According to laws enforced by the UK Environment Agency, effluents containing phosphates cannot be discharged directly into water bodies as it can cause problems with aquatic life.
Water companies are required to treat effluents in order to remove phosphates, often using ferric sulphate or ferric chloride. It is important that the dose rate is accurate, as high iron content would result in a fine from the UK Environment Agency.
Dosing chemicals to remove phosphates often change the pH balance of the final effluent. Sodium hydroxide or lime is often dosed alongside to balance this change in pH.
The control and measurement of the pH level is directly linked to the dosing speed and controls offered on the pump.
Dosing and circulation of lime
At numerous water treatment plants in the UK, Verderflex dosing pumps have been supplied to circulate lime mixture in the tank. The VF hose pump is used to keep the lime slurry blend, mixed to the required state. This unit was specifically chosen due to the duty level the VF dosing pump could provide to circulate the fluid from the base to the top of the tank. The suction properties of the VF dosing pump ensured there were no dead spots in the base of the tank and the working principle guaranteed there were no blockages and a long MTBF.
The homogenous state of the mixture meant less lime chemical was wasted in the tank and a consistent fluid was being delivered by the dosing system.