Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2001-12-10
2003-05-27
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S613000, C210S623000, C210S742000, C210S743000, C210S758000
Reexamination Certificate
active
06569334
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for a high-concentration incubation of nitrifying bacteria (marine nitrifying bacteria and freshwater nitrifying bacteria) or denitrifying bacteria (marine denitrifying bacteria and freshwater denitrifying bacteria) using activated sludge as a raw material, to an incubation promoter used therefor and to a method for a weight reducing treatment of the activated sludge.
BACKGROUND OF THE INVENTION
With regard to a method for the elimination of pollution by nitrogen, particularly by ammonia, in an aqueous system, there are a physicochemical method and a method utilizing organisms.
Examples of the physicochemical method are an ammonia stripping method, a discontinuous point chlorine injection method, a zeolite method and an ion-exchange method.
However, in those methods, there are many problems in view of the efficiency and the secondary environmental pollution due to by-products.
On the other hand, with regard to a method utilizing organisms, it has been well known that a method by treating with microorganism using nitrifying bacteria (ammonia oxidizing bacteria and nitrite oxidizing bacteria) and denitrifying bacteria (nitrate oxidizing bacteria) is most useful. Harmful residual nitrogen in an aqueous system is accumulated as nitrate ion as a result of action of nitrifying bacteria under aerobic environment, reduced to safe nitrogen gas by denitrifying bacteria under anaerobic environment and exhausted into air.
However, nitrifying bacteria have a slow growing rate and do not live by means of formation of colonies and, therefore, there has been no report on the success in a high-concentration incubation in a large quantity in an industrial scale up to the present time where more than one hundred years have passed since their presence was confirmed.
Thus, the conventional incubating method is in a small scale of a test tube level with an object of pure culture and, in the case of incubation of about two months, the result is that the medium in a flask is not suspended whereby it is not an incubating method which can be applied in industry.
To be more specific, when nitrification begins in the incubation of nitrifying bacteria, pH lowers and, until now, no method for an effective increase in the pH has been known. On the other hand, carbon sources decrease as a result of nitrification and, until now, carbon dioxide has been used for supplying the carbon source. Although it is of course possible to prevent the exhaustion of carbon sources when carbon dioxide is supplied, the above-mentioned lowering of the pH further proceeds by that whereupon activity of the nitrifying bacteria stops and that is a limit of the growth of the bacteria.
DISCLOSURE OF THE INVENTION
Reference to the Deposited Biological Materials
(1) Name of the Depository Institution: Patent Microorganism Depository Center, National Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, MITI
Address: Postal Code 305-0046
1-1-3 Higashi, Tsukuba-shi, Ibaraki-ken, Japan (Telephone: 0298 54 6029)
(2) Deposited Date: Apr. 27, 2000
(3) Accession Number: FERM BP-7150
The present invention relates to a method for the incubation of nitrifying bacteria in a high concentration which are contained in a few amounts in activated sludge such as sewage sludge and excrement sludge and is a method for a high-concentration incubation of nitrifying bacteria which is characterized in that the above-mentioned activated sludge is subjected to nitrification and acclimation culture by a liquid containing NH
4
—N for a predetermined period under such a condition that that dissolved oxygen is not less than 2 mg/liter, pH is 7.0-9.0 and temperature is 20-40° C. and, at the same time, the pH which is apt to tend to an acid side during the process of acclimation culture is constantly maintained within the above-mentioned range by addition of an incubation promoter comprising a mixture of sodium carbonate and sodium hydrogen carbonate whereby the nitrifying bacteria contained in the above-mentioned sludge are subjected to acclimation culture and are accumulated.
The present further relates to a method for the incubation of denitrifying bacteria in a high concentration which are contained in a few amounts in activated sludge such as sewage sludge and excrement sludge and is a method for a high-concentration incubation of denitrifying bacteria which is characterized in that the above-mentioned activated sludge is subjected to denitrification and acclimation culture by a liquid containing NO
3
—N for a predetermined period under such a condition that dissolved oxygen is not more than 2 mg/liter, pH is 6.0-9.0, temperature is 10-40° C. and ROH (R is CH
3
— and/or C
2
H
5
—) is present as an external carbon source whereby the denitrifying bacteria contained in the above-mentioned activated sludge are subjected to acclimation culture and are accumulated.
In accordance with the present invention, it is now possible to incubate the nitrifying bacteria or the denitrifying bacteria in a large quantity and also in a high concentration.
Activated Sludge
Examples of the activated sludge used in the present invention are sewage sludge and excrement sludge. They may be either subjected to a diluting treatment with fresh water or subjected to a diluting treatment with sea water but, when nitrifying bacteria or denitrifying bacteria are incubated using a sludge diluted with sea water as a raw material, marine nitrifying bacteria and marine denitrifying bacteria which are of scarcity values can be obtained in large quantities and, therefore, it is appropriate to use an activated sludge which is diluted with sea water.
To be more precise, in natural sea water, there are marine nitrifying bacteria which are believed to have higher resistance to salt than freshwater nitrifying bacteria but, since their amount is very small and their separation in a pure state is difficult, studies thereof are in the rear of freshwater nitrifying bacteria. However, in accordance with the incubating method of the present invention, the activated sludge which is diluted with sea water as mentioned already is used whereby it is possible to prepare the marine nitrifying bacteria of a high concentration. The marine nitrifying bacteria are equipped with multi-layered cell walls and have a strong resistance to changes in osmotic pressure and to various chemical substances which inhibit the growth.
Incubating (Acclimation Culture) Conditions for Nitrifying Bacteria
In the incubation of nitrifying bacteria contained in activated sludge, the said activated sludge is subjected to nitrification and acclimation culture for a predetermined period (for example, for one month, two months or three months) using waste liquid in sludge treatment such as dehydrated filtrate of sludge and (anaerobic) digested eluate and, since the nitrification and acclimation culture are to be carried out aerobically, it is necessary to make the dissolved oxygen (DO) at that time 2 mg/liter or more. However, it has been firstly found by the experiment at this time that, when the dissolved oxygen concentration is made too high, the growing speed rather tends to lower. That will be illustrated in detail as hereunder.
The more the dissolved oxygen, the quicker the nitrifying speed by the nitrifying bacteria. Therefore, it has been believed that the more the dissolved oxygen, the quicker the nitrification and the acclimation culture as well but, quite unexpectedly, it has been found now that speed of the acclimation culture and the accumulation lowers when the dissolved oxygen (DO) is more than about 5 mg/liter. Incidentally, it is most preferred that the dissolved oxygen (DO) concentration is 2-4 mg/liter.
It is also necessary that pH is 7.0-9.0 and (,especially when activated sludge diluted with sea water is used,) the pH is preferably 7.5-8.5 and, more preferably, 7.5-7.8.
With regard to the temperature for incubation, growing speed is high when it is within a range of 20-40° C. and the range of 25-35° C. is more preferred.
Incide
Barry Chester T.
Bicom Corporation
Jordan & Hamburg LLP
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