US2200581A
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Purification of gases by biological means
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Separating of heavy materials from a stream of liquid of varying quantity
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Sludge digestion tank
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Sludge digestion chamber
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GB381799A
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Improvements in and relating to decomposition chambers for sewage sludge
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Settling pond
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GB365630A
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Improvements in and relating to liquid clarification tanks
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Improvements in settling tanks
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US1930457A
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Method of artificially heating sludge digestion chambers
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Method of accelerating the sludge digestion for sewage treatment
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Sewage-treatment plant
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Discharging device for sludge basins
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