Don’t Cut Corners When Specifying A Diffused Aeration System

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Imagine you are buying a new house. You decide that houses are a commodity. In other words, they are all functionally the same – they are places to eat, sleep and relax. So, you decide to select the lowest-cost house. Instead of investing in a well-constructed $250,000 ranch home, you buy a low-priced home constructed of materials that cost 30% less.

Does this approach meet your needs? Not at all. The roof leaks, the floorboards squeak and the pipes rattle whenever you run the water. Your inexpensive home continues to have problems for years, long after the builder’s warranty has ended. In the long run, repairing and replacing everything that goes wrong with this low-cost house costs you more than the well-constructed alternative would have.

A similar scenario plays out in the world of diffused aeration systems. Owners hire engineers and contractors to procure systems and components for wastewater treatment plant projects because they are the experts. However, diffused aeration systems continue to be considered a commodity. If the owners and engineers do not value the lowest cost of ownership, why would a contractor? Faced with a variety of domestic and overseas options and procurement documents requiring the lowest first cost, contractors often gravitate toward the lowest-cost supplier.

Why does this happen? There are several common reasons:

  • Owners are charged with operating and maintaining their facilities within budget. Increasing rates to pay a higher first-time cost for the best 20 year life-cycle cost may not seem logical or politically correct.
  • Owners rely on design engineers to specify equipment for a new or retrofit wastewater treatment project – a contractor does not. All participants are motivated by the bottom line. The less it costs to procure, the more money one makes or saves at the time of initial purchase and construction. As a result of this process, an owner with no preference and an engineer with no preference force the contractors to provide equipment that doesn’t align with the actual intent of the design engineer and owners or consider the lowest cost of ownership.

Inevitably, you get what you pay for.

During the first several years of operation, while the manufacturers’ warranties are still in effect, system performance is roughly the same. But as the systems age, the system that cost less tends to have more problems.

When you cut corners, here are the most common points of failure in low-cost, low-quality diffused aeration systems:

  • Piping connections begin to leak.
  • Membranes become fouled, lose their flexibility and fail to produce adequate oxygen and/or mixing.
  • Leaks between the distribution pipe and the membrane holder become increasingly more common.
  • Blowers must work harder to maintain adequate air pressure throughout the system, shortening the service life of the blowers and the diffusers.

As a result, maintenance costs and downtime are higher on this low-quality system. Each time it must be taken off-line for repairs, a critical part of the wastewater treatment process is lost.

In the case of a complete failure, some wastewater treatment plants must replace their diffused aeration system with a new one, while continuing to pay for the existing one. They end up paying on two loans at the same time.

What’s the solution?

Here are two ways you can solve this common problem:

First, as an owner make it a point to have a preference for a supplier of one of the most critical systems in the wastewater treatment plant. Work with engineers who are willing to evaluate suppliers and specify around the one that offers the best life cycle cost. Engineers must make their specifications clear and their preferences known through the procurement documents.

Allow the contractor to do what he does best – construction and installation. They will thank you. Far from being a commodity, your wastewater treatment plant’s diffused aeration system is actually one of its most critical components. The contractor should not be forced into making decisions that should really be made by the design engineer and plant owner.

Second, insist on value-based procurement. This encourages major equipment submissions to state reviewing and funding agencies to identify the manufacturer named as the basis of design. It also states that bids must list the specifications reflecting the design utilized in the plant’s life cycle cost evaluation. This helps eliminate the need for contractors utilizing “or equal” products, which can lead to undesirable results.

Wastewater treatment plants are typically financed by municipal bonds or state/federal funds. If the actual operating cost of the diffused aeration system is trending well above your estimated life cycle cost, that’s a major problem for operational cost budgets and performance. Don’t get blinded by a low capital cost for this technology. Do your homework and compare life cycle costs, side by side. You may be surprised by the results.

When you buy a home, you expect it to outlast the mortgage used to finance it. Don’t settle for anything less when specifying a diffused aeration system for your wastewater treatment plant. Focusing on life cycle costs can help you make a well-informed purchasing decision that will ultimately cost you less in the long run.