When considering storage solutions for chemicals used in the wastewater process, two options available are fiberglass reinforced plastic (FRP) and polyethylene (“poly”).
Whereas FRP tanks are constructed with numerous layers including a structural layer comprised of chopped glass or filament wound fiber and resin, polyethylene storage tanks are composed of either linear polyethylene or high-density crosslinked polyethylene (specifically engineered material for critical applications, like chemical storage).
Let’s take a brief look at why chemicals are used in the wastewater process, before further comparing the differences between the aforementioned storage tank options.
Reasons for Chemical Usage in the Wastewater Treatment Process
Neutralization is common in wastewater treatment. During this process, sulfuric acid, or a basic chemical such as sodium hydroxide, may be added to the water to achieve pH balance.
Removing Solid Particles
To facilitate the removal of solid particles within the wastewater, chemicals such as ferric chloride, alum, and other flocculants and polymers are used to produce positive charges to neutralize negative charged solid particles.
Unsurprisingly, the collection and treatment of industrial wastewater results in some unpleasant odors, and chemicals are used to control such odors at the treatment facility.
To prevent the spread of disease, microorganisms that are pathogens must be destroyed or removed from the wastewater.
Sludge Treatment and Removal
A polymer chemical may be used to remove water from the sludge to reduce volume, making transporting the sludge to the landfill easier and less expensive.
Highlighting Major Differences Between FRP and Polyethylene Tanks
Now that we’ve established some of the reasons why chemicals are used in wastewater treatment, let’s compare some of the differences between FRP and Poly tanks:
FRP storage tanks are not one-piece vessels – they contain seams. These are weak areas of the tank where leaks tend to occur. Poly storage tanks are created using one-piece molded (monolithic) construction and lack the seams where leaks tend to develop.
Leaks are especially dangerous when dealing with highly corrosive and toxic chemicals, such as hydrochloric acid, which is used to control harsh odors in wastewater treatment.
FRP tanks are sometimes handcrafted in production, which is labor intensive and creates opportunities for human error. In the creation of a poly tank, an automated process controls engineered production, thus eliminating the risk of human error.
It’s important that your chemical storage tanks can withstand years of chemical storage, and removing human error is a great way to minimize mistakes when storing heavy chemicals such as sulfuric acid, used during wastewater neutralization.
In addition to the challenge of controlling the quality of manufacture, FRP is expensive. Resin rich corrosion barriers designed for common chemicals can increase these costs significantly.
Due to lower cost of materials and expense of the manufacturing process, crosslinked polyethylene storage tanks are more economical than FRP storage tanks.
Since FRP storage tanks are subject to leaks at the seams and corrosion of the tank develops over time, very careful maintenance and inspection of the storage tank is frequently needed, often requiring confined space entry. Without seams and different interior coatings (and given the corrosion resistance of poly storage tanks), maintenance and inspection is less of a chore for poly tanks.
This means that you can continue to safely store your sodium hypochlorite, which can be dangerous if it escapes from the tank, and all of the other wastewater treatment chemicals stored at your plant.