Biological denitrification is the conversion of nitrate (NO3) into nitrogen gas (N2) and carbon dioxide (CO2) by a consortia of bacteria. This process requires good control over the ratios of three elements- carbon (generally must be supplied externally), phosphorus (nearly always in Ag runoff), and nitrogen (from the nitrate nutrients in the runoff). Since the nitrate and phosphorus are almost always available, the focus for a commercial process is on supplying a suitable, biologically available, form of carbon.
Commercial utility-scale denitrification plants (millions of gallons per day of wastewater) generally rely on methanol. These big plants have full time operators, extensive safety and control procedures, and are heavily regulated. Methanol is problematic to use- very volatile (explosive), toxic if ingested, and the price can be subject to dramatic changes as the price of natural gas varies (methanol is made on a commercial scale using the so-called steam reforming process). You can learn much about this process from the Methanex Corporation at https://www.methanex.com/about-methanol/how-methanol-made.
But for agriculture operations, like our business, transport and handling of a HAZMAT like methanol is a concern. Ideally, we would like to get our external carbon from a source nearby. The close proximity reduces the transport cost. Researchers and operators of these denitrification plants have been busy identifying possible low-cost/no-cost sources of carbon. Among those identified include glycerol ( waste product from the production of biodiesel), molasses, corn syrup, acetic acid, carbohydrate-based waste products, and sodium acetate. The US EPA maintains a very informative fact sheet on the external carbon sources for denitrification (see https://bit.ly/2HOPZTO to read in more detail).
A key consideration to lower the external carbon cost, or to make it go to $0.0 is using the carbohydrate rich waste from a neighboring plant that is currently paying to have their waste water treated or disposed of. Under the right financial conditions they might pay to remove some of their waste. You can then use that waste carbon to meet the nitrate removal system carbon needs.
Before you consider which type of carbon to use in your system, contact us and we'll let you know how to adjust the operation of our nitrate removal system to accomodate the external carbon source.