Manual of water supply practices: Biological drinking water treatment

As drinking water regulations grow stricter and utilities look for more sustainable treatment approaches, biological filtration is reemerging as a powerful tool. These systems use naturally occurring microorganisms to break down contaminants, offering a low-energy, cost-effective solution for removing everything from natural organic matter to nitrate and trace chemicals.

The newly released Manual of Practice M80 – Biological Drinking Water Treatment, published by the American Water Works Association (AWWA), offers the most comprehensive guidance to date on biological treatment systems for drinking water. The manual covers both aerobic and anoxic systems, applications in reuse, and real-world case studies. Several Carollo employees contributed chapters that shed light on the growing use of biofiltration in diverse contexts.

Aerobic Surface Water Filtration: Optimizing Existing Systems for Bioactivity

In the chapter “Aerobic Surface Water Biological Filtration,” Carollo’s Jennifer Nyfennegger and her co-authors explore how surface water treatment plants can enhance conventional gravity filters to function as biologically active filters (BAFs). By limiting chlorine residuals across the filters, these systems allow microbial activity to develop naturally, supporting the biological breakdown of organic and inorganic compounds.

The chapter details planning, evaluation, and operational strategies for converting conventional filters into BAFs, with design considerations that include filter media selection, pretreatment integration, and disinfection placement. It also features case studies from three full-scale surface water facilities, demonstrating real-world benefits such as improved water quality stability and better removal of manganese and organics.

Anoxic Biological Treatment: Tackling Nitrate and Perchlorate in Groundwater

The chapter “Anoxic Biological Treatment,” co-authored by Carollo’s Jess Brown and Giridhar Upadhyaya, focuses on the removal of inorganic contaminants like nitrate and hexavalent chromium from groundwater sources. Unlike aerobic systems, anoxic treatment occurs in the absence of oxygen and typically requires the addition of a carbon substrate.

The authors provide insights into treatment mechanisms, system design, and operational considerations, including substrate selection and process monitoring. They also highlight full-scale applications treating nitrate, offering practical examples of how this technology can address regulatory and water quality challenges.

Aerobic Biofiltration in Potable Reuse: A Sustainable Alternative to RO

In her second contribution, Jennifer Nyfennegger turns to potable reuse in the chapter “Aerobic Biofiltration for Reuse.” This section highlights how biofiltration, when paired with strong oxidants like ozone or advanced oxidation processes (AOPs), can be used to remove trace organic compounds and pathogens without relying on reverse osmosis.

As more reuse projects seek alternatives to RO due to brine disposal and energy concerns, aerobic biofiltration is proving to be a viable solution. The chapter outlines key considerations for design and operation and includes case studies from three potable reuse facilities that are currently implementing this strategy.

Biological Treatment Gains Ground in Drinking Water and Reuse Applications

Whether it’s surface water, groundwater, or advanced reuse, the manual brings together decades of research and recent advancements, offering utilities practical guidance on how to plan, design, and operate these sustainable systems.

Explore the full manual to learn more about the role of biofiltration in building resilient and regulatory-ready water treatment solutions.