aerosols from a pilot-scale wastewater treatment plant with intermittent aeration

Atmospheric emissions from a pilot wastewater treatment plant performing aerobic and anoxic processes were investigated. The experiment was performed by sealing the whole aeration tank with an airtight cover of polyethylene in order to obtain a de"ned #ow rate of the o!-gas. By measuring concentrations in the known #ux of the o!-gas emission rates were determined. Due to the dimensions of the pilot plant and the air and water #ows these emission rates represent upper limits. The emission rates were put into relation to CO 2 to obtain normalized data that can be used for emission inventories. Normalized emission rates (g component]g~1 CO 2 ) were 8.9]10~3 for TVOC, 6.6]10~6 for nonmethane hydrocarbons C 2 }C 7 (NMHC), 2.1]10~5 for NO and 3.0]10~6 for particulate organic carbon (POC). Emission rates per capita equivalent per year accounted at the most for 244 g C TVOC, 0.18 g C NMHC, 0.58 g NO and 0.08g C POC on a basis of 27,400g CO 2 per capita. The non-aeration periods also contributed to the production of NO and TVOC emissions of approximately one-third of the total emissions. From this, we conclude that the implementation of denitri"cation stages in European wastewater treatment plants according to the EU-directive 91/271/EEC will increase trace gas emissions in Europe. However, according to our estimates, emissions of trace gases and aerosols from wastewater treatment compared to anthropogenic sources will still remain very low. ( 2001 Elsevier Science Ltd. All rights reserved.