Treatment Plant Egg-Shaped Digester
Massachusetts Water Resources Authority - Deer Island Treatment Plant
Water and Wastewater

The Massachusetts Water Resources Authority's Deer Island Treatment Plant (DITP) maintains 12 anaerobic, egg-shaped sludge digesters. The configuration of the digesters, while providing for efficient treatment of municipal wastewater residuals, also presents challenges to the performance of the internal inspection and condition assessment necessary for asset management.

Constructed in 1994, the digesters are carbon steel with an internal epoxy coating. Each has a height of 134 feet, an equatorial diameter of eighty-four feet, and a capacity of 3 million gallons. Inspection of the interior of such a structure required the development of a unique approach utilizing a two-phase inspection, one for the lower portion and one for the upper. The lower inspection involved a standard entry through a manway and use of scaffolding erected for piping modification work.

Inspection of the upper portion involved filling the digester with water, and performing the inspection from an inflatable boat while the digester was drained. Development of the approach first required consideration of the unusual safety complications of a boat inspection performed in a confined space. Procedures for entry, egress, communication, and rescue were specially adapted to the tanks. Also required were determination of scheduling based on the drainage rate, and minimizing entry and egress time. The results of the inspection provided valuable information on the performance of the coating and condition of the structural shell.


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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