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GB412065A
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Improvements relating to the purification of sewage
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DE523581C
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Digester with facility to destroy the floating sludge
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DE582965C
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Process for the purification of wastewater through gradual biological treatment
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DE484443C
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Device for the biological purification of wastewater with activated sludge
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DE492568C
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Device for accelerated sludge digestion
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DE441851C
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Process for accelerated sludge digestion
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DE494294C
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Device for the biological purification of wastewater with activated sludge
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