Mathematical model development for odor emission from landfills and composting plants toward residential cities, a case study for ammonia emission from Kahrizak landfill

Odour emission has been an obstacle for the development of composting facilities. Composting is an environment friendly process which produces secondary pollutants. Ammonia is the most existing compound in these facilities; therefore Odour dispersion studies depended on geographic and metrological conditions of these kinds of places toward residential cities are required. Ammonia is a Tang, toxic, reactive and corrosive compound. Determination the place of landfills and composting facilities must concord with environmental laws; otherwise the blowing wind could transmit pollutants toward residential cities. Industrial source complex is the most common method for modeling of odour emission from volume and area sources. Kahrizak landfill is located in the south of Tehran with latitude and longitude of 51°20'39" E and 35°28'05" N. The amount of waste discharged to this landfill is about 7000 ton per day. A mathematical model for odour and ammonia emissions from Kahrizak landfill based on Gaussian fluctuating plume theory has been developed in this paper. Using the two-dimensional theory of dispersion, the odour emission from that landfill has been calculated. Since the Gaussian dispersion equation is used for point sources, this equation should be changed to determine the ammonia concentration emitted from volume sources. Virtual point method is used to consider this problem. The mathematical dispersion model is based on Pasquill Gifford and Gauss theory. By using meteorological data cumulated from Emam airport meteorological station, In Pasquill Gifford equations, dispersion parameters and emission equation were calculated. WRPLOT software was used to determine the wind direction and Land gem software was used to calculate the ammonia emission rate. The data needed for this software cumulated from Kahrizak waste management Organization of Tehran. Monin obokhov length and net radiation used for stability class specification. Radiation angle and topographic parameters effects were considered in these calculations The wind velocity and temperature were respectively about 3.6 m/s and 8.4°C.. Bowen ratio, albedo ratio and surface roughness of the site were respectively 1.5, 0.35 and 1. The stability class in the mentioned condition was calculated C. Results show that ammonia emission rate from this landfill and composting facility are respectively about 60 g/s and 103g/s. According to EPA reports these values are reasonable. Finally ammonia dispersion equation was solved by Matlab computing program. Maximum ammonia concentration is about 180mg/m3 when x, the distance, is 80 meters and He, effective height, is1.5 m. Emitted ammonia from Kahrizak landfill could transport toward 2kms from this landfill. Since the nearest residential city is about 8.1 km far away from this landfill, therefore there is not a serious problem threatening people who live there. In order to protect environment and people, It’s recommended not to build any residential, commercial or industrial organization about 2 km from here.