No legal regulations and methodological recommendations have been adopted or developed in Poland, as yet, which could be used for olfactory impact assessment purposes. Objectives of this paper include a comparison between two olfactometric research methods employed in an olfactory impact assessment of municipal wastewater treatment plants (WTPs), and determination of their possible use in Polish conditions. Another objective of the paper was to identify the most odour nuisance facilities in the technological line of a WTP placed in Warsaw and currently undergoing modernisation and enlargement. In 10 measurement series 87 receptor points were determined for measurements to be taken using field olfactometer (FO); other 50 receptors were selected for tests using delayed olfactometry (DO). On the basis of FO and DO tests, the most significant odour sources were identified, namely the biofilter (which do not works correctly), screen room, collection chamber and the sand trap. Those sources are a part of the mechanical section of the WTP. Subsequent stages of wastewater treatment, namely the biological and sludge section, were substantially less nuisance in olfactory terms. On the basis of the results obtained by each of the methods employed, the facilities were put in order of their olfactory impact: from facility generating the highest odour concentrations to these generating the lowest ones. The order of the facilities is quite similar both in the case of DO and FO method. No significant relationship was observed after comparison of two tested methods, marking the correlation coefficients. The average correlation (R~2 = 0.653) was only observed at the sand separator where there was small odour concentration.
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