Assessment and design of a vermifilter for the post-treatment of digestate from low-tech digesters implemented in rural areas of Colombia

A vermifilter has been designed at a pilot-scale to evaluate the post-treatment of a digestate from the anaerobic co-digestion of cow manure, cheese whey, and biochar.

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The design was carried out through a bibliographic review of the vermifilters used mainly for the treatment of wastewater and domestic water, taking into account the specific characteristics of the effluent to be treated. In a preliminary phase, three different feed rates were tested in order to determine the best-operating conditions for this design. In the main experimental phase, several physicochemical, agronomical, and microbiological parameters were monitored during the vermifiltration process. Finally, the quality of the digestate and vermicompost was analysed.

The results showed reductions of 80% in Chemical Oxygen Demand (COD) and more than 90% in ammoniums. Moreover, a Germination Index (GI) of 70-90% was obtained in the effluent and 160% in the vermicompost. The vermifilter has proven to be a promising low-cost technology for the post-treatment of a digestate, due to its high efficiency in the removal of organic pollutants, nutrient fixation, and reduction of phytotoxicity. However, further research is needed to optimize the process and improve pathogens reduction