JP3013358B2 - Liquid purification method using expanded plastic particles - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for removing soluble contaminants in wastewater by an aggregate of expanded plastic particles.

[Prior Art] A liquid purification method using an aggregate of particles as a filter medium and a purification microorganism carrier is described in, for example, JP-B-56-6324 and JP-B-63-63.
Known as No. 85. Purification of sewage using an aggregate of spherical porous artificial stone particles is called "Water and wastewater" in 1987 Vo
l.29, No. 1 (Industrial Water Research Committee). Sewage purification using anthracite is also known.

[Problems to be Solved by the Invention] Using an aggregate of particles as a filter medium makes it easy to backwash or purify the filter medium when the filter medium is clogged with contaminants, and to increase the surface area of the filter medium. It has the advantage that it can be used as a carrier for purified microorganisms. However, various types of pollutants are contained.Especially, the removal of soluble contaminants by biological treatment and the efficient reduction of COD and BOD of sewage require selection of materials that serve as carriers for microorganisms. Difficult and difficult. In addition, the above-mentioned porous artificial stone particles and anthracite particles are very brittle because they are inorganic porous,
It is destroyed by backwashing and the particle size changes easily and does not last long,
In addition, it is not possible to manufacture such that the porosity and the specific gravity are at desired values.

[Means for Solving the Problem] The inventor has found that when purifying sewage by passing through a particle aggregate, foamed plastic beads having an average particle diameter of 0.1 to 50 mm, or crushed or cut soft plastic foam are used as particles. When particles are used, soluble contaminants in wastewater can be removed very efficiently, and the particles are not brittle,
Withstands many backwashes and discovers that it is very durable,
The present invention has been completed.

In the present invention, the soluble organic contaminant is an organic contaminant literally dissolved in water and cannot be removed by simple filtration. Soluble organic pollutants are substances that cause BOD and COD as well as insoluble substances, and are aerobicly and anaerobically decomposed by purified microorganisms on the surface of particle aggregates, and the BOD of the treated material after purification is obtained. And COD is significantly reduced.

The particle aggregate of the present invention can serve as a filtration zone for insolubles, but serves as a carrier for purification microorganisms that aerobically and anaerobically decompose organic substances. The particle aggregate is simply a collection of discrete particles and need not be particularly bound or entangled. However, the particles may be fixed to some extent as long as they can be separated by applying an appropriate force.

The average particle size of the particles is 0.1 to 50 mm, and good purification efficiency cannot be obtained with particles having a particle size larger than 50 mm. In addition, particles with a particle size of less than 0.1 mm are liable to be clogged with general sewage, increasing the size of the equipment due to the increase in backwash frequency and backwash water volume, and for sedimentation due to a large amount of backwash water treatment. The running cost for chemical dosing increases and becomes impractical.

The shape of the particles in the particle aggregate is preferably indefinite in order to improve the purification efficiency. If the particle shape is a fixed shape such as a spherical shape, water particles will be formed in the particle aggregate, from which wastewater flows out at high speed, and purification efficiency tends to deteriorate. For the same reason, it is preferable that the particle size in the particle aggregate is not uniform.

Each particle of the particle aggregate must be expanded beads (eg expanded polystyrene beads) or soft plastic foam crushed or cut. If hard plastic particles that do not foam are used, the familiarity with the microorganisms on the surface deteriorates. However, in order to eliminate clogging and effectively perform backwashing, the material must be soft but not degraded in shape. Foamed plastic may be closed cells or open cells, but a number of irregularities are generated on the surface by being foam beads or foam crushed or cut,
The contact surface between microorganisms and sewage must be large. Particles formed by randomly pulverizing a closed-cell foamed plastic body are particularly preferred.

The porosity of the whole particle aggregate is up to about 98% for expanded polystyrene beads, and otherwise 50 to 90%
Preferably, the lower the porosity, the higher the cost of the particles. If the porosity exceeds 90%, the higher the porosity, the lower the efficiency of purification by microorganisms.

As a method of passing the sewage through the particle aggregate, a zone of the particle aggregate is provided in a flow path of the sewage flowing upward, downward, or gently in the horizontal direction, or a retention container in which the sewage moves.
As a method of providing the band of the particle aggregate, for example, there is the following method.

I. One or both sides of the band are closed with a wire mesh or the like so that particles cannot move.

B. The specific gravity of the particles is made lighter than the sewage, and the particles are floated under a wire mesh or the like in the ascending or descending sewage flow path, and contaminant removal ports are provided above and below separately from the flow path.

Organic pollutants are decomposed anaerobically by microorganisms and are also decomposed aerobically. Therefore, it is preferable to occasionally or constantly aerate the particle aggregates.

 The present invention will be described in more detail by way of examples.

Example 1 Aggregates of irregularly sized and irregularly sized polypropylene foam particles of various average particle sizes over the entire cross-section of a septic tank that has separate upper and lower contaminant outlets for inflowing paper mill effluent and for purifying effluent. A band was provided. That is, a paper mill wastewater (28.5 ° C, pH 6.3) is converted into a 0.4m diameter x 5.3m height with a 3m particle aggregate layer (prevention from floating with an inhibitor from above).
^* Two-stage purification was performed while constantly aerating using a septic tank, and COD reduction was observed. The results are shown below. ^* : (BOD load 6Kg / m ³ / day) A particle size of 0.1 mm was possible and the removal rate was even better, but clogging was slight. From the above table and the above description, the smaller the particle size, the better the COD removal rate in the particle size range of 0.1 to 50 mm. However, in practice, particles with a size of 3 mm or smaller increase the frequency of backwashing because the clogging becomes more frequent. At 3 mm or less, the COD removal rate did not change in the case of biological treatment, but the amount of backwash water increased 5 to 10 times as compared with the above 15 mm. Further, when the thickness is 3 mm or less, the sludge concentration in the backwashed water is low and floc formation is also bad, so precipitation treatment by chemical injection was required, but with the particles of the present invention, turbidity of 3 mg or less is possible by single precipitation treatment without chemical injection Met. This means that if the particle diameter is 3 mm or less, the amount of backwash water is large and the equipment must be enlarged, but it has utility value depending on the application.

Example 2 Using polypropylene foam particles and non-foam particles, household wastewater (artificial wastewater was added to the ratio of human waste 1 to kitchen 2 to make BOD 258 mg / l (16 ° C, pH 7.2)). The first stage is a 0.4 m diameter x 4 m height similar to Example 1 having a 3 m height particle aggregate layer (particle diameter 15 mm), and the second stage is a 0.5 m height particle aggregate layer ( Purification was performed using a two-stage 0.75 m diameter x 1.5 m height septic tank having a band of 2 mm in particle size in the drainage flow path while constantly aerating, and the reduction of BOD and COD was examined.

Example 3 Papermaking Water Recycling Papermaking water (pH 5.5) was purified for water reuse using polypropylene foam particles. A vertical septic tank (1 m diameter x 4 m height, constantly aerated) with 15 mm particles at a height of 2 m, and a vertical septic tank (1 m diameter with 1 mm diameter particles of 2 mm) × 1.5m height, filtration only), 2.5m / h
Slime did not adhere to the pipe even after 10 days, and 2/3 of the scum was removed in the first stage.
One-third of the scum was removed by the step, and the septic tank was less clogged. The reductions of various contaminants are shown in the table.

Example 4 River Purification Model A vertical purification layer having a polypropylene foam particle aggregate layer zone (3 m height, particle diameter 15 mm) in the flow path of low BOD papermaking wastewater (25 ° C.) assuming river purification. (0.4m diameter x
(5.3 m height). Since the BOD was low load, the flow rate was changed and the BOD reduction rate was observed.

As described above, it can be seen that the present invention achieves a reduction in BOD (about 5 mg / l) at a high flow rate (5 to 10 m / h) and short contact (20 to 30 minutes).

Example 5 Two-stage simple filtration (kitchen drainage treatment) Oil cannot be collected by aeration due to sewage containing a large amount of edible oil.
mm (flow rate 8.8m / h), 2nd stage filter with average particle size 2mm
Simple filtration was performed without aeration using 800 mm (flow rate 4.2 m / hour), and the purifying power of microorganisms naturally occurring in water flow was used. Oil,
The reduction of suspended solids and COD is shown below.

Oil mg / l Suspended solids mg / l CODmg / l sewage 31.8 211.8 176.9 Treated water 3.7 10.2 27.6 Removal rate 88.3% 95.1% 83.8% Example 6 Effect of change in flow velocity (treatment of tap water at Inba-numa) Particle size 15mm Filter layer 1000 of aggregate of expanded polypropylene particles
Raw water from tap water was flowed down to a flow rate of 0.5 to 7 m / hr at various speeds. No sedimentation accelerator was injected.

[Effects of the present invention] The method of the present invention enables efficient removal of soluble organic contaminants, and easily obtains particles having a desired foaming ratio and size, and can be used for a long time. Not broken.

Continuation of the front page (56) References JP-A-57-30596 (JP, A) JP-A-55-18266 (JP, A) JP-A-60-47673 (JP, A) JP-A-50-43756 (JP, A) JP-A-57-150492 (JP, A) JP-B-56-6324 (JP, B2)

Claims (2)

(57) [Claims] The present invention relates to a filter medium of a particle aggregate in which sewage artificially contains pollutant-purifying active bacteria or adjacent particles in which pollutant-purifying active bacteria naturally exist.
Alternatively, in a method of purifying by passing through without aeration, the particles are made by randomly crushing or cutting a plastic foam, have fine irregularities on the surface, have a lower specific gravity than the sewage, and have an average particle size. Backwashing regardless of whether the particle aggregates are particles having a diameter of 0.1 to 50 mm and the adjacent particles contact each other when the sewage passes through the particle aggregates, with or without aeration. A method for removing soluble organic pollutants in sewage water, the method comprising: 2. Purification of sewage by passing through a filter medium of a particle aggregate in which multi-stage adjacent particles, in which pollutant-purifying active bacteria are artificially present or in which pollutant-purifying active bacteria are naturally present, are in contact with each other. In the method, at least the first step of the above step is performed by aeration and the particles in the step are formed by randomly crushing or cutting a plastic foam. Also, the specific gravity is small, the average particle size is 0.1 to 50 mm particles, the other stages are not aerated and the particles at that stage are made by crushing or cutting the plastic foam. Particles having an average particle diameter of 3 mm or less, regardless of whether the state of the particle aggregate in which the adjacent particles contact each other when the sewage passes through the particle aggregate is with or without aeration. Backwashable Characterized in that it is a touch state, a method for removing the non-soluble and soluble contaminants in wastewater.