Worms in a field would never be directly in contact with pure effluent. It’s diluted into the soil quickly and even if they did come into contact with it, they wouldn’t be submerged in it like they are in the study. Also, biodigester effluent loses its VFA content if the biodigester finishes digesting. VFAs are an intermediary group of chemicals in the system used to produce biogas by methanogens. Pathogens are present in manure which is spread around gardens everywhere. Just don’t put it on plants you’ll be consuming the greens of raw. Tomatoes, potatoes, corn, and anything peeled is fine. Biodigester effluent, while maybe not as good for soil as compost or manure, is still an excellent quick-release fertilizer option for those growing organically.