Posted by Katie Anorve-Andress on Wednesday, July 16, 2025
Wastewater treatment systems thrive on consistency, yet industrial wastewater is rarely consistent. From product changeovers and sanitation days to the surprise corporate visit requiring top-to-bottom plant cleaning, the wastewater from an industrial process can vary wildly in pH, solids, and organic loading. This inherent variability is why equalization for an industrial wastewater plant should be based on the production process and its variability, rather than solely on the wastewater process it feeds. Before we examine how we can minimize and manage wastewater variability through equalization strategies, let’s define industrial equalization.
Equalization is a process in wastewater treatment that helps to balance variations in flow rate and pollutant load before the water enters treatment units. By temporarily storing and mixing wastewater in one or more tanks, equalization helps produce a steady, uniform influent, which improves the efficiency and stability of treatment processes
Is Equalization Always Necessary?
Not all industrial facilities need equalization. Some operations have low variability, or their downstream processes can handle the process swings without affecting the effluent quality. There are four main situations where equalization is strongly recommended to optimize wastewater treatment and protect your systems:
The production process is highly variable, and the wastewater process needs consistency.
This is a common situation with food manufacturers. The wastewater produced during a batch is typically low in solids and organic loading, but product changeovers and sanitation events produce periods of high loading or concentrated chemicals. Sizing an equalization tank to mix several batches and changeovers produces a consistent wastewater stream that is easier to treat and manage.
There are pH and chemical swings.
Equalization can help reduce chemical costs in these situations by allowing the wastewater to self-neutralize. Consider Clean-in-Place (CIP) procedures. These use a caustic wash, followed by an acid wash, then finish with a sanitize step. Without equalization, additional chemicals would need to be added after each step to neutralize each pH swing. With enough equalization, chemical adjustment may not be required after mixing an entire CIP event. The neutralization capabilities of some production practices can also be stored in a high-strength waste tank for later use or diluted into the process without needing additional chemicals.
Sanitation chemicals are used with a biological wastewater process.
Sanitation chemicals are a double-edged sword: what efficiently kills bacteria on a product line is equally efficient at destroying a biological wastewater plant. To protect a biological wastewater process, adding equalization or retention time beforehand can help minimize the risk of these chemicals. Equalization not only dilutes the strength of these chemicals, but oxidizers, like hypochlorite and hydrogen peroxide, naturally degrade when exposed to air and sunlight. Even an hour in an aerated equalization tank can nearly eliminate the risk of toxicity caused by these types of chemicals to protect your treatment system.
Flows are inconsistent.
This is typical in batch production but can result from cleaning days, night or weekend production shutdowns, boiler/cooling tower blowdowns, and even stormwater events. When flows are inconsistent, equalization can help provide retention time to prevent repeated starts and stops of the wastewater plant. This reduces stress on equipment and helps produce a more consistent effluent quality.
Your Process is Your Guide
Ultimately, your production process determines the need for equalization and its optimal size. When sizing an equalization system, I like to start with a thorough site visit. This allows me to identify what in the production process generates wastewater and when. I’ll also review production schedules and overlay that information with available wastewater data. A production schedule with multiple batches and changeovers in a single day has significantly different equalization needs than a process that runs weekly and washes for a whole day.
I also take the opportunity to look at the space available for equalization. Sometimes, placing a million-gallon tank isn’t feasible, requiring us to be creative about balancing the process variability. Maybe a high-strength tank is enough to remove the variability, or the equalization needs to be split into multiple tanks and blended in the process. Understanding each facility's process and specific needs is essential in building a process that works for them.
Think your process could benefit from equalization? I’d love to walk through your process and see how we can help reduce production variability.
Katie Anorve-Andress
industrial engineering designer
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Categories: Industrial & Manufacturing
Tagged: Wastewater | Environmental