In viewing a presentation for a conventional jet aeration system or a Slot Injector™ aeration system, typically there will be a list of life cycle benefits which include energy savings, capital cost savings, and small plant footprint to name a few. These claims are of interest to both industry and municipalities but many people do not know how inter-related they are.
On a recent industrial MBR project we came across a situation where energy and capital savings and their relationship to plant footprint could be used to educate both a new sales representative and the end user. The industry had recently acquired a moth-balled facility and in recommissioning the treatment plant, wanted to evaluate an MBR process with a conventional jet aeration system. They had two empty tanks available. Each had a volume of 220,000 gallons but with different dimensions. One tank was 50-ft. diameter and would operate at a 15-ft. liquid depth. The other tank was approximately 39-ft. diameter and with a planned operating liquid depth of 25-ft. The customer inquired as to which tank to use so we proceeded to give him a design for both options as follows:
- The 50 ft. diameter tank required an aeration system that had one 75 Hp pump and two 60 Hp operating air blowers.
- The 39-ft. diameter tank required an aeration system that had one 40 Hp pump and two 50 Hp operating air blowers.
In terms of operating brake horsepower there was a 30% energy savings in going with the smaller diameter, deeper tank. There is a 36% capital cost savings by going with the deeper tank with most of the savings due to the smaller liquid recirculation pump, smaller diameter jet aerator, and associated piping system. The land area required is reduced by 40% by going with the deeper tank option.
Unlike fine pore diffuser systems, both a conventional jet aeration system or a Slot Injector™ aeration system show a marked improvement in oxygen transfer performance with increases in liquid depth. The improved performance results in lower energy usage, reduced capital cost, and allows for a smaller plant footprint which can be a tangible benefit in older industrial facilities stretched for available production square footage.