Demanda bioquímica de oxigênio: aspectos históricos, metodológicos, climatológicos e socieconomicos

Abstract

The traditional Biochemical Oxygen Demand (BOD) detection method measures differences in dissolved oxygen (DO) concentrations before and after a 5-day incubation period at a constant temperature of 20°C. Despite of being extremely traditional and accepted in the scientific community, the method (DBO520) presents larges experimental difficulties being the biggest of them the time needed to obtain the results (5 days), significantly hindering environmental monitoring. The quantification of BOD is extremely important for many companies, research laboratories and environmental agencies, which commonly find themselves in emergency situations (such as environmental accidents or natural degradations of the environment) that require quick and effective operational decision-making in search of reduction of possible damage to the environment; making it necessary to obtain results in shorter periods of time than the five days stipulated by the traditional method. Thus, this dissertation is divided into two chapters that seek alternatives for carrying out the analysis, reducing the time stipulated to complete the experiment. The first chapter reviews scientific works from the most diverse areas of education that were developed in order to reduce the analysis time. After an extensive literature review, there has been a steady increase in the development of sustainable methods and technologies to estimate BOD. The various methodologies and technologies available, like the biosensors, already provide alternatives to reduce analysis time and perform environmental monitoring in real or reduced time, adding unique advantages to the new methods. From the second chapter on, an experiment is developed to evaluate different scenarios for using the method, considering the temperature rise, according to the geographic location of the test, reducing the incubation period of the samples. Therefore, the work studies the effect of temperature on the time needed to determine BOD, according to the climatic conditions of tropical countries, in which Brazil is located. The results show that increasing the temperature decreases the incubation period for 3 days, producing similar results to traditional methodology for rivers and streams (p=0,941; f=0,07). In a simple and concise way, it is corroborated that the temperature increase can be applied to perform the method in tropical environments, without compromising the data. Thus, it is shown that all that was studied, including the temperature change, the creation of biosensors and the development of sustainable technologies applied exclusively to the method, generated extremely positive responses. The reduction in analysis time enables the qualification of water bodies and treatment stations with more accurately and precisely, in addition to providing more frequent data, facilitating the environmental monitoring and providing incalculable benefits to the environment and all consumers in the extensive chain that depends on quality water resources.