JP2004049941A - Treatment method and apparatus for combined sewage under rainy weather - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize solid-liquid separated sludge discharged from a solid-liquid separator for sewage under rainy weather to improve the effect of biological dephosphorization and denitrification treatment of the sewage. <P>SOLUTION: The treatment method comprises coagulating and separating at least part of the sewage under rainy weather and feeding the coagulated and separated sludge to an anaerobic section or a biological denitrification section of a biological dephosphorization step of a sewage treatment facility. After the coagulated and separated sludge is subjected to acid fermentation, the sludge is fed to the anaerobic section or biological denitrification section of the biological dephosphorization step of the sewage treatment facility. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a purification and denitrification treatment apparatus for rainwater overflow (abbreviated as CSO) of a combined sewer system containing organic suspended particles, or an increased amount of sewage flowing into a sewage treatment facility.
[0002]
[Prior art]
Recently, the pollution load of public water bodies due to rainfall overflow (CSO) in a combined sewer has become a major problem. Since the stormwater overflow (CSO) of the combined sewer system generates an enormous amount of water in a short time, solid-liquid separation can be performed at a high speed, and a technology of discharging treated water from which SS has been removed to a public water area is applied. .
[0003]
In addition, since the amount of sewage during rainy weather that flows into the sewage treatment facility increases more than that during fine weather, a portion corresponding to the amount of sewage during fine weather, which is a part of the sewage 1 during rainy weather, will be described with reference to FIG. Was first settled and separated in the sedimentation basin 2 and then activated sludge treatment in the activated sludge treatment step 4, and the remaining sewage 1a was discharged as it is to the public water area as effluent water, but recently, as shown in FIG. A method of coagulating and separating the remaining sewage 1a in the coagulation / separation step 16 and discharging the separated water 17 is being studied. FIG. 2 is a block diagram showing a recent rainy sewage system in which coagulation and separation are performed on the remaining sewage 1a, and reference numeral 6 denotes a final sedimentation basin.
However, any of the recent methods for treating and coagulating and separating sludge is applied to a method in which the coagulated and separated sludge 18 flows into the first sedimentation basin 2 of the sewage treatment plant, is separated and separated, and the sludge is treated. Effective utilization of coagulated and separated sludge has not been studied.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and is intended to improve the biological dephosphorization and denitrification treatment effects of coagulated and separated sludge discharged from a coagulation and separation device for sewage in rainy weather. The task is to provide new concepts that can be used effectively.
[0005]
[Means for Solving the Problems]
The present invention has solved the above problem by the following means.
(1) A combined type wherein at least a part of sewage in rainy weather is coagulated and separated, and the coagulated separated sludge is supplied to an anaerobic part or a biological denitrification part in a biological dephosphorization step of a sewage treatment facility. Sewage treatment method.
(2) The sewage treatment method according to (1), wherein after the coagulated and separated sludge is subjected to acid fermentation, the sludge is supplied to an anaerobic part or a biological denitrification part in a biological dephosphorization step of a sewage treatment facility. .
[0006]
(3) A treatment apparatus for purifying an increased combined sewage in rainy weather, wherein the coagulation / separation apparatus introduces at least a part of the increased inflow sewage in rainy weather and separates it into separated water and coagulated / separated sludge; A pipe for discharging water, a first sedimentation basin for introducing a part of the inflow sewage and separating it into separated water and sedimentation sludge, and a separated water from the first sedimentation basin and a coagulated sedimentation sludge from the coagulation separation device. Anaerobic part to introduce and dephosphorize, denitrification part, or anaerobic aerobic biological dephosphorization equipment having an aerobic part, and treated water by introducing dephosphorized water containing sludge from the dephosphorization equipment A combined sewage treatment apparatus for rainy weather, comprising: a final sedimentation tank that separates into sedimentation sludge.
(4) The coagulation / separation sludge from the coagulation / separation apparatus is introduced into an acid fermentation tank, and a pipe is provided to send the acid fermentation sludge from the acid fermentation tank to an anaerobic section of an anaerobic-aerobic biological dephosphorization facility. (3) The combined sewage treatment apparatus for rainy weather according to (3).
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of the combined sewage treatment apparatus in rainy weather of the present invention.
Portions having the same functions as those shown in FIG. 2 are denoted by the same reference numerals.
[0008]
A coagulant (an inorganic coagulant, a polymer coagulant, or a combination thereof) is added to a part 1a of the sewage 1 in rainy weather, and coagulated and separated in the coagulation separation step 18. As the coagulation separation method, for example, any of coagulation sedimentation, coagulation flotation separation, coagulation filtration using a sparse filter, and the like are applied. In the coagulation separation step 18, the separation water 19 from which SS, phosphorus, SS BOD and COD of the sewage 1a during rainy weather have been removed is separated from the coagulation separation sludge 20 which is rich in organic matter in the sewage.
On the other hand, the remainder of the sewage during rainy weather 1 is initially settled in a sedimentation basin 2 and SS is separated to some extent. After activated sludge treatment by a denitrification step (also referred to as “biological nitrification denitrification process” in the sense of a method) 13, activated sludge is precipitated and separated from the activated sludge mixture 6 in a final sedimentation tank 7 and treated water 8 It becomes.
[0009]
However, in rainy weather, the organic matter supplied to the biological dephosphorization process 12 or the biological nitrification denitrification process 13 is diluted by rainwater, and the concentration of the organic matter decreases. However, there is a problem that the phosphorus removing effect is deteriorated. In addition, there is a problem that the denitrification reaction does not sufficiently proceed due to a shortage of an organic carbon source for the denitrifying bacteria.
[0010]
The point of the present invention is that the coagulated and separated sludge 20 is supplied to the anaerobic section 14 of the biological dephosphorization process 12 or the denitrification section 15 of the biological nitrification and denitrification process 13, and the abundant organic matter in the coagulated and separated sludge 20 is supplied. Is used as a phosphorus release promoting biodephosphorus bacterium or a hydrogen donor of denitrifying bacterium in the biodephosphorization process 12 and the like, and iron hydroxide and aluminum hydroxide in the coagulated / separated sludge 20 retain the phosphorus adsorption ability. Therefore, this is used for removing phosphorus from the sewage 1 flowing into the biological treatment step in the biological dephosphorization process 12 or the like.
By this technology, even in the case of rainy weather, the anaerobic part 14 in the biological dephosphorization step or the organic matter in the biological denitrification part 15 does not run short, and the biological dephosphorization and denitrification reactions are effectively advanced. Now you can do it.
[0011]
In another preferred embodiment, the coagulated and separated sludge 20 is anaerobically retained in the acid fermentation section 21 at room temperature or under warming conditions (temperature of about 30 to 40 ° C.), and is subjected to acid fermentation. When the fermented sludge 22 is supplied to the anaerobic section 14 or the biological denitrification section 15 in the biological dephosphorization step, it is more effective for promoting phosphorus discharge or denitrification.
In FIG. 1, reference numeral 11 denotes excess sludge, and reference numeral 3 denotes initial sludge from the first settling tank 2.
[0012]
【Example】
Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.
[0013]
(Example 1)
A test for applying the present invention to sewage of 120 mg / liter, BOD of 80 mg / liter, and phosphorus of 3.6 mg / liter flowing into a sewage treatment plant during rainy weather was conducted.
First, 2/3 of the amount of inflow sewage is branched, and ferric chloride is added thereto at 40 mg / l. After stirring for 1 minute, 3 mg / l of anionic polymer (Ebagrose A151; product of Ebara Corporation) is added. As a result of stirring for minutes, a floc having a large particle diameter of about 1 cm was formed and coagulated and precipitated at a sedimentation speed of 350 mm / min. The SS of the separated water from the coagulation / sedimentation separation step was as small as 3.6 mg / L and the phosphorus was as small as 0.3 mg / L, and SS and phosphorus in the sewage were highly removed.
Next, 1/3 of the amount of inflowed sewage (this amount corresponds to the amount of sewage treatment in fine weather: designed amount) is first flowed into the sedimentation basin, and the settling overflow and the coagulated sediment sludge are anaerobically aerobic (AO method). Flowed into the biological dephosphorization facility. As a result, the phosphorus in the treated water was stable at 0.1 mg / liter or less even when rain continued.
[0014]
(Comparative Example 1)
For comparison, a method was examined in which the coagulated sediment sludge was first caused to flow into the sedimentation basin to settle, and the overflow of the first sedimentation basin was caused to flow into the anaerobic part of the biological dephosphorization step. As a result, 1.6 mg of treated water phosphorus was averaged. Per liter.
[0015]
【The invention's effect】
According to the present invention, the following excellent effects can be obtained.
(1) The treated water quality of the biological dephosphorization and biological denitrification facilities does not deteriorate even in rainy weather.
(2) Sewage in rainy weather can be effectively purified, and public water bodies are not polluted by untreated sewage in rainy weather.
(3) It is possible to effectively use sewage purification instead of simply disposing of the segregated sludge from sewage in rainy weather.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a combined sewage treatment apparatus for rainy weather according to the present invention.
FIG. 2 is a block diagram showing one embodiment of a conventional combined-type sewage treatment apparatus in rainy weather.
[Explanation of symbols]
1 rainy sewage 1a part of sewage in rainy weather 2 first settling basin 3 first settling sludge 4 separated water 5 activated sludge treatment process (equipment)
6 Activated sludge mixture 7 Final sedimentation basin 8 Treated water 9 Separated sludge 10 Returned sludge 11 Excess sludge 12 Biological dephosphorization step 13 Biological nitrification denitrification step 14 Anaerobic part 15 Denitrification part (Biological nitrification denitrification) Process)
16 aerobic part (biological nitrification denitrification process)
17 Circulating fluid 18 Coagulation separation process (equipment)
19 Separated water 20 Coagulated separated sludge 21 Acid fermentation section 22 Acid fermentation liquid

Claims (4)

Combined sewage treatment characterized by coagulating and separating at least a part of sewage in rainy weather, and supplying the coagulated and separated sludge to an anaerobic part or a biological denitrifying part in a biological dephosphorization step of a sewage treatment facility. Method. The sewage treatment method according to claim 1, wherein after the coagulated and separated sludge is subjected to acid fermentation, the sludge is supplied to an anaerobic part or a biological denitrification part in a biological dephosphorization step of a sewage treatment facility. In a treatment device for purifying increased combined sewage in rainy weather, a coagulation separation device for introducing at least a part of increased inflow sewage in rainy weather and separating it into separated water and coagulated separated sludge, and discharging the separated water And a first settling tank for introducing a part of the inflow sewage to separate into separated water and settled sludge, and introducing separated water from the first settled tank and coagulated settled sludge from the coagulation / separation apparatus. An anaerobic aerobic biological dephosphorization facility having an anaerobic part, a denitrification part, or an aerobic part for dephosphorization, and introducing dephosphorized water containing sludge from the dephosphorization facility into treated water and settled sludge. A combined sewer system for rainy weather, comprising a final sedimentation basin for separation. The coagulation / separation sludge from the coagulation / separation device is introduced into an acid fermentation tank, and a pipe is provided to send the acid fermentation sludge from the acid fermentation tank to an anaerobic part of an anaerobic aerobic biological dephosphorization facility. Item 3. The combined sewage treatment apparatus in rainy weather according to Item 3.

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