JPS6031895A - High degree treatment of organic sewage - Google Patents

Abstract

PURPOSE:To efficiently treat org. sewage, by a method wherein ozone treatment is applied to org. sewage which undergone biological nitration and denitrification treatment and the treated sewage is subsequently held under an anaerobic atmosphere with a specific dissolved oxygen amount or less. CONSTITUTION:After known biological nitration and denitrification treatment is applied to org. sewage, flocculative precipitation treatment due to aluminum sulfate is performed and gas (with an ozone concn. of 28mg/Nm<3>) obtained by ozonating gas containing 90vol% of oxygen is injected into the obtained supernatant water to treat the same. Subsequently, biological anaerobic treatment (with DO concn. of<=0.5mg/l) is applied to treated water in an anaerobic bed packed with honeycomb tubes. By this method, the high degree treatment of org. sewage can be performed extremely efficiently and treated water with excellent water quality is obtained but, when higher water quality is required, treatment such as sand filtering is subsequently performed.

Description

[Detailed description of the invention] Technical field The present invention relates to an advanced treatment method for organic wastewater.

Background of the Technology Biological nitrification and denitrification is a well-known method for removing BOD and nitrogen compounds from organic wastewater such as human waste and sewage. This is a method in which organic wastewater is subjected to nitrification and denitrification treatment by the action of microorganisms.

However, biological nitrification and denitrification methods have a problem in that they cannot remove biologically persistent organic matter and nitrogen compounds. For example, when processing human waste without dilution,
The limit for total nitrogen (T-N) is 20 to 50 q/l, and it is difficult to achieve more advanced treatment by biological methods.

Conventionally, the ion exchange resin method, activated carbon method, ozone treatment method, etc. are known as methods for further advanced treatment of secondary treated water that has been subjected to multiple treatments by biological nitrification and denitrification. In the ion exchange resin method and the activated carbon method, sufficient treated water cannot be obtained, and in some cases, predetermined water quality standards may not be satisfied. On the other hand, it is known that when an ozone treatment method is applied and advanced treatment is performed using ozone, the BOD component increases. That is, ozone decomposes biologically difficult-to-decompose components in the secondary treated water into biologically degradable organic substances. In such ozone treatment, although COD, chromaticity, etc. are efficiently removed, the increase in BOD components is extremely undesirable.

Summary of the Invention In the course of various studies on the advanced treatment of secondary treated water with ozone as described above, the present inventors discovered that biologically persistent organic matter was decomposed into biologically degradable organic matter by ozone treatment. At the same time, biologically persistent nitrogen components are also decomposed into nitrite nitrogen (No□-N) or nitrate nitrogen (NOS-N). They discovered that organic matter and nitrogen can be easily removed by chemical treatment.

Therefore, the present invention provides an advanced treatment method for organic sewage, which involves subjecting organic sewage to biological nitrification and denitrification treatment, treating this treated water with ozonation, and then performing the following steps. The ozonated water is maintained in an anaerobic atmosphere with an amount of dissolved oxygen of 0.5 μ/cm as follows.

Detailed Description of the Structure of the Invention Biological nitrification-denitrification rice treatment can be performed by any known method. Moreover, this treated water may be directly subjected to ozonation treatment, or this treated water may then be subjected to 1-collection sedimentation treatment, and the supernatant water may be ozonated.

Ozone treatment can also be performed by any known method.

Ozonation is generally performed by injecting atmospheric air passed through an ozone generator into the secondary treated water. Alternatively, this ozone treatment can also be carried out by ozonizing a gas containing at least 50% oxygen by volume using an ozone generator and injecting it into the secondary treatment water. This is preferable because the decomposition of biologically persistent organic substances and nitrogen compounds is more accelerated than in the case of using air.

In the method of the present invention, the ozonated treated water is
Next, the amount of dissolved oxygen (Do) is maintained in the following anaerobic atmosphere at 0.5 .mu./. As a result, anaerobic biological treatment is achieved, and denitrification progresses by assimilating BOD components produced by decomposition of difficult-to-decompose components. At this time, a carbon source such as methanol may be added depending on the case. Alternatively, if the BOD component is in excess, biological treatment may then be performed in an aerobic atmosphere.

Any method may be used to maintain the ozonated water in an anaerobic atmosphere. For example, it can also be carried out by sealing the system to cut off contact with the oxygen-containing gas. However, in general, ozonated water d has already been subjected to biological nitrification and denitrification, so BOD, TN, etc. are all kept at low concentrations, and therefore, unlike the normal activated sludge method, It is difficult to maintain sludge concentration with suspension type systems.

Therefore, useful treatment methods include, for example, an anaerobic three-bed method in which a biofilm is formed by filling a pipe with nicum, a method using a rotating disk, or a method using a furnace material (e.g. sand). There are contact filtration methods that allow filling to form a biofilm.

According to the method of the present invention, highly efficient advanced treatment of organic wastewater can be achieved and treated water of excellent quality can be obtained. However, when even higher water quality is required, Then, a further treatment such as sand filtration may be performed.

Example The present invention will be further explained below with reference to Examples.

Example 1 Removed human waste was subjected to biological nitrification and denitrification treatment using a nitrification solution circulation method without dilution, and then subjected to coagulation and sedimentation treatment using sulfuric acid clay. A gas obtained by ozonizing a gas containing 90% by volume of oxygen (ozone concentration 28111) was added to the obtained supernatant water.
After ozone treatment by injecting F/Nms), biological anaerobic treatment (
DoO, 5 tq/) followed by biological aerobic treatment. The treatment conditions and the quality of treated water at each stage were as follows.

Ozone treatment conditions Ozone injection rate: 400 q/ Reaction tower residence time 60 minutes Biological treatment conditions Anaerobic section residence time 60 minutes Metal/-ol addition rate 301nf/ Aerobic section residence time: 30 minutes Treated water quality The treated water quality is summarized in Table 1 below.

Table 1 Example 2 The treatment was carried out under the same conditions as in Example 1, but here ozonized air (ozone concentration 8/Nm3) was used.
) was used for ozone treatment.

The quality of the treated water at each stage was as shown in Table 2 below.

Claims (1)

[Claims] 1. Subject organic wastewater to biological nitrification and denitrification treatment, treat this treated water with ozonation, and then maintain this ozonated water in an anaerobic atmosphere with a dissolved oxygen amount of 0.511Q/ below. Features: Advanced treatment method for organic wastewater.