The practical scientific ...

The practical scientific method is, as stated by others, the addition of Lime or Sodium Carbonate solution. This is effected by using a smart pH sensor connected to a pH transmitter which sends the pH value to a controller. This controller has a set point and when the solution is above the setpoint, ( ie Alkaline) the controller activates a valve which adds Acid or Sodium Carbonate to the water. When the ph is low or acidic, the controller then opens a damper feeding lime or other alkaline substance into the water. The controller has a split range whereby both valves are closed at centerline ( on setpoint, 12mA output) as the alkalinity increases, so the controller output ramps up from 12 mA, until the water has returned to the setpoint and the controller output is once again center-line, 12mA. If the pH of the water drops, becoming acidic, the controller output drops from 12mA down in a sequence of steps ( controlled by the gain & Integral action settings) , thereby opening the lime or other alkaline substance valve. Once the water has returned to the setpoint, which is normally around 7.1pH ( very slightly Alkaline) this valve will close. Lime needs to flow continually, as it is a substance that solidifies when not flowing in a pipe; as such a 3 way diverter valve or an overflow weir is used to control this dosing action. A normal open/closed control vale will not function due to the coagulation of the lime in the pipe.