In sanitation of “flooded” wells, such professional procedure should be selected, which shall result in improvement of water so that it may be used for drinking. In cleaning the wells, the principles of labour safety should be observed and protective aids should be used.
The following basic procedure is recommended:
Mechanical cleaning of the external walls of the well (best by a brush) or by a strong water spray. This includes also the pumping device, including repair of the protective lid of the well. Upon opening the well, water in the well should be pumped out (best by a sludge pump). The pumped water is discharged to the outfall or to a safety distance from the well.
Prior to entering the well, presence of poisonous gases should be ascertained. The simplest way is to let a lit candle down to the bottom of the well. If the air is oxygen-free, the candle will go off. If any poisonous gases (methane) are present, the candle flame will be more intensive.
Thorough mechanic cleaning of the internal walls of the well and the pumping device will be performed. The walls will be sprayed by a concentrated disinfecting solution based on chlorine. The disinfecting solution should be left on the walls for at least 1 hour, and then the internal walls will be rinsed by clean water. Such water shall then be pumped out.
Dirt like sludge and mud will be removed form the well and if appropriate, the intake holes to the well shall be cleaned. Final washing of the walls and the bottom of the well will be performed and the water shall be pumped out. New gravel or coarse grained sand will be returned to the bottom. The well will be filled-in. If the water is still cloudy, pumping out will continue. In the end, disinfecting solution for disinfection of drinking water will be added. Disinfection of a water resource shall be made by a chlorine preparation.
The working procedure for selected types of disinfecting solutions:
Chloramine: per each m3 of water, even if partial, in the well: 15 – 20 gr (2 full spoons)
Savo: per each m3 of water, even if partial, in the well: 50 ml (1/2 dl ).
Presept: 3 mg of active chlorine per 1 liter watery.
Selection of an appropriate disinfecting solution for disinfection of flooded wells depends on the type of the well. The basic period of contact of the disinfecting solution with water varies. In respect of chlorine, it is generally determined as 30 minutes, in respect of chloramine disinfection, the period is extended to several hours and is counted from the moment of applying the chemicals in the water.
Disinfection may be inefficient in the event the water in the well is cloudy. If the water contains large volume of organic substances, the application of chemical disinfection shall result in creation of undesirable side products of disinfection.
For drinking purposes, water from alternative sources (transported in tanks, originally packed water, etc.) shall be supplied.
The efficiency of disinfection as well as efficiency of the procedures described above should always be verified by a laboratory analysis of a sample of water. From the aspect of health, water may be used again for drinking purposes only after confirmation by the laboratory.
Information & Contact
Ing. Zuzana Bratska
Statny zdravotny ustav
(State Health Institute)
Ipelska c. 1,
042 20 Kosice,
Tel.: 00421 55 6436317
