Civil and Architectural Engineering
Civil and Architecural Engineering
Department-College of Engineering-Sultan Qaboos University
Application of an Air Dispersion Model of
Hydrogen Sulfide for Alansab Sewage
Treatment Plant
Abdullah Mohammed Salim Al Jabri
Abstract
The management and operation of sewage treatment plants (STP) usually involve the
release of malodorous substances into the atmosphere with the potential to reduce the quality of
life of people living nearby or crossing over the area. The present study describes AERMOD
dispersion model of Alansab STP applied to assess the odor impact of the plant on the
surrounding area. Modeling investigation was carried out considering all emission sources from
the STP that has significant and continuous emission of H2S. The site source measurements
were for two weeks on February 2015 considering all operation conditions since the plant is
running 24 hours for the whole year. Three to four measurements were taken every day at each
source for two weeks and then daily maximum source emission level was used in the model as
worst conditions. The daily maximum source emission was used with the calculated flow rate,
through the dimensions of the source, to calculate the emission rate of each source. Average and
low source emissions were also modeled. Furthermore, the impact of surface roughness on the
dispersion of H2S was evaluated.
Certified filled meteorological data from Muscat International Airport meteorological station
representative of Alansab STP was obtained from Breeze Trinity Consultant for the modeling
study. Then, the meteorological data was processed using AERMET taking into consideration
the land-use of the area to obtain surface and upper air data that can be used in AERMOD.
The atmospheric dispersion model AERMOD was used to predict the dispersion of H2S from
the STP utilizing the meteorological data, elevation data and H2S survey results. The results
showed that based on the maximum 24hrs, the ground level concentration outside the STP
fence- line can exceed the ambient air quality standard recommended by the Ministry of
Environment and Climate Affairs of 40 µg/m3. The most affected area from the STP’s odor is
the nearby highway. The impact of the odor nuisance will be greater at summer season due to
the elevated temperature which will increase the
H2S generation from the different sources.