How does H2S destroy concrete and what coating resists it?

H2S gas in the headspace above wastewater dissolves in condensation on concrete surfaces. Thiobacillus bacteria oxidize it to sulfuric acid, which attacks the calcium silicate hydrate in Portland cement, progressively softening and eroding the concrete surface. 100% solids epoxy and polyurea liners create an impermeable barrier that prevents the acid from reaching the concrete substrate. Calcium aluminate-based mortars resist direct acid attack better than Portland cement when used for repairs.

How do you handle confined space entry safely?

All Zimcoat crew working in classified confined spaces are trained to applicable Canadian OH&S standards. We prepare site-specific confined space entry plans, provide continuous atmospheric monitoring (O2, H2S, LEL), use supplied-air or SCBA where required, and maintain full rescue capability at the point of entry throughout the work. We coordinate entry plan approval with your safety department before mobilizing.

Can you work in a treatment plant that needs to stay operational?

Yes. We develop phased work plans in coordination with your plant operators to isolate individual structures — one digester at a time, one wet well cell at a time — while the rest of the plant remains in service. We are experienced working around live process equipment and communicating daily with operations staff.

How much service life can we add with a rehabilitation program?

A properly specified and applied liner system on sound (or restored) concrete substrate typically provides 20–40 years of protection against H2S attack in wastewater environments. CFRP structural strengthening restores design-level load capacity to deteriorated elements with design service lives of 50+ years. The key is assessing concrete condition accurately before specifying — we do not coat over unsound substrates.

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Wastewater Treatment & Utilities

Concrete Protection & Repair for Wastewater Treatment Facilities in Ontario

Biogenic sulfuric acid corrosion from hydrogen sulfide (H2S) is the dominant cause of concrete deterioration in wastewater infrastructure. Left unchecked, it destroys centimetres of concrete per decade. Zimcoat delivers 100% solids epoxy and polyurea liner systems, calcium aluminate repair mortars, and CFRP structural strengthening specifically engineered for the wastewater environment — with confined space entry compliance built into every project plan.

Request a Facility Assessment Call 905.450.2989

The problem wastewater treatment facilities face: H2S gas produced by anaerobic biological activity converts to sulfuric acid on moist concrete surfaces above the waterline, attacking cement paste and aggregate aggressively. Standard coatings fail within years. Unprotected concrete in digesters, wet wells, and headworks structures can lose 10–25mm of cover depth per decade, exposing rebar and compromising structural capacity.

Where Zimcoat Works in Wastewater Treatment Facilities

Digesters

High-build 100% solids epoxy and polyurea liners resistant to H2S attack and continuous immersion. Applied to digester walls and domes above and below the liquid level. CFRP structural strengthening where wall section loss has occurred.

Clarifiers & Sedimentation Tanks

Liner systems for primary and secondary clarifiers resisting both chemical attack and mechanical contact from rotating mechanisms. Crack repair and joint sealing integrated into the liner scope.

Wet Wells & Pump Stations

Aggressive environment coatings for wet wells operating with high H2S concentrations. All work performed under confined space entry procedures with trained personnel and monitoring.

Headworks & Screening Areas

Coatings and repair for grit chambers, screening channels, and headworks structures where H2S concentrations are often highest due to incoming raw wastewater.

Pipe Galleries & Tunnels

Wall and overhead coatings for below-grade galleries subject to condensation, H2S, and intermittent flooding. Anti-slip floor coatings on walking surfaces.

Chemical Feed & Control Buildings

Protective floor and wall coatings for chemical storage, dosing, and MCC rooms. Secondary containment liners for chemical storage areas.

Coating and Repair Systems for Wastewater Infrastructure

System	Best For
100% Solids Epoxy Liners	Thick-film, zero-VOC epoxy systems with proven resistance to H2S and sulfuric acid. Applied by brush, roller, or spray to 1,000–4,000 μm DFT. Primary choice for above-waterline digester and wet well protection.
Polyurea Spray Liners	Rapid-cure, flexible liners applied by plural-component spray for large surface areas, complex geometry, and return-to-service requirements measured in hours rather than days. Excellent elongation for structures with movement.
Calcium Aluminate Mortars	Acid-resistant repair mortars for concrete surfaces with active H2S/sulfuric acid exposure. Resists chemical attack that degrades Portland cement mortars. Used for section restoration prior to lining.
CFRP & FRP Structural Reinforcing	Carbon fibre reinforced polymer (CFRP) laminates and aramid/glass FRP systems for restoring load capacity to deteriorated walls, beams, and columns. Applied externally without demolition.
Crack Injection	Epoxy injection for structural (dormant) cracks. Polyurethane foam injection for water-active cracks. Both systems applied under confined space protocols in live structures.

What a Facility Assessment Includes

Facility tour with plant operators covering all process structures and confined space locations
Concrete condition assessment: H2S exposure mapping, delamination testing, rebar exposure survey
Confined space inventory and entry classification for all proposed work areas
Review of operational constraints: which structures can be isolated and for how long
Structural condition review for areas with visible section loss or rebar corrosion
Written scope, system specifications, confined space work plan, and budget estimate

Request a Facility Assessment

Common Questions from Wastewater Treatment Facility Teams

How does H2S destroy concrete and what coating resists it?: H2S gas in the headspace above wastewater dissolves in condensation on concrete surfaces. Thiobacillus bacteria oxidize it to sulfuric acid, which attacks the calcium silicate hydrate in Portland cement, progressively softening and eroding the concrete surface. 100% solids epoxy and polyurea liners create an impermeable barrier that prevents the acid from reaching the concrete substrate. Calcium aluminate-based mortars resist direct acid attack better than Portland cement when used for repairs.
How do you handle confined space entry safely?: All Zimcoat crew working in classified confined spaces are trained to applicable Canadian OH&S standards. We prepare site-specific confined space entry plans, provide continuous atmospheric monitoring (O2, H2S, LEL), use supplied-air or SCBA where required, and maintain full rescue capability at the point of entry throughout the work. We coordinate entry plan approval with your safety department before mobilizing.
Can you work in a treatment plant that needs to stay operational?: Yes. We develop phased work plans in coordination with your plant operators to isolate individual structures — one digester at a time, one wet well cell at a time — while the rest of the plant remains in service. We are experienced working around live process equipment and communicating daily with operations staff.
How much service life can we add with a rehabilitation program?: A properly specified and applied liner system on sound (or restored) concrete substrate typically provides 20–40 years of protection against H2S attack in wastewater environments. CFRP structural strengthening restores design-level load capacity to deteriorated elements with design service lives of 50+ years. The key is assessing concrete condition accurately before specifying — we do not coat over unsound substrates.

Schedule a Facility Assessment for Your Wastewater Treatment Plant

Our team will survey your structures, assess H2S exposure levels, identify confined space requirements, and deliver a rehabilitation plan and budget.