By: Thomas Doran, PE
When most people think of wastewater treatment, they envision a dirty, smelly place that pollutes rivers and streams and makes that infamous byproduct: sludge.
While it’s true that sewage isn’t pleasant, and that odors and wastewater treatment often go together, there have been many advancements in the last several decades that make current wastewater practices sophisticated science rather than a necessary evil.
Biological treatment of wastewater, where microorganisms “consume” pollutants, has progressed from only a handful of options to now offering dozens of variations and innovations, depending on the characteristics of the wastewater and the desired outcomes.
Biological nutrient removal uses microorganisms to remove nutrients from the wastewater, thus preventing these nutrients from “fertilizing,” or depleting oxygen in, streams and lakes. This is accomplished by fostering an environment that favors the proliferation of these organisms.
Better still, biological nutrient removal can be accomplished with fewer, or no chemicals. Membranes (microscopic sieves), having tiny or microscopic openings, are now used to enhance treatment of wastewater by retaining microorganisms and untreated waste while allowing clean water to pass through. The use of membranes can even produce “tap quality” water at some water-starved locations.
The disinfection of wastewater to kill pathogenic organisms is being enhanced at many locations by using substitutes for chlorine, such as ultraviolet radiation and/or hydrogen peroxide, methods that are more environmentally benign. Even techniques for handling sludge have greatly advanced. Sludge digestion processes, using microorganisms to decompose and detoxify the sludge, can now produce a product that is suitable for application on farms and home gardens, as well as producing electrical energy. Solar drying of sludge is increasingly being practiced, even in northern climates, to greatly reduce the volume and to make it attractive as a renewable energy source.
That’s not to say there aren’t challenges. Not all wastewater plants utilize these newer techniques. Better wastewater analytical methods now allow us to detect compounds like hormones and other pharmaceutical products at parts per billion or parts per trillion. The long-term impact of these micro-constituents is not yet known.
Thomas M. Doran, P.E., is a Director of the Engineering Society of Detroit and an adjunct professor at Lawrence Technological University. He has been actively engaged in wastewater treatment for over 35 years. In 2008, he received the Purdue University Alumni Achievement Award.