Total Hardness and Total Alkalinity in Water

Taxonomy

• Treatment Methods
• Water Softener
• Drinking Water Treatment
• Alkaline
• Reverse Osmosis
• Water Treatment Solutions
• Brackish Water
• Drinking Water
• Minerals
• water treatment
• Water Hardness

11 Answers

1. Geographical formation is the cause, although the previous usage of land it might be a cause. In short you need to conduct visibility study of the area and you can get the cause of the high values of parameter. 

2. Geographical formation is the cause, although the previous usage of land it might be a cause. In short you need to conduct visibility study of the area and you can get the cause of the high values of parameter. 

3. Brackish water is a mixture of salt water and river water.  The total hardness is present from both of these sources and consists of Calcium and Manganese.  Not measured in the hardness but relevant is the sodium content.  The alkalinity, as Mr Amiri says, consists of hydroxide and carbonate.  Water sources rising in granite will have a low total alkalinity because the carbonate level is low but will have non-carbonate ions such as chloride, silicate and sulphate.  In brackish water the chloride level will be relatively high in proportion to the total hardness because it is in the form of sodium (salt).  The level of 517 microsiemens would suggest that proportion of water with high alkalinity water is low because sodium chloride rapidly increases the conductivity of the water.  A water from a "soft water" area will have a conductivity between 100-150 microsiemens and may only have a total alkalinity of between 10-30 ppm.  A harder water may have a conductivity of 350 -400 microsiemens and have an alkalinity of 150-200 ppm.   Some of this will be carbonate alkalinity while some will be non-carbonate alkalinity.  If a water comes from chalk for a conductivity of 400 microsiemens almost all of the total hardness will be bound to carbonate alkalinity.  So it depends on the water source flowing to the site where the brackish water forms.

4. There is no relation between alkalinity and hardness.

   If acidic water is mixing with water body, alkalinity will get reduced.

5. Alkalinity is a measurre of buffering capacity of water and it is made of hydroxide and carbonate controbutes to the buffering capacity.

   Hardness is a measure of concentrations of divalent metal ions such as calcium, magnesium, etc.

   So, there are no reasons to expect the to be the same.

6. Is it possible taht CaCl2 as well as NaCl are not rejected ?

   Is this an indicator of membranes damages! 

   1 Comment

   1. The RO produced water quality is depending on Feedwater quality, Membrane quality, reject ratio and operating pressure. At higher salty feedwater, higher operating pressure, lower rejection and lower membrane separation quality, there will be higher TDS (including hardness, alkalinity, chlorides or whatever exists in feedwater) on produced water. 

7. There are other non-carbonate anions. You need to get full analysis of water quality done. 

8. It is due to Feedwater quality. There is high concentration of CaCl (salty water), a part of which is passing to Product water through the membranes. If you measure the Chloride concentration you can verify that. 

   1 Comment

   1. The alkalinity is around 27, TH around 47, chloride may be 35. pH is around 6.7

      2 Comment replies

      1. You can increase the rejection of water to minimize the pressure, in order to minimize these values. 

      2. Exactly! If you take into account the equivalent weights of Ca, CaCO3 and Chloride, you will find that there is CaCl in produced water. 

9. alkalinity makes apparent hardness and hardness makes apparent alkalinity that added to hardness and alkalinity make totals respectively; of course pH and temp ever affect water quality

10. What is your pH?  Since it is RO permeate, somewhere 5-6?  Lower pH causes carbonate ions to convert to CO2.  It will show up as conductivity, but not alkalinity. 

11. It is probably due to calcium and magnesium cations being bound to non carbonate anions in the water like Cl, SO4, and others, increasing your total hardness concentration but not your alkalinity.