Evaluation of water treatment sludges toxicity using the Daphnia bioassay.
Alum and ferric chloride sludges from two water treatment plants (WTPs) were analyzed regarding their physicochemical characteristics and toxicity to Daphnia similis. Experiments were carried out in the dry and rainy seasons. Acute and chronic toxicity was measured using survival and reproduction as measurement endpoints. No acute toxicity of the sludge was observed in 48 h exposure. Ferric chloride sludge caused chronic toxicity, demonstrated by low fecundity and some mortality, while alum sludge caused chronic toxicity characterized by low fecundity. Some sludge characteristics varied between samplings, including turbidity, solids contents, N, P and metal (Al and Fe) concentrations. These variables and the increase of chemical oxygen demand (COD) were identified as the main cause of degradation of the receiving waters. However, no relationship was observed between these variables and degree of toxicity. It is apparent from these results that water treatment sludges may be toxic and therefore may impair receiving waters. Alum sludge was less toxic than ferric chloride sludge.
Sotero-Santos
Rosana B
RB
Departamento de Ecologia e Biologia Evolutiva, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, Rodovia Washington Luis, km 235, CEP 13.565-905, São Carlos, SP, Brazil. rmabarb@yahoo.com.br
Rocha
Odete
O
Povinelli
Jurandyr
J
D000534:Alum Compounds; D000818:Animals; D001681:Biological Assay; D002712:Chlorides; D003621:Daphnia; D005290:Ferric Compounds; D012722:Sewage / Q000737:chemistry*; D018675:Toxicity Tests; D014865:Waste Disposal, Fluid; D014873:Water Pollutants / Q000633:toxicity*
D000534:Alum Compounds; D002712:Chlorides; D005290:Ferric Compounds; D012722:Sewage; D014873:Water Pollutants; C041524:aluminum sulfate; C024555:ferric chloride