Vermifiltration of Dairy Wastewater for Reuse: The Earthworm Revolution

Abstract

The viability of using vermifiltration to remediate wastewater from a dairy processing plant to City of Phoenix disposal requirements was investigated. Contaminant species of concern were COD, BOD, and TSS. Vermifiltration uses a packed bed reactor with an active layer of worms and compost, where worms and associated microbes decompose contaminants from the wastewater. A pilot scale vermifiltration unit was built to investigate the feasibility of using Red Wiggler worms (Eisenia fetida) to treat wastewater from Shamrock Farms dairy processing plant. Approximately 80% of total organic carbon was removed from the wastewater in a 24 hour time period, while the experiment had not reached steady state. Projected removal of organic carbon at steady state matches literature values of over 90% removal. A full scale process was designed to remediate 600,000 gallons per day of wastewater onsite at the dairy processing plant. This optimized process includes an inlet stream heat exchanger to reduce the temperature to worm operating conditions and six vermifiltration beds with in-situ cooling. Water leaving the system meets disposal requirements. As designed, this process is not economically viable. Further research into species of worms with higher operating temperatures and heat dissipation methods could make this process economically sustainable.