JPH1099898A - Treatment of waste water in waste refuse incineration treatment facilities - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize treatment equipment by adding a chemical agent consisting of an alkali agent, a flocculant and a flocculation aid to inorg. waste water not only to insolubilize heavy metals as hydroxides but also to flocculate a suspended substance to sediment and separate them and mixing org. waste water with supernatant waste water to biologically treat org. matter. SOLUTION: Inorg. waste water stored in a first raw water tank 1 is sent to a reaction tank 2 and a chemical agent, a flocculant and a flocculation aid is added to inorg. waste water not only to insolubilize heavy metals as hydroxides but also to flocculate a suspended substance. Next, this inorg. waste water is sent to a sedimentation tank 3 and, after flocs are sedimented and separated, alkaline supernatant waste water is sent to a neutralization tank 4 and a neutralizing agent is added to the supernatant waste water to neutralize the same. Subsequently, the waste water is sent to a second raw water tank 5 to be stored therein and org. waste water is added to the waste water and this mixed waste water is sent to a biological treatment tank 6 and org. matter is metabolized and decomposed by aerobic bacteria bonded to a contact material. Thereafter, the waste water is sent to a sedimentation tank 7 and sludge composed of decomposed matter of org. matter is sedimented and separated to be sent to a treated water tank 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater generated in a refuse incineration facility for incinerating municipal waste.

[0002]

2. Description of the Related Art Wastewater generated in a municipal solid waste incineration plant is roughly classified into inorganic wastewater containing heavy metals and suspended substances and organic wastewater containing organic matter. Specifically, the inorganic wastewater includes ash sewage generated from an ash cooling water tank (clinker channel) for cooling incinerated ash, ash extruder sewage generated from an ash extruder,
Ash pit drainage leaching from the bottom of the incineration ash layer deposited in the ash pit, pure water regeneration drainage generated when the ion exchange resin in the pure water equipment is regenerated, continuous blow from the boiler drum or full blown during idle There are boiler blow drainage and floor wash drainage generated when cleaning floors in factory buildings. On the other hand, organic wastewater includes garbage pit wastewater leached from the bottom of the garbage layer deposited in the garbage pit, domestic wastewater generated from toilets, baths, kitchen facilities, etc., and car wash wastewater generated when cleaning garbage trucks. , And platform floor cleaning drainage generated when the platform is cleaned.

Conventionally, inorganic wastewater and organic wastewater have been separately treated. That is, the inorganic wastewater is added with a chemical consisting of an alkali agent, a coagulant and a coagulation aid to insolubilize heavy metals as hydroxide and coagulate suspended substances, and then to form hydroxides and suspended substances of heavy metals. After sedimentation of the agglomerates, the supernatant was treated by neutralizing the wastewater. In addition, organic wastewater decomposes organic matter in organic wastewater by biological treatment,
The sludge generated was treated by settling.

However, the quality of the treated water treated as described above may not conform to the water quality standards set by the Water Pollution Control Law, the Sewerage Law, and the like.

[0005] In order to investigate the cause, the present inventors first analyzed the water quality of wastewater generated in a municipal waste incineration plant. Table 1 shows the results.

[0006]

[Table 1]

[0007] Note that SS in Table 1 represents a suspended substance.

As apparent from Table 1, the BOD and COD values of ash wastewater, ash extruder wastewater, ash pit wastewater, and floor cleaning wastewater among inorganic wastewaters are lower than those of organic wastewater.
It was found that these values were equivalent to the values of OD and COD, and therefore, it was necessary to subject these inorganic wastewaters to biological treatment.

Therefore, recently, in view of the above-mentioned situation, a method of treating wastewater as shown in FIGS. 2 and 3 has been considered.

The method shown in FIG. 2 is as follows. That is, the raw water tank (2
The mixed wastewater is sent to a neutralization tank (21) and neutralized by adding a neutralizing agent. Next, biological treatment tank (22)
The organic matter is metabolically decomposed by the aerobic microorganisms attached to the contact material immersed in the tank (22). At this time, the tank (2
2) Keep aeration inside. Then, the mixture is sent to the reaction tank (23), and a chemical consisting of an alkali agent, a coagulant and a coagulation aid is added to insolubilize heavy metals as hydroxide and coagulate suspended substances. Then, it is sent to the sedimentation tank (24) to separate sedimentation of metabolites of organic substances, hydroxides of heavy metals and aggregates of suspended solids. And neutralization by adding a neutralizing agent.
Finally, after sending to a sand filtration tank and filtering, treated water is discharged or reused.

The method shown in FIG. 3 is as follows. That is, the organic wastewater and the inorganic wastewater are mixed and mixed in a raw water tank (3
0) and send this mixed wastewater to the reaction tank (31),
A chemical consisting of an alkali agent, a coagulant and a coagulation aid is added to insolubilize heavy metals as hydroxide and coagulate suspended substances. Then, it is sent to the sedimentation tank (32), and the sedimentation of hydroxides of heavy metals and suspended solids is settled.The supernatant water showing alkalinity is sent to the neutralization tank (33), and the neutralizing agent is added. Neutralize with Next, biological treatment tank
(34), and organic matter is metabolically decomposed by aerobic microorganisms attached to the contact material immersed in the tank (34). At this time,
The tank (34) is aerated. Finally, after sending to the sand filtration tank (35) for filtration, the treated water is discharged or reused.

However, in the above two methods,
Since the entire amount of the mixed wastewater of the organic wastewater and the inorganic wastewater is sent to all the treatment steps, the treatment equipment must be increased in size and the cost increases. In addition, a certain amount of an alkali agent, a coagulant and a coagulation aid for coagulating suspended substances while insolubilizing heavy metals as hydroxides must be added to the entire amount of the mixed wastewater. The amount of the drug increases and the cost increases as compared with the case where the system wastewater is treated alone.

Further, in the method shown in FIG. 2, when the amount of heavy metals in the mixed wastewater increases, the aerobic microorganisms in the biological treatment tank are adversely affected, and the treatment efficiency is reduced.

An object of the present invention is to solve the above-mentioned problems, eliminate the need for increasing the size of processing equipment, and use a relatively small amount of a chemical comprising an alkali agent, a flocculant and a flocculant.
Moreover, it is an object of the present invention to provide a wastewater treatment method in a refuse incineration facility capable of effectively performing biological treatment of organic matter.

[0015]

Means for Solving the Problems and Effects of the Invention A wastewater treatment method in a refuse incineration plant according to the present invention comprises adding a chemical comprising an alkali agent, a flocculant and a flocculant to inorganic wastewater to remove heavy metals from the wastewater. A first step of insolubilizing oxides and aggregating suspended substances, a second step of sedimentation of hydroxides of heavy metals and aggregates of suspended substances, and a third step of neutralizing supernatant wastewater in the second step It includes a step, a fourth step of mixing organic wastewater into the supernatant wastewater neutralized in the third step, and a fifth step of biologically treating and decomposing organic substances in the mixed wastewater.

According to the method of the present invention, a chemical comprising an alkali agent, a flocculant and a flocculant is added to the inorganic wastewater to insolubilize heavy metals as hydroxides and to coagulate suspended solids. Sedimentation and separation of aggregates of hydroxides and suspended solids, neutralize the supernatant wastewater, mix organic wastewater into the supernatant wastewater, and biologically treat and decompose the organic matter in the mixed wastewater Therefore, unlike the conventional method shown in FIGS. 2 and 3, it is not necessary to send the entire amount of the mixed wastewater of the organic wastewater and the inorganic wastewater to all the treatment steps. Therefore, the processing equipment can be relatively reduced in size, and the cost can be reduced. Also, it is only necessary to add a certain amount of an alkali agent, a flocculant and a flocculant aid for coagulating suspended substances while insolubilizing heavy metals as a hydroxide, relative to the amount of inorganic wastewater. 2 and the conventional method shown in FIG. 3 requires a smaller amount of drug, and the cost is reduced.

Furthermore, even if the amount of heavy metals in the inorganic wastewater is increased, it is removed before the biological treatment step, so that the treatment efficiency is improved as compared with the conventional method shown in FIG.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings.

In FIG. 1, an inorganic wastewater is supplied to a first raw water tank.
Sent to (1) and stored here. Then, the inorganic wastewater stored in the first raw water tank (1) is transferred to the reaction tank (2).
And a chemical comprising an alkali agent, a coagulant and a coagulant is added to insolubilize heavy metals as hydroxide and coagulate suspended substances. Then, it is sent to the sedimentation tank (3) to settle and separate the hydroxides of heavy metals and aggregates of suspended solids.The supernatant water showing alkalinity is sent to the neutralization tank (4), and the neutralizing agent is added. Neutralize with

Next, the waste water from which heavy metals and suspended substances have been removed is sent to a second raw water tank (5), where it is stored and mixed with organic waste water. Then
The mixed wastewater is sent to the biological treatment tank (6), where organic substances are metabolically decomposed by aerobic microorganisms attached to the contact material immersed in the tank (6). At this time, the inside of the tank (6) is aerated. Next, the wastewater from which the organic matter has been decomposed is sent to a sedimentation tank (7), where the sludge composed of the organic matter decomposed is settled and separated, and then sent to a treatment water tank (8). If the quality of the treated water in the treated water tank (8) satisfies the discharge standard value, the treated water is discharged. If the quality of the treated water in the treated water tank (8) satisfies the required water quality of the destination, the treated water will be reused. From the viewpoint of resource saving and energy saving, it is preferable to reuse the treated water.

If the quality of the treated water in the treated water tank (8) does not satisfy the discharge standard value or the required water quality of the destination, the treated water is transferred from the treated water tank (8) to the sand filtration tank (9) and the activated carbon is adsorbed. Layer (10),
It is sequentially sent to the sterilization tank (11) and subjected to advanced treatment including sand filtration, activated carbon adsorption and sterilization, and then discharged or reused. When advanced treatment is performed, the quality of the treated water satisfies the discharge standard value and the required water quality of the destination.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an embodiment of the method according to the present invention.

FIG. 2 is a flow sheet showing a conventional method.

FIG. 3 is a flow sheet showing another conventional method.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 9/00 503 C02F 9/00 503G

Claims (1)

[Claims] 1. A first step of adding an agent comprising an alkali agent, a coagulant and a coagulation aid to an inorganic wastewater to insolubilize heavy metals as hydroxides and coagulate suspended substances, and to hydroxylate heavy metals. Second step for sedimentation and separation of aggregates of substances and suspended solids, third step for neutralizing supernatant wastewater in the second step, and mixing of organic wastewater containing organic matter into the supernatant wastewater neutralized in the third step A wastewater treatment method in a refuse incineration plant, comprising: a fourth step of performing a biological treatment of organic matter in the mixed wastewater to decompose the organic matter.