Water and Effluent Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/831969
14 WET NEWS JUNE 2017 Much of modern life, especially its technology, is about speed. However, with climate change having a growing impact on our water – increasing the risks from disease-causing pathogens such as Legionella, Giardia lamblia, and Cryptosporidium – is it time we renewed our interest in a slower technology? Ryan Jackson, from CDEnviro, certainly thinks some things are worth waiting for. Puriing water through the sands of time INSIGHT Water treatment W ater is vital for life, but unless it is clean, it contains many hidden dangers. The World Health Organization (WHO) reports that there are more than 1,415 species of infectious organisms known to be pathogenic to humans. It states: "Many of these organisms are associated with diseases that have been known for many years, a small but significant percentage are associated with more recently emerged diseases, such as Acquired Immunodeficiency Syndrome (AIDS), Ebola and Severe Acute Respiratory Syndrome (SARS)." These disease-causing agents are passed on through food, water and animals. Climate change may be allowing certain diseases to proliferate as extreme changes wreak havoc THE CONCEPT • The slow sand filtration method is the most effective way to ensure water quality • The sand and biolayer is submerged in water allowing organisms to eat potentially harmful pathogens • The new screening technology ensures a consistent supply of clean, dry filter sand, of uniform size • New high-frequency screens use vibrations to move the screen. NEED TO KNOW 1 Surface tension means screening flowrates in more traditional static screens are reduced to what can be forced through under pressure 2 High performance, high efficiency materials recovery and recycling systems have been developed to reduce waste to landfill 3 There are more than 1,415 species of infectious organisms known to be pathogenic to humans 4 Climate change may be allowing certain diseases to proliferate as extreme changes wreak havoc with the waters and animals THE VERDICT "Developing and implementing new technology that is faster and smaller is often the right thing to do… sometimes, speed really is not the essence and it is worth taking the time to achieve the right result" Ryan Jackson with the waters and animals that host some of our deadliest diseases, so it is important that steps are taken to ensure the safety of our water. Negative impacts There are circumstances where newer forms of water filtration, such as electro dialysis and reverse osmosis, can be very effective, for example when budget is not the main issue or water of an extremely high quality is required from poor quality raw materials. However, choosing the wrong water purification method, even if it is the latest technology, can have serious negative impacts on our health. The WHO says: "More o'en than not, new technologies have a neutral impact on the ecology of pathogens, but some technologies accidentally introduce new routes of exposure between humans and pathogens. This is particularly evident when dealing with technologies that are used in water treatment, storage and distribution." Slow sand filtration may seem old fashioned and as its name suggests, slow, but its effectiveness at removing pathogens from drinking water before they enter the distribution system has been reliably demonstrated for many decades and in many places. So how does it work? The water filtration process takes place over a large surface area, with wastewater treatment works' having several large beds, and involves the formation of a biofilm of living organisms on top of a fine layer of sand. • High efficiency materials recovery and recycling systems have reduced waste to landfill Contaminated water gets biologically treated Through the process, contaminated water not only gets physically filtered but biologically treated meaning both sediment and pathogens are removed. The sand and biolayer is submerged in water allowing the organisms to eat potentially harmful pathogens, while clean, potable water filters through the membrane. Slow sand filtration systems are characterised by a high reliability and comparatively low lifecycle costs. Their simple nature also means they can be established and maintained with a basic level of skills and equipment. High performance Why isn't it more widely used? One major drawback of the slow sand filtration process is that it