JPH0312284A - Water treatment method - Google Patents

Abstract

PURPOSE:To keep good treatment effect over a long period of time and to extend the regeneration cycle of activated carbon by using activated carbon wherein particle specific gravity is a specific value or less and a pore volume with a pore radius of 1mum or more and a specific surface area are specific values or more. CONSTITUTION:Activated carbon to be used for activated carbon treatment has characteristic values such that particle specific gravity (density) is 0.6g/ml or less, a pore volume with a pore radius of 1mum or more is 30-70% and a specific surface area is 1100m<2>/g or more. Since the substances which are adsorbed by activated carbon are efficiently decomposed and removed by bacteria adhered to activated carbon in the same way, the adsorbing capacity of activated carbon can be kept long. As a result, the regeneration cycle of activated carbon can be extended and the running cost in water treatment is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to advanced purification of tap water and advanced treatment of sewage, Shihara wastewater, etc., using the organic matter decomposition/removal action and ammonia nitrification action of microorganisms. More specifically, it relates to water treatment technology that can exhibit both the adsorption function of activated carbon and the biological regeneration function of decomposing adsorbed matter adsorbed on activated carbon through the action of microorganisms.

[Prior art and its problems] In the conventional activated carbon treatment technology, the main purpose was to remove dissolved organic matter by physical adsorption.

However, a problem with this prior art is the cost involved in regenerating activated carbon.

Normally, activated carbon is regenerated to remove adsorbate from activated carbon by steam heating, and the standard cost is currently around 200 yen/kg of activated carbon. For example, the regeneration cycle for tap water is generally 8 months to 1 year, but since the amount of activated carbon used is extremely large, the activated carbon regeneration cost accounts for a high proportion of the total water supply cost.In order to reduce running costs, There was a need to develop a means to extend the life of activated carbon.

Therefore, in recent years, studies have been actively conducted on so-called biological activated carbon treatment, in which adsorption by activated carbon and self-regeneration by microorganisms are performed simultaneously within a treatment system.

However, the activated carbon used in the biological activated carbon treatment currently under consideration is a repurposed product originally developed as an adsorbent for water treatment, so it is said that it is not able to fully demonstrate the functions of microorganisms. There were also problems. That is, the size of microorganisms is on the order of microns, and even when the size of aerobic microorganisms actually attached to the surface of activated carbon was observed using an electron microscope, most of them were 1 to 20 μm in size. On the other hand, when evaluating the pore distribution of conventionally used activated carbon, micropores and transitional pores (≦pore radius of 100A) account for the majority, and although it is excellent as a physical adsorbent, However, the pores were too small for microorganisms to adhere to, and it was difficult to decompose adsorbed substances adsorbed within the pores.

[Means for Solving the Problems] The present inventors believe that if activated carbon used for activated carbon treatment can be given a high microbial concentration while maintaining its excellent adsorption capacity, the adsorption rate of the adsorbed substance and its biological properties can be improved. We believe that the decomposition rate is well balanced and good treatment effects can be maintained over a long period of time, and as a result, the regeneration cycle of activated carbon can be extended.

As a result of further research, it was discovered that activated carbons that have a large number of microorganisms attached to them and that are good at adsorbing substances such as organic matter are only those that meet certain conditions, and have completed the present invention.

Therefore, the present invention provides activated carbon for activated carbon treatment with a particle specific gravity (density) of 0.6 g/m or less, a pore volume of 30 to 70% with a pore radius of 1 μm or more, and a specific surface area of 1
This water treatment method is characterized by using activated carbon having a density of 100 m2/g or more.

Activated carbon with the above conditions used in the present invention cannot be manufactured under the activation conditions of activated carbon conventionally used in the field of water treatment, and the activation time, activation temperature, water vapor addition rate, etc. It is produced by setting the conditions to what is called overactivation.

Excessive activation means, for example, activation time 5 to 5 times longer than normal activation.
Make it longer or shorter by about 0%, or set the activation temperature to 100% or less.
Increase the temperature by about 300°C or increase the water vapor addition rate by 50 to 20°C.
This is done under conditions such as raising the temperature by about 0%. this house,
The activation time may be shorter than the normal value depending on other condition settings and the degree of material (carbonization degree). For example, when coal with a low degree of carbonization such as peat is used as a raw material, it is necessary to perform rapid activation at high temperature and high amount of steam.

Furthermore, wood-based (charcoal-based) materials also satisfy the conditions required for the activated carbon of the present invention.

The conditions required for the activated carbon of the present invention are specific surface area, pore ratio, and particle specific gravity. Then, the total trihalomethane production capacity (T
As is clear from FIG. 1, which shows the relationship between the specific surface area and adsorption amount at an equilibrium concentration of 30 μg/l using THMFP) as an index, when the specific surface area becomes 1100 m'/g or less, the adsorption amount of the adsorbate decreases significantly. Furthermore, as is clear from Figure 2, which shows the relationship between the pore ratio and adsorption amount, when the pores with a pore radius of 1 μm or more exceed 70%, the pore ratio inevitably decreases, resulting in The adsorption area decreases and the amount of adsorption decreases significantly.

On the other hand, if the percentage of pores with a pore radius of 1 μm or more is less than 30%, the proportion of micropores increases, and the number of so-called micropores that cannot be penetrated by organic substances with large molecular weights increases, so the amount of adsorption does not increase. I can hardly expect it. Furthermore, as is clear from Figure 3, which shows the relationship between the particle specific gravity and the amount of attached microorganisms, when the particle specific gravity becomes larger than 0.6 g/ml, the pore volume to which microorganisms can attach decreases, so the amount of attached microorganisms decreases sharply. However, it becomes difficult to perform biological activated carbon treatment.

The water treatment method of the present invention can be carried out by already known methods except for using activated carbon that satisfies the above conditions. In other words, the general treatment flow sheet for advanced treatment of clean water is coagulation/sedimentation → sand filtration → activated carbon filtration, and the water to be treated is passed through a filtration tower filled with activated carbon that satisfies the above conditions. In addition, if it is necessary to improve the biodegradability of dissolved organic matter, after chemically decomposing the organic matter with an oxidizing agent such as ozone or hydrogen peroxide,
It may be passed through a filtration tower filled with the activated carbon of the present invention.

In this case, the amount of microorganisms adhering to the sheet is larger than that of the flow sheet described above, and the substrate is effectively decomposed.

In addition, if water pollution is advanced or it is difficult to maintain an aerobic atmosphere in the activated carbon bed when performing aerobic treatment on water with low dissolved oxygen, aerate the inside of the packed tower. This allows effective processing. Aeration is preferably performed by diffusing air from within or below the packed bed.

[Effects of the Invention] According to the water treatment method of the present invention, adsorbates adsorbed on activated carbon are efficiently decomposed and removed by microorganisms also attached to the activated carbon, so the adsorption capacity of the activated carbon can be maintained for a long time. It becomes possible to do so. As a result, the regeneration cycle of activated carbon can be lengthened, and running costs in water treatment can be reduced.

[Examples] Next, the present invention will be described in more detail with reference to Examples and Reference Examples, but the present invention is not limited to these Examples in any way.

Reference Example 1 Activated carbon A was obtained by using peat as a raw material and activating it for 2 hours by adding 23 times the amount of steam at an activation temperature of 1100''C.

Example 1 Targeting lake water with advanced eutrophication, an advanced water treatment experiment was conducted using the activated carbon obtained in Reference Example under the flow sheet shown in FIG. 4 and the treatment conditions shown in Table 1.

The basic treatment process was to collect sample water from the receiving well of a water treatment plant whose water source is lake water, subject it to coagulation and sedimentation, and then ozone treatment to obtain a pre-treated liquid. This was then introduced into a biological activated carbon treatment process to treat tap water.

In the biological activated carbon treatment, in order to compare the treatment effects of the method of the present invention and the conventional method, the pretreatment liquid was equally divided into four series, and each series was continuously passed through a column filled with activated carbon having the physical properties shown in Table 2. . Among the activated carbons in Table 2, activated carbon B is used in the conventional method, and has a larger particle specific gravity and a smaller pore ratio of 1 μm or less and a smaller specific surface area than the activated carbon A of the present invention.

Activated carbon C and activated carbon porcelain were prepared as comparison targets for activated carbon A of the present invention, and activated carbon C differs from activated carbon A in that the specific surface area is small, and activated carbon porcelain differs from activated carbon A in terms of pore distribution ratio. .

Chapter 2 Basic Treatment Conditions Water Intake Quantity Flocculant Flocculant Injection Rate Ozone Injection Rate Ozone Reaction Time Activated Carbon SV Activated Carbon LV 50 m3/day Sulfuric Acid 40 mg/I 9/1 10 minutes 5 (/h 10 phantom/ h and Table Activated carbon A Activated carbon B (method of the present invention) (conventional method) Activated carbon C (comparative method) Activated carbon D (comparative method II) Average particle diameter (IIlffl) Packing density (g/ml) Porosity particle specific gravity (geIll ) True specific gravity (g/a+1) Total pore volume (mouth 1/g) 1 μm or more (%) Specific surface area (acute 2/g) 1.0 0.20 0.47 o, 38 1.80 1.0 0.44 0.45 o, 80 1.82 1.1 0.30 0.48 0.58 1.85 0.95 0.31 0.48 0.60 1.90 2.19 0.70 1. 24 1.10
45 31 39 182380
The results of the 1150 890 1210 test are shown in FIG. As is clear from this result, activated carbon A
The treatment effect of the method of the present invention using the method always exceeded the treatment effect of the conventional method. In addition, the breakthrough rate of the method of the present invention (100
%-removal rate) maintained an almost equilibrium state at around 50%. In contrast, in the case of the conventional method, the initial breakthrough rate is relatively slow, but the pore volume is small due to the large particle specific gravity, resulting in a treatment system that relies only on physical adsorption, resulting in activated carbon approaching saturated adsorption. As time goes on, it will break through to nearly 100%.

In addition, in Comparative Method I using activated carbon C, the adsorption capacity is small because the specific surface area of activated carbon is smaller than the other methods, and the breakthrough of activated carbon progresses rapidly before the biological regeneration effect of activated carbon can be expected. . On the other hand, comparative method II using activated carbon
, the pore volume of activated carbon is relatively large, but the radius is 100
Since there are many pores of size A or smaller, a sufficient biological regeneration effect cannot be obtained.

Example 2 Using lake raw water, coagulated treated water, and ozonated water as test waters, the adsorption ability of THM precursors to activated carbon by the method of the present invention was compared using tRTHM production ability as an index. The results are shown in FIG.

As is clear from these results, the apparent adsorption amount of adsorbed substances such as THM precursors increases when the method of the present invention is applied to water that has been subjected to coagulation treatment or ozonation treatment, rather than when the method is applied directly to lake raw water. It was advantageous in that respect.

This is because adding ozone treatment before activated carbon treatment increases the biodegradability of dissolved organic matter and promotes the biological regeneration function within the activated carbon layer.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the relationship between specific surface area and adsorption amount. FIG. 2 is a drawing showing the relationship between the proportion of pores and the amount of adsorption. FIG. 3 is a diagram showing the relationship between particle specific gravity and the amount of attached microorganisms. FIG. 4 is a drawing showing a flowchart of continuous biological activated carbon treatment. FIG. 5 is a diagram showing the breakthrough rate of continuous biological activated carbon treatment. FIG. 6 is a drawing showing the results of a comparison between a combination of ozone treatment and biological activated carbon treatment and a single biological activated carbon treatment. Above diagram

Claims (1)

[Claims] (1) Particle specific gravity (density) as activated carbon for activated carbon treatment
A water treatment method characterized by using activated carbon having a carbon content of 0.6 g/ml or less, a pore volume of 30 to 70% with a pore radius of 1 μm or more, and a specific surface area of 1100 m^2/g or more. (2) The water treatment method according to item 1, characterized in that the inside of the activated carbon packed column is aerated.