Managing coffee processing water in Hawaii

Hawaii is the only state in the USA that grows, processes, and roasts coffee. Coffee processing, however, poses some challenges. One is the processing water, which must be treated, and should be re-used. We surveyed and collected several coffee processing water samples, both influent and effluent, from four small-scale (2-5 ha) coffee farms in Kona on Hawaii (Big Island), and from a large (1200 ha) coffee farm on Kauai. The samples were kept refrigerated during transport and storage. Subsamples were filtered and analyzed for biological oxygen demand (BOD), pH, and plant nutrient content. Aeration and lime (CaCO3) were applied in an attempt to lower BOD and phosphorus (P). Our findings showed that the Kauai coffee effluent and its reuse (irrigation) is more environmentally friendly in terms of BOD and plant nutrients than those in Kona. This is perhaps because the Kauai processing uses the hydropulping technique, which does not involve fermentation. Farms in Kona use the wet fermentation technique to remove the mucilage from the parchment coffee. Aeration for 7 days with 1% lime helped reduced BOD to about 300 mg L and P by several fold.