Hydrogen sulphide dispersion modelling - urban and rural case studies

Abstract

Sewage treatment works are subject to a range of parameters governing the quality of effluent and sludge produced. An additional product from treatment plants is odorous air. The causes, source, formation and measurement of odour are widely reported and reasonably understood. An important factor in the design and management of works is the prediction of such odours. The importance of this work is explained by the possibility of future legislation controlling odour at wastewater plants. Odour dispersion modelling involves the on-site measurement or prediction of the emission rate of an odorous compound, oftenhydrogen sulphide, and the subsequent prediction of the atmospheric concentrations of that compound downwind of the source. This paper used the USEPA models SCREEN3 and ISCST to determine hydrogen sulphide contour concentrations emitted from unit processes at two different sewage treatment works in the United Kingdom. Results indicated that the first site, locatedin an urban catchment, emitted hydrogen sulphide at varying rates. The predicted downwind concentrations using “urban” dispersion coefficients correlated well with measured concentrations. At the second site, emission rates were less variable. Results from the second site produced the best correlation using “rural” dispersion coefficients. Results from both sites suggest that the definition of the surrounding land use is critical in predicting odour dispersion. The problem of determining land use is highlighted and the importance of correct meteorology is stressed. Both sites were predicted to be capable of producing hydrogen sulphide concentrations at a detectable level outside the site boundary. Odour complaints were therefore anticipated. The operational performance of a unit treatment operation is proposed as a major influence on hydrogen sulphide emission. The idea of a large database of expected emission rates from individual unit treatment processes is proposed as an input for dispersion modelling and as an aid to future design.

Odorous Volatile Organic Sulfides in Wastewater Treatment Plants in Guangzhou, China

“…The primary concern about these sulfur compounds in WWTPs is their irritating nature, which would cause a nuisance to people in the surrounding neighborhood. Many studies about the malodorants in offgases from WWTPs typically focus on hydrogen sulfide (H 2 S) ( Al‐Shammiri, 2004 ; Parsons et al, 2000 ; Stuetz et al, 1999 ), partly because of a relatively large share of hydrogen sulfide in odorous sulfur‐containing compounds. However, hydrogen sulfide seemed not to be a good marker measuring odor concentrations, although it also had a low odor threshold based on dynamic dilution olfactometry ( Cheng et al, 2005 ).…”

Modelling of hydrogen sulfide fate and emissions in extended aeration sewage treatment plant using TOXCHEM simulations

“…Furthermore, the available surface area for gas transfer is believed to affect the emission of H 2 S from open surfaces to the atmosphere. This was also proved by Parsons et al 20 whom found that the greater open surface area of the source the greater H 2 S concentration emitted to atmosphere. Figure 5 shows the concentration of H 2 S (ppm) emitted to atmosphere from each unit.…”

“…This was also proved by Parsons et al . 20 whom found that the greater open surface area of the source the greater H 2 S concentration emitted to atmosphere.…”

Modelling hydrogen sulphide emission in a WWTP with UASB reactor followed by aerobic biofilters

“…Odour emission can be experimentally determined by laboratory simulations (Cohen et al, 1978;Mackay and Yeun, 1983), by micro-meteorological methods (Rege and Tock, 1996;Parsons et al, 2000), and by gas phase direct sampling (Bliss et al, 1995;Jiang et al, 1995;Jiang and Kaye, 1996). However, owing to their simplicity and low cost involved, empirical mathematical equations are usually used to estimate odour emissions.…”