JPS58133888A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To reduce the high concn. COD in waste water effectively by controlling the pH of the waste water, then adding a proper amt. of sodium hypochlorite and introducing ozone through said water to treat the waste water. CONSTITUTION:After the pH of waste water contg. oxyacid ions of nitrogen and chlorine, etc. is adjusted to >=7pH, sodium hypochlorite is added until the oxidation reduction potential of the waste water soln. attains the highest potential to decrease COD and the remaining chlorine in the waste water. Ozone is introduced through such waste water to minimize the remaining COD. This method decreases the COD in the waste water by oxidizing the reductive materials in the waste water effectively by the oxidative effect of both sodium hypochlorite and ozone.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating wastewater, and particularly to a method for treating wastewater with high concentration of C.
Wastewater treatment method suitable for efficiently (reducing OD) K1
Take 1l.

Wastewater discharged from laboratories containing N oxygen acid ions such as NOs and CI oxygen acid ions such as Cl0r, NO
Sodium chlorite (NaCjOw) 11 liquid that absorbed C
This is because the OD concentration is high and does not meet the wastewater standards.

Cannot be drained directly.

For this reason, conventional methods have been adopted such as leaving the wastewater in a reservoir or adding an appropriate oxidizing agent to the wastewater. However, the former method has problems such as limited amount of accumulated water and low odor, while the latter method has sufficient ticOD reduction efficiency and the solution after licking treatment has COD
A & Ill determination was carried out and dilution was performed with a large amount of water to comply with wastewater standards. Therefore, high −11 in wastewater
It has been desired to establish a treatment method that can efficiently and sufficiently reduce cODt.

An object of the present invention is to provide a wastewater treatment method that efficiently and sufficiently reduces highly concentrated RCOD in wastewater and complies with wastewater standards.

The present invention skillfully utilizes the characteristics of sodium hypochlorite (Na(JO)) and ozone (01), effectively utilizes the oxidation rate of NaCj0, and utilizes the strong oxidizing power of NaCj0. At the same time, by eliminating the generation of residual chlorine, which is a drawback of NaCJO, the oxidizing action of both NaCjO and 01 efficiently oxidizes reducing substances that are difficult to oxidize in wastewater, thereby reducing COD in wastewater. It is something.

Therefore, the wastewater targeted by the present invention is wastewater containing a high concentration of COD, and in particular, the wastewater contains Na CI
Wastewater containing reducing substances that are difficult to oxidize even when O is added is effective in the present invention. Examples of wastewater containing such reducing substances include wastewater containing N oxygen acid ions such as N01- and/or CI prime acid ions such as tlcIch-. In wastewater containing these oxygen acid ions, various N and Cl-based reducing reaction products present in the wastewater are considered, and these components become a load on COD, giving a high CODt-.

In the present invention, after adjusting the pH of the wastewater to 7 or higher in the first step, sodium hypochlorite is added until the oxidation-reduction potential (ORP) of the wastewater solution reaches the highest potential.

The reason why the pH of the wastewater is adjusted to 7 or more in the first step is that when the wastewater solution is under acidic conditions, the added NaCjO itself decomposes and no longer contributes to the oxidation reaction. The pH of the wastewater in the first step is desirably adjusted to a range of 7 to 9. The pH of the wastewater is 91! If you fall, NaC
Although decomposition of 10 itself does not occur, the oxidation reaction rate sharply decreases, so in order to more efficiently oxidize high-concentration COD in wastewater, the pH of the wastewater should be kept under alkaline conditions in the range J that does not exceed 9. This is desirable. In this way, wastewater p
After adjusting H, adding NaCl0' into the wastewater increases the redox potential (ORP) and maintains a constant potential after reaching the highest potential. That is, it contains oxygen acid ions of HN and CI in Figure 1, and the reducing reaction products formed by these ions produce highly concentrated [C0D
t for the wastewater that gives.

When NaCJO is added, ORP increases as the amount of NaCl0 increases in the pH range of 7 to 9.
The figure shows that the voltage increases, but once it reaches the highest potential (approximately 900 mV), it remains constant. Therefore, in the first step, NaCjOtORP is added to the wastewater while checking for a rise, and when ORP stops changing to the highest potential KJL, the addition of NaCjOt is stopped. Such Na CI
By adding O, a large part of the COD in wastewater can be reduced.

In the 1st construction (1), the ORP is constant.

Even when added to NaC10', the complex reducing N in wastewater
and/or N compounds etc. are not pickled.

It cannot be reduced to C0D1. therefore.

Adding Na Cl O even after the ORP reaches its maximum potential not only increases the consumption of NaCl 0 but also increases the amount of residual chlorine in the wastewater solution, which is undesirable.

Next, in the second step, COD remaining without being oxidized in the first step is reduced by passing Os into the wastewater. That is, NaCl0 used in the IEl process
Treatment cannot completely reduce COD2), especially when COD is due to various N- and C1-based reducing reaction products. In the second step, the oxidizing power of OI is utilized to further reduce the residual COD. In this way c.

The D-reduced treated water is then pH-adjusted to meet wastewater standards according to known methods.

Drain.

As described above, according to the present invention, in the first step, NaC
Most of the COD can be effectively reduced by adding pictures of jO,
In addition to reducing residual chlorine in wastewater,
The COD remaining in the process is removed using 0. It is particularly effective for wastewater containing reducing substances that are difficult to oxidize.

Example N and COD 4630pp containing Cl oxyacid ions
m (D waste lI200sj'lJ7 beaker VC removal, H
(After adjusting the pH of the solution to 8 using J, available chlorine 1
The ORP of the NaCl0 solution is at its highest potential (approximately 900
mV) to reduce COD, and then 01 treatment (flow rate 400 nil/min -On).
#11''0.8jl/h, time 1h).The results.

As shown in Table IK, the COD of the waste liquid is 20 ppm! It was possible to reduce the amount of heat.

Table 1

[Brief explanation of drawings]

Figure 1 shows the potential titration curve at 9 o'clock when NmCl0 was added in highly concentrated #COD wastewater. Agent Tatsuyuki Unuma (and 2 others) Figure 1 0 5 10 15 NoCIO (12%) 4 additions (ml)

Claims (3)

[Claims] (1) After adjusting the pH of the wastewater to 17 or higher, add primary hypochlorite (IJ) to the oxidation-reduction potential (0RP) of the wastewater solution.
The first step of adding until the maximum potential is reached, and the first step a
112. A method for treating fresh water, comprising: 112 steps of passing ozone through the wastewater that has passed through the wastewater. (2) The wastewater treatment according to claim 1, wherein the wastewater supplied to the Ill Process 1i#IC is wastewater containing nitrogen oxygen acid ions and/or chlorine oxygen acid ions. Method. (3) In the first step, the pH of the wastewater is adjusted to 7 to 9! I. The method for treating wastewater according to item 1 or 1m2.