Identification and quantification of heavy metals, parasites and bacteria in urban wastewater before and after treatment in the sewage treatment station of Ribeirão preto, s.p

Identification and quantification of heavy metals, parasites and bacteria in urban wastewater before and after treatment in the Sewage Treatment Station of Ribeirão Preto, S.P.

 TONANI, K.A.A.*; NIKAIDO, M**, TREVILATO, T.M.B.***; TAKAYANAGUI, A.M.M.****; SEGURA-MUÑOZ, S.I.****

 In developing countries with highly densely populated urban areas with fragility public sanitation systems, urban effluents without treatment are responsible for several waterborne diseases. Effluents carry a microbiological load (bacteria, virus, eggs/larvae of helminthes and protozoa) and chemical pollutants, such as heavy metals. This study aimed to evaluate heavy metals levels and to identify and quantify parasites and coliforms in urban wastewater before and after treatments by means of activated sludge system at the Sewage Treatment Station of Ribeirão Preto (STS-RP). The STS-RP receives and treats almost 57% of total sewage generated in Ribeirão Preto city, since November, 2002. This study was developed in the Environmental Health Laboratory at College of Nursing in Ribeirão Preto/USP with collaboration of the Metal’s Sector of Laboratory of Pediatric at university Hospital of the Faculty of Medicine at Ribeirão Preto/USP. The samples were collected since October, 2006 until October, 2007. It was analyzed Cd, Cu, Cr, Mn, Pb and Zn in untreated and treated effluents by Atomic Absorption Spectrophotometry Techniques. Microbiological analysis was performed using Sedgwick-Rafter Chamber and Colilert Technique. The obtained data showed that heavy metals levels in treated effluents remain within the established levels by Brazilian resolutions. The parasitological analysis showed parasite density above the established levels by World Health Organization, that limit the parasites number in ≤ 1 viable egg of intestinal nematode per liter of wastewater. The levels of total coliforms and fecal coliforms are above the levels set by the above cited national regulations. This study represent the first characterization of parasites and bacteria of effluent collected at STS-RP and a initial evaluation of the chemical and microbiological remotion capacity  of that biological treatment system, aiming to produce information for the authorities responsible for environmental management in municipal, regional national and international scope, under the perspective of public health.