| 摘要 |
The present invention relates to a process and a treatment system for biologically removing phosphorus and nitrogen from wastewater. In the anaerobic contact and settlement zone 1, wastewater 7 is first mixed with the returned activated sludge 8 to form a mixed liquor which is then allowed to settle in zone 1, and organic matters present in influent are mostly taken up by the sludge. The supernatant from zone 1 is passed through an aerobic reaction zone 2, furnished with packings, for complete nitrification; the settled sludge from zone 1 is hold in an anaerobic zone 3 for a sufficient period of time for controlling the sludge carbohydrate content to low levels in order to enlarge the sludge capacity for phosphorus removal because the extended anaerobic sludge degradation in zone 3 is very effective in controlling the sludge carbohydrate content to low levels. The sludge from zone 3 is then allowed to be remixed with the nitrified supernatant from zone 2 in zone 4, where the products of the extended anaerobic reaction allowed very high denitrification rates and efficiencies. The aerobic zone 5 is supplemented to complete phosphorus uptake by the activated sludge, in which the dissolved oxygen (DO) level is controlled at relatively low levels in order to limit the aerobic synthesis of sludge carbohydrate. The aerated mixed liquor is then transferred into a final clarifier where settled sludge is separated from purified supernatant. At least a portion of the settled sludge is recycled back to zone 1 to be mixed with raw wastewater, while a portion of the settled sludge is wasted.
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