Aquaculture and Seafood Processing Plant Design : The importance of Mixing, Solids Management & Venturi Systems | Aqua-Terra Consultants Spotlight

We recently spoke with Alan Ismond of Aqua-Terra Consultants to better understand how he approaches mixing, solids management, and process efficiency in seafood processing systems — and where multi-venturi injectors fit into that work.

Aqua-Terra Consultants provides process and environmental engineering services to the seafood processing, rendering, and aquaculture industries. Their work spans a wide range of operations, from at-sea processors of Pollock in Alaska to onshore facilities in Washington and Oregon processing whiting, salmon (wild caught, farm raised, and organic), shrimp, crab, and tilapia.

In addition to system design and optimization, Aqua Terra has developed a patented Advanced Foam Separation™ system used to recover additional by-products from seafood processing water streams. Their work often focuses on helping facilities reduce water use, improve solids recovery, and meet increasingly complex wastewater discharge requirements.

Understanding the core challenge

In seafood processing systems, water is constantly moving through the plant — carrying solids with it at every stage of the process. These solids still hold value if they can be recovered efficiently.

As Alan explains: “Seafood processing plants do not create pollution, only lost recovery of the seafood resource.”

From that perspective, the issue is not simply treatment — it’s how well the system preserves recoverable material throughout the process.

Water use in these facilities can range from 0.2 to 2.5 million gallons per day. Along the way, processed water is collected in inground sumps and above-ground tanks.

“Inground sumps and above ground tanks are used to collect and contain the process waters throughout the plant. Poorly designed plants and sumps will result in solids settling to the bottom… which can decompose and make recovery of solids more difficult.”

Shrimp processing wastewater before and after treatment. Image courtesy of Aqua-Terra Consultants.

Once solids settle, they begin to break down. This makes them harder to remove and increases the amount of dissolved material in the system — which is more complex and costly to treat.

“The cost of treating the combined process waters from the plant depends, in part, on the size of the suspended particles to remove (finer is more expensive to remove than coarser) and the percentage of dissolved solids (increases the cost and complexity of solids recovery).”

Because of this, system design is not just about moving water — it’s about controlling how solids behave within it.

Why mixing must be controlled

Preventing solids from settling is critical, but the way that mixing is applied matters just as much.

“The challenge is to find a way to gently keep the solids in suspension so that they are quickly removed by the sump pumps… without turning them into a very fine suspension that is more difficult to remove, or solubilizing the solids which are more costly to remove.”

Too much mixing can break solids down into smaller or dissolved forms. Too little allows them to settle and decompose. Alan summarizes the balance clearly:

“Ideally, the James Bond approach (gently shaken but not stirred) should be followed.”

Mechanical mixers are one option, but they introduce additional complexity.

“One option is to use mechanical mixers but it is difficult and expensive to find the ideal mixing blade geometry, angle, rotation speed, and number of mixers to install.”

Instead, the goal is to maintain suspension while preserving particle integrity — keeping solids recoverable and easier to separate.

Where venturi-based systems are used

In some systems, Aqua-Terra has incorporated venturi-style mixing approaches to help achieve this balance.

“The Grow Greenie multi-venturi is ideal for this application. It is readily available, cost effective, low maintenance, has adjustable process water flow and gas addition rate, and adjustable bubble size.” These systems allow for flexibility in how mixing is applied.

“Multiple units can be installed in different patterns in the sumps / tanks to create complete turbulence or more gentle vortex mixing.”

Depending on placement and configuration, operators can create different flow patterns to match system needs — from broader circulation to more targeted mixing zones.

Current work and testing

Aqua-Terra is currently evaluating different configurations in processing environments. “For the next 6 months we will be testing different configurations of the Grow Greenie venturi in a fish processing plant sump and in a shrimp processing sump.”

The focus is on preventing solids from settling while also limiting the formation of dissolved solids. “These solids are a food source for bacteria that consume oxygen. Lower oxygen content increases the cost of treating the process waters.”

Maintaining proper suspension and oxygen levels upstream can help reduce treatment demands and improve system performance overall.

How system performance is improved

From Alan’s experience, improving mixing and solids handling influences several parts of the process.

Venturi-based systems are used for:

• keeping sumps and tanks from becoming anoxic
• mixing treatment chemicals with process water to form a floc that can be easily separated
• injecting gases in chemically treated process waters to separate the solids from the water

He also notes consistent operational benefits:

• cleaner treated effluent
• lower treatment cost
• easier and faster control of plant systems

Where the greatest impact occurs

Ultimately, the most significant improvements come from how solids are conditioned before removal.

“Chemical addition and better mixing  creates a better floc that can easily be recovered.”

By focusing on how solids are managed within the system — rather than only how they are treated downstream — operators can improve both recovery and overall efficiency.

To learn more about Aqua-Terra Consultants and their work in seafood processing, aquaculture, and water system design, visit their website to explore their services and patented technologies.