New Air Purification System for Pig Production Units Based on Membrane Technology

Abstract

In Denmark, two brand new systems for reducing odour from swine production units are being developed. One of these systems is based on air purification using membrane technology, and the other system is based on treatment of slurry using ozone. This paper will focus on the former. The membrane air purification system was composed of 3 modules. The first was an acid module, and the other two were alkaline modules. Each module consisted of approx. 7,000 vertical membrane tubes with a diameter of 2 mm. The acid liquid in the first module (aqueous solutions of H2SO4 with pH 2) and the alkaline liquid in the other modules (aqueous solutions of NaOH with pH 11) were recirculated in the membrane tubes, while the air from the swine production unit was blown between the membrane tubes. The small-scale air purification system was investigated in a finisher unit with fully slatted floor and under-pressure ventilation. The trial was conducted over a period of 3 weeks. Six samples for olfactory analysis and a number of other measurements were taken after 8, 14 and 21 days. A statistically significant reduction in odour, ammonia and hydrogen sulfide was recorded (P<0.05). The odour concentration was reduced from 5250 OUE/m3 ± 670 to 1680 OUE/m3 ± 560. The ammonia concentration was reduced from 17 to 1 ppm. The hydrogen sulfide concentration was reduced to a level close to 0 ppb. The pressure drop across the purification unit was 40 Pa, corresponding to the level in several other air purification systems on the market. The investigation has shown that membrane technology has considerable potential as a method for reducing odour. Unlike biological purification, chemical air purification is effective immediately after installation. However, there are two areas that require further development. Firstly, the price of the membrane tubes has to be reduced. Secondly, a dust filter or cleaning system must be installed in front of the membrane modules to prevent the space between the membrane tubes from getting clogged.