ETA GUANDU ? THE MAIN WATER TREATMENT PLANT IN RIO DE JANEIRO AND THE BRAZILIAN CYANOBACTERIAL LEGISLATION

摘要

The first report of human deaths from exposure to cyanotoxins in Brazil occurred in Caruaru (Pernambuco) in 1996, when during a hemodialysis procedure, 76 patients died from the syndrome now known as ?Caruaru Syndrome?. Microcystins were found on the dialysis clinic?s carbon filter and in the patient?s blood and liver. On 29 December 2000, the Brazilian Health Minister published the 1469th Decree, including guidelines for cyanobacteria and cyanotoxins in raw and treated water based on the World Health Organization recommendations. The decree was then modified to the 518th Decree on 25 March 2004 and despite minor revisions, the cyanobacteria and cyanotoxin guidelines were kept. The monitoring of cyanobacteria at Guandu Water Treatment Plant (ETA Guandu) began in October 2001. ETA Guandu produces 43.000 cubic meters per second of treated water and supplies nine million people in the Rio de Janeiro metropolitan region. During the monitoring, a flood plain lake (Lake Guandu) was identified as the main cyanobacterial source in the raw water. The cyanobacteria have been monitored monthly in Lake Guandu and three times a week (or daily) in the raw water. Microcystins have been analyzed weekly by tube kit, ELISA kit and/or HPLC in treated water. The monthly average cyanobacterial concentrations in raw water was more than 10.000 cells mL-1 in five periods between 2002 and 2004. Aphanocapsa holsatica (Lemmermann) Cronberg & Komárek and Chroococcus cronbergae Komárek & Novelo were the main species. Rainy days and the position of the water intake were identified as factors that influence cyanobacterial plant entrance. Analysis on raw and treated water during the blooms indicated cyanotoxins concentrations below the guideline values (1μg L-1). Changes in the position of the water intake have been made during the periods of bloom to reduce the entrance of cyanobacteria in the treatment plant and a project to by pass the Lake Guandu?s water from ETA Guandu intake has just been approved.