Will raising pH of well water cause minerals to precipitate?
Published on by Terrence Magee in Social
Current well water has a pH of 6.2 and is corroding copper pipes. It is also high in iron and manganese. Will raising the pH with a calcite upflow system cause the minerals to fall out of suspension and create other problems?
Taxonomy
- Treatment
- Water Quality
- Water Wells
- Infrastructure
- Corrosion Prevention
- Pipes and Pipelines
7 Answers
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Hi Terrence,
The optimal pH for your water will be 8 to 8.3. At this pH you will eliminate the problem with copper pipe corrosion and will not cause a signficant preciptation of minerals on the pipe walls. You will observe problems with signficant scaling above pH of 8.6.
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Please take a look at this reference.
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Check if the pipelines are properly grounded. At pH 6 water is not buffered, pH excursion, high chloride if this is a possibility and dissolved oxygen could be causing pitting. Calcite contactor could be tried out. The process would be slow. Precipitation of ferric hydroxide is unavoidable at pH 7-7.5 corrosion. Mn+4 precipitates > pH 9.5, may not be an issue. Your target pH of water should be 7.7-7.8; this will give about 70-80 ppm bicarbonate hardness. LSI turns positive. If calcite contactor does not work you can try injection of controlled quantity of lime water and CO2 injection keeping final pH
1 Comment
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In addition to my commments above , please look at this reference. http://www.fwr.org/copper.pdf. Under deposit corrosion of iron and manganese is also a possibility.
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I would agree and suggest raising the pH to a level just below 7. But again, it depends upon what is in the water.
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Various parameters determine the corrosion - scaling balance in water. This can be assessed by calculating the Langelier Saturation Index (LSI) or Ryznar Stability Index (RSI).
1 Comment
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I agree
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Depends on high the pH as well as the bicarbonate level in the water.
If the pH can be kept to no higher than 7, should be OK with regard to both corrosion and precipitation.
Another option is the oxidize the Fe and Mn with chlorine and filter them out.
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It might if the water comes in contact with some type of oxydizing agent like air, chlorine or dissolved oxygen contains in water. Manganese will need a pH around 8 before to precipitate while iron will be around 7.