|UNHCR Guidelines on Selecting and Using Disinfectants (WHO - OMS, 1997, 45 p.)|
|VII - Technical specifications for implementing disinfection|
Reservoirs must be disinfected whenever external pollution may have occurred. That is to say:
- after construction
- after repair or maintenance
- after a period of non-use (before being put back into service)
- after accidental pollution (after a landslide, if an animal falls in or if drainage water has entered, etc.).
Reservoirs must be regularly maintained (emptied, the sediments which have accumulated on the bottom removed, the wall brushed if possible and then disinfected).
Begin by draining the water, removing any sediments accumulated on the bottom and, if possible, brushing the wall
· brush walls with a solution of 200 ppm (1)(6) of active chlorine obtained by diluting 10 times a 2000 ppm solution (see the "Products for generating chlorine" instructions on page 24?) and ensuring proper ventilation in the reservoir to avoid the inhalation of toxic chlorine vapours,
· allow to take effect for 30 minutes and rinse,
· fill and then continue using as normal.
· fill the reservoir with chlorinated water at 50 ppm active chlorine
- for one cubic metre, you need 70 g of 70% calcium hypochlorite or 33 dichloro-isocyanurate (NaDCC) 1.5 g active chlorine tablets,
- add the chlorinated product dissolved in buckets of water at the start
· wait 12 hours,
· remove the water and continue using as normal.
DISINFECTING CONDUITS BRINGING WATER TO RESERVOIRS OR DISTRIBUTION POINTS.
Wash the conduits with water then fill them with chlorinated water at 50 ppm (see above).
Leave in contact for several hours. Remove this water. During the period of contact, work the valves and taps so that all surfaces come into contact with the chlorinated solution.