Groundwater Week 2019 presenter.
By Jennifer Strawn
Founded in Lubbock, Texas, in 1949, Cotey Chemical strives to provide products that can be easily applied for the maintenance, development, or sterilization of residential, industrial, and irrigation water wells.
The company works with customers in the United States and around the world. McGinnis has supervised water well rehabilitation projects in the Middle East, the Far East, and Latin America. He has also delivered technical papers to Saudi Arabia’s Ministry of Agriculture and Water in Riyadh, and to the Philippine Water Works Association in Pampanga.
McGinnis has presented workshops across this country for the National Ground Water Association, the American Groundwater Trust, and state organizations.
Water Well Journal recently sat down with McGinnis to discuss his upcoming presentation at Groundwater Week titled “Chlorine, the Most Misunderstood Chemical in the Water Well Industry.”
Water Well Journal: What do you think is the perception of chlorine in water well rehabilitation?
Kevin McGinnis: There are a few common misconceptions that people have about chlorine. One is that chlorine removes all bacteria and slime from a water well. Chlorine, granular calcium hypochlorite (also known as HTH), and liquid sodium hypochlorite (also known as bleach) works well at killing free-swimming bacteria. However, once the bacteria become attached in the form of biofilm (slime), the chlorine is not able to efficiently penetrate the biofilm where the bacteria reside.
Another is that chlorine is a long-term solution. Chlorine only kills bacteria while it is in the water well. Once the pump is turned on, the chlorinated water is pumped from the well and fresh water-laden bacteria begin to recolonize the well. Some in the industry refer to chlorinating a well as a “snapshot” of disinfection.
The last major misconception is chlorine is a great well rehabilitation chemical. This is mostly false. We know that chlorine is an oxidizer, so it does not dissolve the hard stuff in the well. We also know that chlorine is very inefficient at removing the soft stuff (penetrating and dispersing the biofilms). So, the best time to chlorinate a well is once the pump, pipe, wire, etc., are placed in the well. Then, chlorination is
important. These parts have potentially been lying in the field, on the back of a trailer, or on the shop floor where potential contamination exists.
WWJ: Your workshop description mentions it will also answer the question, “Is water well disinfection an oxymoron?”
Kevin: Yes, it’s an oxymoron. You have to ask yourself, “Can we really remove all of the bacteria from a water well?” Bacteria are everywhere—on our hands, our equipment, in the ground, in the groundwater, etc. Also, once the pump is turned on, all of the chlorinated water is pumped from the well and new bacteria recolonize the well surfaces.
WWJ: Your company, Cotey Chemical, has produced chemicals to rehabilitate water well systems for more than 60 years. What do you think the biggest advancement has been in that time?
Kevin: From a chemistry perspective, the biggest improvement is in chemical formulations that include polymers. We are using long-chain polymers to improve rinse out of a water well by changing the charge of the dissolved particles (ions) to prevent them from recombining even as the pH of the water rises in the well.
The more dramatic changes in the well cleaning industry are in the mechanical tools that have been developed. These tools include video systems for downhole inspection, CO2 injection, and other percussion-type tools including AirBurst and SonarJet. Many contractors that use these percussion-type tools will use them in conjunction with our chemicals. Mechanical cleaning prior to injecting chemicals removes interior screen deposits and ensures more uniform chemical access outside of the screen and into the formation.
It takes a lot of energy to remove all of the cemented deposits in a water well; both mechanical and chemical energy are needed.
WWJ: What is the most common mistake made by groundwater professionals in terms of well rehabilitation?
Kevin: There are two common mistakes. The first is selecting the wrong chemicals. This is the one-size-fits-all mentality. Many water wells have unique problems, so it is important to diagnose the problem properly, then determine the correct prescription. When diagnosing a
problem well, it is always best to gather as much information as possible, such as reviewing the history of the well, downhole video, scale, and water analyses.
The second common mistake made by groundwater professionals is not using aggressive agitation methods and tools. The real culprit in water well plugging is the heavy cemented deposits that accumulate in the flow paths of the well. It’s important to spend extra time and energy to properly break down and dissolve these deposits so they can be removed from the well. We believe this can be most efficiently accomplished using both mechanical and chemical means.
WWJ: When it comes time to purchase chlorine-type products, what does a contractor need to know?
Kevin: First, it’s important to remember that these types of products do not dissolve scale or biofilm.
Second, these products have a relatively short shelf life. Calcium hypochlorite (HTH) has a shelf life of about one year. Sodium hypochlorite (bleach) has a shelf life of a few months. Be sure to purchase these products as you need them and store them in a cool, dry place.
Third, chlorinating a water well is most effective if you keep the pH of the well water around 7.0. Sodium hypochlorite and calcium hypochlorite have a high pH. There are some disinfecting chemistries available in the industry that are neutral pH products such as Jet-Lube’s Sterilene and Cotey Chemical’s Wel-Chlor PLUS.
WWJ: How best can a contractor determine when chlorine is necessary for disinfection?
Kevin: The best time to chlorinate a water well is when the well is newly drilled, rehabilitated, and pumping equipment has been set in place. The pump, wire, pipe, etc., have probably been stored where potential contaminants exists. Introducing bacteria that are not native to the groundwater could result in more serious problems.
WWJ: You have led sessions at Groundwater Week before. Do attendees talk to you about issues they have had with chlorine? What advice do you give them?
Kevin: There are many reasons why chlorination fails to give the desired results. These include high bacterial numbers, water temperature, turbidity, and water pH.
Turbidity and pH are somewhat controllable. For example, any suspended particles (turbidity) in the water will interfere with the chlorine’s disinfection ability. It’s best to pump the well for several hours before chlorinating.
The pH of the water is also an issue. When sodium or calcium hypochlorite are added to water, the available chlorine produces hypochlorous acid (HOCl), a potent, fast-reacting disinfectant. Hypochlorous acid is the workhorse in any chlorine application for sanitizing purposes. It will form most readily in waters ranging from pH 6.5 to 7.5. When the pH increases above 7.5, HOCl increasingly dissociates to the hypochlorite ion, which is up to 250 times less effective as a disinfectant than HOCl, in terms of concentration.
For this reason, we recommend chlorinating a water well using 200 mg/L of chlorine and some type of chlorine enhancer manufactured by Johnson, Jet-Lube, or Cotey Chemical.
WWJ: Cotey Chemical offers an app that determines approximate volume of a water well in gallons as well as an approximate amount of treatment chemicals necessary for well rehabilitation. What prompted the app and how has it been received?
Kevin: Cotey Chemical strives to take a relatively complicated topic, stimulating water wells with chemicals, and make it relatively simple to understand. We provide solutions to the water well industry that are safe and easy to apply. The app is just another tool to help the water well contractor. It improves the convenience, safety, and accuracy when using our products.
WWJ: What is the most important thing you want those attending your Groundwater Week workshop to take back to their groundwater businesses?
Kevin: The most important thing we want the attendee to take home is that Cotey Chemical is here to help them. We want to partner with them to give their customers the best possible water well. A win-win-win situation exists when water wells are correctly rehabilitated. It’s good for the well owner, good for the contractor, and good for the environment.
Jennifer Strawn was the associate editor of Water Well Journal from 2004 to 2007. She is currently in the internal communications department at Nationwide in Columbus, Ohio. She can be reached at firstname.lastname@example.org.