8 Signs Your Wastewater Infrastructure Needs a Condition Assessment

The decision to update your wastewater infrastructure is not an easy one. Here are signs it may be time.

How good is good enough? How bad is too bad? Every wastewater facility manager grapples with these questions. In this article, you’ll find a variety of cues signifying a need for a professional condition assessment. This assessment, in turn, will help you determine if you should begin planning to build new wastewater treatment facilities or renovate your current ones.

1. Equipment age

Different equipment has different life expectancies. Looking at the actual age of your facilities is a sensible place to start.

Generally, mechanical equipment can be expected to last 15 to 20 years, so long as you are maintaining these components regularly. Structures can last much longer, as much as 50 to 100 years, depending on what they are used for and what is in them.

It’s important to recognize that things can wear out much faster, particularly in the extreme conditions found at most wastewater facilities. There are a number of issues listed below which may indicate that a condition assessment is warranted much sooner than at the end of the expected useful life.

One city had an 80-year-old anaerobic digester that was leaking biogas. Given the harsh conditions of anaerobic digesters, we were sure parts of the structure required rebuilding. A structural inspection found that, aside from a crack, the concrete was still in great shape. Making repairs instead of rebuilding saved this city lots of money.
Susan Danzl, PE
An aging digester with evidence of leaks.

2. Corrosion and deterioration

The most obvious cue for a professional condition assessment is the presence of exterior corrosion or deterioration. Some corrosion or deterioration is purely cosmetic. Discoloration or staining of a concrete structure is not always serious. However, if you are seeing exposed aggregate or reinforcing steel on a concrete structure, the issue is likely more serious.

Pipes and conveyance facilities can require special attention. These facilities may be the most difficult and expensive to access for inspection, but they are often the most susceptible to corrosive damage. The risks associated with corrosion and deterioration are high, and can include structural collapse and endangerment to the safety of your personnel.

Minor leakage, as pictured here in a concrete tank tunnel, can lead to major ones without warning.

Related Content: 5 Tips to Help Your Building Facilities Age Gracefully

3. Evidence of leakage

Here are a few ways to identify signs of liquid or gas leakage. 

  • Liquid leakage – free-flowing process liquid from pipes, tanks, structures and recurring alarms from sensors in secondary containment systems
  • Aeration piping leakage – may be indicated by a loss of process efficiency or increased air demand
  • Gas leakage – check anaerobic digesters for methane gas leaks on a routine basis
Sometimes corrosion isn’t evident until you see puddles on the floor. I’ve seen small leaks unexpectedly lead to several major ones erupting at once on an overhead influent pipe that flooded areas of the tunnel, damaging equipment. You can only spot weld and wrap for so long!
Kathy Crowson, PE

4. Excessive repair and maintenance

Occasional repair of your equipment is expected. However, mechanical equipment has a limited useful life. Eventually you reach a point where time and resources spent repairing the equipment is better spent elsewhere in the plant. Certain repairs and repair frequencies could be telling you should update. A few examples.

  • Equipment needs frequent replacement of bearings (every few months)
  • Excessive gate and valve actuator failures
  • Recurring electrical faults, such as failure of electrical breakers and components, evidence of arcing, or issues with unstable power supply
  • Equipment item taken out of service, “locked out/tagged out” for extended periods of time

5. Evidence of unrepaired damage

Look for telltale signs that damage went unrepaired. These can include:

  • Recurring sinkholes near buried pipes and structures
  • Burns or scorch marks on electrical equipment and switchgear
  • Valves locked in closed position

6. Diminished process performance

How are your facilities performing? Does it take more energy for a unit process? Are you seeing a sharp drop in performance or a steady decrease over a longer period? These are signs you may need a more detailed investigation.

Here are examples of poor performance:

  • Achieving effluent limits has become more challenging
  • A pump isn’t pumping as many gallons per minute or can’t achieve enough pressure
  • Aeration blowers use more KW of power to maintain the same aeration basin dissolved oxygen content
  • Anaerobic digesters don’t produce as much gas
  • A dewatering process isn’t achieving the same percent sludge cake solids
Aeration basin foaming is one example of decreased process performance.

7. Difficulty getting spare parts and replacement components

If you’re having a difficult time getting parts and components because they are no longer available or require long lead times, you may want to consider replacement or rehab.

Valve actuators for gates and large butterfly valves are one example. You repair and replace as long as you can, but eventually it’s time to find a different, more reliable valve.

Prioritize repairs or replacements with a risk-based asset management approach. It accounts for processes and equipment with the greatest probability of failure AND the most dire consequences if they do. Simplified: Risk Exposure = Probability of Failure x Consequences of Failure.
Al Bush, PE
Getting replacement parts for this out-of-date control panel? Not easy.

About the Experts

Al Bush

Al Bush, PE, is a senior wastewater engineer, project manager and believer in better, more efficient wastewater treatment facilities. Contact Al

Susan Danzl

Susan Danzl, PE, is senior wastewater engineer and project manager with a history of helping small and large wastewater facilities plan and build for the future. Contact Susan

Kathy Crowson

Kathy Crowson, PE, is a senior wastewater operations specialist and longtime public servant dedicated to budget-minded and operations-friendly wastewater solutions. Contact Kathy

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