JPS62279887A - Surface immobilized anaerobic bacteria granule and treatment of waste water using same - Google Patents

Abstract

PURPOSE:To prevent the formation of anaerobic bacteria self-granule (hereinafter referred to as G-sludge), by coating the surface of the anaerobic bacteria self- granule formed in an anaerobic upward flow sludge blanket reaction container with a synthetic or natural polymer gel. CONSTITUTION:For example, G-sludge is formed in a UASB (anaerobic upward flow sludge blanket) reaction container using artificial waste water of which the nutrients are adjusted on the basis of sucrose. This G-sludge is drawn out from the UASB container and drained to be stirred in an aqueous solution containing an acrylamide monomer and N,N'-methylenebisacrylamide as polymerizable monomers and beta-dimethylaminopropionitrile as a polymerization promoter to allow the chemical agents to penetrate into the surface layer of G-sludge. The impregnated G-sludge is taken out and drained to be stirred in an aqueous solution of potassium persulfate being a polymerization initiator intermittently and gently and polymerization is performed to form gel beads.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention provides an anaerobic microbial granule particularly suitable for treating persistent wastewater, and a method for treating wastewater using the same. It is related to.

[Conventional technology]

Anaerobic microorganisms, especially methane bacteria, have a slower growth rate than aerobic microorganisms, so in order to maintain a high concentration in the reactor with a short residence time, it is necessary to make them self-adhere to a carrier or use a membrane such as an OF membrane. Measures must be taken to prevent leakage. In addition, one method of maintaining microorganisms at a high concentration in a reactor is to immobilize anaerobic bacteria using a polymer gel such as polyacrylamide or polyvinyl alcohol, and then introduce it into the reactor. There is a limit to the amount of microorganisms that can be included in one immobilized product, and the microorganism concentration in the reactor that can be achieved by charging the immobilized product is about 10 g-VSS/1 at most. It is said that it is difficult to form an immobilized product that achieves a higher concentration than this.

On the other hand, an anaerobic upflow sludge blanket reactor (hereinafter referred to as UASB reactor), for example,
ulshoff Pot, W, J de Zeeuw
, C.T.M., Velzeboer and G.
Lettinga, Volume 15 Number
rs8/91983 Water 5science a
nd Technology ANAEROBICTR
EAT Gate ENT OF WASTEWATERIN
rGRANULATrON IN UASB announced at FIXED FILM REACTORS
-REACTOR3J (P, 291-304), G,
Lettinga, A.F.M. van Velse.
n, S, W,) Iobma+ W, de Zee
uw, and Klapwijk, Biotec
hnology and bioengineering
g, Vol.

'Else of' announced in XXII (1980)
the Upflow, SludgeBIanket
(IJsB)Reactor Concept for
BiologicaI Wastewater T
reatment, Specially for
Anaerobic Treatment (P, 6
99-734), Pere-Nod culture of r-methane bacteria J (
P, 3-15 to 3-21), Toshihiro Hoaki et al. presented in the abstract of the 39th Annual Academic Conference of the Japan Society of Civil Engineers, the effect on the treatment performance of the r-upflow type anaerobic sludge ped reactor. As disclosed in ``Influence of Temperature'', wastewater flows from the bottom of the reactor and undergoes biological reactions as it passes upward through the sludge bed formed by the deposition of anaerobic microorganisms. ,
It removes organic matter and simultaneously generates methane.

The biggest feature of this UASB reactor is that it allows anaerobic microorganisms to self-agglomerate, with a ball-shaped particle size of 0.5 to 3.0 fl, and excellent sedimentation properties, without using an attached carrier. The objective is to form granular sludge (hereinafter referred to as G sludge). As a result, the sludge concentration within the reactor reaches a maximum of 100 g/l. In addition, this G sludge contains Methano, which is responsible for the methane production reaction from acetic acid, which is the rate-limiting step in the anaerobic microbial reaction.
Since it is formed by a high density of bacteria belonging to the genus Thrix, it has a characteristic of high methane production activity per unit weight of sludge.

[Problem that the invention seeks to solve]

However, in the case of G sludge formed so far, organic matter in wastewater is dominated by low-molecular carbohydrates and lower fatty acids.
It is only in the reactor where biologically easily degradable wastewater with medium and high concentrations of 00 to 15000 g-CODcr/j2 was treated at 25 to 40 °C. Concentration of wastewater.

If the organic matter composition or treatment temperature does not fall under this category, for example (1
) Wastewater with CODcr below 1000mg/42, (2)
The CODcr equivalent of proteins and lipids in wastewater is the total organic C
In wastewater that accounts for 30% or more of the ODcr and at a treatment temperature of 20° C. or less, G sludge is not formed, or even if it is formed, it is thought that long-term cultivation is required. Also, in the UASB reactor (3) CO of suspended organic matter in wastewater
When wastewater containing a relatively large amount of suspended solids, such as wastewater whose Dcr equivalent accounts for 30% or more of the CODcr of the wastewater, flows in, there is a phenomenon in which suspended solids accumulate at the bottom of the reactor and G sludge is washed out of the system. Occur. In addition, when the aforementioned wastewater is treated using the formed G sludge, the G sludge has the property of taking in suspended substances in the wastewater, so the G sludge is
It is thought that the sludge expands and collapses.

As a practical example, urban sewage is treated anaerobically using G sludge obtained in a reactor for treating sucrose press wastewater, but the inside of the sludge bed formed by the G sludge depositing Problems such as suspended solids being mixed in and deposited on the upper part of the tank are occurring. Furthermore, although highly active G sludge was introduced, the treatment efficiency was about twice as high as when using digested sludge, and the effect was not exhibited.

[Purpose of the invention]

The present invention was made to solve such conventional problems, and its purpose is to anaerobically extract the G sludge in which anaerobic microorganisms formed in the UASB reactor are gathered at a high density. The surface of the sludge is coated with a thin film of polymer gel to form surface-immobilized granules, which are then introduced into a reactor.
The objective is to achieve anaerobic biological treatment of wastewater or treatment conditions in which G sludge is not formed even in a reactor.

[Means for solving problems]

The surface-immobilized anaerobic microorganism granules according to the present invention cover the surface of anaerobic microorganism self-granules formed in an anaerobic upflow sludge blanket reactor with a synthetic or natural polymer gel. This is what I did.

Furthermore, the wastewater treatment method according to the present invention provides anaerobic microorganisms formed by coating the surface of anaerobic microorganism self-granules formed in an anaerobic upflow sludge blanket reactor with a synthetic or natural polymer gel. Fill the granulated material into an anaerobic treatment reactor,
Wastewater with a CODcr of 1000 ■/l or less, or the CODcr equivalent of proteins and lipids in the wastewater is the CODcr of all organic matter.
Wastewater or floating organic matter in wastewater that accounts for 30% or more of c.

It is configured to purify wastewater whose Dcr equivalent accounts for 30% or more of the CODcr of the wastewater and to recover methane gas.

[Action of the invention]

Surface immobilization of G sludge as in the present invention not only increases the amount of microorganisms inside it several times compared to conventional comprehensive immobilization, but also increases the physical capacity compared to G sludge that is not surface immobilized. This increases the physical strength of the G sludge, and prevents the G sludge from collapsing due to the adsorption of suspended solids to the G sludge. Since the G sludge can be stably maintained in the reactor for a long period of time, the attributes are completely different from the method of simply transferring the G sludge and using the UASB reactor configuration as before.

As a result, wastewater with CODcr of 1000mg/# or less,
or wastewater in which the CODcr equivalent of proteins and lipids in the wastewater accounts for 30% or more of the CODcr of total organic matter, or the CODcr equivalent of floating organic matter in the wastewater is 3 of the CODcr of the wastewater.
It becomes possible to purify wastewater that accounts for 0% or more, and when the wastewater is purified at a temperature within the reactor of 20° C. or lower, more efficient purification becomes possible, and methane gas can be recovered.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

5000 mg with adjusted nutrients using sucrose as the main ingredient
-U at 35 °C using artificial wastewater of CODcr/l
Attempts were made to form G sludge in an ASB reactor.

G sludge is formed 90 days after the start of operation, and G sludge is formed after 160 days.
The properties of the sludge were an average particle size of 1.50 mm, an average sedimentation rate of 1.10 m/min, and an SVI (sludge capacity index) of G sludge of 20.0 to 35.0 m 1 /g.

This G sludge was surface immobilized using polyacrylamide. The method will be explained below.

After G sludge is pulled out from the U, ASB reactor, it is drained and acrylamide monomer is used as a polymerization agent.

The mixture is stirred in an aqueous solution containing N,N'-methylenebisacrylamide and β-dimethylamine propionitrile as a polymerization accelerator to allow these agents to penetrate into the surface layer of G sludge. After that, G sludge is taken out from this aqueous solution, drained, and acrylamide is polymerized on the surface of G sludge by intermittent and gentle stirring in a potassium persulfate aqueous solution of a polymerization initiator. Coated gel beads were formed. This operation was carried out in an anaerobic atmosphere as much as possible.

Although a method using polyacrylamide as a surface immobilization method has been described here, the present invention is not limited to this. Natural polymeric materials, synthetic polymeric materials such as polyvinyl alcohol, and photocurable resins that can be easily immobilized can be used. The surface immobilization method using these materials is similar to the method using polyacrylamide, in which the removed G sludge is poured into an aqueous solution of these polymeric materials, stirred, and then transferred into a gelling agent, or exposed to ultraviolet light. It polymerizes or gels by irradiating it to easily obtain a surface-immobilized product.

The G sludge extracted from the UASB reactor and surface-immobilized using the above method using acrylamide was put into a chemostat type reactor and then charged with the above Sea! When artificial wastewater containing sugar as the main component was supplied, methane gas began to be generated approximately 24 hours later. After 28 days of culture, surface-immobilized G sludge and UAS
A batch experiment was conducted to determine the methane production activity of both sludge G and sludge taken out from reactor B using the above artificial wastewater as a substrate using a 500 ml vial kept at 35°C.

Methane production rate of the latter 2.011- CHa/g
- Compared to VSS day, the former is 1.521- c
H4/g-VSS-day, and the methanogenic activity was only reduced to about 73% by surface immobilization. Acrylamide is known to be toxic to microorganisms during immobilization, and when airborne bacteria cultured in suspension are entrapping immobilized with acrylamide,
There are also reports that the methanogenic activity was reduced to 1/10 or less.

In the immobilization method of the present invention, only the surface of the G sludge where anaerobic microorganisms are densely aggregated comes into contact with the gelling agent, so that the decrease in microorganism activity that occurs during immobilization can be minimized.

In addition, in the chemostat type reactor in which the culture was carried out for 28 days, the rotation speed of the magnetifukustara was set to 10 Or, p,
The G sludge fixed on the surface did not disintegrate at all, and there was no problem with its physical strength.

As mentioned above, the SVI value measured by surface immobilization of G sludge with an SVI value of 35.0 ml/g using acrylamide was approximately 48.5 ml/g in terms of sludge. The increase in SVI that occurred was about 1.39 times. This is 39m to fix 100m1 of G sludge on the surface! It can be estimated that 2 polymer gels were required.

Generally, in order to comprehensively immobilize microorganisms, concentrated microbial sludge 1
00 mJ, the polymer gel material has a minimum of 500 to 1
000 m/ is necessary, so it is clear that the surface immobilized product of the present invention can efficiently immobilize microorganisms.

Incidentally, although waste water was explained in the above embodiment, it goes without saying that the treated water may be sewage.

Effects of the invention C] As described above, according to the surface-immobilized anaerobic microorganism granules of the present invention, since the G sludge is surface-immobilized, the amount of internal microorganisms increases and the physical strength increases. Moreover, it is possible to prevent the G sludge from collapsing due to adsorption of suspended solids to the G sludge.

Furthermore, according to the wastewater treatment method of the present invention, since the G sludge is fixed on the surface as described above, it can be stirred relatively vigorously in the reactor, and it can be stably maintained in the reactor for a long period of time. This makes it possible to treat particularly persistent wastewater.

Claims (5)

[Claims] (1) An anaerobic microbial granule, characterized in that the surface of the anaerobic microbial self-granulation product formed in an anaerobic upflow sludge blanket reactor is coated with a synthetic or natural polymer gel. (2) After the anaerobic microbial autogranules are anaerobically drawn out from within the anaerobic upflow sludge blanket reactor,
The anaerobic microorganism granule according to claim 1, wherein the surface is coated with a synthetic or natural polymer gel. (3) The synthetic or natural polymer gel is composed of polyacrylamide, sodium alginate, galrageenan, polyvinyl alcohol, photocurable resin, etc. Anaerobic microbial granules. (4) Anaerobic microbial granules formed in an anaerobic upflow sludge blanket reactor and coated with a synthetic or natural polymer gel on the surface of the anaerobic microbial self-granules are subjected to anaerobic treatment. Fill the reactor with CODcr of 1000mg/
CODcr of wastewater or proteins and lipids in wastewater less than l
Wastewater characterized by purifying wastewater in which the CODcr equivalent of total organic matter accounts for 30% or more of the CODcr of the total organic matter, or wastewater in which the CODcr equivalent of floating organic matter in the wastewater accounts for 30% or more of the CODcr of the wastewater, and at the same time recovering methane gas. Processing method. (5) The method for treating wastewater according to claim 4, characterized in that the temperature inside the reactor is kept at 20° C. or lower.