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Water treatment plant (waterzuivering)

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Have you ever wondered where all the rainwater goes? Or the snow, once it melts? Or the water in your sink, tub or toilet after you have used it? This wastewater flows through the underground sewer system to a treatment plant The plant removes most of the pollutants, then releases the water into a lake or river The underground sewer network feeds into a regional intercepter, which is kind of sewer highway that runs to the treatment plant The action begins at the plant's pumping station It doesn't look much much from above but the building extends some fifteen stories below ground right through solid rock The wastewater collects in huge underground wells It's not a pretty sight, it's full of dirt, rubbish and...well you know the rest It also contains high levels of phosphorus a poisonous member of the nitrogen family... ...harmful for waterways because it promotes the growth of algea The water flows from the wells to giant pumps that force it to the surface The plant has backup generators to keep the pumps working in case of a blackout ...and devices the prevent water from backing up, should a pump have to be shut down for servicing Once the wastewater reaches the surface, it flows through the pumping station down discharge channels into the treatment building Along the way it is sprayed with either aluminium sulfate or ferrite chloride... ... two chemical coagulants. They gradually transform phosphorus in the water from liquid the solid so it can be removed later on Once the water reaches the treatment building it flows through screens This preliminary filtration removes any solids larger than 2.5 centimetres in diameter Such things as stones, paper and plastic Giant presses compact this rubbish, squeezing out the excess water Trucks then haul the stuff to a landfill where it's buried The wastewater meanwhile flows into large tanks, called 'grit chambers' Grit refers to the particles in the water, such as gravel... ...that are inorganic, meaning they don't decompose or burn These particles some as tiny as a grain of sand gradually settle to the bottom Then they're pumped out and dropped to the landfill To remove organic particles, mainly phosphorus, they add a polymer a type of chemical compound This demonstration shows what happens Remember as the wastewater left the pumping station it was sprayed with a coagulant That transformed the phosphorus in the water into solid particles The polymer solution completes the process. It binds those particles forming what are called 'flocks' masses of phosphorus that look like snowflakes They are heavier than water, so they sink to the bottom And that's exactly what occurs in the plant's plurifier tanks It takes about two hours for the flocks to settle at the bottom... ...forming a layer of sediment called 'sludge' A system of rakes and pumps collects it and transfers it to the sludge treatment building Unless testing shows a need for additional treatment the clarified, fully-treated wastewater now flows into the outfour, ...a series of channels that discharge into the river In the sludge treatment building they spray the sludge with another type of polymer. This further solidifies it so that the filter presses can more easily squeeze out the water Most of the sludge goes into giant incinerators to be burned The ashes go into a landfill The gas the incinerators emit powers several machines that dry and transform the remaining sludge into pellets These pellets are sold as organic fertilizer When it has arrived at the plant the wastewater was full of contaminants that can harm life Now after treatment it contains 80% less suspended solids and 75% less phosphorus And it also smells a lot better

Video Details

Duration: 5 minutes and 3 seconds
Country: United Kingdom
Language: English
Views: 316
Posted by: mathijs177 on Jan 6, 2011

Nederlands ondertiteld filmpje (wel even CC (closed caption) aanzetten) van How it's made over een waterzuiveringsinstallatie. Geschikt voor 4vwo/havo

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