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Fig. 71 A diagràmihatic illustration of the changes in concentiation of the various
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logical system
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haŸe a large surface area, and they should -h_e fai—y
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0.4 in. (2 — 5 mm). The depth of the graVelshould“?b-ë’ün—iforr
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flows evenly through it in all'regi0ns;
develop anae‘robic conditions With ‘c‘osequent
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circulation rate of the
the bed should besuchthatthe
water is not soiich… in-oxy‘gehàS/tO _be —.supersaturated,
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fastenot‘1gh to maintain aer”obiç conditions.
A figure of half a' ga11‘on‘
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mOst easily at theî‘air-‘liftoutputtube “Caremust bei—taken
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