高考英语押题作文素材：水的净化 Water Purification
<p> 水的净化(<span word="Water">Water</span> <span word="Purification">Purification</span>)</p><p> <span word="The">The</span> <span word="provision">provision</span> <span word="of">of</span> <span word="safe">safe</span> <span word="water">water</span> <span word="necessitates">necessitates</span> <span word="one">one</span> <span word="of">of</span> <span word="the">the</span> <span word="rnajor">rnajor</span> <span word="expenditures">expenditures</span> <span word="of">of</span> <span word="manpower">manpower</span> <span word="and">and</span> <span word="revenue">revenue</span> <span word="in">in</span> <span word="our">our</span> <span word="modern">modern</span> <span word="cities">cities</span>. <span word="The">The</span> <span word="purification">purification</span> <span word="of">of</span> <span word="water">water</span> <span word="is">is</span> <span word="basically">basically</span> <span word="a">a</span> <span word="two">two</span>-<span word="step">step</span> <span word="or">or</span> <span word="three">three</span>-<span word="step">step</span> <span word="process">process</span> <span word="carried">carried</span> <span word="out">out</span> <span word="under">under</span> <span word="the">the</span> <span word="strict">strict</span> <span word="supervision">supervision</span> <span word="of">of</span> <span word="public">public</span> <span word="health">health</span> <span word="scientists">scientists</span> <span word="and">and</span> <span word="engineers">engineers</span>.</p><p> <span word="As">As</span> <span word="the">the</span> <span word="first">first</span> <span word="step">step</span>, <span word="natural">natural</span> <span word="water">water</span> <span word="from">from</span> <span word="the">the</span> <span word="least">least</span> <span word="contaminated">contaminated</span> <span word="source">source</span> <span word="is">is</span> <span word="allowed">allowed</span> <span word="to">to</span> <span word="stand">stand</span> <span word="in">in</span> <span word="large">large</span> <span word="reservoirs">reservoirs</span>, <span word="where">where</span> <span word="most">most</span> <span word="of">of</span> <span word="the">the</span> <span word="mud">mud</span>, <span word="clay">clay</span>, <span word="and">and</span> <span word="silt">silt</span> <span word="settle">settle</span> <span word="out">out</span>; <span word="this">this</span> <span word="is">is</span> <span word="called">called</span> "<span word="sedimentation">sedimentation</span>". <span word="Often">Often</span> <span word="in">in</span> <span word="water">water</span> <span word="with">with</span> <span word="high">high</span> <span word="mud">mud</span> <span word="content">content</span>, <span word="lime">lime</span> <span word="and">and</span> <span word="aluminum">aluminum</span> <span word="sulfate">sulfate</span> <span word="are">are</span> <span word="added">added</span> <span word="to">to</span> <span word="the">the</span> <span word="water">water</span> <span word="in">in</span> <span word="the">the</span> <span word="settling">settling</span> <span word="reservoirs">reservoirs</span>. <span word="These">These</span> <span word="chemicals">chemicals</span> <span word="react">react</span> <span word="in">in</span> <span word="the">the</span> <span word="water">water</span> <span word="to">to</span> <span word="form">form</span> <span word="aluminum">aluminum</span> <span word="hydroxide">hydroxide</span>, <span word="which">which</span> <span word="settles">settles</span> <span word="slowly">slowly</span> <span word="and">and</span> <span word="carries">carries</span> <span word="much">much</span> <span word="of">of</span> <span word="the">the</span> <span word="suspended">suspended</span> <span word="material">material</span>, <span word="including">including</span> <span word="most">most</span> <span word="of">of</span> <span word="carries">carries</span> <span word="much">much</span> <span word="of">of</span> <span word="the">the</span> <span word="suspended">suspended</span> <span word="material">material</span>, <span word="including">including</span> <span word="most">most</span> <span word="of">of</span> <span word="the">the</span> <span word="bacteria">bacteria</span>, <span word="to">to</span> <span word="the">the</span> <span word="bottom">bottom</span> <span word="of">of</span> <span word="the">the</span> <span word="reservoirs">reservoirs</span>. <span word="As">As</span> <span word="the">the</span> <span word="second">second</span> <span word="step">step</span>, <span word="the">the</span> <span word="water">water</span> <span word="is">is</span> <span word="filtered">filtered</span> <span word="through">through</span> <span word="beds">beds</span> <span word="of">of</span> <span word="sand">sand</span> <span word="and">and</span> <span word="grovel">grovel</span>, <span word="which">which</span> <span word="remove">remove</span> <span word="other">other</span> <span word="impurities">impurities</span> <span word="and">and</span> <span word="chemicals">chemicals</span> <span word="in">in</span> <span word="it">it</span>. <span word="During">During</span> <span word="or">or</span> <span word="after">after</span> <span word="filtration">filtration</span>, <span word="chemicals">chemicals</span> <span word="are">are</span> <span word="ordinarily">ordinarily</span> <span word="added">added</span> <span word="to">to</span> <span word="the">the</span> <span word="water">water</span> <span word="to">to</span> <span word="kill">kill</span> <span word="any">any</span> <span word="remaining">remaining</span> <span word="harmful">harmful</span> <span word="bacteria">bacteria</span>. <span word="Chlorine">Chlorine</span> <span word="is">is</span> <span word="one">one</span> <span word="of">of</span> <span word="the">the</span> <span word="most">most</span> <span word="common">common</span> <span word="chemicals">chemicals</span> <span word="used">used</span> <span word="for">for</span> <span word="this">this</span> <span word="purpose">purpose</span>. <span word="A">A</span> <span word="third">third</span> <span word="step">step</span> <span word="taken">taken</span> <span word="by">by</span> <span word="some">some</span> <span word="rmnicipalities">rmnicipalities</span> <span word="is">is</span> <span word="adding">adding</span> <span word="to">to</span> <span word="the">the</span> <span word="water">water</span> <span word="other">other</span> <span word="beneficial">beneficial</span> <span word="chemicals">chemicals</span> <span word="such">such</span> <span word="as">as</span> <span word="fluoride">fluoride</span> <span word="to">to</span> <span word="make">make</span> <span word="tooth">tooth</span> <span word="enamel">enamel</span> <span word="hard">hard</span>, <span word="and">and</span> <span word="soda">soda</span> <span word="ash">ash</span> <span word="to">to</span> <span word="make">make</span> <span word="the">the</span> <span word="water">water</span> <span word="itself">itself</span> <span word="soft">soft</span>.</p><p> <span word="The">The</span> <span word="water">water</span> <span word="purification">purification</span> <span word="process">process</span>, <span word="carried">carried</span> <span word="out">out</span> <span word="with">with</span> <span word="little">little</span> <span word="variation">variation</span> <span word="from">from</span> <span word="one">one</span> <span word="large">large</span> <span word="city">city</span> <span word="to">to</span> <span word="another">another</span>, <span word="is">is</span> <span word="perhaps">perhaps</span> <span word="the">the</span> <span word="biggest">biggest</span> <span word="factor">factor</span> <span word="in">in</span> <span word="the">the</span> <span word="prevention">prevention</span> <span word="of">of</span> <span word="major">major</span> <span word="outbreaks">outbreaks</span> <span word="of">of</span> <span word="disease">disease</span> <span word="in">in</span> <span word="this">this</span> <span word="country">country</span>.</p>
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