Treatment of Dairy Wastewater using a Low-cost Vermifilter Technology
Primary Author: Gilbert Miito
Faculty Sponsor: Pius Ndegwa
Primary College/Unit: Agricultural, Human and Natural Resource Sciences
Category: Agricultural and Natural Resource Sciences
The dairy industry generates wastewater streams characterized by high organic and nutrient contents. When discharged untreated, the wastewater streams can lead to several environmental problems which include eutrophication, ground water contamination and greenhouse gas emission. Technologies such as membrane filtration, struvite precipitation, Ammonia stripping, and aerobic treatment have been suggested as viable treatment and recovery options, but these are expensive in terms of resources, labor and energy. Vermifiltration is an emerging low-cost and environmentally sustainable technology for the treatment of wastewater and recovery of nutrients using earthworms. This study evaluated the efficacy of a pilot scale vermifilter at treating a side-stream of dairy wastewater on a commercial dairy. The vermifiltration unit was set up and was monitored for a period of 6 months to study the effect of the process on the chemical oxygen demand, total ammoniacal-nitrogen, orthophosphates, and gas emissions. Influent and effluent samples were collected bi-weekly and analyzed using standardized methods. Gas emissions were also measured on site using the static chamber method. Overall, the vermifilter removed 42% of Chemical Oxygen Demand, 80% of Total Ammoniacal Nitrogen, and 7% of ortho-Phosphates. The vermifilter reduced ammonia emissions by 84–100%, nitrous oxide by 0–59%, carbon dioxide by 58–82% and Methane by 95–99%. These removals are attributed to the synergistic action of earthworms and the microorganisms in the units. Basing on these findings, vermifiltration is a viable low-cost alternative for nutrient recovery and treatment of dairy water while also reducing gaseous emissions.