Man-made ponds a success
Purpose-built ponds that provide a safe haven for whitebait are being hailed as a success by Bay of Plenty Regional Council staff, following the results of a recent overnight trapping operation.
The new mixer has been designed to eliminate the problems of crusting and agitation of dairy effluent ponds, he says. It also meets the challenges of high input farms and large effluent ponds.
Reid says the mixer will break up the thickest crust and mix the contents of any shaped effluent pond quickly and efficiently.
“No longer will you be left with a metre or two of sludge at the bottom of your pond that you cannot pump,” he says. “Superior mixing will let you utilise the entire pond, not just the top 70%, enabling you to reclaim back all of your storage pond capacity. No longer will you need multiple mixers on your pond, or mixers that require to be run for long periods of time.”
The mixer is positioned in the centre of the pond on a pontoon. Two opposed mixer blades pointing downwards draw the effluent towards the mixer and create a swirling motion in the pond. Blade speeds are selected depending on the pond dimensions and thickness of the material that requires mixing. The blade speeds are controlled through a variable speed drive that can also be programmed to rotate at slower speeds as the pond level reduces which helps prevent liner damage.
The lower unit, incorporating both propellers, rotates through 360o. It can be locked in eight different ‘stir time’ positions for variable lengths of time (see chart). “We have found that time intervals of between 5-8 minutes per position are best,” says Reid.
These stir times can be altered and programmed with the variable speed drive.
After the pond has been mixed in position #1, the lower unit rotates to position #2 where the change in directional flow ensures it begins mixing a new section of the pond.
When the mixer has moved through its eight different stir positions it has mixed all 360o of the pond leaving no dead or unmixed areas of the pond, irrespective of shape.
The Numedic pond mixer has been operating on a 60 x 20m storage pond since September 2012 where it has been operating well.
Reid says typical responses from farmers are “brilliant” and “performing flawlessly”. He says on one farm, before the Numedic pond mixer was installed the pond had severe crusting with one third of the pond having a 1m thick crust. The rest of the pond had crusting 300-500 mm thick. The mixer broke up the crust in 2.5 hours.
The machine will be supplied with variable speed drives wired up and programmed to suit the buyer’s pond.
Tel. 0800 686 334
