Analysis of Air Pollutant Emissions in a Wastewater Treatment Plant Using Dispersion Models

Abstract

The dispersion of air pollutants such as Ammonia (NH3) and Hydrogen Sulphide (H2S) emitted by a municipal wastewater treatment plant (WWTP) was studied for a period of over one year. The main intent was to support the environmental impact assessment focusing on the diffusion of annoying odours over surrounding areas during the regular activity of the sewage treatment facility. The adopted methodology consists in comparing, in three test cases, the performance of the Gaussian plume model AERMOD, an American Meteorological Society and U.S. Environmental Protection Agency Regulatory Model, against the performance of the 3-D Lagrangian model AUSTAL2000, a German Dispersion Model developed according to the Technical Instructions on Air Quality Control. Both models were run over a domain of about 30km 2 made of hilly zones and located in the centre-eastern Italy. Ten sources of airborne pollutants, located along the sludge treatment line and considered as area sources, were taken into account. The diffuse emissions associated with odour production within WWTP were estimated considering the pollutant emission factors suggested by the American Environmental Protection Agency (EPA). The test cases included different emission scenarios deriving from three different operative plant configurations set in order to investigate the most impacting one. The results show a good agreement between the two model outputs since the annual average for NH3 and H2S are almost equivalent. These concentrations are below the legal limits while the highest values, measured at closest receptors, are beneath the odour perceptibility thresholds. Some noteworthy differences concern the AERMOD distribution maps that show a sort of pollutant stagnation over complex topography areas, especially in valleys, and a farer allocation of the highest pollutants levels from the source, while the AUSTAL2000 model is more biased to distribute the highest values closer to the sources.

Simulating the dispersion of poisonous organic chemical compounds in wastewater treatment process through the active sludge method using the TOXChem model

“…The following are some of the air contaminants that emerge from wastewater ef luents and are simply releasable: 1) Hydrocarbons 2) Volatile compounds 3) Greenhouse gases 4) Airborne microbial contaminants 5) Nitrogen oxides and sulfur oxides 6) Heavy metals [24,32]. Wastewater treatment systems that employ air for separation (air lotation units), for oxygenation (aerobic biological processes), or pollutant removal (air stripping units) will eventually result in the release of VOCs and noxious gases from the wastewater at levels that are potentially harmful to human health [32].…”

Evaluation of air pollutants emitted from wastewater treatment processes in Egypt

“…[3,[11][12][13][14][15] Moreover, it was reported that the levels of pollutants are usually influenced by tank volume, the mechanical or technological approach used for the thickening of sludge, wastewater flow rates, daily working hours, wastewater temperatures, concentrations of pollutants in the wastewater entering the plant, and local wind speed. [16] In addition, agriculture activities, burning of agriculture wastes, and residential activities of nearby surrounding areas could affect the concentration levels of gaseous pollutants of Abu-Rawash WWTP.…”

“…The detected high concentrations of particulate matter (PM 2.5 , PM 10 , and TSP) at the sludge thickening and dewatering process, and cyclone devices can be attributed to the aerobic and anaerobic digestion, mechanical thickening of sludge, sludge drying and flaring, and volatilization of chemicals from the liquid's surface. [4,[12][13][14][15][16] In addition, particulate matter concentrations were affected by the mechanical technology of sludge thickening, wastewater flow rates, daily working hours, concentrations of pollutants in the wastewater entering the plant and local wind speed. [18] In addition, agriculture activities, burning of agriculture wastes at residential areas surrounding the plant, dusty nature around the plant, and main highway road (Cairo-Alexandria desert road) near to the plant could be responsible for the increase in concentration levels of detected particulate matter.…”

“…Unfortunately, although the main aim of WWTPs is to decontaminate wastewater so that the discharged water is safe for humans and ecosystems, the chemical and physical processes involved render WWTPs a major source of air pollutants. [3,[11][12][13][14][15][16] These processes include aeration, digestion, mechanical thickening, and drying of sludge and result in the release of a wide array of air pollutants for example, total volatile organic compounds (TVOC), carbon monoxide (CO), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), suspended particulate matter (SPM), hydrogen sulfide (H 2 S), and ammonia (NH 3 ). [3,[17][18][19][20][21][22] TVOCs can be very toxic and are categorized as hazardous air pollutants particularly for human health.…”

Ammonia emissions from livestock facilities around an international airport, Tehran, Iran: An experimental and mathematical study

“…6,8,9 The majority of previous studies regarding air pollutants dispersion, including NH 3 , have focused on pollution generated by industrial facilities such as wastewater treatment plants (WWTPs). 10,11 Additionally, AERMOD modeling of the dispersion of ammonia pollutants from urban traffic infrastructure has been considered. 12 Furthermore, municipal solid waste (MSW) landfills can contribute to unpleasant odors in urban areas.…”