Water Treatment Basics – Water Sources

2. Water Sources


(A) How Municipalities Treat Water

  • Clean and filter visible particles
  • Make it safe by disinfecting the water (Primary and secondary disinfection)
  • Make it safe by reducing chemical and heavy metal contamination within guidelines
  • Municipalities are primarily concerned about safety of water


(B) Primary and Residual Disinfection

  • Kills disease-causing microorganisms & makes water safe to drink
  • Primary disinfection can be by chlorine, UV, membranes etc.
  • But water has to travel through long pipes and can get re-contaminated. So a disinfectant is added to keep water safe in the pipes. This is called Secondary disinfection

(C) Primary Disinfection – Chlorination

  • Chlorine is the most common chemical used for water disinfection in Canada because
    • Chlorine is effective against a wide range of microbiological contaminants
    • Chlorine stays with the water through the long distribution pipes from the treatment plant to your home
    • It is cheap & readily available
    • It is very effective against microbes
  • Chlorine renders a bad taste and odour to water – affects taste of beverages & is not good for plants, fish etc.
  • Some people are allergic to chlorine

(D) Primary Disinfection – Chloramination

  • Chlorine can react with some organics and form compounds called TRIHALOMETHANES (THM), which can be potentially carcinogenic. Where raw water has the potential to form THM, municipalities also add AMMONIA to the water in a process called Chloramination
  • Chloramination results in the formation of “Chloramines” (CHLORine + AMMonia)
  • As a disinfectant Chloramines are not as strong as chlorine and thus require longer contact time with water
  • Chloramines are corrosive, toxic to fish and also impart a distinct taste and odour to the water. The long term effects of chloramines on human health are still under study

DUG Wells

  • For individual or small communal use
  • Shallow hole in the ground
  • Sometimes covered with concrete or other slabs but mostly uncovered
  • Bacteria, insects, rodents can get in, some die in it
  • Dirt, mud, leaves etc can also get in
  • Generally low in dissolved minerals
  • What to expect – Generally low in mineral content, but high possibility of bacteria, cyst or fertilizer contamination. Affected by seasonal changes and can be high in suspended dirt


Lake or River water

  • Intake from a lake, river or surface
  • Extremely high possibility of bacteria or cyst contamination
  • Generally affected by seasonal changes and can be high in suspended dirt
  • Can have tannic acids due to decaying vegetation and leaves


Drilled Wells

  • Drilled by professional well drillers
  • Properly covered and protected from insects, rodents and run-off
  • Contamination can still occur from animal waste, fertilizer use etc.
  • As drilled wells are deep, they can be high in dissolved minerals such as hardness or iron
  • What to expect – Generally higher in mineral content (hardness, iron, TDS etc.), not greatly affected by seasonal changes

How are wells connected to homes

  • Drilled wells usually have SUBMERSIBLE pumps (inside the well)
  • Pumps are connected to a pressure tank which has a pressure switch
  • When pressure drops in the tank to a certain point (CUT-IN), the switch signals the pump to come on
  • When the tank is full again, pressure increases (CUT-OUT) and well pump switches off
  • Most pumps operate between 30 – 50 psi, but this is generally adjustable


What is Water Flow Rate and Water Pressure

  • Flow rate is the volume of water that flows through a pipe in a second
    • Measured in gallons per minute (GPM) or LPM
    • Imagine a highway – flow rate would relate to how many cars are moving in a second
  • Pressure is the force required to move the water
    • Measured in psi or Kg/cm2 or kPa (Kilo Pascals)
    • Imagine a highway – pressure would be how fast the car is moving
  • You can have a lot of water flow but low pressure (river) & conversely very little water but very high pressure (pressure washer)


Well Pump Flow Rate

  • This is the amount of water that the well pump pushes to the pressure tank in 1 second
    • Measured in GPM (Gallons per minute or Liters per minute)
  • This is different from “Well Recharge Flow Rate” – this is how quickly the well fills up with water once the pump stops
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