Fixed vs. Moving Bed Systems: Cost

The differences between fixed and moving bed systems are significant, as discussed in the four previous blog articles. Therefore, a comparison between the two systems should not be made on the basis of a single parameter, such as specific surface area, kinetic rates, or media cost. A fair evaluation requires measuring the total installed capital and operating costs.

Capital Cost
When comparing capital costs, all necessary components and labor required to install the system must be included. Carefully evaluate the scope of supply included in the manufacturer’s proposal. As noted in a previous post, fixed bed systems typically have lower energy consumption. Based on this, the cost of a larger blower is often needed for moving bed systems and should be included when assessing capital cost.

Operating Cost
The most significant operating cost is aeration energy, so a comparison of energy costs should account for the specific air requirements for each system. Brentwood typically provides a power requirement based on 65% blower efficiency for our AccuFAS fixed-film system. Care should be taken to ensure that energy requirements provided by alternative manufacturers utilize the same type of blower and comparable efficiency ratings.

Moving bed system costs should also include periodic replacement of lost, worn, or abraded media. Structured-sheet systems using membrane diffusers, on the other hand, only require membrane replacement after 10 years.

Total System Lifecycle Cost
These capital and operational costs must be assessed based on the overall lifetime expectation of the system, on either an annual or present-worth basis. A full evaluation of competing technologies should also include non‐tangible items such as ability to work in existing tanks, hydraulic profile changes, potential for foaming, and other operational constraints.

Brentwood works with customers to provide preliminary process design, budget pricing, and estimated aeration energy required for a given system. The same information should be optioned from a moving bed media manufacturer.

We’ve found, when all parameters are taken into account to compare treatment capacity, the Brentwood AccuFAS system yields capital and operational costs that are 20-40% less than moving bed systems. Contact us to get your questions answered by emailing accufas@brentwoodindustries.com!