JPH0226689A - Sewage treatment apparatus - Google Patents

Abstract

PURPOSE:To especially purify car washing waste water to a reutilizable state by mounting a specific drain pit, a purifying tank, a froth collection tank and a chemical adding apparatus. CONSTITUTION:Car washing waste water is stored in a secondary storage tank 2 from a drain pit 1 and, thereafter, a prescribed amount of said waste water is thrown in a purifying tank 3. Subsequently, a flocculation aid (anionic surfactant, flocculation collector and carbonate) is added to said tank 3 from a chemical liquid adding device 6 and the waste water is stirred to be allowed to stand. Thereafter, a flocculant (barium sulfate for tap water) is added to the waste water to perform stirring. After standing for a predetermined time, a polymer flocculant (nonionic surfactant) is added to stir the waste water. Thereupon, the suspended particles in the waste water are flocculated as flocs and, after the waste water is allowed to stand for a relatively long time, the flocs float naturally to be accumulated on the surface of the water. When fine air bubbles are injected in the waste water from an air diffusion pipe 4, said bubbles are adhered to the flocs to float said flocs to the surface of the water and the waste water is violently stirred. By this method, the flocculant in the waste water acts to generate a large amount of bubbles and the flocs are pushed up by said bubbles to be discharged to a froth collection tank 7. The froth also overflows out of the tank and the surfactant itself is removed from the waste water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention mainly relates to a sewage treatment device that purifies car wash wastewater discharged from a car wash to a state where it can be reused.

[Conventional Problem 1] In recent years, in response to calls for water pollution and conservation of water resources, the idea of purifying and reusing car wash wastewater discharged from Finn car washes or car wash corners of service stations has been proposed.

Car wash wastewater generally contains various suspended solids, including sand and dust, as well as wax and detergent.In order to remove these suspended solids and purify the wastewater, it is necessary to add foaming detergent ingredients and other suspended solids. It has to be removed at the same time, and with conventional equipment, the treatment of foam with detergents has been a problem. Furthermore, car wash wastewater does not always contain detergent components, and there are problems such as the need to change the treatment method depending on whether the wastewater contains detergent components or not.

[Objective of the Invention 1] The present invention has been made to address the above-mentioned problems, and provides a sewage purification device that utilizes the foam generated during purification treatment to obtain a sufficient purification effect for car wash wastewater under any conditions. is intended to provide.

[Embodiment 1 of the invention Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a system explanatory diagram of a sewage treatment apparatus according to an embodiment of the present invention. Reference numeral 1 designates a drainage bit that collects and temporarily stores car wash wastewater discharged from a car wash, etc., and 2 designates a secondary storage tank that pumps up the wastewater with a pump and further stores it. The secondary storage tank is composed of a plurality of tanks communicating with each other, and has the role of precipitating impurities such as sand and dust contained in the wastewater and purifying the wastewater to some extent. 3 is a sewage septic tank equipped with an aeration pipe 4 and having a funnel-shaped bottom. The air diffuser pipe 4 is connected to a compressor 5 and supplies fine bubbles into the tank. Reference numeral 6 denotes a drug collecting liquid addition device 7a that adds a flocculating chemical liquid to wastewater during purification treatment, and 7 is a foam collection tank that surrounds the septic tank 3. Therefore, during the purification process, the flocs formed in the waste water are floated by the foam ejected from the air diffuser W4, and are caused to overflow into the foam collection tank together with the flocs accumulated on the water surface of the waste water.

8 is a filter device that filters residual flocs contained in purified water pumped from the septic tank; 9 is a treated water inlet; 1
0 is a fresh water supply port, and 11 is a water tank for storing treated water and fresh water. Reference numeral 12 denotes a floc dewatering tank which receives impurities precipitated at the bottom of the secondary storage tank 2, flocs received in the foam collection tank 7 during purification treatment, and impurities deposited at the bottom of the septic tank. Returned to the pit.

The sewage purification process using the above system configuration is not performed continuously, but once the septic tank 3 is full, the injection of wastewater is stopped, and after purification, the wastewater is injected again. Batch processing is performed discontinuously in units of capacity, and the treated water is sent to a water storage tank each time.

Next, a description will be given of the coagulation treatment process of wastewater carried out in the treatment tank in the above configuration. In this process, the chemical solution is added by the flocculating chemical solution addition device 6, and the agitation and foam treatment using the fine bubbles ejected from the aeration pipe 4 are performed.

The chemical solution added at that time and the amount added are shown below. The numbers in parentheses indicate the order of addition, and all amounts added are based on the amount of wastewater 2001.

Table 1 After a specified amount of wastewater from the secondary water storage tank 2 is poured into the treatment tank 3, a coagulation aid is first added and stirred.

This aggregation aid consists of an anionic surfactant, an aggregation promoter, and a carbonate, of which the 7-ionic surfactant has foaming properties. At this time, since the stirring time is short, the waste water only foams slightly and no noticeable change is observed. After a predetermined period of time, when a flocculant is added and stirred, the waste water becomes cloudy. After leaving the mixture for a predetermined time again, a polymer flocculant is added and stirred, and the turbid particles in the wastewater begin to precipitate as flocs. So, after waiting for 70 tsuku to completely precipitate, this time, compared to the previous leaving time, let it stand for a relatively long time (here, 15 minutes).
As a result, most of the flocs deposited in the wastewater float to the surface and accumulate on the water surface, with only a small amount floating in the water.

Therefore, foam treatment is performed by ejecting fine foam from an aeration tube 4 provided at the bottom of the treatment tank. The fine bubbles adhere to the floating flocs, causing them to rise to the surface of the water, and also violently agitating the wastewater. Then, the initially added flocculant with foaming properties acts and the wastewater begins to foam, generating a predetermined amount of foam during foam treatment. These bubbles push up the flocs floating on the water surface and discharge them out of the tank, and when the bubbles overflow to the outside of the tank, the foaming surfactant itself is also removed from the waste water. At this time, if detergent components are contained in the wastewater, they will of course be removed at the same time.

As described above, according to the present invention, car wash wastewater that does not contain detergent components can also be purified using the foam flotation method. The results are shown in Table 2.

tjS2 surface visibility N-hexane car wash wastewater (untreated) 4 degrees 28 pp chewing rice method 10 to 18 degrees 17 pages, theoretical invention 30 degrees or more 5 Ppee system explanatory diagram.

1 is a drainage bit, 4 is an aeration pipe, 3 is a septic tank, 7 is a foam collection tank, and 6 is a chemical solution addition device.

[Effects of the Invention 1 As explained above], according to the present invention, even car wash wastewater that does not contain detergent components (or has a low detergent concentration) is treated with foam to generate foam, and the foam is utilized. The flocs that could not overflow from the treatment tank and were accumulated on the surface of the drainage water can be removed together with the floating flocs in the drainage water into the foam collection tank outside the tank. Furthermore, this has the effect of making purification treatment possible with a simple device, without the need for a scraper to scrape up lumps of floc accumulated on the surface of the waste water in the treatment tank, which was required with conventional devices. is obtained.

[Brief explanation of the drawing]

Claims (1)

[Claims] A drainage pit for storing car wash wastewater, a septic tank equipped with an aeration pipe, a foam collection tank configured to surround the septic tank and receive foam that overflows from the septic tank, and a chemical solution addition device that adds a flocculating chemical solution with foaming properties into the septic tank. and float the flocs formed by the flocculating chemical solution together with bubbles,
A sewage treatment device characterized in that overflow is treated in a foam collection tank.