Liquid Manure Pipes Clogged? You Might Have Struvite.
Adapted by Deanne Meyer, PhD - Livestock Waste Management Specialist, UC Davis
Most manure lagoons in California are anaerobic. The microbes digest manure (residual cow food). This removes some of the solids from the lagoon and generates carbon dioxide, methane, and other volatile gases. Depending on your lagoon nutrient content, you may also end up with magnesium, ammonium and phosphate in just the right proportion to form struvite.
Perhaps you’ve had crystalline formation problems in pipes, elbows, pumps or valves. Once, a dairy producer brought a large cup of crystals to an Environmental Stewardship Class. These were nice long brown crystals. Another producer sent me a photo last fall and said, “It’s not tri-tip.” True enough! If this sounds familiar, think about the time of year it occurs. Does it seem like pipes slowly clog or are they on some regular cycle? If it occurs on a regular cycle, there may be a clue to follow for prevention.
Most people talk with their equipment dealers to manage the precipitate. First be sure you have a struvite precipitate. If you suspect struvite formation in your pipes, take a chunk of crystals and get them analyzed. The lab that runs your manure samples can do this. Ask for magnesium, nitrogen, phosphorus, and calcium analyses. Chemically, struvite is NH4MgPO4•6H2O. Also, you should look at the pH of your pond water. Pond pH values run between 7.2 to 7.8. There are some ponds with lower or higher values. Usually, the higher the pH, the higher the probability of struvite formation in pipes as long as the ammonium, magnesium and phosphate are present in about equal amounts.
Prevention when possible! Have a conversation with your nutritionist to determine that you are not over-feeding magnesium, nitrogen or phosphorus. Each of these elements is important for animal health and production so they are needed in diets, you just want to be sure you are not adding to the problem.
Determine which pipes in your liquid manure flow are most likely to clog. Are these pipes coming from animal housing and going to the pond or are the clogging pipes occurring between the pond and the return water to animal housing? This may pin-point the origin of the problem and help troubleshoot where intervention is appropriate.
Liberating the struvite can be done mechanically or chemically. Either method takes expertise. Some producers just include a rotor rooter type activity of suspect lines annually. Others use chemical treatment. If calcium is present in the struvite (likely in a carbonate form), use of an acid can dissolve the calcium carbonate and return the elemental components into solution. If you’re going down this route, talk with someone who is familiar with acid use in wastewater.
Things to think about. Safety and cost are important things to remember. Both the mechanical and chemical ways to remove struvite require expertise in use and safety measures to be sure no one is harmed in the process. Also, if you have an anaerobic digester agreement, be sure to have the discussion with your vendor to ensure your approach to struvite is acceptable. Remember, if you have a history of struvite in your pipes, plan to manage it and not let it get the best of you.
Link to PDF Version: Liquid Manure Pipes Clogged- You Might Have Struvite