By April Hirsch / Published February 2017
Putrefy is a word not much used, perhaps because it instantly conjures up the foul odors to which its etymology points. Yet putrefaction keeps the Earth a pleasant place.
In ecosystems, the energy requirements of bacteria (and fungi) and the slow combustive effects (oxidation) via exposure to oxygen ensure that we are not tripping over carcasses, digestive waste, and so on. Tapping the activities of bacteria, fungi, and oxidation in industrial processes has long been a way to do great things–including removing pollutants from water.
Some bacteria thrive in aerobic (oxygen present) environments and others in anaerobic (oxygen absent) environments, which means that there are many options for dealing with contaminants in water by tapping biological processes. The options are part of a robust repertoire for treating water.
No longer does the responsibility of contractors end with containment and redirection (e.g. to special sewers) of wastewater, as in preventing runoff into storm sewers by erecting barriers. The onus for capture and even for treatment increasingly belongs to the contractor/company using the water.
It’s a lot to tackle—adding time and expense to an operation. It’s also a fascinating sphere: Not all natural resources are amenable to reuse, but water is.
Both physical and biological methods can be used to remove contaminants from water. From the force of agitation to simple gravity-encouraged sediment removal to filters, physical methods have a long history of use
in removing particles from water. Biological processes ranging from osmosis to deployment of oil-consuming microbes are newer methods of treating water.
Flocculants or other surfaces (e.g., glass beads) that encourage aggregation of waste in water (for removal) are among the many other tools, some of which are more common in laboratory settings. Almost every industrial process involving water treatment has an analog in nature. Septic tanks—organic scum on top, sludge on bottom—certainly do (think ponds).
Treatment may either restore water that’s been used to a condition that makes it acceptable for non-potable paths and uses, or it may restore it to a potable condition.
The less water used for any process, be it cleaning a parking a garage or taking a shower, the less water there is to capture and restore. Using as little as possible is always the better option, and minimizing use of water is something that members of our industry do as a matter of course.
Note: An April 2015 article that focused on water reclamation makes a good companion to this text. See www.cleanertimes.com/magazine/cleaner-times-articles-2/the-color-purpleexpanding-efforts-in-water-reclamation.
Using less applies in every dimension to the resource water. Just as we would rely on a household sponge mop and not a water vacuuming system to clean up after a small breach in a pipe, we would not use a bigger water vacuuming system than necessary under any circumstance. Unfortunately, the latter is just what happens in some cases.
In short, one hardly does a good job of conserving water if one is using more of other resources (fossil fuel, for example) to capture water for reuse or proper disposal. More is not always better, and often it is worse.
Spartan Manufacturing Corpora-tion, d.b.a. Pressure Power Systems in Kernersville, NC, makes heavy-duty industrial and commercial grade machines. Among them is the Vacu-Boom for capturing water at jobsites. To make the optimal use of that tool, a contractor must first do an analysis of need, explains Ron W. Robarge, P.E., director of engineering at the company.
“Most people tend to overestimate what size of our water capture tool is needed for their work,” says Robarge. “By evaluating location factors such as direction of runoff, location of storm drains, and natural slope of paved areas, a much smaller and more economical system can be used.”
To ensure that customers get the best fit between not only size, but also type, of system and job at hand, Robarge’s company offers a comparison between its systems and other methods at the company website. Those who wish to call the company and discuss needs can do that.
What Robarge anticipates adopters of his company’s capture system will discover is that it is a “practical, efficient, time-saving, and cost-effective way to capture water at a jobsite,” he explains.
Contractors have ever-more responsibility for water capture and proper disposal or reuse of water. So the attributes Robarge cites are welcome in every context.
For instance, readers know that the National Pollution Discharge Elimina-tion System (NPDES) authorized by the Environmental Protection Agency (EPA) allows publically owned treatment works (POTW) to perform permitting and enforcement regarding discharges to surface waters (e.g., storm sewers). The EPA has further authorized the POTW to carry on permitting and en-forcement of pretreatment programs.
Under the tougher pretreatment program requirement, water captured at a jobsite may not meet standards for disposal in a sanitary sewer. To meet standards, it may have to be pretreated.
The purpose of the pretreatment permitting is twofold: to reduce conventional and toxic pollutant levels, and to protect infrastructure of the POTWS, infrastructure that may be susceptible to deterioration on exposure to certain pollutants. (A septic tank is a device that accomplishes pretreatment.)
Capture has always been the first priority in the prudent use of water. Increasingly—and much depends on the region or state where a jobsite is—a contractor must also be tied to the treatment of the water. It could be as simple as hauling wastewater to a facility that undertakes pretreatment. But it is another step, as well as another cost center. And a permit to demonstrate it is taken may be required.
How is treatment—more specifically to contractors, pretreatment—being accomplished? Contractors can use systems at jobsites or they can rely on consolidator-treatment facilities to which they haul their wastewater.
“At Mi-T-M, around 75 percent of the treatment systems that we sell are biological systems,” says Aaron Auger, water treatment division manager at that corporation headquartered in Peosta, IA.
Using microbes to reduce harmful contaminants in water to harmless entities is sophisticated and energy efficient. It is also a process that must be implemented with care.
“All too often people think that they can match up a system with the gpm that their pressure washer is spraying,” says Auger. “For a biologically-based system to be effective, we need the microbes to be in contact with the dirty water for a period of about 20–24 hours in order to get the water as clean as it can be.”
Bacteria used in biological processes multiply as they ingest contaminants. As more of them become active, the contaminant-reducing activity greatly accelerates. “Therefore residence time for the microbes to be in contact with the dirty water becomes a critical factor,” says Auger. “If you don’t have enough time for the bacteria to consume the impurities that are in your waste water, then the quality of your water won’t be as clean as one would expect.”
Microbes effective in biological treatment of water literally consume (as energy/nutrient source) contaminants. They break down complex organic molecules to simpler ones (e.g., carbon dioxide, nitrogen).
“There have been a few instances in the past where we have been called in to help with a poorly performing system and all that was needed was more time for the microbes to do their job,” says Auger. “By adding capacity to a system, you can do just that. Give the ‘bugs’ more time to do what they do best.”
Get the best fit in a treatment system by talking with manufacturers or distributors. “All manufacturers offer training on their products,” says Auger. “I speak to a lot of end users and educating them on products is a great start, but getting them in touch with one of your local distributors is key in making this type of a sale a success.”
Maintenance matters. “Water treatment systems are definitely something that you don’t install and walk away from, so having a local dealer to take care of the customer and ensure that the system is properly maintained is essential to its overall performance,” says Auger.
Most of the water treatment systems that Auger’s company sells are biological. “This is due to a couple of factors,” he says. “The biological systems have a great range of applications that they have been successful in. Every place from rental and equipment dealers to golf courses are good homes for biological treatment. The systems are capable of handling a wide variety of waste streams that are predominantly grease and oil.”
Low maintenance is the second big plus for biological systems, says Auger. “No systems are maintenance free, but a biological system has less maintenance than a mechanical system due to the fact that it’s the bacteria doing the majority of the work.”
Choosing capture and treatment systems with an eye on economy of scale reduces costs. So, too, do good fundamentals, such as using as little water as possible—an approach manufacturers in our industry improve upon each day.