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.
Highlights
Increases in world population, urbanization, and water use for irrigation have led to irregular and disordered water supply, limiting water availability
The samples with a turbidity of 5, 50, 100, 200, and 300 nephelometric turbidity units (NTU) showed an approximate transmittance of 84%, 49%, 27%, 8%, and 2%, respectively
The results showed that the samples with a turbidity of 5 and 50 NTU presented the highest levels of disinfection
Summary
Urbanization, and water use for irrigation have led to irregular and disordered water supply, limiting water availability. Short UV radiation (100 - 280 nm) causes changes in DNA and RNA molecules, which absorb radiation at wavelengths between 200 and 300 nm, especially at about 260 nm This radiation range alters the structure and function of nucleic acids, inhibiting DNA replication and inactivating microbial cells (Gibson et al, 2017). Physicochemical properties of wastewater may affect UV light transmittance, and treatment efficiency In this sense, the efficiency of UV radiation can be affected by water turbidity, suspended solid concentrations, microorganisms, cellular aggregates, leachate, and fluid density, requiring higher doses for disinfection process (Hassen et al, 2000; Brahmi et al, 2010; Uslu et al, 2015; Azimi et al, 2017; Bolyard et al, 2019). In this study, we assessed at a bench scale the effect of wastewater turbidity and radiation dose on microbial inactivation using a UV sterilizer for effluent treatment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
