DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
Water treatment. Sand filtration lagoon at a water treatment works, covered with floating mats of the green alga Cladophora. The excessive algal growth indicates contamination by nitrates & phosphates from agricultural fertilisers. The water undergoes initial cleaning in sedimentation tanks before being pumped into the filtration lagoons. The bed of the lagoon is a thick layer of sand containing hosts of water fleas & protozoa which consume the algae in the water. The water filters down through the sand & is then chlorinated & fed into the mains supply. Photo taken at Ormesby water works, Norfolk, which supplies the Great Yarmouth area with drinking water taken from the Norfolk Broads.
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