The company quickly offered a solution.
A favoured method is often to add 12.5% chlorine dioxide, e.g. Softchlor or similar, particularly to remove E-coli, but until recently equipment for that was either difficult to set up or temperamental in operation.
Singhs’ proposal was for a system based on its proven series 2-32 Se-Tech dispenser, suitable for injecting 2 - 50 parts per million (ppm) of chlorine dioxide while, importantly, guarding the user against contact with the corrosive and volatile concentrate.
The Singh system can inject at pressures from 10 - 210psi, treat up to 6000L of water per hour and is fully proportional over a wide flow range.
Importantly, most standard concentrate dispensers at best can only dispense at 0.2 - 2% addition rates, which equates to 2000 - 20,000 ppm. But chlorine needs to be added at 2 - 3ppm for maintenance or 50ppm for shock dosing, i.e. at a ratio 40 -- 10,000 times lower than standard dosing capabilities.
Dosing chlorine raises three concerns: the minute amounts required, repeatability and an accurate mix throughout the water sample.
The Se-Tech unit uses three stages to address these concerns.
First is a peristaltic pump to prime a tall, small-diameter tube to a level dictated by an external sensor. That tall tube is attached by a valve to a large calibrated bulk water container, ensuring the small amount of concentrate is mixed with the same volume of water during each milking cycle. From the bulk water container, the pre-mixed high concentrate is dosed into the water system by a modified Se-dispenser, via a fixed standard addition valve.
Bonenkamps have found the apparatus easy to use, importantly delivering a clean, reliable supply to the house, dairy shed and the water troughs on the 70ha property that carries 265 dairy cows.
Operating cost is about $200 per month.
Eric Bonenkamp describes the Singh system as “faultless”.
“In just under two years, we have had three fault warnings, signalled by a red light on the exterior of the pump shed. Sadly, in all three cases the cause was human error: I had forgotten to replace the bulk concentrate container when it was empty.”
