Chemical pre-treatment of fugate from biogas stations.

Dealing with the digestate liquid phase from biogas stations has become a problem, due to the rapidly increasing number of biogas stations, tighter legislation, and the nature of the digestate that remains after anaerobic digestion of a biodegradable feedstock. The present solution is a farmland disposal. Standard biological treatment is not applicable because of the extremely high Chemical Oxygen Demand (COD). The method proposed here places chemical pre-treatment of the digestate before the biological stage. This reduces the COD to an acceptable level, from about 100 kg m −3 to about (2–4) kg m −3 . The separated water phase can then be treated in a standard biological aerobic wastewater treatment plant. The chemical sludge can be treated by composting, together with the biological sludge. With the use of proper additives, a digestate material can be produced that raises the fertilizing and adsorption properties of the soil. [ABSTRACT FROM AUTHOR]