Clean water is becoming a scarce resource. There is an increasing need to treat waste water, both in developed countries and emerging countries alike. New, large waste water treatment plants are continually being built in Latin America, Asia and Africa.

However, in all those countries many waste water treatment plants have now severely aged and suffered various degrees of degradation – mostly due to biogenic corrosion in areal parts of confined pits in the plant or within the sewer network.

Count on Sika’s expertise to help solve this and related problems in waste water treatment plants.

Typical Exposures for Sewers

Damages at the bottom

Heavy abrasion and erosion of the concrete and prefabricated elements are often found at the bottom of the sewers. In general rules, these elements shall be replaced and reassembled properly by bonding them in place with an epoxy adhesive. In the case of the concrete substrate, the erosion can be repaired with a high abrasion resistant mortar that will increase the service life of the substrate

 

 

Localized defects of the concrete

Lateral walls and the crown often show localized defects of the concrete and some- times defects due to the corrosion of the reinforcement. After appropriate preparation, these defects can be repaired using sulfate resistant repair mortars.

Full degradation of the concrete surface

The resistance of tamped concrete against a strong water current is generally not enough and often the full surface of the concrete is eroded. It is recommended in these zones to proceed with a full resurfacing.

Cracks with water leaks

Due to shrinkage or settlements, concrete in sewers often cracks. These cracks need
to be fi lled in order to prevent leakage of pollutant to surrounding ground water. It is often necessary to use expanding materials to fi ll these cracks.

Damages at the crown

Exposed tamped concrete surfaces show very low resistance against carbonation and the aggressive substances contained in the waste water. Therefore, these surfaces can be protected using EpoCem® technologies which are extremely resistant and watertight against urban waste water.

At the crown area, the structure can be protected against condensation water using a hydrophobic impregnation. Additionally, the aerial part of the sewer can suffer from biogenic corrosion or microbial induced corrosion (MIC). To repair and protect these areas a 100% Calcium Aluminate Mortar must be used.

General Refurbishment Considerations

Before defining the repair and protection strategy, the specific sewage treatment plant requirements on refurbishment must be considered. These requirements can have an important influence in determining the correct design, planning and construction procedures, together with the future maintenance works necessary for the sewage treatment plant.

Examples of such project related requirements include:

Durability
Duration of closure / Downtime
System compatibility
Total life cycle costing
Exposures / Site Conditions
Ecology

Waste water treatment plant in Wroclaw in Poland

Systems Plus Knowhow

Waste water treatmant plant in Zurich, Switzerland

For many decades, Sika has been a reliable partner with waste water treatment plant contractors supplying products and systems on all continents. Sika has shown the industry we are a partner in whom they can trust.

The products and systems used in new waste water treatment plants, sewage facilities and retrofitted structures are thoroughly tested in Sika laboratories before being independently checked. Sika materials are further proven by long term site testing to withstand harsh conditions in the real environment.

The proposed solutions below are typical and may not be available in all countries. Check with your local Sika expert to find the best locally available solution.

Solutions for Waste Water Treatment Plant Repair

1. Screening Channel

In a large treatment plant, the removal of large objects is automatically performed in the screening channel.

Abrasion and erosion

Problem

In waste water treatment plants, erosion is mainly due to abrasion or by chemical attack. Erosion damage results from the abrasive effect of waterborne silt, sand, gravel, and other debris being circulated over a concrete surface during operation. The compounds present in hardened Portland cement are attacked by the aggressiveness (low pH) of the waste water.  

Sika Solution

Sika MonoTop®-3400 Abraroc

Chemical attacks

Problem

Chemical attacks, depending on the aggressiveness of the waste or industrial water.  

Sika Solution

Sikagard®-720 EpoCem®
Sikagard®-63 N

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete.

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® PRO-3
Sika® Injection-451

Microbial induced corrosion (MIC) in covered areas

Problem

Damage in concrete due to microbial induced corrosion (MIC) in covered areas where the sewage is in a turbulent flow.

Sika Solution

Sika MonoTop®-4400 MIC

Construction elements of cleaning waste water - Illustration

2. Grit, Fat and Grease Removal Chamber

In some plants, pre-treatment may include a grit channel where the waste water velocity is adjusted to allow settlement of the sands/grits or other hard particles. Sands/grits must be removed as they may damage pumps or other equipment. Fat and grease removal is generally done in a large plant in the primary settlement tank using mechanical surface skimmers.

Abrasion and erosion

Problem

Abrasion and erosion due to sand, grit or other particles.

Sika Solution

Sika MonoTop®-3400 Abraroc

Chemical attacks

Problem

Chemical attacks depending on the aggressiveness of the waste or industrial water.

Sika Solution

Sikagard®-720 EpoCem®
Sikagard®-63 N

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete. Very often in waste water treatment, joints sealed with average sealant fails due to the lack of chemical resistance to these products. Instead of proceeding to the full removal of the failed joint, Sika has developed a joint system that can be applied over the original failed material.


The Sikadur-Combiflex® SG system is the second generation development of the globally proven Sikadur-Combiflex® with even improved performance such as advanced adhesion properties. The unique system consists of the Sikadur Combiflex® SG tape and the Sikadur® adhesives. It is widely used as joint waterproofing in watertight concrete structures.

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® PRO-3

Microbial induced corrosion (MIC) in covered areas

Problem

Microbial induced corrosion (MIC) in covered areas where the sewage is in turbulent flow

Sika Solution

Sika MonoTop®-4400 MIC

Construction elements of cleaning waste water - Illustration

3. Primary Sedimentation Tanks

In the primary sedimentation tank, sewage flows through large tanks, commonly named “primary clarifiers” or “primary sedimentation tanks”. These tanks are equipped with mechanically driven scrappers that drive the collected sludge towards a hopper. Some primary sedimentation tanks can be covered to control odor. In such conditions, they can be subjected to biogenic corrosion.

Chemical attacks and damaged waterproofing

Problem

Chemical attacks depending on the aggressiveness of the waste or industrial water.

Sika Solution

Sikagard®-720 EpoCem®
Sikagard®-63 N

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® PRO-3

Damaged concrete and steel reinforcement corrosion

Problem

Abrasion and erosion due to sand, grit or other particles at the bottom of the concrete floor.

Concrete spalling due to sulfate attack or other aggressors on the wall of the tank.

Sika Solution

Sika MonoTop®-412 NFG
SikaTop® Armatec®-110 EpoCem®
Sika MonoTop®-2400 Reseaux
Sika MonoTop®-3400 Abraroc

Mechanical abrasion

Problem

Heavy abrasion on the rolling pad of the scrapper.

Sika Solution

Sikadur®-42
Sika® Icosit®-KC 330 FK

Microbial induced corrosion (MIC) in covered areas

Problem

In covered areas of tanks, biogenic corrosion may occur - leading to microbial induced corrosion (MIC).

Sika Solution

Sika MonoTop®-4400 MIC

Construction elements of cleaning waste water - Illustration

4. Aerated and anoxic biological tanks

Biological tanks are designed to substantially degrade the biological content of the sewage. These biological contents are originated from human waste, soap, and detergents.

Chemical attacks

Problem

Chemical attacks depending on the aggressiveness of the waste or industrial water.

Sika Solution

Sikagard®-720 EpoCem®

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete.

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® PRO-3

Concrete Spalling

Problem

Concrete spalling due to reinforcement steel corrosion.

Sika Solution

Sika MonoTop®-412 NFG
SikaTop® Armatec®-110 EpoCem®
Sika MonoTop®-2400 Reseaux 

Construction elements of cleaning waste water - Illustration

5. Secondary Sedimentation Plant

Secondary treatment is intended to degrade further the organic content of sewage water originating from human waste, soap, detergent, etc. Most of the plants treat the sewage using aerobic biological processes.

Erosion

Problem

Erosion due to water flow

Sika Solution

Sikagard®-720 EpoCem®

Chemical attacks

Problem

The water has already received some treatment, hence the level of chemical aggressiveness in this sedimentation tank is reduced.

Sika Solution

Sikagard®-720 EpoCem® can be used alone in secondary treatment tanks

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® PRO-3

Reinforcing steel bar corrosion

Problem

Steel reinforcement corrosion due to reduced concrete cover.

Sika Solution

Sika MonoTop®-412 NFG
SikaTop® Armatec®-110 EpoCem®
Sika MonoTop®-2400 Reseaux 

Construction elements of cleaning waste water - Illustration

6. Filtration Beds

In the filtration bed, the treated water flows through various layers of sand beds for final filtration before being discharged in the environment. Filters are periodically cleaned using air and clean water at the counter stream. The cleansing water is then pumped back to the aeration basin for retreatment.

Abrasion

Problem

Abrasion and erosion due to sand, grit or other particles.

Sika Solution

Sika MonoTop®-3400 Abraroc

Damaged waterproofing

Problem

Chemical attacks depending on the aggressiveness of the waste or industrial water.

Sika Solution

Sikagard®-720 EpoCem®

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete.

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® PRO-3

Construction elements of cleaning waste water - Illustration

7. Digestion Tanks

The sewage sludge digestion tank is where the sludge is stabilized, reduced in volume, made innocuous through the process of dissolving organic substance with the help of anaerobic bacteria and finally, where energy is recovered.

Abrasion and erosion

Problem

Abrasion and erosion due to sand, grit or other particles.

Sika Solution

Sika MonoTop®-3400 Abraroc

Chemical attacks

Problem

Concrete or steel above the sludge may suffer heavy attack due to the formation of the sulfuric acid. Additional stress is caused by the elevated temperature originating from the biological process. Downtimes always create problems and difficulties for the owners, as well as the loss of money. Sika offers solvent-free, high build coating systems that can be applied in one layer on a well-prepared surface. Therefore, downtimes can be minimized without the reduction of protective properties.

Sika Solution

Sika® Permacor® 3326 EG H
Sikalastic®-8440

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete.

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® TS Plus

Construction elements of cleaning waste water - Illustration

8. Gasometers

Within the process of biological deterioration in the biological tank or the digestion tank, biogas (methane, CO²) will be produced and be stored in gasometers. These gasometers are generally built-in steel. Biogenic sulfuric acid is highly aggressive to steel. Additional stresses are caused by the elevated temperature.

Chemical attacks

Problem

Concrete or steel above the sludge may suffer heavy attack due to the formation of the sulfuric acid. Additional stress is caused by the elevated temperature originating from the biological process. Downtimes always create problems and difficulties for the owners, as well as the loss of money. Sika offers solvent-free, high build coating systems that can be applied in one layer on a well-prepared surface. Therefore, downtimes can be minimized without the reduction of protective properties.

Sika Solution

Sika® Permacor® 3326 EG H
Sikalastic®-8440

Cracks, untight joints

Problem

Leakage and risk of pollution due to cracks, untight joints or damaged concrete.

Sika Solution

Sikadur-Combiflex® SG System
Sikaflex® TS Plus

Construction elements of cleaning waste water - Illustration

9. Structural & Non-structural Steel Parts

Waste water treatment plants have structural or non-structural steel components or areas which are highly subjected to various aggressors causing corrosion.

Sika provides a large range of extensively tested products in the field of corrosion protection:

  • For digesters, gasometer and MIC (microbial induced corrosion) of steel structures in anaerobic conditions.
  • For steel components not subject to microbial induced corrosion.
  • Coating systems for structural steel work.
Steel corrosion

Problem

Corrosion protection - protection of new structures on site or shop application.

Sika Solution

Sikalastic®-844 XT or Sikalastic®-8440
Sika Permacor®-3326 EG H
Sikagard®-63 N
SikaCor® EG-System
Sika® Poxicolor Primer HE

Steel Beam Corrosion Protection

10. Service Buildings, Concrete & Masonry Exterior

Most waste water treatment plants have a technical service building. External surfaces of the building as well as of the above-ground tanks are exposed to weathering and therefore often need protection.

Flooring

Problem

In these technical buildings, chemicals are handled. Therefore, the floors in the chemical storage area also need protection.

Sika Solution

Sikafloor®- 381
Sikafloor®-21 PurCem

Roofing

Problem

Roofs in the buildings (technical and office) of the sewage treatment plants may require waterproofing.

Sika Solution

SikaPlan® PVC or FPO membrane
Sikalastic® liquid applied membrane

External concrete protection

Problem

External concrete surfaces may undergo natural weathering due to carbonation. When the plant is located close to the sea, they may also suffer chloride attack.

Sika Solution

Hydrophobic impregnations: Sikagard®-705 L and Sikagard®-740 W
Protective coatings: Sikagard®-675 W ElastoColor and Sikagard®-555 W Elastic

External masonry protection

Problem

External masonry surfaces may undergo natural weathering due to water penetration that may lead to mold growth and reduced thermal performance of the structure.

Sika Solution

Hydrophobic impregnation: Sikagard®-703 W

Technical service building of a waste water plant

Sika’s Experts Provide Assistance to Benefit your Business

Local Contact

Contact a Sika expert near you for technical support and locally available products and systems.

Global Support

Contact Sika's global representative in case you need our support in an international project.