Design of an Affordable Silage Leachate Treatment System

Natural Resources Conservation Service

NRCS Team: Cecilia Aponte, Ansha Zaman, Shelby Richards

2013-2014: In collaboration with the Natural Resources Conservation Service (NRCS), this student team developed an affordable, scalable treatment system for sileage leachate to be used on small dairy farms, continuing work from a 2011-2012 Design Clinic team.

Silage leachate is the liquid effluent that results from fermenting high-moisture crop materials to produce food for farm animals. It is acidic and nutrient-rich and has high biological oxygen demand (BOD) so it cannot be applied directly to crop lands or allowed to discharge to local streams. The team investigated multiple ways to mitigate the contaminant levels in silage leachate, including experiments with biochar, activated carbon, limestone, and gypsum. Both flow-through and stirred configurations were evaluated. None of the media reduced nutrients or BOD enough to allow discharge of the treated leachate to waterways, but a combination of limestone and gypsum increased the pH sufficiently to allow application on selected crops. The team designed a treatment system to mix the leachate with gypsum and lime overnight and use an irrigation system to apply the treated effluent on land. Residual solids can be applied to crops with manure.

The team’s deliverables included experimental procedures and results, recommended design and cost estimate, and documentation of implementation and maintenance requirements.