Engineered Reed Beds can be optionally added in series to the Bio-Digester Tank for  the secondary treatment of water generated from the Bio-Digester Tank. They comprise of a bed of sand and pebbles along with natural reed plants that can grow in wet areas and can withstand water-logging. Reed Beds improve the Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) of the effluent.