A Pilot Study Of UV Disinfection Technology In Reclaimed Municipal Wastewater

Urban wastewater reuse is an important way for resolve water pollution and water shortage.As the final part of treatment process,disinfection plays a vital role in recycling water system.In this paper,a pilot plant was built in Beishiqiao Wastewater Treatment Centre to disinfect recycled water with UV.The disinfection efficiency and influencing factors were studied,to ensure the safety of using recycled water.The results showed that:(1) UV transmittance rates have a great impact on reclaimed wastewater disinfection treatment efficacy.The total coliform removal rates increased with the increase of UV transmittance rates.The biggest discrepancy of UV transmittance was close to 2 log.When UV transmittance rates are more than 72%,and UV dosage is 103mJ/cm~2(the irradiation time was 5.6 seconds),the survived total coliform is less than three CFU per liter.So it is satisfied the request of《Reuse of recycling water for urban—Water quality standard for urban miscellaneous water consumption》(GB/T 18920-2002).(2) The turbidity had some impact on reclaimed wastewater disinfection treatment efficacy.When the turbidity was less than 2 NTU,the impact on UV disinfection treatment efficacy was not obvious.(3) The increase of UV dosage was the available instrument to control photo reactivation and dark reactivation of coliform.When UV dosage reached 88 mJ/cm~2, and the irradiation time was 4.8 seconds,the sample water which was keeped without light for 24 hours did not have dark reactivation.When UV dosage reached 138 mJ/cm~2, and the irradiation time was 7.5 seconds,the sample water which was keeped with irradiation by 30w lamp for 6 hours did not have photo reactivation.(4) To advance UV disinfection efficiency,the influent recycling water must be tried to decrease the turbidity and increase UV transmittance rates by the pretreatment technics.Because UV disinfection did not have a long haul disinfection ability,the recycling water must be added some chlorin.So it can ensure the water biology stability in the pipe net,and prevent the recycling water from the second pollution because of the outgrowth bacteria.