Análise sobre tecnologias de tratamento de esgoto para as cidades do estado do Tocantins

Abstract

The need for the expansion of sanitation services in Brazil is urgent and becomes evident through the large number of people – approximately 100 million – to be served and how the lack of this service affects the quality of life of the population. In view of this, the New Sanitation Framework sets the goal of universalizing sanitation services for 90% of the population by 2033, which, in turn, requires a high amount to be invested – around 350 billion Brazilian reais. Among the regions of Brazil, the North is the one with the lowest coverage rates of sanitation services, and, as a result, the highest rates of diseases due to lack of sanitation are observed. Tocantins is one of the states with the lowest coverage rates and a high volume of investments to be made, especially regarding the implementation of Sewage Treatment Plants (STP). Thus, it is necessary to evaluate technically and economically the sewage treatment alternatives to be implemented in Tocantins to achieve the financial viability of the projects so that this does not become an impediment to the progress of this area of sanitation. In this context, this work aims to support municipalities in conception studies and decision-making regarding the treatment technology to be adopted. Furthermore, this work focused on cities in Tocantins with a population below 20 thousand inhabitants, representing about 92% of the municipalities, and divided into three population ranges. Three sewage treatment technologies were evaluated for each population range: 1) Australian System – Anaerobic Ponds followed by Facultative Ponds, 2) Facultative Ponds followed by Maturation Ponds, and 3) UASB Reactor followed by Activated Sludge. After dimensioning each technology, the implementation (CAPEX) and operational (OPEX) costs were analyzed to enable the financial viability analysis of each alternative. On the one hand, the results showed that simpler alternatives for implementation and operation, such as the Australian system of ponds, may be more attractive technically and financially. On the other hand, in cases of difficulty in acquiring an area and restrictions on the self-purification capacity of the receiving body, the implementation of UASB Reactor systems followed by Activated Sludge may be more viable. The alternative of Facultative Ponds followed by Maturation Pond, due to the need for a large area for its implementation, proved to be economically unfeasible.