Sistemas de tratamento biológico descentralizados, com diferentes configurações, tratando efluentes domésticos: avaliação do desempenho técnico e operacional

Abstract

Although the sanitation regulatory mark, Law 11.445/2007 updated by Law 14. 026/2020, which advocates the universalization of sanitation services in Brazil, the National Information System on Sanitation (SNIS) indicates that Alagoas is served by sewage collection networks, only 28.1% of the urban population and its capital, Maceió, only 42.2% of the total population (urban and rural) is effectively served by sewage collection networks, with an estimate that 14.7 million m³ of sewage are disposed of without treatment. Although the privatization of the water supply and sanitary sewage services in Maceió, which occurred in Sep/2020, is responsible for the expansion of the sewage collection network coverage to 90% by 2033, the compact ETEs, installed in commercial and residential developments, also contribute to the achievement of these goals. However, the operation and monitoring of these systems is still a challenge for those who have limited infrastructure and financial resources, having as an alternative the outsourcing of these services, in order to ensure that the effluent produced meets the current legislation. In this sense, compact WWTPs should be simple, efficient, sustainable and economically feasible. Thus, this study aimed to evaluate four compact sewage treatment plants, with anaerobic treatment followed by aerobic post-treatment, with different configurations (three mechanically aerated and one with natural aeration), in order to identify how they are operated and monitored, their main limitations, and whether the treated effluents meet the release standards of CONAMA 430/2011. The results showed that all of them can fit the treated effluent to the release standards, with standard operating procedures and application of sodium hypochlorite for disinfection. In three of them the excess sludge is removed by tank cleaning trucks with treated effluent disposed on the soil and only one of them uses a drying bed for dehydration of the excess sludge with treated effluent in non-potable urban reuse. The monitoring e effluent quality is aimed only at checking compliance with discharge standards without concern for monitoring the anaerobic and aerobic processes. The main limitation occurs due to the lack of measurement of the affluent flow of the ETEs, which prevents the verification of operational parameters and the adjustment of the dosage of sodium hypochlorite. The average efficiency of organic matter removal of the four ETEs was 87.1±2.2%