ECO-Minded Beer

Two-Hour COD Test

For scheduled COD testing, the brewery uses the closed-reflux micro method using COD digestion vials. The pre-dosed reagents are contained in 16mm glass tubes, or vials, that fit directly into most commercially available COD reactors and spectrophotometers. COD testing is a very straightforward procedure at the brewery. After 2 mills of sample are added to a vial, the vial is capped and placed in a reactor to digest at 150°C for two hours. After the vial is cooled, results are then read directly on a spectrophotometer. The lab uses a spectrophotometer, which provides personnel the ability to save COD and other frequently used programs for quick access.

Once COD and BOD data has been gathered over time, the average BOD result is divided by the average COD result to determine the ratio, or conversion factor. The COD results are multiplied by this factor to estimate BOD concentration. COD values are almost always higher than BOD results for the same sample; therefore the conversion factor is most always less than one.

In addition to scheduled COD monitoring of its process water effluent, the brewery has also periodically used the COD closed-reflux micro method in its brew house. For example, the brewery recently conducted a weak wort recovery test to determine the volume of extract and actual sugar loss following the dumping of spent grain. The brewers wanted to determine if they were simply dumping extra sugars, or was the weak wort worth recovering. A series of COD tests on the weak wort determined substantial levels of unused food remained. Based on this testing, the brewery now recovers this material for re-use in the brewing process.

Current Expansion

New Belgium is expanding its process water treatment plant to include additional anaerobic and aerobic digestion capacity. Holding ponds are also being added prior to the anaerobic digesters. The amount of methane produced has varied according to effluent volumes entering the digester, which has depended primarily on the amount of beer production at the time. The new holding ponds will serve to level out flow volumes entering the digesters, resulting in the production of higher, more consistent levels of biogas. This, in turn, will allow the on-site power generator to run for much longer periods, thereby reducing power costs for the brewery even further. In addition, a reverse osmosis unit is being installed to further polish the final treated water.

From an average BOD of 7,500 mg/L in flows entering the process water treatment plant, water leaving it has an average BOD of less than 25 mg/L, making it ideal for non-potable uses at the brewery, including evaporative cooling, cleaning, and for landscape purposes. COD and BOD reduction through the entire plant in 2004 was 98 percent and 99.8 percent, respectively.

Conservation, Treatment & Recycling

The combination of water conservation, treatment and recycling is allowing water consumption at the New Belgium Brewery to be controlled to a minimum. It has also eliminated the discharge of high organic loadings to the local municipal treatment system, which is verified quickly and systematically through accurate COD analysis. And, through the use of methane-fueled cogeneration, on-site process water treatment is significantly reducing the amount of purchased energy required to operate the brewery.

Mandy Miller is the quality assurance analyst for New Belgium Brewery Company (Fort Collins, Colo.). Reach her at 970-221-0524.