Avaliação de efeito tóxico do desinfetante Cloreto de Benzalcônio em processos de lodos ativados.

Abstract

Although the use of activated sludge processes is growing for the treatment of industrial effluents, some characteristics of these effluents can compromise the efficiency and stability of the system, among them the presence of toxic compounds. Use of disinfectants in the food industry is increasingly high due to the requirements of sanitary control agencies with consequent discharge of these compounds in the treatment of industrial effluents stations. To evaluate the toxic effect by respirometry test, three types of activated sludge were collected: one coming from the food industry, one from the pharmaceutical industry and other acclimatized with effluent produced synthetically and intoxicant-free, and kept in contact with Benzalkonium chloride concentrations in the range of 4,95 to 1267mg/L. The sludge from the pharmaceutical industry, because it contains many toxic compounds in the effluent, including antibiotics, showed the lowest oxygen consumption rate values, even for white test, indicating that an intoxicate sludge and so the Benzalkonium Chloride had less effect on the metabolism of microorganisms, presenting acute toxicity EC(I)50;10min between 298.6 and 469.8 mg/L. The food industry tests showed intermediate TCO results, with EC(I)50;10min that ranged from 73.3 to 244,3 mg/L, and the sludge from pilot reactor showed the highest TCO values, indicating good adaptation to the synthetic effluent and EC(I)50;10min between 18.4 and 39.4 mg / L Benzalkonium Chloride, indicating that this sludge was more sensitive to intoxicant possibly due to the absence of toxic substances in the effluent feed. They were added to tests microscopic observations of sludges and analysis of physical-chemical parameters of the affluents, effluents and activated sludge which presented results as expected. It was also studied the acute toxicity of Benzalkonium Chloride to Allivibrio fischeri, resulting in EC50 values = 0.28 mg/L ± 0,014 after 15 minutes of exposure and 0,29 mg/L ± 0,011 after 30 minutes exposure.