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.