Every community depends on its water treatment plant to provide clean, safe water. It’s a commitment that requires staying ahead of routine maintenance, aging infrastructure and shifts in raw water quality over time. Add to the mix state or local regulatory challenges and budgetary concerns, and the job becomes even more complex. As you look for solutions in your municipal water systems, consider how a process evaluation or a filter evaluation could help you see issues more clearly and guide you to make the right choices for better performance.

A filter evaluation could detect optimizations ranging from a simple flow adjustment to a full underdrain and media replacement. Evaluating an aging water treatment plant is complex and requires thorough knowledge of what is happening and what could go wrong. Conventional water treatment relies on multiple processes often consisting of coagulation, flocculation, sedimentation, filtration and disinfection.

While some of these issues are easily assessed by looking, it can be difficult to recognize inefficiencies beneath the surface — from air scour inconsistences, backwash issues, media loss or mixing, or failing infrastructure. And although a filter evaluation will explore all potential issues related to filter media, troughs and underdrains, filtration issues could actually be caused or exacerbated by an upstream process.

Dive Deeper to Find the Problem

Extending the life of equipment is generally less expensive than replacing it. The key is addressing all the factors and correcting the issues that make up the overall inefficiency. For example, when lime is delivered as pebbles, then slaked and used for softening, unreacted lime could end up precipitating in the filters, forming chunks of calcium carbonate that rob capacity and prevent optimal filtration. A filter evaluation can help uncover the issue of calcium carbonate, but at that point, a process evaluation may need to be considered to evaluate proper lime dose and optimal primary treatment. 

Another issue that cannot be seen or recognized from the surface is media loss and media sizing. In some instances, poor media sizing and poor backwash flow correlation can lead to loss of significant volumes of media. This can lead to reduced run times and may ultimately limit the ability to meet finished water quality goals.

Another component of a filter evaluation is the backwash analysis. This looks at addressing how often filters are washed, and uses data analysis, physical testing and discussion with operations staff to determine if they are washed because of an identified problem or if they are simply being washed as a matter of habit during shift changes. Issues like turnover and staff experience levels could mean the time is right for switching the mentality from “this is the way it’s always been done” to a more proactive approach.

What to Expect During an Evaluation

An evaluation can take between one and five days and is typically conducted by a small team. The analysis is not invasive and can be conducted during normal operations with a single filter out of service for as little as 1-2 hours. A report follows, and the data helps inform about the urgency of each issue. Opinions of probable cost in the report can be used to set budget priorities.

Process evaluations can help determine the root problems that could place your plant in violation. An experienced team can help address the varied causes, including overall process inefficiencies. In some cases, just improving the mixing energy or adjusting a chemical feed point or dosing rate can address inadequacies that can lead to poor filter performance and can be difficult to assess without a hands-on evaluation.

After an evaluation you should expect thorough analysis, discussion and direction to help you prioritize your water treatment plant’s issues, identifying those that require immediate attention and those that can be addressed in future budgets.


Think you might need a filter or full process evaluation? Download our presentation about how they can benefit your plant and see pictures of common filter issues uncovered during evaluations.

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Jessica Borries specializes in the design of treatment plant processes and evaluations for water and wastewater projects. Her experience includes industrial and municipal water and wastewater treatment, including treatment plant and pump station condition assessments, filter evaluations, and water treatment process evaluations to identify opportunities to improve performance and evaluate compliance.