JPS59160593A - Treatment of waste liquid of high ammonia concentration with activated sludge - Google Patents

Abstract

PURPOSE:To perform treatment of waste liquid of high ammonia concn. without pretreatment or dilution by adjusting the concn. of dissolved oxygen in an aeration tank contg. waste liquid of high ammonia concn. to 0.1-0.5ppm and performing treatment with activated sludge for the adjusted waste liquid. CONSTITUTION:Ammonia liquor having 5,000ppm ammonia concn. is charged to an aeration tank and aerated to 0.3ppm dissolved oxygen. and then subjected to the treatment with activated sludge. As the result, SCN<-> is held always at <=3ppm; the superiority of the performance of the treatment is thus recognized. The control of the dissolved oxygen in the aeration tank is performed by the control of the working number of stirrers in accordance with detection signals issued by a measuring instrument for the dissolved oxygen installed in the aeration tank, or by other means. For the control of the dissolved oxygen, it is desirable to use simultaneously oxidation-reduction potential and pH as the measure for the operation. By this way, treatment of waste liquid of high ammonia concn. is possible without dilution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an activated sludge treatment method for high ammonia waste liquid such as ammonium chloride.

Ammonium water generated from a coke oven is separated and recovered from various components contained therein, then subjected to activated sludge treatment and coagulation sedimentation treatment, and then treated with activated carbon before being discharged. Activated sludge treatment is a method of removing BOD using bacteria.
Aqueous solution contains many substances that are toxic to bacteria, such as NH4 and CN. Therefore, the processability is influenced by the concentration of these toxic substances. Generally, the permissible NH4 concentration for bacteria is said to be 1000 to 500 ppm. Therefore, conventionally, if the NH4 in the liquid to be treated is higher than this value, it is necessary to add water vapor, alkali, etc. and distill it to remove it to this value (see Figure 1).
, or diluted.

However, in the case of dilution, equipment such as an aeration tank becomes larger and construction costs increase. Also, when removing ammonia by distillation,
Requires distillation equipment and steam to decompose the fixed ammonia.

Since it is necessary to add alkali or the like, there is a problem that running costs become high.

The present inventor conducted extensive research to solve this problem, and as a result, obtained the following knowledge.

Experimental example 1 Ammonia ion in wastewater was increased from 6001)pm to 150pm
After increasing the concentration to 0 ppm, changes in the treated water were investigated.

The results are shown in FIG.

From Figure 2, even if ammonia ions rise.

It can be seen that the thiocyan ion (8ON) concentration began to decrease from about the 15th day, and the processability was recovered. Therefore, one of the following can be inferred from this experimental result. The toxicity of ammonia ion itself is compatible.

Alternatively, the recovery in treatability occurred because the nitrification reaction of O,..., No3 to NH4I stopped due to a decrease in the number of bacteria.However, if nitrification is suppressed from the beginning, NH4 can be produced even at a high level. Well, no.

Experimental Example 2 A confirmation experiment was conducted regarding the adaptability of bacteria to ammonia ions obtained in Experimental Example 1.

As shown in Figure 3, the ammonia ion concentration was set to 600~8.
It increased by 200ppm from 00ppm. As is clear from the fluctuations in SCN, no adaptation of Tsukukuchiria to ammonia ions was observed during the approximately two-month test.

Experimental Example 3 Regarding the effect of nitrification on activated sludge obtained in Experimental Example 1,
Confirmation experiments were conducted.

Focusing on the fact that the nitrifying bacteria that cause the nitrification reaction are aerobic, the aeration tank was maintained so that the dissolved oxygen (DO) was 0.1 to 0.5 ppm. As a result, as shown in Figure 4, the nitrification reaction stopped and the treatability (indicated by the concentration of SCN) was restored. At this point 2400→2600pp
Although the ammonia ion concentration was increased to m, the processability did not change. Although not shown, the processability did not change even when the concentration was 3090 ppm.

From Experimental Examples 1 to 3, in order to prevent nitrification, the aeration tank Do (
It was found that the amount of dissolved oxygen (dissolved oxygen content) must be kept at 0.5 ppm or less. However, if the amount is less than 0.01 ppm, even if nitrifying bacteria are not activated, the activity of other bacteria is lost, resulting in poor processability.

The present invention was made by paying attention to this knowledge.

The amount of dissolved oxygen in the aeration tank containing high ammonia waste liquid was reduced to 0.
By treating activated sludge with a concentration of 1 to 0.5 ppm, high ammonia wastewater can be treated without dilution.

The advantage of this treatment method is that it does not require pretreatment equipment or dilution.

The present invention will be explained below with reference to the drawings.

In the present invention, activated sludge treatment is performed by setting the amount of dissolved oxygen in the aeration tank containing the high-concentration ammonia waste liquid to 0.1 to 0.5 ppm.

High ammonia waste liquid includes ammonium water, etc. According to the present invention, even waste liquid with an ammonia ion concentration of about 6000 ppm can be treated. The reason why the amount of dissolved oxygen in the aeration tank is limited is to suppress nitrification and improve processability.The reason why we set the upper limit to 0.5 ppm is because nitrification cannot be suppressed if it exceeds this limit.
Also 0. The reason why lppm was set as the lower limit is that below this value, bacterial activity is lost and processability is reduced. The amount of dissolved oxygen in the aeration tank is controlled by, for example, installing a dissolved oxygen measuring device in the aeration tank and adjusting the number of operating agitators based on the detection signal of this measuring device.

When controlling the amount of dissolved oxygen, the redox potential (0RP
) and pH as a guideline for operation. There is a relationship between the oxidation-reduction potential (ORP) and SCN, which indicates processability, as shown in FIG. It is preferable to follow. Also pH and SCN
There is a relationship as shown in FIG. Therefore, the pH should be set to 6.5.
It is preferable to operate as above.

Note that if the bacteria in the aeration tank are extracted from the system (for example, expressed as bacteria%), nitrification will not occur even if the DO is ippm. In addition, if bacteria are removed from the system and the amount of wastewater treated is increased (for example, bacteria as %,
Nitrification does not occur even if the drainage volume is increased by 1.3 times) and the DO is 11)I)m.

Next, an example of the present invention will be described. Ammonium water (ammonium ion concentration 5000 ppm) was placed in an aeration tank, and activated sludge treatment was performed by operating the tank so that the DO was 0.3 ppm. As a result, 5CN- is always 3
ppm or less, indicating excellent processability.

As explained above, according to the present invention, high-concentration ammonia waste liquid can be treated without pretreatment or dilution, and the remarkable effect is that the equipment becomes compact and running costs are reduced.

Figure 1 is an explanatory diagram showing the treatment results of the conventional activated sludge treatment method for ammonium water (high ammonia waste liquid) - Figures 2 to 6 show the method of the present invention, and Figure 2 is the treatment in Experimental Example 1. Figure 3 is an explanatory diagram showing the treatment results in Experimental Example 2. Figure 4 is an explanatory diagram showing the treatment results in Experimental Example 3. Figure 5 is an explanatory diagram showing the treatment results in Experimental Example 3. Figure 5 is an explanatory diagram showing the treatment results in Experimental Example 3. Characteristic diagram showing the relationship,
FIG. 6 is a characteristic diagram showing the relationship between pH and thiocyanine ions.

Applicant's agent: Patent attorney Takehiko Suzue Figure 1 (Day) Figure 2 Figure 4

Claims (1)

[Claims] The accumulated amount of dissolved acid in the aeration tank containing high ammonia waste liquid was reduced to 0.
A method for treating high ammonia waste liquid with activated sludge, characterized in that the activated sludge treatment is carried out at a concentration of 1 to 0.5 ppm.