Fact: Fine Bubble Aeration systems require huge energy expenditures which usually are the largest or next to the largest line item in municipal wastewater utility budgets.
Prediction: Energy costs will continue to rise during this decade that will force utilities to phase-out fine bubble aeration systems. Nationally, this will save billions of tax dollars and reduce demand on the nation’s electrical grid.
Fact: Fine Bubble Aeration systems were created decades ago to replace outdated technology. It was considered a temporary solution. Why temporary? In college engineering classes in the 1960s, it was described as being “mixing limited” and not very efficient for oxygen transfer when using ambient air as a source of oxygen. 100 cubic feet of ambient air has only about 8 lbs. of O2 and most fine bubble systems transfer only about 4-6% of that 8 lbs. of O2. That means these systems are actually 94-96% inefficient! The lack of mixing actually adds BOD demand requiring even more diffusers and larger blowers.
Prediction: Utilities will be forced to consider more efficient ways to introduce oxygen into their biological processes. Large Bubble Mixing will provide a solution to assist in the phase-out of fine bubble diffusion. One bubble release plate creates a mixing zone of influence of about 40 feet in diameter in a tank that has a SWD of 20 feet. That means ½ of the fine bubble diffusers in that area can be removed in the beginning and all will be eliminated in the future.
Fact: Fine bubble aeration creates an “aerosol dome” over aeration tanks. This is the result of overdesign (too many diffusers which results in over-aeration). Realization during the Covid pandemic in the early 2020s that wastewater contains viruses means that these basins should be considered potential disease vectors for the surrounding municipalities during the next pandemic.
Prediction: Utilities will face the reality that these basins need to be covered if over-aeration is not remediated by new technology. This additional expense will certainly provide incentive to abandon an already inefficient and costly technology.
Fact: There are other sources of oxygen that can be utilized in existing aeration basins during the phase-out period of fine bubble aeration. Super saturated oxygen (500-600%) final effluent can be pumped back to BNR tanks which eliminates all aeration piping and diffusers. Pure oxygen systems in covered BNR process basins are also a possibility. These both need reliable and complete mixing systems in the process tanks to eliminate FOG layers from forming on the water surface in these tanks. Complete mixing will eliminate sludges from accumulating on tank floors which will reduces endogenous BOD loading that sludges add to the influent waste and RAS flow in fine bubble aeration systems.
Prediction: Large Bubble Mixing (LBM) will serve as the link to future BNR processes during the phase out of fine bubble aeration. Whatever future treatment technology turns out to be, complete and energy efficient mixing will always be required.
LBM costs less to buy, less to install, has virtually NO maintenance and mixes completely. LBM is defined as using bubble masses that are at least 24-inches in diameter and released at floor level. Insist that any company claiming LBM technology meets that definition.