A new wastewater treatment system that is more energy efficient than current conventional methods has been developed by a professor of civil, architectural, and environmental engineering at Missouri S&T, according to a recent press release.
In addition to the above-mentioned system itself, multiple other technologies have been developed for use in conjunction with the system or in related applications — producing “freshwater” that is actually cleaner than the treated wastewater resulting from conventional methods, while using less energy and requiring less maintenance. The technologies can reportedly be used to “easily” retrofit wastewater treatment plants already in use.
The professor who developed the technologies, Missouri S&T researcher Jianmin Wang, noted while speaking on the subject of his new system that wastewater treatment in the US accounts for roughly 0.8% of the country’s total energy use. The majority of this energy use relates to wastewater tank aeration — in other words, keeping the water well oxygenated so that the microbes that “clean” the water can go to work.
It is current practice to maintain an oxygen concentration of around 2 milligrams per liter in order to keep the microbes metabolizing relatively rapidly. According to Wang, though, it isn’t necessary to keep the oxygen level so high — noting that “if you feed them at a lower concentration, such as 0.5 milligram per liter, it makes them a little less happy, but the microorganisms will live longer and enrich more.” This allows for cuts in energy use as high as 30% — while still achieving the “same” results.
A recent press release provides further information:
He has also developed another treatment system called an Alternating Anaerobic-Anoxic-Oxic (A3O) process that “can achieve superior effluent quality since it can remove organic pollutants plus nitrogen and phosphorus nutrients,” Wang stated. It does this without chemicals, and its effluent contains only 5 milligrams per liter of total nitrogen and 0.5 milligram per liter of total phosphorus. It also saves more than 10% of energy compared to the conventional pre-anoxic process, which has significantly less total nitrogen and total phosphorus removal.
With its high performance, high energy efficiency and low operational costs, on a large scale the technology could help curb global surface water eutrophication, which is one of the National Academy of Engineering’s Grand Challenges. Eutrophication is the “enrichment” of an ecosystem with chemical nutrients, typically nitrogen, phosphorus or both. When excessive nitrogen and phosphorus levels are present, algae blooms can occur. Algae blooms also produce algal toxins that directly pollute the source of drinking water intake.
Wang has also developed a self-mixing anaerobic digester, which can effectively convert wastewater sludge and other organic waste to biogas energy. It improves environmental quality by removing the sludge, and it also recovers a useful resource during the process. Additionally, his high-rate digester operates itself, without an external energy hookup. Based on his calculations, Wang says a combination of his technologies can produce a net 10% energy gain in contrast to the 27% net energy use the wastewater industry currently operates on.
While the water produced from these systems is already suitable for most types of irrigation, the possibility of making it potable (drinking water) is also a possibility, according to Wang. Presumably, that would be done with the addition of secondary systems or future improvements to the technology.
Interesting, but personally I’m always sceptical of these sorts of technologies/systems until they’re put into actual practice. There always seems to be an element of self promotion to them that leaves a bad taste in my mouth.
Image Credit: Missouri University of Science and Technology
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