Bradley Unwin, Business Development Manager of Lubron Water Technologies ponders alternative water sources for food and drink manufactures.
The Federation House Commitment was very successful in reducing water consumption in food and drink manufacturing by 15% between 2007 and 2014, but the sector is still one of the largest of the UK’s industrial consumers.
Most of that water is taken from potable water supplies, the cost of which continues to rise. The increasing demand for drinking water from a growing population combined with the effects of global climate change mean that water resources are under increasing stress.
Although prices of mains water vary from area to area, the average is about 120p/m 3 so, with one eye on sustainability and one on economics, many food and drink manufacturers are looking for alternative sources of water.
Several alternatives to mains water supplies are available. Subject to a licence from the Environment Agency, water can be abstracted from surface sources or, via wells or boreholes, from underground aquifers.
Rain water harvesting is, increasingly, a good if unreliable option: rainfall is usually too much or too little, so a back-up mains supply is necessary. Then there is the possibility of re-using or recycling wastewater.
Whatever the source, if it is to be used in the manufacturing process, the water will need treatment to meet the Food Standards Agency requirements. That is that the quality of water to be used in food production in England and Wales should at least comply with the Water Supply (Water Quality) Regulations.
At the same time, the sector’s customers – the big supermarkets – have imposed water quality standards for parameters such as nitrates and Cryptosporidium, which are even more onerous than those set in the Regulations, and the cost of compliance has not been inconsiderable. With increasing competition from overseas producers, food and drinks manufacturers need to manage their water resources to minimise costs.
The good news is that private water supplies – even allowing for the cost of water treatment – can be very cost effective.
Groundwaters from wells and boreholes are the preferred option because, having been filtered through underground rock strata, they generally require very little treatment. Where treatment is required, the processes used are relatively low in cost and are simple to operate.
Iron and manganese, two common problem contaminants, are easily removed by aeration and/or pressure filtration using a variety of special catalytic filter media like that in Lubron’s range.
Hardness salts of calcium and magnesium, common in chalk borehole waters, are removed by ion exchange softening or dealkalisation. Other dissolved salts can, if required, be removed by reverse osmosis or ion exchange deionisation.
Surface waters from rivers, lakes and canals contain a much wider range of impurities, including colloidal material that produces turbidity, natural organic matter derived from moorland vegetation, man-made chemicals from industrial effluents and agricultural run-off and a wide variety of microbiological life.
And because surface waters are natural eco-systems, their characteristics vary seasonally. This makes surface waters much more difficult – and more expensive – to treat.
Traditional surface water treatment processes involve dosing chemical coagulants followed by clarification and filtration. These processes are not only temperamental to operate, but take up a great deal of space. The development of low cost microfiltration and ultrafiltration membranes has made these simple to operate processes economically attractive.
Some food and drink manufacturers prefer to use mains supplies for water that comes into contact with their product rather than treating on-site to potable water standards. There are many reasons for this, ranging from ease of compliance to fear of adverse customer reaction to the view that potable water production is not “core business”.
But the FSA standards do not, of course, apply to utility water – that is water used for heating, cooling, CIP and steam raising. Here alternative water sources can be used to replace mains water either partially or completely. Aside from the reduction in mains water costs, there are other potential benefits.
Rainwater is naturally soft and low in total dissolved solids (TDS) so the cost of treatment to boiler make-up or cooling water standards will be drastically reduced, as will the consumption of chemicals for the treatment process.
With a low TDS make-up water, the concentration factor in boilers and cooling towers can be increased which reduces the volume of blowdown water – which contains expensive, and often environmentally unfriendly, conditioning chemicals – discharged to drain.
Reverse osmosis is probably the most widely used water treatment process but the high pressure waste stream, or “concentrate” produced can be a resource. It can be fed very cost effectively into a second reverse osmosis unit, which can produce a permeate of TDS half that of the feed water to the first reverse osmosis unit.
This recovered water can be used as cooling tower make-up and will result in a reduced cooling tower blowdown, once again effecting a saving in water and chemicals. The cooling tower make-up will, of course, be soft so corrosion control will be necessary in the circulating water but, because of the reduced blowdown, the cost will be lower.
Careful management of water resources, in consultation with a specialist water treatment company such as Lubron, can save money by reducing the volume of mains water consumption as well as being kinder to the environment and conserving water resources.