AWWA Manual M37: Coagulation, clarification, and filtration in water treatment

The Coagulation, Clarification, and Filtration in Water Treatment Manual (Manual M37) has long been a trusted resource for water professionals. Now in its fourth edition, this American Water Works Association manual reflects decades of industry experience and evolving best practices in conventional and membrane-based water treatment.

Unlike design-focused manuals, this edition is written with a clear operational purpose. Its goal is to help operators and the engineers who support them get the most effective and reliable performance from existing treatment facilities. The manual covers the full treatment train from coagulation chemistry and flocculation through clarification, filtration, membrane applications, testing, instrumentation, and real-world case studies, while emphasizing optimization, monitoring, and practical decision-making.

Carollo experts contributed three chapters to this edition, each focused on a critical component of modern water treatment operations: clarification, membrane pretreatment, and instrumentation. Together, these chapters offer actionable insights utilities can apply immediately.

Clarification Processes in Water Treatment

In the chapter “Clarification Processes,” Carollo’s Austin Peters explores the critical step of bulk solids removal in conventional water treatment.

Clarification is the physical process of removing suspended particles from water, typically following coagulation and flocculation and ahead of filtration. While chemistry plays a major role upstream, clarification performance depends heavily on hydraulics, solids loading, and basin configuration.

The chapter explains how different clarifier geometries have evolved to meet specific treatment goals and why there is no one-size-fits-all solution. Austin emphasizes key operational parameters and techniques to improve clarifier performance. This includes essential monitoring practices and instrumentation to provide operators with the feedback they need to optimize performance and respond to changing water quality.

This chapter offers practical guidance for understanding clarifier behavior and improving reliability without major infrastructure changes.

Coagulation and Membrane Filtration for Microfiltration (MF) and Ultrafiltration (UF) Systems

As membrane filtration becomes more common, pretreatment decisions are increasingly important. In “Coagulation and Membrane Filtration,” Carollo’s John Civardi focuses on how coagulation fits into microfiltration (MF) and ultrafiltration (UF) operations.

While membranes provide an absolute physical barrier for pathogens like Giardia and Cryptosporidium, coagulation still plays a critical role in managing natural organic matter, reducing fouling, improving flux, and supporting disinfection byproduct control. John explains that coagulation fundamentals still apply in membrane systems, but their application must be site-specific and carefully tested.

The chapter discusses how different coagulants can influence fouling behavior, why some polymers can create severe operational challenges, and how pretreatment strategies affect energy use and long-term membrane performance. The chapter also provides guidance regarding the use of oxidants and adsorbents.  It also provides guidance on troubleshooting variable source water conditions, such as high turbidity or elevated total organic carbon.

For utilities operating or considering MF/UF systems, this chapter connects core coagulation principles to day-to-day membrane performance.

Instrumentation for Monitoring and Control in Water Treatment Plants

Reliable treatment depends on good data. In “Instrumentation for Monitoring and Control,” Carollo’s Ali Leeds addresses the tools utilities rely on to monitor raw water quality, control coagulant dosing, evaluate clarification and filtration performance, and meet regulatory requirements.

The chapter provides an overview of commonly used online instruments, explaining how they work, what their data means, and how to troubleshoot common issues. Rather than focusing solely on technology, Ali emphasizes practical considerations, including sensor placement, data interpretation, and integration into operations.

By helping operators understand both the strengths and limitations of analytical instrumentation, the chapter supports more confident, data-driven decision-making across the treatment process.

Learn More in AWWA Manual M37

Together, these three chapters reflect the broader intent of Coagulation, Clarification, and Filtration in Water Treatment: to help utilities optimize performance using the systems they already have. From solids removal and membrane pretreatment to instrumentation and control, the fourth edition of Manual M37 offers practical guidance grounded in real-world operations.

To access the full range of chapters and case studies, consider purchasing and reading the complete manual from AWWA.