Water Well Journal
Issue link: http://read.dmtmag.com/i/617280
A visual inspection also shows the degree of plugging or biofouling. "We'll see the perforations that are completely closed off," Watson says. "You can see the shape of them, but if you can't see into them because of biological slime or iron bacteria, then we know it's a perfect candidate for a rehabilitation." Analyzing scale samples and the water for pH, hardness, alkalinity, iron, manganese, sulfate, and so on, is the final piece of the puzzle and can often most accurately help you select the right chemical. Step two: Select your chemical Once you know what's plugging your well, you pick the chemical to remove it. For hard encrustations, mineral acids including hydrochlo- ric acid, phosphoric acid, and sulfamic acids are generally the most effective. Most companies have blended these strong mineral acids with other chemicals to protect metal surfaces and hold dissolved solids in suspension. Among proprietary blends are: • Baroid Aqua-Clear MGA • CETCO DPA • Cotey Chemical Corp. Dry Acid Special and Liquid Descaler • Jet-Lube (formerly Design Water Technologies) Unicid Granular Acid • Johnson Screens NuWell 100, 110, or 120 • Laval Underground Boresaver IKL. For biological growth, organic acids including glycolic acid and acetic acids are good for penetrating and dispersing biofilms or bacteria-produced slime. Oxalic acid is used to a lesser extent because it's not very effective at removing bio- logical growths, but is good for dissolving oxides of iron and manganese. Some of the proprietary blends of organic acids include: • Baroid Aqua-Clear AE • CETCO LBA • Cotey Chemical Corp. BioClean and Liquid Descaler • Jet-Lube (formerly Design Water Technologies) Unicid Catalyst • Johnson Screens NuWell 310 • Laval Underground Boresaver BLS Liquid Enhancer. Chlorine, while readily available, should be used only for disinfection purposes. "Chlorine is an oxidizer, not an acid. So it does not dis- solve the hard mineral deposit, which is the primary plugging problem in water wells," McGinnis says. "Chlorine is very good at killing free-swimming bacteria, but once the bacteria have become encapsulated in biofilm, the chlorine solution cannot reach it." Instead, chlorine should be used to disinfect a well after it has been drilled or when the equipment has been pulled and put back into the well. Chlorinating the well with ±50 ppm chlorine solution will disinfect the surfaces of the equipment that has been lying on the ground, on the back of a trailer, or on a shop floor—where it might have come into contact with harmful bacteria. Neubecker has used various manufacturers' chemicals over the years including Johnson Screens, Jet-Lube, and Cotey Chemical. "Everybody seems to be making good products these days," he says. "It's just a matter of applying them to the right application and using them correctly." Step three: Use the chemicals Before adding the chemicals to the well, it's important to loosen as much of the encrustation as possible from the inte- rior screen, using mechanical cleaning such as compressed air or nylon brushes. This removes the interior screen deposits and allows the chemistry to get outside the screen. The chemicals shouldn't just be added to the top of the well, McGinnis says. They should be injected into the zones where it has a better opportunity to penetrate into the sur- rounding formation. Then, agitate them using a tight-fitting surge block or other isolation tool to dislodge material soft- ened by the chemicals and push the chemical solution further into areas it may otherwise not be able to reach. "Our experience tells us most wells need both properly designed chemicals and mechanical tools used together to achieve the desired results," McGinnis says. "For example, the hard, cement-type material in most wells require a lot of energy to remove. Both mechanical and chemical energy are needed." Neubecker remembers John H. Schnieders, Ph.D., from Water Systems Engineering Inc. in Ottawa, Kansas, saying if you're going to wash your clothes, you have to scrub them against a washboard or put them in the washing machine to get them clean. The same goes for well rehabilitation. "You can't just put chemicals in the well and expect them to do the work on their own," Neubecker says. "It would be like putting a pair of dirty jeans in a bucket of soapy water and expecting them to be clean when you pull them out. It just doesn't work." Step four: Prevent recurring problems Preventive maintenance can help well owners and opera- tors avoid costly and time-intensive rehabilitations of a well falling into such disrepair that it needs replaced. But it's often difficult to sell them on the value. WELL REHAB from page 19 DACUM Codes To help meet your professional needs, this article covers skills and competencies found in DACUM charts for drillers and pump installers. DO refers to the drilling chart. The letter and number immediately following is the skill on the chart covered by the article. This article covers: DOB-1, 3, 4; DOF-1, 2, 3, 4, 5, 6; DOG-1, 2, 3, 4; DOG-9, 10; DOJ-8 More information on DACUM and the charts are available at www.NGWA.org. 20 January 2016 WWJ waterwelljournal.com