title: Toxic effects of cadmium (Cd²⁺) on anaerobic biomass: kinetic and metabolic implications.
abstract: Cadmium ion (Cd(2+)) toxicity on anaerobic systems, used for organic matter removal, was assessed by studying its effect on kinetic parameters and metabolic changes. This fundamental study was performed in a continuous fixed bed anaerobic bioreactor that treated synthetic wastewater simulating domestic sewage. The biomass was immobilized on a fixed bed made of polyurethane foam. Under influent cadmium concentrations of 0.0, 0.4, 4.4 and 6.2 mg Cd(2+) L(-1) the organic matter removal efficiencies were 84%, 82%, 72% and 52%, respectively. At influent concentration of 6.2 mg Cd(2+) L(-1) the reactor had reached its limit for cadmium toxicity. In the removal of dissolved organic matter, the first-order apparent kinetic coefficients (k(1)(app)) were 0.84, 0.67 and 0.10 h(-1) for the operations with 0.0, 0.4 and 4.4 mg Cd(2+) L(-1), respectively. The apparent inhibition coefficient for cadmium (k(i)(app)) was 1.69 mg L(-1). Despite the toxic effects of cadmium on anaerobic organic matter removal at large Cd(2+) concentrations, the results demonstrated that the anaerobic process was suitable for cadmium concentrations below 29.8 mg Cd(2+) L(-1), considering the bioavailable fraction of adsorbed cadmium in the support when the cadmium influent concentration was 6.2 mg Cd(2+) L(-1).
authors.affiliation: Hydraulics and Sanitation Department, São Carlos Engineering School, Universidade de São Paulo (SHS/EESC/USP), Av. Trabalhador São-Carlense 400, CEP 13.566-590, São Carlos, SP, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: Mockaitis
authors.forename: J A D
authors.initials: JA
authors.lastname: Rodrigues
authors.forename: E
authors.initials: E
authors.lastname: Foresti
authors.forename: M
authors.initials: M
authors.lastname: Zaiat
mesh_terms: D000327:Adsorption; D000693:Anaerobiosis; D001105:Archaea / Q000187:drug effects / Q000378:metabolism; D001419:Bacteria / Q000187:drug effects / Q000378:metabolism; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D002104:Cadmium / Q000633:toxicity*; D004867:Equipment Design; D007700:Kinetics; D011140:Polyurethanes; D012722:Sewage; D013696:Temperature; D055549:Volatile Organic Compounds / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
chemical_list: D011140:Polyurethanes; D012722:Sewage; D055549:Volatile Organic Compounds; D002104:Cadmium; C028279:polyurethane foam