Municipal Wastewater Treatment

Sample Engagements:

Relining/Recoating of WWTP Structures and Equipment:


During inspection of their primary clarifiers and related structures, a large, regional wastewater treatment plant in the northeastern United States found widespread coating failure and concrete substrate deterioration.


CPI performed existing coating failure analysis and concrete condition survey services for the primary clarifiers, influent/effluent channels, one wet well, and various other structures. The original coatings could not resist the unexpectedly high H2S concentrations and related biogenic corrosion mechanisms in these covered structures. CPI concluded that lack of acid resistance, permeation resistance, and bacterial action resistance were the main causes of coating failure. An intensive evaluation of coating and lining products used throughout the world was conducted by CPI and exposure conditions were carefully defined based on pH testing and an H2S gas sampling program. Field inspections of various in-service candidate lining and coating materials were performed by CPI in Miami, Los Angeles, Boston, and Charleston, SC.


CPI selected two different types of lining systems for varying degrees of exposure severity for concrete headspace surfaces and one type of high-build coating system for protection of carbon steel, ductile iron, and other metal substrates. These included a PVC Retrofit Sheet Lining for higher H2S conditions, a modified amine-cured epoxy lining (trowel applied to 1/8" thick) for lower H2S conditions, and a high-build, amine-cured, sprayable epoxy coating (30 to 40 mils thick) for metal components.

CPI subsequently provided specification writing and detailed drawing design for all lining terminations and transitions for the relining/recoating work. CPI also provided onsite quality assurance inspection and engineering support to this very large corrosion protection contract.


Customer Benefits

The project was performed over a 3-year time period and was completed on schedule. The linings and coatings have performed extremely well, based on follow-up inspections. This project resolved a significant corrosion problem for the customer.


Service Areas

  • Corrosion and Materials Engineering
    • Corrosion Control/Protection Design
    • Corrosion Analysis and Material Selection Consulting
    • Failure Analysis - Mode and Root Cause Analysis
    • Cathodic Protection System Design and Evaluation
  • Structural and Mechanical Rehabilitation Services
    • Structural Design Engineering
    • Mechanical Design Engineering
    • Condition Assessment Evaluations
    • Structural Evaluation and Analysis
    • Shop and Field QC Inspection and Support
  • Mechanical Integrity and Inspection Design Services
    • Pressure Vessel and Tank Program Development and Implementation
    • Systematic Inspection Design (SID)
    • Risk-Based Inspection
    • Integrity Evaluation and Analysis
    • Fitness-for-Service Evaluations
    • Welding Consulting and Inspection
  • Coatings and Linings Engineering
    • Consulting
    • Failure Analysis
    • Project Management
    • Quality Control and Inspections
  • Project and Quality Management Services
    • Cost Estimating Services for all Construction Disciplines
    • Project Management Services, Including Planning, Scheduling, and Project Controls
    • Quality Control Inspection and Testing Services
    • Quality Assurance Program Development for New and Rehabilitation Construction
    • Quality Assurance Program Auditing and Oversight Services
  • Training Services
    • Alloy Selection for Corrosive Environments
    • Solving Corrosion and Materials Problems for Plant Engineers
    • Welding Essentials for Plant Engineers
    • Brick and Tile-Lined Equipment Inspection and Repair
    • FRP Essentials for Pulp and Paper Mills
    • Concrete Restoration and Protection
    • Quality Assurance for Capital Projects

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