Cyanobacteria and cyantoxin in the transposition of water of the system Billings-Guarapiranga (São Paulo State)

Abstract

Urban reservoirs destined to public supply have been suffering accelerated eutrophization process, due to the expansion of agricultural, industrial, and urban areas without adequate planning. The main eutrophization sources are the diffuse and punctual discharges of domestic and industrial sewers from urban centers and agricultural regions. Eutrophization in excessive levels causes ecological imbalance, negative effects in the ecosystem biota and water quality degradation. Algae blooms in eutrophic reservoirs, increases turbidity, alter water flavor and smell and some cyanobacteria lineages can produce toxins. These toxins in the when are a great problem to water supplying systems and to population. Therefore, reservoirs need to be carefully monitored to avoid any potential adverse risk to human health. Billings Complex and Guarapiranga System are eutrophic urban reservoirs with strategic importance to the city of São Paulo and the cities in ABCD area of São Paulo, because its waters has multiple uses, including water supply. Rio Grande System produces 4.7 thousand liters of water per second and supplies 1.6 millions of people in Diadema, São Bernardo and Santo André. Guarapiranga System produces 14 thousand liters of water per second and supplies 3.8 millions of people in the south and southwest of São Paulo city. In 2000 August, SABESP started the operation of the intake system of rough water of the Taquacetuba branch to Guarapiranga, with an operation license for 2.0 m3/s. At present, it operates between 3.0 to 4.0 m3/s.That transposition is performed to regularize the water level in Guarapiranga reservoir. In partnership with the Laboratory of Limnology of the Ecology departament (IB, USP), I have been developing some researches that evidenced abundance of cyanobacteria: (Microcystis spp, Cylindrospermopsis raciboskii and Plankthotrix agardhii) in Taquacetuba brach, near the water intake spot to reverted for Guarapiranga reservoir. SABESP applies peroxide of hydrogen and copper sulphate in the water for public supply. This treatment is carried out only in Guarapiranga reservoir and Taquacetuba branch receives no treatment. The use of increasing amounts of copper sulphate for the management of cyanobacteria biomass, can impair public supply and population health. The aim of this research is to analyze the influence of the water transposition from Taquacetuba branch (Complex Billings) to Guarapiranga reservoir, with emphasis in the phytoplankton community, in particular the cyanobacteria. Intends to evaluate the phytoplankton community in Taquacetuba branch (Complex Billings), as inoculum of cyanobacteria and, consequently, of cianotoxin, increasing the deterioration of water quality of Guarapiranga reservoir. (AU)