JPH0231896A - Treating apparatus for waste water - Google Patents

Abstract

PURPOSE:To reduce running cost for the treatment of waste water by constituting a treating apparatus of a wet oxidation tower, an insolubilizing tank for insolubilizing P by adding an insolubilizing agent for P to the treated water of the wet oxidation tower, and a membrane separator for separating the reaction liquid from the insolubilizing tank for P through a precision filtration membrane or ultrafiltration membrane. CONSTITUTION:Waste water contg. materials to be oxidized and P from a feed liquid feeding line a is fed to a wet oxidation tower 1, where it is heated and pressurized to oxidize the material to be oxidized in the waste water, and the materials to be oxidized are decomposed to gaseous CO2, N2, and water. The gas/liquid mixture is transported to a gas/liquid separation tower 3, and treated water decomposed by the oxidation in the tower 3 is transported to an insolubilizing tank 10 for P, where it is mixed and stirred with slaked lime and a pH adjusting agent in a mixing and stirring zone 12. Thus, the P in the treated water is insolubilized. The treated water contg. the insolubilized P overflows a top of a separating wall 11 and is introduced into a pump pit 13, then fed to a membrane separation device 20 hosing an ultrafiltration membrane therein through a line 19. Permeated water of the membrane separation device is discharge out of the system. Thus, the frequency of washing in the membrane separation device 20 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in an apparatus for wet oxidation treatment of wastewater containing oxidizable substances and phosphorus.

(Prior art) Excess sludge or digested sludge generated when biologically treating wastewater containing oxidizable substances at a relatively high concentration, such as human waste, sewage, or human waste 1 Coal gasification/liquefaction wastewater , wastewater generated by pyrolysis of municipal waste, silk mills, textile dyeing factories, 1 food factory.

Chemical Factory 1 Wet oxidation treatment is performed on factory wastewater discharged from oil refineries and other various factories.

In this wet oxidation treatment, the above-mentioned wastewater is introduced into a wet oxidation reaction tower consisting of a high-pressure tank, and is maintained at high temperature and pressure in the presence of oxygen to convert the oxidized material into carbon dioxide gas.

It is decomposed into nitric acid, nitrogen gas, and water.In order to carry out the oxidative decomposition reaction efficiently, a tank packed with an oxidation catalyst is built into the wet oxidation reaction tower.

Titania (titania oxide) is used for catalytic oxidation.

Iron, manganese, cobalt, and nickel can be added to a single metal porous body such as zirconia (zirconia oxide), alumina, silica, silica-alumina, activated carbon, or nickel, nickel-chromium, nickel-chromium-aluminum, or nickel-chromium-iron. , ruthenium, rhodium, palladium, iridylam, platinum, copper, gold and tungsten and their oxides, as well as chlorides such as ruthenium dichloride and platinum dichloride, and ruthenium sulfide. A sulfide such as rhodium sulfide supported on a compound that is insoluble or poorly soluble in water is used.

Furthermore, the treated water from the wet oxidation reaction tower is used to remove decomposition products such as sodium sulfate using a reverse osmosis membrane device (hereinafter referred to as "R○ device") with a built-in reverse osmosis membrane, and the permeated water is reused. has been carried out (for example, JP-A-62-132)
Publication No. 589).

(Problem to be solved by the invention) However, since the conventional treatment equipment described above is configured to treat the treated water from the wet oxidation reaction tower with the RO equipment, the permeated water from the R○ equipment is recycled. Although there are some benefits when using this method, there is a drawback that the cost is high when the permeated water is simply discharged outside the system.

This is because the treated water from the wet oxidation reaction tower contains a large amount of phosphorus and other salts in addition to the decomposition product sodium sulfate, so if an RO device is used, the reverse osmosis membrane will be heavily contaminated and must be cleaned frequently. This increases the cost of cleaning chemicals, and the R◯ device requires a high-pressure pump, which increases equipment costs.

(Means for Solving the Problems) In view of the above-mentioned problems, the present invention aims to provide an apparatus that can easily treat treated water of a wet oxidation reaction tower up to the discharge standard, and the structure is such that the water to be oxidized is and a wet oxidation reaction tower that introduces wastewater containing phosphorus and performs wet oxidation treatment; a phosphorus insolubilization reaction tank that adds a phosphorus insolubilizing agent to the treated water from the wet oxidation reaction tower to insolubilize phosphorus; and the phosphorus insolubilization. A membrane separator that performs membrane separation treatment on a reaction liquid from a reaction tank using a precision filtration membrane or an ultrafiltration membrane.

(Function) In the present invention, the phosphorus component in the treated water from the wet oxidation reaction tower is insolubilized in the insolubilization reaction tank and removed by a membrane separator equipped with a microfiltration membrane or an ultralach membrane.

(Example) Hereinafter, the apparatus of the present invention will be explained based on the illustrated embodiments.

The drawing is a flow sheet showing one embodiment of the apparatus of the present invention, and 1 is a wet oxidation reaction tower consisting of a high-pressure tank filled with a well-known oxidation catalyst. This wet oxidation reaction tower 1 is supplied with waste water containing oxidized substances and phosphorus from a raw solution supply line 1a, and heated to a temperature of 250 to 290 nm by heating means (not shown).
It is heated to 0℃ and heated to 70-90k by means of pressure.
It is pressurized to g/cm2, and oxygen is further supplied by a gas supply means.

Note that heating is performed using an external heat source when starting the device, but
When the device is in a steady state of operation, oxidative combustion in the stock solution can be performed.

Further, although it is not necessarily necessary to fill the wet oxidation reaction tower 1 with an oxidation catalyst, efficient oxidation can be achieved if the wet oxidation reaction tower 1 is filled with an oxidation catalyst as in this embodiment.

The oxidizable substances in the wastewater are oxidized in the wet oxidation reaction tower 1,
It is decomposed into carbon dioxide gas, nitrogen gas, and water, and the gas-liquid mixture is sent to the gas-liquid separation column 3 via line 2. This line 2 is provided with a heat exchanger (not shown), by which the waste water in the stock solution supply line 1a is heat exchanged, heated, and heat is recovered.

The gas components separated in the gas-liquid separation tower 3 are sent to a cyclone separator 6 through a line 5 with a pressure reducing valve 4 interposed therebetween. The gas separated by the cyclone separator 6 is discharged to the atmosphere, and its liquid component is sent via a line 7 to a phosphorus insolubilization reaction tank, which will be described later.

The liquid oxidized and decomposed in the gas-liquid separation tower 3, that is, the treated water, is sent to the line 7 via a line 9 with a valve 8 interposed therebetween. The opening and closing of the valve 8 is controlled by a detection signal from a level meter (not shown) provided in the gas-liquid separation tower 1, and the liquid level in the gas-liquid separation tower 1 is controlled to always be at a predetermined level.

Reference numeral 10 denotes a phosphorus insolubilization reaction tank, which is divided by a partition wall 11 into a mixing and stirring section 12 and a pump pit 13. In the mixing and stirring section 1.2, the treated water from the wet oxidation reaction tower 1 received from the line 7 via the line 9, the pH#Il adjustment agent storage tank 14, and the slaked lime (calcium hydroxide) storage tank 1.
p added by dosing pump 16 and ]7 from 5
H adjuster.

The slaked lime is mixed and stirred by air bubbling.

Note that this mixing and agitation is performed using a well-known machine h'1. instead of air bubbling. Stirring may also be used.

The pH adjuster storage tank 14 contains raw wastewater (raw solution supply line 1a).
An acid or alkali agent is prepared depending on the nature of the waste water (waste water inside), and is added from there by the chemical injection pump 16. That is, the flow meter 81 measures the amount of treated water supplied to the mixing and stirring section 12.
At the same time, the pH is detected by a pn meter 82, and the chemical injection pump 16 is controlled so that the pH is at a predetermined level.

The amount of slaked lime added is determined by controlling the chemical injection pump 17 to insolubilize just the right amount of phosphorus in the treated water based on the average phosphorus concentration in the raw wastewater determined in advance and the detection signal of the flow meter 81. It is done. In addition, instead of slaked lime, quicklime, calcium chloride, aluminum compounds, which insolubilize phosphorus,
Ferrous chloride.

An insolubilizing agent such as ferric chloride, ferrous sulfate, or ferric sulfate may be used, and in this case, the slaked lime storage tank 15 stores the insolubilizing agent instead of slaked lime.

When slaked lime and treated water are mixed and stirred in the mixing and stirring section 12, phosphorus in the treated water is converted into hydroxyabatite 1□ (Cas○
H.(PO4)3), which becomes insolubilized and aggregates or crystallizes out. The treated water containing insolubilized phosphorus is transported to the partition wall 1.
It overflows the upper part and is introduced into the pump pit 13, from where it is supplied via one line with a pump 18 interposed therebetween to the membrane separator 20 containing the ultralacrimal membrane. The built-in ultrafiltration membrane may have a molecular weight cut-off or higher that allows ions to pass through, and the membrane separator 20 may be of the well-known flat membrane type or tubular type. A precision filtration membrane may be used instead of the filtration membrane.

The permeated water from the membrane separation 1a20 is obtained via the line 21, and after having its pH adjusted as necessary, it is discharged to the outside of the system.

Concentrated water containing insolubilized phosphorus and ash produced in the wet oxidation reaction tower 1 is sent to a concentration tank 23 via a line 22. Further, a part of the concentrated water is branched from the line 22 and sent to the above-mentioned mixing and stirring section 12 via a line 25 with an ejector 24 interposed therebetween. For this reason, the mixing and stirring section 1
In step 2, a portion of the concentrated water containing air is supplied and bubbling is performed, thereby effectively performing mixing and stirring.

The concentration tank 23 undergoes solid-liquid separation using gravity, and the supernatant liquid is returned to the pump pit 13 via a line 26. The solid content in the concentration tank 23 flows through the inlet 27 to the mixing tank 28.
Here, the chemical injection pump 30 is introduced from the dehydrating agent storage tank 29.
After being mixed with the dehydrating agent supplied by the centrifugal dehydrator 3
Solid-liquid separation is performed by 1. The dehydrated sludge from the centrifugal dehydrator 31 is received in a hopper 32 and then sent to landfill, etc., and the dehydrated r-liquid is sent to the phosphorus insolubilization reaction tank 10 or raw wastewater (not shown) via a line 34 that includes a pump 33. Returned to storage tank. Note that instead of the centrifugal dehydrator 31, a belt press dehydrator or other known dehydrator may be used.

(Effects) As described above, the present invention decomposes the organic substances to be oxidized in the wastewater introduced into the wet oxidation reaction tower, and then sends the treated water to the phosphorus insolubilization reaction tank, where the organic matter contained in the treated water is decomposed. The structure is configured to insolubilize the phosphorous that is produced using slaked lime, iron salts, or aluminum compounds, and then perform solid-liquid separation using a membrane separator with a built-in ultrafiltration membrane or precision filtration membrane. The phosphorus concentration can be lowered to below the discharge standard and can be discharged outside the system.

Moreover, the membrane separator does not remove ionic substances like an RO device and has a small molecular weight cutoff. Since the SS component is simply removed by the membrane, the load on the membrane is small, so there is less membrane contamination, and the number of times of cleaning can be reduced.

Furthermore, equipment costs can be reduced because a high-pressure pump is not required like in an RO device.

In addition, when insolubilized phosphorus is separated into solid and liquid by sedimentation, it is necessary to cool the phosphorus insolubilized liquid to atmospheric temperature to prevent convection, but since membrane separation is performed in the present invention, this is not possible. There is no need to worry about this, and all you need to do is cool it down to a temperature that does not adversely affect the film, for example, 10 to 15 degrees below atmospheric temperature.
It is sufficient to cool the membrane to a temperature higher than 0.degree. C., and since the temperature is high in this case, the effect of increasing the amount of permeation through the membrane separator can be obtained.

Furthermore, since solid-liquid separation is performed by membrane separation, there is no leakage of SS unlike in sedimentation separation treatment, and the inconvenience of coloring components being discharged outside the system can be prevented.

[Brief explanation of the drawing]

The drawing is a flow sheet showing an embodiment of the apparatus of the present invention. 1... Wet oxidation reaction tower 3... Gas-liquid separation tower 10... Phosphorus insolubilization reaction tank 20... Membrane separator

Claims (1)

[Scope of Claims] 1. A wet oxidation reaction tower that introduces wastewater containing oxidized substances and phosphorus and performs wet oxidation treatment, and a phosphorus insolubilizer is added to the treated water from the wet oxidation reaction tower to insolubilize the phosphorus. A wastewater treatment device comprising: a phosphorus insolubilization reaction tank; and a membrane separator that performs membrane separation treatment on the reaction liquid from the phosphorus insolubilization reaction tank using a microfiltration membrane or an ultrafiltration membrane.