Patent Application
20100288698
Pursuant to 35 U.S.C. §119 and the Paris Convention Treaty, this application claims the benefit of Chinese Patent Application No. 200910115350.1 filed May 15, 2009, the contents of which are incorporated herein by reference.
1. Field of the Invention
The invention relates to a method for removing phosphorus, and more particularly to a method for removing phosphorus using a membrane bioreactor and without sludge discharge.
2. Description of the Related Art
Conventional methods of phosphorus removal mainly focus on a biochemical process which requires a combination of a facultative aerobic condition and an aerobic condition. Under an aerobic condition, phosphorus-accumulating microorganisms in the sludge absorb phosphorus in a large amount. Subsequently, the sludge flows to an anaerobic zone or a facultative aerobic zone where the absorbed phosphorus is released, and then part of sludge is discharged so as to remove phosphorus from the sewage treatment system. The method for removing phosphorus is based on the sludge discharge from the system, so it has the following disadvantages:
Accordingly, in view of the above-described problems, it is one objective of the invention to provide a method for removing phosphorus that need not discharge sludge and occupies a small area.
To achieve the above objectives, in accordance with one embodiment of the invention, there is provided a method for removing phosphorus, the method comprising
In a class of this embodiment, the aerobic zone is about less than one third by volume of the whole reaction zone of the membrane bioreactor, and the rest is the facultative aerobic zone or the anaerobic zone.
In a class of this embodiment, the aeration is in a manner of blower aeration or jet aeration with a gas-water ratio of less than 19:1.
Upon aeration, the sludge flows circularly along the aerobic zone, the facultative aerobic zone, and the anaerobic zone, which provides a biochemical reaction environment of phosphorus absorption at aerobic zone, phosphorus release at facultative aerobic zone, and phosphorus removal by gasification process at anaerobic zone. The proliferation and self-digestion of the sludge can maintain in a dynamic equilibrium, so no sludge needs to be discharged.
In a class of this embodiment, phosphine-reducing bacteria in the sludge are filtered by a membrane material having a pore size of between 0.01 and 10 μm and retain in the membrane bioreactor.
In embodiment of the invention, inorganic phosphorus is firstly transformed into organic phosphorus by microorganisms for cell synthesis. The organic phosphorus is reduced by phosphine-reducing bacteria and transformed into phosphine in the anaerobic zone. The phosphine is treated by an aeration system.
Advantages of the invention are summarized as below. In embodiment of the invention, the aeration intensity is concentrated on the lower part of the membrane module, so an aerobic zone is formed, which provides a biochemical reaction condition for phosphorus absorption and cell synthesis. Subsequently, the sludge flows to the upper part of the membrane module where dissolved oxygen is little and phosphorus is released. By the filtration of the membrane module, the phosphine-reducing bacteria are accumulated and multiply in the bioreactor, which prompts the phosphorus removal of gasification process and no sludge discharged.
The invention is described hereinbelow with reference to accompanying drawings, in which:
For further illustrating the invention, experiments detailing a method for removing phosphorus that need not discharge sludge and occupies a small area are described below. It should be noted that the following examples are intended to describe and not to limit the invention.
In a membrane bioreactor comprising a membrane module having a lower part, the lower part of the membrane module is aerated intensively, and the dissolved oxygen concentration around the membrane module is more than 2 mg/L and the dissolved oxygen concentration in the rest zone less than 1 mg/L. Thus, an aerobic, zone, a facultative aerobic zone, and an anaerobic zone are formed respectively (as shown in
Using filtration at the membrane module, phosphine-reducing bacteria are accumulated and multiply in the bioreactor, which provides conditions for phosphorus removal of gasification. The following is the process of the biochemical reaction:
Thus, the invention provides a novel method for removing phosphorus by gasification process, no need to discharge sludge.
EXAMPLE 1
In a sewage treatment plant, the daily sewage treatment is 80 m3/d. The membrane bioreactor is facultative aerobic, and the treatment process adopts the method of the invention, involving in no sludge discharge. The TP concentration of the sewage is monitored, and the effect of phosphorus removal is as follows.
The mean value of total phosphorus of influent is 2.82 mg/L, and that of effluent is 0.84 mg/L, the mean value of phosphorus removal is 1.98 mg/L. The total phosphorus content in the sludge is between 1.22% and 1.69%, with mean value of 1.49%. This is equivalent to phosphorus removal by a conventional biochemical process, and phosphorus is not accumulated in the sludge. Although no sludge discharged, the total phosphorus loss reaches 70%. Monitoring the gas at the top of the treatment system shows the phosphine content is between 1 and 3 ppm, which is much higher than that in the air (0 ppm). Thus, without sludge discharge, the phosphorus is successfully removed using a gasification process.
While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200910115350.1 | May 2009 | CN | national |
