Wastewater treatment plants (WWTPs) are fundamental for water ecosystems conservation but when they are located in the proximity of residential areas may produce odour nuisance. One of the most common odours pollutants emitted in WWTPs is hydrogen sulphide (H2S) and release to the atmosphere (in waste-waterfalls, manholes), producing a strong unpleasant smell. In this work, field olfactometry and H2S measurement enabled to identify the main odour source, located in the inlet of the WWTP.

   The maximum H2S concentration in this emission point measured was 15 ppm and odour concentration was D/T 60, enough high to produce odour nuisance despite they were produced in open atmosphere. By means of a thorough data analysis of the essential variables involved, such as wind speed, wind direction and the H2S concentrations in its role as the central pollutant, it could be shown via contrasting annual, monthly and daily patterns, that the probability to be affected for these residential areas is the highest in summer from 19:00 hours.

  Odours are typically released into the atmosphere as diffuse emissions from area and volume sources, whose detailed quantification in terms of odour emission rate is often hardly achievable by direct source sampling. Indirect methods, involving the use of micrometeorological methods in order to correlate downwind concentrations to the emission rates, are already mentioned in literature, but rarely found in real applications for the quantification of odour emissions.

   The instrumentation needed for the development of micrometeorological methods has nowadays become accessible in terms of prices and reliability, thus making the implementation of such methods to industrial applications more and more interesting.


  The aim of this study was to assess the cost of not regulating odour emissions. For that we have specified a domain in the Spanish region of Euskadi situated in the North of Spain. To perform this analysis, two factors have been considered: 1) The decrease in the property value affected by odour impact and 2) The economic impact on public health.

   To assess the cost of depreciation of odour-affected properties, a list of Activities Potentially Generating Odour Impact (APGOIs) was selected in the Basque Country. With this data, buffers were generated for different areas of odour nuisance, classifying them as serious, moderate and slight. Subsequently, the number of properties with the potential to be affected by odour impact was calculated. This analysis took into account the price per m2 of each municipality in Euskadi. The results showed that the total cost of depreciation of the value of the properties affected by odour impact was 778 and 1164 million euros for areas affected by serious and moderate odour impact, respectively.


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