JPH07121387B2 - Organic wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable to BOD, COD, NH (normal hexane soluble substance or oily substance) and suspended solid substances (S
S: suspended solid) (sometimes referred to as flocs in the text below)

[Conventional technology]

Most conventional methods for purifying wastewater are chemical treatment methods and biological treatment methods (activated sludge method), and a combination of the two. High concentration of BOD, COD, N-
When treating raw wastewater containing H, flocs (suspended solid substances), etc., it is usual to first remove a large amount of contaminants by a chemical injection treatment and then perform a biological treatment. There are two methods of separation by this chemical treatment: floating or precipitation. The former is mainly used for organic substances and the latter is mainly used for inorganic substances.
Moreover, in most cases of separation of organic wastewater, it is customary to generate flocs by chemical injection to cause them to aggregate and then to inject pressurized water or positively inject air to effect floating separation.

[Problems to be solved by the invention]

The disadvantages of the above conventional method include the following items: (1) The flotation speed is slow, and it usually takes 4 to 5 minutes to float and separate, so that the throughput is low; The use of pressurized water (30-40% of the raw water) leads to an increase in the volume of the biological treatment equipment and it is necessary to have a pressurized water production device; for example, 30% of the pressurized water is used to treat 100 tons of raw water. Then, a large amount of 130 tons will be handled, and if the raw water is pushed up with pressurized water, flocs will contain 95% or more of water, making it easier to interfere with the treatment; (3) With the method by positively injecting air The flotation ability is influenced by the size of the produced flocs and / or impurities, and some large flocs may settle, resulting in a problem of separation ability. That is, in order to float a large floc, it is necessary to increase the amount of air at the time of injection or to increase the air-introducing pressure. Therefore, the state of agitation is caused, so that the floc is hard to float and difficult to separate; (4) The flocs separated by flotation generally have a high water content (95% or more) and are thus inconvenient for post-treatment.

Regarding the organic wastewater that needs to be subjected to the floating treatment as described above, especially for the food factory wastewater, the present inventor has previously issued a patent regarding the method for treating the marine product factory wastewater by the high-speed stirring method (Patent No. 101964
No. 3, Japanese Examined Patent Publication No. 55-6435), but the drawback of this method is that the problem remains in the equipment for large-scale processing.

[Means for solving problems]

The inventor has obtained various satisfactory results by the jet method as a result of various experiments conducted on the improvements of the prior art and the method of the above patent.

The features of the present invention are as follows: (1) BOD, COD, NH, and suspended solid substances are removed from an organic wastewater having a pH value adjusted in advance and / or a coagulant added thereto. In the method for treating organic wastewater to be removed, the wastewater to be treated is jetted under pressure into the jet ejector from a height of about 2 m or more, and a reduced pressure state is formed by the jetting, and air suction and polymer The above-mentioned method in which the wastewater to be treated is dropped into the floating solid substance floating separation means while inhaling the flocculant solution or is dropped onto the water surface of the means, and thus the floating solid substances are separated within a short time. .

(2) Organic wastewater feeding means, pH adjusting agent and / or coagulant feeding means, mixing means for mixing the organic wastewater with the pH adjusting agent and / or coagulant, and the mixed liquid obtained by the means In an organic wastewater treatment apparatus comprising a feeding means for feeding and adding air and a polymer flocculant solution and a separating means for separating floating solid substances after the feeding and adding, mixing is performed between the mixing means and the separating means. The apparatus described above, which is provided with a jet ejector for ejecting and dropping the liquid, and with a supply port for supplying air and a polymer coagulant by sucking air and a polymer coagulant to a reduced pressure state forming portion of the ejector.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Organic wastewater, especially wastewater from a food factory, is sent to a mixing tank (1) or (2) at a rate that maintains a constant flow rate through a flow rate adjusting tank (L) while using a pump (P). The operation can be performed in a batch system, a continuous system, or a combination of both systems. Using a pump (P) to the wastewater to be treated in the mixing tank, a pH adjuster such as an aqueous solution of caustic soda or a chemical substance (slaked lime,
Hydrochloric acid or the like) is added from a regulator storage tank (5) through a pump (P), and mixed by using a pH meter to generate flocs.

A flocculant such as a sulfuric acid band or PAC (abbreviation of polyaluminum chloride; used by Taki Kagaku Co., Ltd. in the present invention) was added to the flocculant storage tank (5) simultaneously with or separately from pH adjustment or without pH adjustment. From the above, a floc may be generated by adding and mixing it to the mixing tank via the pump (P). When the mixed solution (water to be treated) thus pretreated is fed to the jet ejector, a pressure of about 2.0 to 7.0 atm is required, so a multistage turbine pump (not shown) is usually used.

Also in the present invention, when the turbine pump set in the jet ejector is used, a height of about 2 m or more
The mixture is dropped from the jet ejector inlet (8) through the nozzle (9) under a pressure of 2.0 atm or more.
In this case, only the mixed solution is dropped without adding pressurized water as in the prior art. At that time, the falling water forms a depressurized state in the machine, and the air is sucked to hold air bubbles to facilitate the floating separation of the flocs from the falling water.

An adjusting valve is provided at the supply port (6-A) for supplying air by suction so that the degree of pressure reduction inside the machine can be kept constant. At the same time, the polymer coagulant solution is sent from the polymer coagulant solution storage tank (3) into the jet ejector through the supply port (6-B) by utilizing the reduced pressure in the machine and dropped while being mixed with the mixed solution. An adjusting valve and a flow meter are provided at the supply port (6-B) to adjust the addition amount of the polymer coagulant solution. As the polymer flocculant, various commercially available products can be used, but those which are preferably used in the present invention are, for example, Nippon Pure Chemical Co., Ltd. trade name Aronbis, Kurita Kogyo Co., Ltd. trade name Cliflock, Taki Kagaku. The trademark name is Takiflock manufactured by Mitsui Co., Ltd., the trademark name Akofrock manufactured by Mitsui Cyanamid Co., Ltd., and the like. The amount of polymer flocculant added is 5 to 60 PP for the wastewater to be treated according to the conventional method.
M, around 30PPM on average.

When the falling water falls from the jet ejector discharge port (12) into the flotation separation tank (7), the flocs are floated and separated within about 10 seconds in a short time. The separated liquid is separated and discharged according to a conventional method.

[Action]

The separation conditions that can be considered when achieving floc float separation according to the present invention in a short time of about 10 seconds are as follows: (1) Keeping the pressure of the treated wastewater fed to the jet ejector constant (2) Jet Adjust the amount of air and polymer flocculant solution fed from the ejector suction port, that is, the feed port, so that the flocculation separation of flocs is about 10 seconds; (3) Use a flocculant to prepare the mixture If necessary, use the flocculant in an amount such that flot flotation is achieved in the desired short time.

It is believed that the action of the combination of the above conditions will make the method successful.

Example 1 BOD 5000PPM, COD 3200PPM, suspended solids 1800PPM, N
-H Addition of PAC to the cleaning wastewater of mackerel with 500 PPM
After adjusting it to around 5.0, the adjusted drainage is dropped directly into the multi-jet ejector installed at a height of 3 m above the ground by a three-stage turbine pump at an amount of 30 m ³ / hour and the degree of pressure reduction produced at that time is used. After adding 30PPM of polymer flocculant (Trade name: Akofloc C447), floatation separation is performed instantly (about 10 seconds or less), BOD of about 80% is removed, and residual suspended solid matter is 10PPM, NH The residual amount was 1 PPM or less.

Example 2 BOD 1800PPM, COD 860PPM, NH 60PPM, suspended solids
Wastewater from a noodle manufacturing plant with 350 PPM is adjusted to pH 8 with slaked lime.
After adding PAC300PPM after 5, the mixture was thoroughly mixed and floated and separated by using a jet ejector in the same manner as described above. As a result, flok floating and separation time were exactly the same as in Example 1. In the case of wastewater from a noodle factory, the floc formation is better and the flotation is easier when the normal treatment is performed after adjusting the pH of the water to be treated to the alkaline side by using slaked lime.

〔The invention's effect〕

The effect of the present invention is that the flocs are floated and separated instantly (around 10 seconds) without actively injecting air as in the conventional method or without using pressurized water, and the water content of the separated flocs is also in the conventional method. Much lower than
85-90%, and the mass processing equipment is simple,
The cost is also extremely low.

[Brief description of drawings]

FIG. 1 of the accompanying drawings outlines the arrangement of the device and each means of the present invention. FIG. 2 shows an example of the jet ejector used in the present invention. 1 and 2 ... Mixing tank, 3 ... Polymer flocculant liquid storage tank, 4 ...
… Alkaline liquid storage tank, 5 …… PAC liquid storage tank, 6 …… Jet ejector, 6A …… Air supply port, 6B …… Polymer flocculant liquid supply port, 7 …… Separation tank, 8 …… Pressurized Mixed liquid inlet, 9 ... Nozzle, 10 ... Throat, 11 ... Diffuser, 12 ... Discharge port, L ... Flow rate adjusting tank, P ... Pump, PH ... pH value measuring device, M ... Agitation Machine, F ... levitating floc, T ... treated water.

Claims (2)

[Claims] 1. A method for treating organic wastewater, wherein BOD, COD, NH, and suspended solid substances are removed from the organic wastewater having a pH value adjusted in advance and / or a coagulant added thereto. Is ejected from a height of about 2 m or more into the jet ejector under pressure, a depressurized state is formed by the ejection, and the treated wastewater is suspended while inhaling air and the polymer coagulant solution under the state. The method as described above, characterized in that it is dropped into the solid material floating separation means or dropped onto the water surface of the means, and thus the floating solid material is floated and separated within a short time. 2. Organic wastewater feeding means, pH adjusting agent and / or
Flocculant feeding means, mixing means for mixing organic wastewater with pH adjusting agent and / or flocculant, and feeding means for feeding and adding air and polymer flocculant solution to the mixed liquid obtained by the means In a treatment apparatus for organic wastewater having a separating means for separating suspended solid substances after feeding and adding, a jet ejector for ejecting and dropping the mixed liquid is provided between the mixing means and the separating means, and a reduced pressure state of the ejector is formed. The above-mentioned device, which is provided with a supply port for supplying air and polymer coagulant by inhaling the air and the polymer coagulant.