Odour Abatement of Waste Gases from Sludge Thickeners in Wastewater Treatment Plant Using Bioscrubber

Abstract

The research objective was to determine odour abatement efficiency of waste gases from sludge thickeners with the use of bioscrubbers. Olfactometric measurements were performed in the large mechanical-biological wastewater treatment plant in one of the biggest cities in Poland. The installation assessed was the 3-stage British system comprised of two identical bioscrubbers from lava rock media at the beginning, and dry chemical scrubber at the end.A three-day measuring session was conducted in October 2012. Nine observations of the relative difference in odour concentration in the crude and clean gas stream in determined conditions were carried out in each stage. In total, 36 samples were taken - 9 samples for each of the four measuring points. The lung principle method was used for sampling. Parameters necessary to calculate the odour flow rate, such as gas temperature, absolute pressure or volume flow rate were measured using the TESTO 400 meter. The samples were transported to the Olfactometric Mobile Laboratory of the Laboratory for Odour Quality of the Air, located ca. 6 km from the object of study. Odour concentration was measured using the Ecoma TO7 dynamic olfactometer and the experienced panel that met the selection criteria of the EN 13725 standard for the olfactory sensitivity. The quality parameters determined in the Interlaboratory Comparison of Olfactometry 2012 for 1-butanol in nitrogen, were: precision r = 0.453 and accuracy Aod = 0.234.The results confirmed the high odour abatement efficiency of over 90 % for the first bioscrubber, with the odour flow rate order of magnitude of 100,000 ouE/s in the crude stream as well as the second bioscrubber where the odour flow rate order of magnitude was below 9,000 ouE/s. The effectiveness of the use of the two series-connected bioscrubbers exceeded 99% and the overall effectiveness of the three-stage installation equalled 100 %.