Wastewater treatment and biogas production at US dairy plant

One of the United States’ newest dairy processing plants features wastewater treatment technology that not only improves biomass recovery and effluent quality, but also harnesses green energy from waste streams. The technology is represented in Australia and New Zealand by CST Wastewater Solutions.

Dairy farmers collective Cayuga Marketing constructed the Cayuga Milk Ingredients (CMI) plant to reduce its milk-hauling costs, transport emissions and carbon footprint. It selected Global Water & Energy (GW&E) - the US branch of Global Water Engineering - to design, build and start up its new wastewater treatment facility, specified to achieve good effluent discharge qualities while producing biogas for future utilisation and electricity production.

“We determined that the ideal solution for wastewater treatment from a dairy plant such as Cayuga was provided by GWE’s Flotamet system,” said GWE engineer Natascha Janssens. “This unique GWE system offers high-rate anaerobic treatment with GWE’s Anamix reactor (completely mixed continuous flow stirred tank reactor, CSTR) followed by biomass recovery in a combined sludge separation system consisting of GWE’s Supersep-CF followed by GWE’s dissolved biogas flotation (DBF) unit Superflot-Biogas.”

Cayuga's completed Superflot-Biogas system.

The Cayuga plant is designed to treat 950 m³/d of wastewater and 95 m³/d of whitewater, together resulting in a total COD load of 6000 kg/d. Approximately 80% of the COD load and 85% of the BOD load is removed in the Flotamet system, with the waste removed converted to biogas. This results in the production of up to 1900 Nm³/d (at 75% CH4) of biogas, with an energy content of 590 kW.

Janssens says the biogas will be used partially to heat up the wastewater in order to ensure optimal anaerobic digestion. As such, the anaerobic treatment plant does not create an additional energy demand to the factory for heating purposes. The aim is to use the remaining biogas to generate electricity in order to meet CMI’s goal to further decrease the carbon footprint of the factory.