In addition to physical treatment, such as screening and filtering processes, and biological treatment, which includes oxidation ponds and lagoons, chemicals are essential in wastewater treatment. Wastewater treatment requires more aggressive usage and larger amounts of chemicals than municipal drinking water treatment. As a result, proper storage of the chemicals used in the wastewater treatment process is important.
Let’s look at the chemicals used during the wastewater treatment process, and highlight the chemical storage considerations.
Neutralization, adjusting the pH levels of wastewater with the addition of acid or base, is common in wastewater treatment. Sulfuric acid, or a base chemical, typically sodium hydroxide, may be added to the water to achieve pH balance. Both sulfuric acid and sodium hydroxide are highly corrosive and present serious storage challenges, requiring specialized chemical storage systems.
Removing Solid Particles
To facilitate the removal of solid particles within the wastewater, chemicals such as ferric chloride, polymers, and alum are used to produce positive charges to neutralize negative charged solid particles.. As a result, the solid particles clump together, making removal easier. Since more solids exist in wastewater than municipal water, more chemicals are required for this coagulation process. To ensure safe storage, ferric chloride, aluminum chloride, and polymers require specialized chemical storage tank solutions.
With recent regulatory changes reducing the amount of nutrients such as nitrogen and phosphates has been a growing area for the use of polyethylene tanks. It is becoming more common to see chemicals like acetic acid and sugar water being used to help provide a carbon source to facilitate this biological process.
The collection and treatment of industrial wastewater results in some unpleasant odors. Chemical treatment is used to control odor at the treatment facility. In addition to activated carbon, wet scrubbers are used to reduce odors. It’s very common to see sodium hydroxide and calcium nitrate. Hydrochloric acid is also used in conjunction with media in the scrubbers. Hydrochloric acid is extremely pungent smelling and highly corrosive and therefore requires a special storage system solution. Here is more information regarding polyethylene storage tank systems for hydrochloric acid.
To prevent the spread of disease, microorganisms that are pathogens must be destroyed or removed from the wastewater. A common, relatively safe and inexpensive disinfecting chemical is chlorine. Sodium hypochlorite presents several major chemical storage challenges. It breaks down under UV light exposure, tends to contain transition metals such as nickel, iron and copper that accumulate in the tank and create off-gassing exposure, and it aggressively oxidizes. A chemical storage system solution specifically engineered to handle sodium hypochlorite is required.
Sludge Treatment and Removal
Finally, 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.
Proper use and storage of chemicals during these five stages of the wastewater treatment process is a must to protect injury to water treatment plant workers, the public, and damage to property and the environment.