Purifying River Water for Medical and Food Products with Dynasand(R)
Manufacturing a wide range of paper and non-woven tissue products from medical gowns and masks to tea-bags, Ahlstrom plc's Chirnside plant depends on the quality of its process feedwater.
Ahlstrom Chirnside's Engineering Services and Utilities Supervisor, Manse Young, explains: "The Whiteadder is a typical spate driven river, running through farmland upstream of us. Water conditions can vary widely from almost black to brown and muddy when the farmers are ploughing and, even when clear and low, it has a peat stained character.
"We need 475m3/hr of high purity water to feed our processes, so to ensure it is of the optimum quality, it is dosed with poly aluminium silicate coagulant and then passed through the DynaSand(R) DST50D filters. In this way, we are able to remove all the sediments and silts, and strip out the colouration.
"Provided the recommended daily routine filter checks are completed, the DynaSand® filters do an excellent job and virtually run themselves, with little maintenance and management."
The DynaSand(R) units comprise a sand filter bed held within a hopper into which the water, pre-dosed with coagulant, is pumped via a manifold to deep within the sand. The water flows up through the sand bed, where solids are trapped on the grains of sand, into the open space above the sand, and the cleansed water exits via a weir at the top to a buffer tank.
The sand containing the entrapped solids is continuously air lifted from the bottom of the hopper, washed by a turbulent mixing action, and the clean sand allowed to return to the sand bed at the top to ensure a circular cleansing cycle. The wash water with separated solids is discharged separately for treatment.
The DynaSand(R) filtration plant is packaged with pumps, flowmeters and dosing equipment, in a compact installation. The backwash of extracted colour and other solids is treated in an effluent plant, then compressed with a belt filter and spread on the land locally.
Before discharge from the factory, the process water is treated in the effluent plant and released into the river, at around 10ppm of solids, an important factor as the Whiteadder is a renowned salmon river, and a tributary of the River Tweed.
If you would like any further information on DynaSand(R) filters or any of Hydro International's wastewater, stormwater and sewage treatment systems, please call 0800 269371.
For further information please email Hydro International