A Cost-Effective Way to Reduce Nitrogen in Wastewater

In Bozeman, Montana, life centres around outdoor recreation. An afternoon of world-class fly fishing on the state’s pristine waters often follows with a refreshing visit to one of the area’s many microbreweries.

The convergence of those two pastimes took an innovative twist when a group of engineers asked: What if the carbon-rich byproduct of brewing beer could be used as a cost-effective way for the city to reduce nitrogen in its wastewater?

The idea meets a serious need for communities facing stringent nutrient criteria limits for wastewater discharged into rivers and streams. As governing bodies continue to lower the nitrogen effluent limits, cities face the challenge of expensive upgrades to their wastewater facilities. One alternative involves adding carbon to the plant’s post-anoxic zone to reduce levels of nitrogen before discharge into the river. However, glycerin- or methanol-based carbon products such as microC can be expensive to transport and hazardous to store.

Meanwhile, owners of growing microbreweries face their own high cost of treating and hauling brewery waste, or paying municipal fees associated with discharging high-strength waste into the public collection system. However, that high-strength waste contains a large concentration of carbon.

With that in mind, engineers proposed a pilot study to test the viability of collecting the "second runnings" from a brewery and dosing specific amounts in the post-anoxic zone at a wastewater facility. The City of Bozeman volunteered its water reclamation facility for a three-week pilot using two identical bioreactors — for a control and variable. MAP Brewing Company agreed to participate, running a pump and hoses to an outside tank they donated. The study required frequent water sampling, equipment testing and adjustments to the dosing concentration.

The conclusion: The brewery waste helped consistently lower the nitrogen output 1.5 to 2 milligrams per liter. That equates to 25 to 40 percent less nitrogen being discharged into the stream. Ultimately, the results offer a wide applicability to municipalities across the world searching for a cost-effective way to increase biological nutrient removal performance at wastewater treatment facilities.