| Disinfection is the essential and final process of municipal wastewater treatment for reuse.Therefore,it plays a vital part in guaranteeing reclaimed water healthy and safe.In this work,a pilot plant was built in Xi'an Beishiqiao Water Purification Center to disinfect a tertiary municipal effluent with UV.To provide reference and technical support for using UV disinfection technology in the reclaimed water treatment engineering,effects of UV dose and on disinfection efficiency was studied,also the influence of UV disinfection on reclaimed water quality was analyzed,at last a preliminary study of the revival of coliforms after disinfection.The experiment results suggested that:inactivation of microorganisms was directly related to the UV dose received.The more UV dose microorganisms received the easier they could be inactivated.When UV dose reached more than 103mJ/cm~2,there were no coliform in effluent and total bacteria count less than 30cfu/mL,which was consistent with State Standard GB/T18920-2002.Ultraviolet transmittance(UVT) is the main factor affecting the efficiency of ultraviolet disinfection system,and reduction of UVT would make UV disinfection system less effective.Furthermore,organic substance would absorb UV light in the reclaimed water,which was the major contributor to the reduction of UVT.Because of photochemical reaction occurred in the reclaimed water in the role of ultraviolet radiation,some organism could be removed in a certain degree. At the same time,reclaimed water quality would change a little,but the physical and chemical properties of reclaimed water almost never varied.Increasing UV dose could control the volume of the resurrection effectively,when UV dose more then 138mJ/cm2, the revival of coliforms were not detected in the reclaimed water samples after saved avoidance light for 24h or irradiated for 6h by 30W fluorescent lamps. Experiments prove that reclaimed water disinfection by UV is entirely technically feasible,however,considering the ultraviolet disinfection capability without constant,if used alone cannot guarantee against microbial pollution and growth in the transport process of reclaimed water.Because of this,other auxiliary means(adding chlorine or chlorine dioxide in reclaimed water,etc.) should be adopted to maintain residual chlorine when UV disinfection have application in engineering,thus to enhance the biological stability of the reclaimed water and ensure reclaimed water can be transported and utilized healthily and safely.
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