Odor Impact of Different Wastewater Treatment Technologies Compared
Research carried out proves that degrading wastewater pollution through mechanical aeration emits less odorous compounds than intensive systems. Additionally, another study has been carried out that shows that the use of biofilters filled with pruning and mud compost are efficient systems to minimize the odoriferous impact of treatment plants.
The smell of sewage treatment plants in cities is one of the social problems that technology has been trying to solve for years. The control and management systems of this type of infrastructure have been concerned with minimizing the environmental and odoriferous impact of this waste, which directly affects the quality of life, especially for those who live near the treatment plants. Among the latest systems that biotechnology has been able to devise, there are two that are trying to break through by demonstrating their effectiveness: mechanical ventilation and biofiltration. Both have been evaluated in two independent studies carried out by two scientific teams from the University of Córdoba and published in the journal Process Safety and Environmental Protection. The first of these works describes the work carried out on a real scale in the wastewater treatment plants (WWTP) of two towns in Cordoba: Espiel and Villaviciosa, and the second, the analysis of the operation of pilot-scale biofilters operated in the facilities in the area. of Chemical Engineering from the University of Córdoba.
In the first study, the analysis of different biological treatments of wastewater has made it possible to prove that the process called activated sludge with prolonged aeration, which is used in the Espiel WWTP, emits a slightly higher rate of odor per inhabitant than the rotating disc system that is used in Villaviciosa. The Espiel system is also more efficient and intensive for the treatment of wastewater and generates a greater amount of sludge, a by-product that can be used correctly, thus favoring the development of the circular economy. In addition, as the analysis of the sludge genome has shown, the presence of nitrifying and denitrifying bacteria allow the elimination of polluting nitrogenous compounds from wastewater.
The second publication analyzes the effectiveness of biofiltration to eliminate odoriferous compounds in devices filled with different organic waste: pruning remains exclusively or mixing them with sludge compost from the treatment plant itself. The results of this work showed that when biofilters are used to eliminate odorous compounds of an acidic nature and soluble in water, such as butyric acid, the efficiency was higher, although less lasting, than in the elimination of less miscible compounds in water, such as D-Limonene. Butyric acid is a compound that is generated in fermentation processes, with a characteristic rancid odor, while D-Limonene is a compound that characterizes the citrus odor.
In any case, and as explained by M. Ángeles Martín Santos, professor of Chemical Engineering at the UCO, "it must be taken into account that all the plants studied comply with the established discharge limits and that the smell of a treatment plant does not always reach to nearby towns. There is a whole process of transport and dilution of polluting odors by the environment that makes their perception decrease. The wind, for example, can disperse them. Hence, an essential aspect in wastewater management is the location of the treatment plants. The problem is that, as a result of urbanization and the reclassification of the land, many treatment plants are very close to towns and, therefore, they must be better equipped with odor emission control systems".
Márquez P, Gutiérrez MC, Toledo M, Alhama J, Michán C, Martín MA. Activated sludge process versus rotating biological contactors in WWTPs: Evaluating the influence of operation and sludge bacterial content on their odor impact. Process Saf. Environ. Prot. 2022;160:775-785. doi: 10.1016/j.psep.2022.02.071
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