Liquid purification or separation – Processes – Preventing – decreasing – or delaying precipitation,...
Patent
1996-03-27
1998-05-05
Hruskoci, Peter A.
Liquid purification or separation
Processes
Preventing, decreasing, or delaying precipitation,...
134 2211, 134 2214, 166 901, 205701, 205740, 210101, 210170, 210192, 2101981, 210698, 210747, 210748, 210754, 210764, C02F 508
Patent
active
057469237
DESCRIPTION:
BRIEF SUMMARY
This invention relates to methods and apparatus for the control of microbial encrustation (biofouling) and microbial corrosion in ground water pumping systems.
BACKGROUND OF THE INVENTION
The major processes that cause deterioration of ground water bores (wells) are physical, chemical, and microbial. The resultant problems affect parts of the pumping system; bore, aquifer, pump, discharge and distribution components. In some cases some of the processes can simultaneously affect parts of the system to differing degrees.
Ground water typically contains a wide range of dissolved chemicals but in the absence of external contamination, aquifers were once assumed to be microbiologically clean. However, it is now recognised that bacteria are endemic in aquifers throughout the world and that aquifers can allow the free transmission of bacteria under suitable conditions. Given a suitable physical and chemical environment, bacteria can thrive and give rise to a multitude of problems.
The phenomenon of microbiological encrustation (biofouling) is now well recognised world wide. It is caused by the accumulation of microbes (bacteria, often called "iron related bacteria"), extracellular polymeric substances and inorganic precipitates, typically iron, manganese, aluminium or other oxides. In the case of iron, the bacteria derive energy during their metabolism through oxidising soluble ferrous iron to insoluble ferric iron. The resultant biofilm is commonly found as a slimy or gelatinous deposit in bore screens, pump inlets, internal waterways and discharge components, sometimes extending well into the distribution pipe system.
Depending on the severity of the biofouling, various detrimental effects may occur including: slots, pump and pipework conditions
Other types of bacteria cause corrosion problems such as: hydrogen sulphide
Many techniques have been used to rehabilitate bores: surging and brushing or swabbing. the use of organic or inorganic acids in conjunction with surfactants and biocides such as chlorine, hydrogen peroxide and quaternary ammonium compounds. Many proprietary bore cleaning products are available using various combinations of these chemicals.
Such treatments often have to be repeated regularly and can be time consuming to carry out, result in significant loss of pumping time, can be very expensive if large quantities of chemical are required and sometimes require considerable ancillary mechanical equipment such as pumps, compressors, and cranes etc.
It would be preferable to implement a system to prevent or control the build up of bacteria in a ground water pumping system by regular disinfection rather than undertaking remedial treatment once the problem has become intolerable.
The problem of dissolved iron in ground water has attempted to be overcome by Patent No SU 1504226 which involves a vacuum section to remove gasses in the water followed by an aeration section with a filter to remove trivalent iron. Also Patent No CN 87106661 uses oxygen aeration to remove iron and manganese from ground water. SU 1161480 describes the use of atmospheric air to remove dissolved iron, while DE 3333842 describes removing iron and manganese from water wells by admitting compressed air to one or two wells in turn. AU8429683 describes a method where oxygen containing water is injected into the ground water and removing cleansed water from the ground water around or adjacent the point of injection. SU 859322 describes passing the water through a filter or bed which is provided with a negative potential to remove the iron.
It is an object of this invention to provide a solution to the above problems and to provide control measures which should minimise the foregoing factors.
While chlorine is known to be effective in controlling bacteria the invention has an object to provide a simple and economical process for the in situ electric generation of chlorine from the ground water being pumped if it has a high enough chlorine content.
The principle of electrolytic generation of chlorine from salt water or concentrate
REFERENCES:
patent: 3335791 (1967-08-01), Patton
patent: 4088575 (1978-05-01), Hilty
patent: 4256552 (1981-03-01), Sweeney
patent: 4297224 (1981-10-01), Macchiarolo et al.
patent: 5025822 (1991-06-01), Guggisberg
patent: 5035796 (1991-07-01), Saylor et al.
patent: 5103914 (1992-04-01), LaHaye
patent: 5360488 (1994-11-01), Heiatt et al.
patent: 5393433 (1995-02-01), Espana et al.
Hruskoci Peter A.
Minister For Infrastructure
Morrison Betsey J.
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