatment with ultrafiltration membranes. This choice was driven by the technology's ability to consistently produce Class A+ reclaimed water, accommodate a smaller footprint, and reduce sludge production. The selection of MBR technology and the collaborative delivery approach contributed to the project's success – increasing the facility's capacity to 15.5 MGD and reliably producing high-quality reclaimed water.

In Fountain Valley, Calif., the much larger-scale Orange County Water District Groundwater Replenishment System (OCWD GWRS) serves as an international model for AWT. The GWRS employs a few different filtration technologies to meet the state of California’s requirements for injection well recharge and indirect potable reuse (IPR). One of the installed treatment technologies is hollow fiber MF followed by RO.

OCWD’s previous facility for IPR, Water Factory 21, was one of the first to incorporate RO for treating wastewater.  As new technologies, like UF and MF, were being successfully commercialized, in parallel with chemistry improvements in RO, these processes were combined successfully at OCWD GWRS to not only achieve reduction in dissolved salts and significant improvement in performance of the RO process, but also to provide major improvements in reduction of Cryptosporidium and Giarda, bacteria, personal care products and PFAS.

The rapid advancement of filtration technology in wastewater treatment has greatly improved effluent water quality, regulatory compliance, and sustainability efforts. Membrane-based filters and MBRs are leading the way in efficient and effective contaminant removal by addressing both traditional and emerging pollutants. With continued innovation and regulatory support, filtration technology will play an even greater role in ensuring safe and sustainable water supplies in the future.

Julie Woodward is preconstruction senior manager with the National Water Services Team at McCarthy Building Companies, and David Faber is a chemical engineer and business development director with the Water Services Team at McCarthy Building Companies’ Southern Pacific Region. Julie can be contacted at jmwoodworth [at] mccarthy.com (jmwoodworth[at]mccarthy[dot]com) and David can be reached at dfaber [at] mccarthy.com (dfaber[at]mccarthy[dot]com).