Carlos Magno de Sousa Vidal

Comparison of methodologies for determination of residual peracetic acid in wastewater disinfection

The use of peracetic acid (PAA) in the disinfection of sanitary effluents provides an opportunity for the study of analytic methods that permit the determination of the residual concentration of the disinfectant in the effluent. The object of the present study is to compare different methodologies for the determination of residual PAA in concentrations recommended for disinfection of wastewater. The methodologies adopted in this study include three redox titration methods and one spectrophotometric method. Preliminary tests were performed by adding PAA (0.1; 0.5; 1.0; 5.0 and 10.0 mg L−1) to distilled water, and later reevaluated by applying the same concentrations of the disinfectant in wastewater. The results obtained were statistically evaluated and showed that the concentrations between 0.5 and 10 mg L−1 of PAA could be determined both by the cerimetric/iodometric titration method and by the spectrophotometric method using DPD chromophore with catalase. For concentrations between 0.1 and 0.5 mg L−1, only the spectrophotometric method provided satisfactory results.

Water and Wastewater Disinfection with Peracetic Acid and UV Radiation and Using Advanced Oxidative Process PAA/UV

The individual methods of disinfection peracetic acid (PAA) and UV radiation and combined process PAA/UV in water (synthetic) and sanitary wastewater were employed to verify the individual and combined action of these advanced oxidative processes on the effectiveness of inactivation of microorganisms indicators of fecal contamination E. coli, total coliforms (in the case of sanitary wastewater), and coliphages (such as virus indicators). Under the experimental conditions investigated, doses of 2, 3, and 4 mg/L of PAA and contact time of 10 minutes and 60 and 90 s exposure to UV radiation, the results indicated that the combined method PAA/UV provided superior efficacy when compared to individual methods of disinfection.

Dissolved Air Flotation for Fiber Removal from Clear Water

We investigated the use of dissolved air flotation (DAF) to treat clear water effluent from the paper industry in order to remove fibers. The dosage of polyaluminium chloride (PAC) was varied in the following concentrations: 0, 75, 100, 125, 150 and 175 mg/L; as well as bubble rise velocity of 18 and 9 cm/min for two types of paper wastewater: print and gloss. Data were statistically analyzed through factorial arrangement 6x2x2. The treatment of the print paper effluent showed better performance in removing the analyzed parameters with an optimal dosage of 100 mg/L PAC, whereas the gloss paper effluent treatment had satisfactory removal of analyzed parameters with an optimal dosage of 150 mg/L of PAC. This led to the observation that the high efficiency directly obtained with the DAF in conjunction with the use of PAC coagulant was an excellent primary treatment option for effluent resulting from the paper industry.

MODELO EXPERIMENTAL DE DESINFECÇÃO DE ESGOTO SANITÁRIO USANDO ÁCIDO PERACÉTICO.

A desinfeccao de esgotos sanitarios tem como objetivo a inativacao de microrganismos patogenicos visando a minimizar a proliferacao de doencas de veiculacao hidrica. No presente estudo, investigou-se o uso do acido peracetico (APA) como agente desinfetante de efluente secundario de Estacao de Tratamento de Esgotos (ETE). Os microrganismos indicadores empregados para verificar a eficiencia da desinfeccao foram coliformes totais (CT) e Escherichia coli . Verificouse efetiva inativacao de CT e E. coli para as concentracoes aplicadas de APA de 5,0 e 10,0 mg.L-1, para os tempos de contato de 10 e 20 minutos. Palavras-chave: tratamento de esgoto; desinfeccao; acido peracetico; Escherichia Coli ; coliformes totais ABSTRACT Experimental model of wastewater disinfection using peracetic acid. The sanitary wastewater disinfection has as its objective the inactivation of pathogens in order to minimize disease proliferation of hydric vehiculation. In the current study, it was investigated the use of peracetic acid (PAA) as a disinfecting agent of effluent from the wastewater treatment plant (WWTP). The indicator microorganisms applied to check the disinfection efficiency were total coliforms and Escherichia coli . Na effective inactivation of total coliforms and Escherichia coli was checked for the applied concentrations of PAA of 5.0 and 10.0 mg.L-1 for contact time from 10 and 20 minutes. Key words: wastewater treatment, disinfection, peracetic acid, Escherichia coli , total coliforms