Biofiltration of odour and ammonia from a pig unit - a pilot-scale study

A pilot-scale biofiltration unit was constructed at a pig finishing building on the University College Dublin research farm. The biofiltration system was investigated over three trial periods. Exhaust air from a single pen was extracted by a variable speed centrifugal fan and passed through a humidifier and biofilter. A 0.5 m depth of woodchips of over 20 mm screen size was used as the biofilter medium. The moisture content of the medium was maintained at 64 +/- 4% (wet weight basis) for trial one and 69 +/- 4% (wet weight basis) for trials two and three using a load cell method. The volumetric loading rate varied from 769 to 1898 m(3) [air] m(-3) [medium] h(-1) during the three trial periods. Odour and ammonia removal efficiencies ranged from 77 to 95% and 54 to 93%, respectively. The pH of the biofilter leachate remained between 6 and 8 throughout the experimental periods. The pressure drop across the biofilter ranged from 14 to 64 Pa. It is concluded that a wood chip media particle size > 20 mm is suitable for use in biofiltration systems on intensive pig production facilities. This will minimize the pressure drop on the system fans to reduce overall operation costs. It is recommended that a filter bed moisture content (wet weight basis) of greater than 63% be used to maintain overall efficiency. An efficient air moisturizing system (humidification and bed sprinkling) along with a properly designed air distribution system must be incorporated in the overall design when operating at such high volumetric loading rates. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.