Managing water quality in a polluted lake of Southeast Brazil

Abstract

Brazil has been suffering from lack of sanitation infrastructure. Great part of domestic sewages does not receive any treatment before final discharge. This study analyzed water quality in Javary Lake, located in Southeastern Brazil. Over decades, this water resource has been progressively polluted due to the raw domestic sewage discharges from local residences. Most of the organic matter introduced in the Lake was already consumed by organisms or has biodegraded. Physico-chemical and microbiological results from 2007 to 2010 corroborated the 'polluted' status of the Javary Lake, mainly by organic matter. An aggregate analysis of the overall results indicates that they were similar to values typically observed in stabilization ponds. These results support the main assumption of this study, which implied that the Lake has been biologically operating as a stabilization pond for a long time. There is an ongoing public project to clean up Javary Lake. Since 2011, there is no more domestic raw sewage being directly discharged. However, a significant portion of the sludge has deposited on the bottom of the Lake. In 2011, there was an attempt to remove this accumulated sludge. This attempt of sludge removal introduced already settled down organic matter into the water, generating algae bloom and fish death. Thus, the sludge dredging operation was interrupted. After this faulty dredging, this study did a follow-up analysis indicating that Javary Lake was still polluted. To reverse this situation, it is still necessary to control the recently implemented sewage treatment system and to dredge the Lake bottom to remove most of the accumulated sludge. Till date, Javary Lake still keeps its 'polluted' status. It is still pending further studies to determine what would be the best alternative for managing the water quality in the Lake and for disposing the sludge. © 2013 WIT Press.