JPS603872B2 - Wastewater treatment equipment - Google Patents

Description

[Detailed Description of the Invention] In recent years, due to the increase in water demand, industrial wastewater is not only treated and discharged, but also advanced treatment that combines physical, biological, and chemical treatment is performed to reuse wastewater. I'm in the mood to move on.

Furthermore, with the development of urban sewage systems, the amount of secondary treated sewage discharged from sewage treatment sites is increasing, and conventional sedimentation biological treatment alone is insufficient to purify the water, resulting in increased pollution of rivers and the sea after discharge. are doing. For this reason, from the standpoint of environmental conservation, more advanced sewage treatment is required, and there is a trend toward highly treating the large amounts of secondary treated sewage water that is produced, purifying it to the point where it can be used as industrial water. The oxidizing power of ozone is used for advanced treatment of industrial water or secondary treated sewage water.

Ozone is effective in deodorizing, decolorizing, sterilizing, and decomposing other organic pollutants, and in particular has the effect of inactivating viruses, making it indispensable for the reuse of wastewater.
In addition, excess ozone remaining in the waste water returns oxygen through self-decomposition, so there are no problems such as residual treatment chemicals or increased salt concentration, unlike conventional chlorine treatment. Furthermore, ozone can be easily generated using only electricity using air or oxygen as a raw material. Ozone is a gas at room temperature, and the ozone concentration obtained from an ozone generator is approximately 1% (by weight) when air is used as the raw material, and approximately 2% (by weight) when oxygen is used as the raw material.
The concentration is about %.

Therefore, in order to treat wastewater using ozone, a gas contacting device is required. Generally, a porous diffuser or a suction type injector is used to increase the gas contact area, and the ozone-containing air is transferred to the wastewater. Or injecting oxygen. In this way, wastewater treatment equipment using ozone increases the gas-liquid contact time, water pressure, etc. in addition to the gas contact area, thereby promoting the solubility and reactivity of ozone. However, the gas discharged from the upper part of the reactor contains several unreacted ozone, which is completely decomposed using activated carbon or a catalyst before being released into the atmosphere to prevent air pollution caused by ozone. In industrial factory wastewater to be treated, detergent periodically flows in from cafeteria wastewater, and in machine factories, wastewater contains a lot of surfactants such as water-repellent cutting oil and crab optical flaw detection liquid. contains not only dyes but also many water-soluble polymeric substances and surfactants as adhesives and detergents.

Furthermore, at sewage treatment plants, substances that are difficult to treat using the activated sludge method, such as detergents from domestic wastewater and protein components from human waste, remain in the secondary treated sewage water. These wastewaters have a strong foaming property and become a hindrance to various wastewater treatment operations. Ozone's strong oxidizing power can oxidize and decompose these foaming components, reduce their molecular weight, and defoam them. However, when treating wastewater containing a large amount of these foaming components, steady operation becomes impossible as described below. In other words, at the initial stage of operation, the foaming components inside the reaction tank are present at a uniform concentration, and when the ozone-containing gas is injected, the ozone is quickly reacted with these foaming components at the bottom of the reaction tank. The ozone concentration in the bubbles that are almost consumed and rises is very low, and in the upper part of the reactor the ozone concentration is the same as that caused simply by gas injection.
This phenomenon also occurs when substances that react more easily with ozone than foaming components coexist in the wastewater, and even in continuous treatment, it occurs due to unexpected changes in water quality. When this foaming occurs in an amount exceeding the space volume at the top of the reactor, it enters the exhaust ozone decomposition tower that comes out from the top of the ozone reactor, wets the activated carbon or catalyst layer, increases pressure resistance, and reduces the effective surface area required for exhaust ozone decomposition. decrease. This means that even when normal operation returns, the gas containing the reacted ozone is exhausted at saturated steam pressure, so the interior of the exhaust ozone decomposition tower is not dried out.
The effective surface area required for decomposition cannot be recovered and unreacted ozone is released into the atmosphere. The purpose of the present invention is to provide wastewater treatment that can detect unexpected foaming due to changes in water quality, etc., and add ozone bubbles directly to the foam based on the detection results, thereby reliably removing the foam without wasting ozone. The goal is to provide equipment.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an ozone reaction tank for injecting ozone-containing gas into wastewater to treat pollutants in the wastewater.

The wastewater to be treated is introduced into the ozone reaction tank 1 through the introduction pipe 2, and the treated wastewater is discharged through the discharge pipe 3 as treated water. The ozone-containing gas generated in the ozone generator 4 is introduced into the porous main diffuser 6 provided at the bottom of the ozone reaction tank 1 through the ozone introduction pipe 5, and the ozone-containing gas is bubbled out from the main diffuser 6. Injected into the water. Ozone discharged without reacting in the ozone reaction tank 1 is sent to an ozone decomposition tank 8 through a 9E ozone pipe 7, where a small amount of reacted ozone is completely decomposed by activated carbon or a catalyst. Reference numeral 9 denotes a sub-diffuser, which is provided in the upper part of the reaction tank 1, that is, near the surface of the wastewater, especially for the purpose of defoaming, and has a bubble-generating hole 4 smaller than the bubble-generating hole of the main diffuser 6.

Ozone-containing gas is supplied to this sub-diffuser 9 through a branch pipe 10 branched from the ozone introduction pipe 5 and a solenoid valve 11, and the ozone-containing gas is extinguished from the foam accumulated near the water surface, and the water-containing foam is removed from the ozone pipe 9E. 7. Suppress the transfer of waste ozone to the decomposition tower 8. Here, the reason why the bubble generation holes of the sub-diffuser 9 are made smaller than those of the main diffuser 6 is as follows.

In other words, since the sub-diffuser 9 is installed near the surface of the wastewater in the reaction tank 1, the larger the generated ozone bubbles, the greater its own buoyancy, and it rises without making sufficient contact with the bubbles, dissolving unreacted ozone. Become. On the other hand, if the bubble generation holes in the sub-diffuser 9 are made smaller and the ozone bubbles generated therefrom are made smaller and more numerous, it is possible to make sufficient contact with the bubbles accumulated near the water surface and evenly break the bubbles. The amount of unreacted ozone generated is also small. A pair of bubble detection electrodes 12 attached to the upper part of the space of the ozone reaction tank 1 are conductive level meters, and when bubbles adhere, a minute current flows, which opens the solenoid valve 11 through the relay circuit 13, and from the sub-diffuser 9. Ozone-containing gas is injected to oxidize the foam accumulated on the water surface and eliminate the foam.

When the bubbles fall below the bubble detection electrode position, relay circuit 1 is activated again.
3 is activated, the solenoid valve 11 is closed, and ozone treatment is performed using only the main diffuser 6. This bubble detection part can be a ball tap type level meter that detects the water surface, or a capacitance type level meter. However, with the ball tap type, precise operation is difficult because the buoyancy caused by the bubbles is small, and with the capacitive type, it is not optimal because it operates due to the bubbles that remain attached. In the conductive level meter used in the present invention, current also flows from the inner wall of the reaction tank that is wet with droplets. Therefore, only the tips of the electrodes are brought as close together as possible to allow a large current to flow due to the adhesion of bubbles, and the electromagnetic valve is controlled to open and close. is designed to operate with a large current value. Also, since scum builds up on the electrodes after long-term use, it is best to use one that can be removed and washed. As described above, according to the present invention, since foaming is detected and ozone bubbles are added directly to the foam, the foam can be effectively removed without wasting ozone. The activated carbon or catalyst for decomposition is wetted, pressure resistance is increased, and exhaust ozone is not completely decomposed and released into the atmosphere, allowing automatic and continuous stable wastewater treatment.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of a wastewater treatment apparatus according to the present invention. 1...Ozone reaction tank, 3...Discharge pipe, 4...
...Ozone generator, 6...Main diffuser,
8...Ozone decomposition tank, 9...Sub diffuser, 12...Bubble detection electrode. Figure 1

Claims (1)

[Claims] 1. An ozone reaction tank into which wastewater is introduced, a main dehydrator user provided at the lower part of the ozone reaction tank to send ozone into the wastewater as bubbles, and a main dehydrator user provided near the surface of the wastewater in the ozone reaction tank. an auxiliary dehydrator having a bubble generation hole smaller than the bubble generation hole and sending ozone into the waste water as bubbles from the bubble generation hole; and a bubble detection electrode provided in a space above the ozone reaction tank to detect bubble formation. and a valve that is provided in a conduit for competitively supplying ozone to the sub-drainage user and is opened by the foam detection output of the foam detection electrode.