title: Assessment of the toxicity of wastewater from the metalworking industry treated using a conventional physico-chemical process.
abstract: This article presents results from a toxicity reduction evaluation program intended to describe wastewater from the metalworking industry that was treated using a conventional physico-chemical process. The toxicity of the wastewater for the microcrustacean Daphnia magna was predominantly expressive. Alkaline cyanide wastewater generated from electroplating accounted for the largest number of samples with expressive toxicity. When the raw wastewater concentrations in the batches were repeated, inexpressive toxicity variations were observed more frequently among the coagulated-flocculated samples. At the coagulation-flocculation step, 22.2 % of the treatments had reduced acute toxicity, 30.6 % showed increased toxicity, and 47.2 % remained unchanged. The conductivity and total dissolved solids contents of the wastewater indicated the presence of salts with charges that were inappropriate for the survival of daphnid. The wastewaters treated by neutralization and coagulation-flocculation had average metallic compound contents that were greater than the reference toxic concentrations reported in other studies, suggesting that metals likely contributed to the toxic effects of the wastewater on freshwater microcrustaceans. Thus, alternative coagulants and flocculants should be assessed, and feasible doses should be determined to improve wastewater treatment. In addition, advanced treatment processes should be assessed for their abilities to remove dissolved toxic salts and ions.
authors.affiliation: Department of Water Resources and Sanitation, Universidade Federal do Rio Grande do Sul, 15029, 9500 Avenida Bento Gonçalves, 91501-970, Porto Alegre, Rio Grande do Sul, Brazil. rmatuella@hotmail.com.
authors.forename: Rodrigo Matuella
authors.initials: RM
authors.lastname: Machado
authors.affiliation: Department of Water Resources and Sanitation, Universidade Federal do Rio Grande do Sul, 15029, 9500 Avenida Bento Gonçalves, 91501-970, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Luiz Olinto
authors.initials: LO
authors.lastname: Monteggia
authors.affiliation: Ecology Center, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Arenzon
authors.affiliation: Department of Mining, Metallurgical and Materials Engineering, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: Curia
mesh_terms: D000818:Animals; D001938:Brazil; D055598:Chemical Phenomena; D003621:Daphnia / Q000187:drug effects; D004784:Environmental Monitoring / Q000379:methods*; D005427:Flocculation; D005618:Fresh Water; D008669:Metallurgy; D062065:Wastewater / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D018508:Water Purification / Q000379:methods*
chemical_list: D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Coagulation-flocculation; Daphnia magna; Metalworking industry; Toxicity reduction evaluation