Synergistic effect of the sequential use of UV irradiation and chlorine to disinfect reclaimed water

Abstract

a b s t r a c tThe effectiveness of UV and chlorination, used individually and sequentially, was investigated in killing pathogenic microorganisms and inhibiting the formation of disinfection by-products in two different municipal wastewaters for the source water of reclaimed water, which were from a microfilter (W1) and membrane bioreactor (W2) respectively.Heterotrophic plate count (HPC), total bacteria count (TBC), and total coliform (TC) were selected to evaluate the efficiency of different disinfection processes. UV inactivation of the three bacteria followed first-order kinetics in W1 wastewater, but in W2 wastewater, the UV doseeresponse curve trailed beyond approximately 10 mJ/cm 2 UV. The higher number of particles in the W2 might have protected the bacteria against UV damage, as UV light alone was not effective in killing HPC in W2 wastewater with higher turbidity. However, chlorine was more effective in W2 than in W1 for the three bacteria inactivation owing to the greater formation of inorganic and organic chloramines in W1 wastewater. Complete inactivation of HPC in W1 wastewater required a chlorine dose higher than 5.5 mg/L, whereas 4.5 mg/L chlorine gave the equivalent result in W2 wastewater. In contrast, sequential UV and chlorine treatment produced a synergistic effect in both wastewater systems and was the most effective option for complete removal of all three bacteria. UV disinfection lowered the required chlorine dose in W1, but not in W2, because of the higher chlorine consumption in W2 wastewater. However, UV irradiation decreased total trihalomethane formation during chlorination in both wastewaters. ª

Removal of pathogenic bacteria from sewage-treated effluent and biosolids for agricultural purposes

“…Ting et al (2011) observed a re-growth and repair potential of E. coli, FC and B. subtilis in reclaimed water after UV disinfection. Wang et al (2012) suggested that the higher number of particles in the treated sewage might have protected the bacteria against UV damage. Based on those studies, it can be indicated that UV technology might have a limitation for the sewage disinfection.…”

Photocatalysis of THM precursors in reclaimed water: the application of TiO2 in UV irradiation

“…(2015) [1][2][3][4][5][6][7][8][9][10][11][12] www.deswater.com doi: 10.1080/19443994.2015.1030710 Recently, use of chlorination in reclaimed water draws increasing attention since it is inexpensive and efficient [3]. Sufficient residual chlorine can also prevent the regrowth of bacteria in reused water distribution system.…”

Cloração de esgoto sanitário: variação de cloro residual e o uso de parâmetros facilmente mensuráveis na indicação de breakpoint

“…Além disso, o tratamento de águas residuárias, na ausência de desinfecção, não fornece remoção e controle de patógenos com eficiência compatível com o padrão microbiológico da água de uso e contato público (WEF, 1996), havendo, consequentemente, a necessidade da desinfecção nas Estações de Tratamento de Esgoto (ETEs) (WEF, 1996;AISSE et al, 2003;BITTON, 2011;WANG et al, 2012).…”