Closed System Nutrient Recovery Cell: Case Study of Advanced Treatment of Dairy Digester Effluent

摘要

A process for removal of suspended solids and the associated nutrients in the effluent from a dairy digester has been developed. The Closed System Nutrient Recovery Cell, (CSNRC) is generally analogous in operation to dissolved air flotation in that gas is utilized to affect initial separation of suspended solids. The process however, involves a "closed cell" which allows the harvest of the flocculated suspended solids in an anaerobic state utilizing biogas as opposed to ambient air. In addition, thecell is self harvesting in that it operates without rakes or float collection devices which tend to shear the fragile digester emulsion, and require significant on-going maintenance. The original CSNRC functioned as part of the manure management facility at the Fair Oaks Dairy South Farm in northern Indiana. This is a sand bedded dairy of 3500 head which operates sand separation, digestion, solid recovery, and irrigation of the treated effluent as part of the total manure management system. As of June2008 the cell has been in operation for 24 months. During this time, daily data specific to flow rates, solids and nutrient recovery and effluent quality has been gathered. This data and associated analysis along with process diagrams will be presented in the proposed paper. The CSNRC is now being operated at several other applications including: a combined hog/heifer manure digester in conjunction with a pelletizing mill; a sand bedded flush dairy without digestion; and a dairy with a digester utilizing manure solids for bedding. A summary of these applications are discussed and data is presented as available.