JPS6043200B2 - Wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating industrial wastewater containing nitrate nitrogen and/or nitrite nitrogen, and particularly to a method for treating industrial wastewater containing nitrate nitrogen and/or nitrite nitrogen. This article relates to a method for adjusting and controlling the amount of organic carbon (organic carbon source) added.

Conventionally, methods for controlling the amount of organic carbon source added in denitrification treatment include (1) a method of detecting and controlling the amount of nitrate nitrogen in inflow water or outflow water;

(2) A method of detecting and controlling ORP (oxidation-reduction potential) in the outflow water or the denitrification reaction tank.

For the former, it is most common to use an ion electrode to detect nitrate nitrogen, but the nitrate ion electrode has many interfering ions, has a large detection error, and is also susceptible to contamination on the electrode surface. Easy to cause errors.

,Re, E5 stroke-1, Ikl^ding" JJL Yamako Hunger JJL Because the detection time is short and there is no method with high detection accuracy, it lacks reliability as a means of detecting organic carbon sources.In addition, the latter lacks reliability as a means of detecting organic carbon sources. There is also a difference in ORP between cases where nitrate nitrogen remains in the water and cases where it has been completely removed. Since it cannot be an accurate indicator to judge whether there is
It is difficult to control the amount of P added. For this reason, conventionally, when controlling the amount of organic carbon source added, it is added in an amount greater than the amount necessary for complete denitrification in response to fluctuations in the amount of nitrogen. That is, a method has been adopted in which an excessive amount of organic carbonate source is always added. However, since methanol, glucose, acetic acid, alcohol, etc. used as organic carbon sources are expensive, adding excess will cause an increase in the operating cost of biochemical denitrification. It was also a source of BOD and a cause of deteriorating the water quality of runoff. The denitrification reaction by microorganisms is represented by a two-step process as shown in the following equation, if methanol is used as the organic carbon source and synthesis by the microorganisms is ignored.

1st stage NOi+O, 33CH3OH→NOi+0.
67 L O...1 In the second step and in the denitrification reaction, the amount of methanol added as an organic carbon source is equal to the amount of methanol required for complete denitrification (C
m) Cm=2.47(NO3-N)+1.53(NO2
-N)+0.87D0 (DO: dissolved oxygen concentration), neither nitrate nitrogen nor nitrite nitrogen is detected in the effluent, but the amount of methanol added is the required amount of methanol (C
Although it is unclear which reaction step in formulas 1 and 2 becomes rate-determining when the amount is less than m), it has been found that nitrite nitrogen always remains in the effluent water.

The present invention was completed based on the knowledge of the above phenomenon, and by detecting nitrite nitrogen, which is simple and measurable even in trace amounts, the amount of organic carbon source added can be adjusted, reducing chemicals and operating costs. The purpose is to measure the reduction in water consumption and prevent the deterioration of the quality of runoff water.

The present invention involves adding a hydrogen donor (organic carbon source) to industrial wastewater containing nitrate nitrogen and/or nitrite nitrogen, and then using a fixed bed type or fluidized bed method filled with granular media to which denitrifying microorganisms are attached. The method for denitrification treatment is characterized in that the amount of the hydrogen donor added is adjusted by detecting the nitrite nitrogen concentration in the denitrified effluent.

That is, organic carbon sources were added to industrial wastewater containing nitrate nitrogen and/or nitrite nitrogen. First, the granular media to which denitrifying microorganisms are attached are introduced into a fixed-bed or fluidized-bed denitrifying reaction tank, and the denitrifying microorganisms biochemically convert nitrate nitrogen and/or nitrite nitrogen. A nitrite nitrogen detection device is installed at the outflow end of the denitrification reaction tank to detect whether a certain amount or more of nitrite nitrogen remains in the denitrified effluent. This system adjusts and controls the amount of organic carbon source added, and increases the amount when it is detected that the denitrification reaction has not progressed completely and more than a certain amount of nitrite nitrogen remains in the effluent. When nitrite nitrogen is not detected in the effluent, control is performed to reduce the amount added.

To detect nitrite nitrogen, the α-naphthylamine sulfanilic acid method or the N-ethylenediamine sulfanilic acid method shown in JIS wastewater testing methods, sewage testing methods, etc. is used.

These test methods involve nitrite ions diazotizing sulfanilic acid, which is then converted into α-naphthylamine or N
-It is quantified by measuring the absorbance of the color produced by combining with ethylenediamine, and there are few interfering substances.0.01m9''
It has the characteristic of being able to accurately detect even minute amounts of nitrite nitrogen. Therefore, it is possible to more reliably adjust and control the amount of organic carbon source added by detecting nitrite nitrogen, and the residual organic carbon source in the effluent can be reduced accordingly. Deterioration of water quality can be prevented, and in some cases, a reprocessing device with 0D residual W output may be unnecessary. Next, one embodiment of the present invention will be described with reference to FIG. 1. First, wastewater containing nitrate nitrogen and/or nitrite nitrogen is subjected to a denitrification reaction by filling granular media 2 from raw water inlet pipe 1. At the same time as being introduced into the tank 3, an organic carbon source 4 such as methanol, acetic acid, sugars, etc. is added and supplied by a pump 5.

In the denitrification reaction tank 3, water is passed from the lower part and flows upward under conditions such that at least a part of the granular medium 2 expands and becomes fluidized, causing a contact reaction.
When the organic carbon source is decomposed into carbon dioxide gas and water using the oxygen in the nitrite ions, the nitrate and nitrite ions are reduced to nitrogen gas and released into the atmosphere. The treated water that has been denitrified in the denitrification reaction tank 3 is discharged or sent to the next treatment process from an outflow pipe 6, but the nitrite nitrogen detection device 7 installed in the middle of the outflow pipe 6 detects the presence of nitrogen in the outflow water. The nitrite nitrogen concentration is detected, and if a certain amount or more of nitrite nitrogen is detected in the outflow water, an organic carbon source is added by the chemical injection pump 5 or the flow control valve 8 that is linked to the detection device 7. The amount is increased, and if it is not detected, the amount added is reduced.
Note that the method of the present invention, which detects nitrite nitrogen in runoff water and controls the amount of organic carbon source added, can also be applied to denitrification treatment using a biological flotation method, but the residence time in the reaction tank 3 is In short, a fixed bed method in which denitrifying microorganisms are attached to the surface of a granular medium, in which the excess or deficiency of organic carbon source relative to nitrate nitrogen and/or nitrite nitrogen in influent water is sensitively reflected in denitrification treatment; This is advantageous in denitrification treatment using a fluidized bed method. As described above, according to the present invention, by detecting the nitrite nitrogen concentration in runoff water, the amount of organic carbon source added can be adjusted and controlled more reliably, thereby reducing the amount of chemicals used and further improving the operational efficiency. It is possible to reduce costs and also prevent deterioration of the quality of runoff water.

Next, examples of the present invention will be shown.

Example 1 Wastewater containing 20m91e of N03-N was poured into a fixed sake bed (10 to 2
0. The results of denitrification treatment when changing the addition ratio of methanol to NO3-N in the influent wastewater when water is passed through φ gravel, bed height 4m at a water flow rate of LV = 15 mIhr are as follows.
It was as shown in the figure.

The same wastewater was also mixed into a fluidized bed with denitrifying microorganisms attached to the surface of the granular medium (sand with an effective diameter of 0.8 and uniformity coefficient of 1.4,
Fluidized bed height 2.5TL. Figure 3 shows the results of the denitrification treatment when the addition ratio of methanol to NO3-N in the influent wastewater was changed when water was passed upward at a water flow rate of LV = 40 ml/hr.

As is clear from Figures 2 and 3, methanol addition ratio (CH
When the ratio (3OH/NO3-N) becomes 2.5 or less, NO2-N remains in the effluent, and when the addition ratio becomes even smaller, NO3-N also remains. Therefore NO in the effluent
It is extremely effective to adjust and control the amount of organic carbon source added by detecting 2-N. Example 2 Activated sludge treated water from urban sewage (NO3-N=10-14.2mgI', NO2-
N=Tr. ) in seconds (effective diameter 0.8 gourd, uniformity factor 1.4)
LV=
Denitrification treatment was carried out by passing water upward at 45 Tt and Ihr.

The amount of methanol added to the inflow water is calculated as the amount of NO2-N in the outflow water.
The results of detecting and adjusting the amount of water were as shown in FIG. As is clear from Figure 4, NO3 in the inflow water
By adjusting and controlling the amount of methanol added in response to fluctuations in 1N, excessive addition of methanol was prevented, and the amount of oxidized nitrogen in the effluent was always below 0.3 ppm.

[Brief explanation of the drawing]

Figure 1 is a system explanatory diagram showing one embodiment of the present invention, Figure 2 is a diagram showing the relationship between the nitrogen component and the methanol addition ratio in the immersed bed, and Figure 3 is the diagram showing the relationship between the nitrogen component and methanol addition ratio in the fluidized bed. Figure 4 shows the relationship between the addition ratio of methanol and the addition ratio of methanol to the influent water.
This is a diagram showing the results of detecting the amount and controlling the adjustment. 1... Raw water inflow pipe, 2... Granular media,
3... Denitrification reaction tank, 4... Organic carbon source, 5... Pump, 6... Outlet pipe, 7
...Nitrite nitrogen detection device, 8...Flow control valve.

Claims (1)

[Claims] 1 Add a hydrogen donor to wastewater containing nitrate nitrogen and/or nitrite nitrogen, and perform denitrification treatment using a fixed bed method or fluidized bed method filled with granular media to which denitrifying microorganisms are attached. A method for treating industrial wastewater, characterized in that the amount of the hydrogen donor added is adjusted and controlled by detecting the concentration of nitrite nitrogen (NO_2-N) in the denitrification treatment effluent.