Liners & Coatings Save Pump Station Concrete

Corrosion of unprotected concrete

Romtec Utilities offers PVC and fiberglass liners and epoxy coatings for the interior surfaces of concrete wet wells and vaults in our wastewater pump stations. These treatments help prevent damage to the concrete from gasses and liquids that may be present in the sewage. The most common concern is hydrogen sulfide gas emitted from municipal wastewater and the sulfuric acid that forms through a bacterially mediated process. A description of the process that causes degradation of concrete from sewage gas is copied from Wikipedia at the end of this article.

We meet your specs for concrete protection

Romtec Utilities works closely with municipal water/wastewater agencies and their civil engineers to develop specifications for concrete protection.

T-Lock heat weld process

Liners

The most common liner used in Romtec Utilities wet wells is Ameron T-Lock. This PVC material is cast into the interior surface of the concrete at the time the parts are being manufactured. Joints between sections of the wet well and where pipes enter and exit the wet well are heat welded in the field at the time of installation. Other types of liners are available on request. These liners form a permanent impervious barrier on all interior surfaces of the concrete wet well protecting it from corrosion and water incursion. The smooth surface also helps in keeping the wet well free of built-up solids. Romtec Utilities offers liners on all cylindrical concrete wet wells and various rectangular concrete vaults.

Epoxy coated wet well interior

Coatings

Epoxy-based coatings are also applied to the interior and exterior surfaces of the concrete underground vessels to prevent corrosion and water incursion. Tnemec and Raven brand coatings are frequently specified. Application of these materials can be done at the factory or in the field.

What exactly is going on here?

Wikipedia gives us this description of the bio-chemical process responsible for damage to concrete wastewater infrastructure:

“Biogenic Sulfide Corrosion is a bacterially mediated process of forming hydrogen sulfide gas and the subsequent conversion to sulfuric acid that attacks concrete and steel within wastewater environments. The hydrogen sulfide gas is oxidized in the presence of moisture to form sulfuric acid that attacks the matrix of concrete. The effect of sulfuric acid on concrete and steel surfaces exposed to severe wastewater environments can be devastating.”

“Fresh domestic sewage entering a wastewater collection system contains an abundance of sulfates, SO₄^2-. In the absence of dissolved oxygen and nitrates, these sulfates are reduced by sulfate reducing bacteria (SRB), identified primarily from the obligate anaerobic species Desulfovibrio, to form H₂S via a complex pathway of biochemical reactions.”

“Once the H₂S gas diffuses into the headspace environment above the wastewater, a sulfur oxidizing bacteria (SOB), primarily genus Thiobacillus aerobic bacteria, which colonize on pipe crowns, walls, and other surfaces above the waterline in wastewater pipes and structures, metabolize the H₂S gas and oxidize it to H₂SO₄. This oxidizing process can take place where there is an adequate supply of hydrogen sulfide gas greater than 2 ppm, high relative humidity, and atmospheric oxygen.”

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