A reactor for rapid water disinfection in rural areas and post disaster situations

Abstract

Solar   Disinfection   (SODIS)   is   the   method   usually   applied internationally to purifying  water in rural areas  when pipe borne water  is  not  available.  Using  Poly  Ethylene  Terephtalate  (PET) bottles   the   process   takes   4   hours   under   the   environmental conditions  of  Trinidad  and  Tobago.  We  have  built  and  tested  a portable  reactor  for  decontamination  on  a  larger  scale  than  that possible  with  bottles.  The  active  surface  of  this  reactor  is  a coating of titanium dioxide nanoparticles on frosted glass or on a flexible  plastic  surface  coated  with  glass  ballotini  of  average diameter  0.5  mm.  The  plastic  surface  is  more  suitable  for  use  in rural  areas  and  post  disasters  situations.  In  each  case  Titanium dioxide nanoparticles (35nm)  were deposited by a sedimentation process. E. coli contaminated water placed in the reservoir of the reactor  was  pumped  over  the  active  surface  at  a  rate  of  48  L/hr while  it  was  exposed  to  sunlight.   E.  coli  degradation  was  rapid for  the  both  surfaces,  total  elimination  taking  place  within  10  to 30   minutes   depending   on   the   solar   conditions. The   photo-catalytic  effect  of  titanium  dioxide  in  the  presence  of  ultraviolet light is the main contributor to the observed decrease in bacterial concentration.  Titanium  dioxide  absorbs  ultraviolet  light  from short  wavelengths  up  to  385nm  and  is  known  to  be  effective  in solar detoxification.