By Peter Chawaga, Associate Editor, Water Online
As focus on resource recovery intensifies, food and beverage operations are under a particularly large microscope.
These operations are numerous, tend to produce wastewater that is ripe for recovery and reuse, and they often directly rely on the availability of freshwater sources to keep running. But too often, their desire to operate more efficiently outpaces the technology available to help them do so.
One solution that has recently emerged has been PurposeEnergy’s Tribrid-Bioreactor, a high-efficiency anaerobic digester that can metabolize organize waste streams, including liquids, solids, and slurries, into biogas.
“The bioreactor allows for the food and beverage operation to replace or eliminate the trucking of high-strength and high-solids waste to land application sites or landfills,” said David O’Keefe, the chief scientist for PurposeEnergy. “The bioreactor can also replace energy-intensive and high-sludge-generating aerobic systems. Finally, the bioreactor can replace conventional, upflow anaerobic sludge blanket (UASB) technologies that can only treat soluble organic pollutants.”
Food and beverage production facilities often produce wastewater streams containing organic waste, including solids and byproducts that need to be trucked away and landfilled, at the expense of the operation. The Tribrid-Bioreactor was designed to pump organic waste into a liquefaction chamber, which renders it soluble so that it can be converted into biogas. Soluble chemical oxygen demand is circulated into a high-rate chamber, which treats the wastewater further and converts more biogas. In a novel and patented process, the bioreactor can treat particulate solids and soluble organics as one, retaining the solids in an outer-loop chamber and conveying the organics to an inner chamber.
The process can be customized to treat between 20,000 GPD to more than 1 MGD. PurposeEnergy claims it can remove approximately 93 percent of the organic content from a waste stream.
“A small portion of the mineral constituents of the wastewater are incorporated into the biomass retained in the digester, while the majority of the mineral constituents that are passed through to the final effluent are removed by various tertiary downstream processes, depending on the site-specific requirements of each facility,” said O’Keefe. “Custom, post-digestion processing can include water reuse/reclamation, suspended solids removal, and phosphorus and nitrogen removal.”
The Tribrid-Bioreactor is usually installed along with tertiary treatment and energy-recovery technology, based on the specific site. These systems can help a food or beverage operation reclaim water and use it again, generate biogas for boiler use or cogeneration, or produce fertilizer.
“Typically, biosolids are removed from the reactor and land applied as a beneficial soil amendment under an approved agricultural management plan,” O’Keefe said. “The methane generated from the digestion process can be used to generate heat, electricity, or both as a natural gas equivalent. Depending on the local costs of natural gas and electricity, PurposeEnergy recommends the most economically-viable solution and proves all necessary equipment.”
This additional equipment could include boilers to burn the biogas into heat, combined heat and power units to generate heat and electricity, or cleaning and compression equipment that can inject biogas into natural gas pipelines.
As an additional cost-saving and ecological feature, the system buffers incoming wastewater pH by mixing high-alkalinity, recirculated wastewater from the end of the process with the influent and removing the need to add pretreatment chemicals for pH control.
This resource recovery, landfill elimination, and reduced need for caustic chemical treatment all adds up to ecological savings. But it also can have significant impact on an operation’s bottom line.
“Virtually all Tribrid-Bioreactor installations generate positive cash flow,” said O’Keefe. “They generate significantly more value in energy, water, and waste handling than they consume in operating expense… Most designs reach simple payback in two to five years. Attractive ROI [return on investment] is achieved through a combination of reduced cost of trucking waste, reduced wastewater surcharges, the value of renewable energy produced, water for reuse, and the elimination of capacity constraints.”
In the solution’s highest-profile application, it helps treat brewery wastewater for Magic Hat in a Vermont facility designed, built, owned, and operated by PurposeEnergy.
Magic Hat sells the electricity it generates and uses the heat for the digester. The facility also takes in waste from other food and beverage facilities, charging for the service, and provides biosolids from the reactor to a local farm for soil improvement. It employs a single operator who works less than full time.
“Magic Hat Brewery has been able to eliminate 70 percent of its costs for waste treatment without any capital investment,” O’Keefe said.
Image credit: "Brewery," K B © 2015, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/