Effect of turbidity on ultraviolet disinfection of domestic wastewater for agricultural reuse

  • Diego Fernando Atoche Garay Centro de Ciências Agrárias. Departamento de Recursos Naturais e Proteção Ambiental. Universidade Federal de São Carlos (UFSCar), Via Anhanguera, km 174, CEP: 13600-970, Araras, SP, Brazil.
  • Lisiana Crivelenti Voltolini Centro de Ciências Agrárias. Programa de Pós-Graduação em Agricultura e Ambiente. Universidade Federal de São Carlos (UFSCar), Via Anhanguera, km 174, CEP: 13600-970, Araras, SP, Brazil.
  • Reinaldo Gaspar Bastos Centro de Ciências Agrárias. Departamento de Tecnologia Agroindustrial e Socioeconomia Rural. Universidade Federal de São Carlos (UFSCar), Via Anhanguera, km 174, CEP: 13600-970, Araras, SP, Brazil.
  • Claudinei Fonseca Souza Centro de Ciências Agrárias. Departamento de Recursos Naturais e Proteção Ambiental. Universidade Federal de São Carlos (UFSCar), Via Anhanguera, km 174, CEP: 13600-970, Araras, SP, Brazil.

Abstract

Water treatment and reuse are fundamental because of the increasing demand for freshwater, especially in agriculture. Accordingly, this study evaluated the effects of turbidity of wastewater processed at the Effluent Treatment Station (ETE) of the UFSCar/Araras and of UV dose on microbial inactivation. The ETE treats up to 2000 L of wastewater daily from toilets and a university restaurant and has five components (grease box, septic tank, microalgae tank, upflow anaerobic filter, and wetlands). Pretreated effluents were used in the experiments, and sampling sites consisted of inspection boxes located after the wetlands. Sample collection, inspection, preservation, and analyses were performed according to standard methods. Sample turbidity was adjusted to 5, 50, 100, 200, and 300 nephelometric turbidity units (NTU), and UV doses of 7.2–28.8 mWs cm-2 were used. A 5 x 5 factorial design (five turbidity levels and five radiation doses) was used, totaling 25 treatments. Each treatment was performed in triplicate. The data were submitted to analysis of variance and Tukey’s test. The results showed that the increase in turbidity significantly decreased disinfection efficiency in samples with turbidity levels higher than 50 NTU. The microbial inactivation coefficients obtained here can be extrapolated to disinfection of wastewater with turbidity up to 300 NTU to eliminate thermotolerant coliforms. The UV sterilizer is feasible for wastewater treatment and its reuse in agriculture.

Keywords: domestic effluent, sustainability, ultraviolet radiation, water reuse.


Published
14/12/2021
Section
Papers