JPH0125636B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating highly concentrated waste liquids such as human waste, and particularly to a method that can treat human waste and other waste liquids to good water quality in a short period of time without dilution or chemical injection. High-concentration wastewater (BOD, wastewater with a high concentration of total nitrogen (hereinafter referred to as TN), such as human waste, septic tank sludge, livestock manure, etc.) that exceeds the scope of application of the normal activated sludge method can be processed without dilution in a short time. In the case of treatment, high-concentration activated sludge (MLSS 10,000 ppm or more) is guided into a reaction tank equipped with an aeration device that has a larger oxygen supply capacity than a normal aeration pipe (porous diffuser, disk user, etc.). In the same reaction tank, the inflow organic nitrogen and ammonia nitrogen are oxidized (nitrified) and its oxidation product nitrite,
Reduction of nitrate nitrogen to _N2 (denitrification) occurs. However, the TN removal rate at this time has an irresistible limit depending on the amount of organic matter in the stock solution (which can be used as an organic carbon source). That is, an organic carbon source is necessary for the denitrification reaction to occur, but if the organic carbon source is small, the denitrification rate is limited. In this case, since the undiluted BOD is used as the organic carbon source, if the inflow amount is small, the denitrification rate will be suppressed. In addition, in the undiluted treatment of these stock solutions, ammonia nitrogen is generally oxidized only to nitrite nitrogen, but this nitrite nitrogen is toxic to purification microorganisms, so ammonia nitrogen is oxidized to nitrite nitrogen. The oxidizing ability of nitrite bacteria, which oxidizes to ammonia nitrogen, deteriorates, and complete removal of ammonia nitrogen is not achieved, and the water quality does not reach a level that can be easily discharged. As described above, the above-mentioned non-dilution reaction step (nitrification step) had the following two problems. (1) There is an unavoidable limit to the TN removal rate depending on the BOD/TN in the stock solution. That is, BOD/TN is the ratio between the organic carbon source and the amount of nitrogen to be denitrified, and when this value is small, the denitrification rate is suppressed. (2) Nitrite nitrogen accumulates and becomes biologically toxic, making complete removal of ammonia nitrogen impossible. The present invention has been made for the purpose of solving the above-mentioned problems, and provides a method for treating high-concentration waste liquid with activated sludge without dilution or at a low dilution rate, using an aeration device with a large oxygen supply capacity. The activated sludge in the tank is guided to a single reaction tank in which the activated sludge is maintained at a high concentration, and an organic carbon source is injected into the reaction tank to perform nitrification and denitrification treatment on the high concentration waste liquid, and then the treated liquid is transferred to a sedimentation tank. The gist of this is to conduct solid-liquid separation by introducing Hereinafter, the present invention will be explained in detail using the accompanying drawings and the like. FIG. 1 is a schematic diagram showing the basic configuration of the process according to the present invention. In FIG. 1, the stock solution 11 is removed from the residue using a decanter or drum screen (not shown).
(highly concentrated waste liquid) flows into this process without dilution from line 1, and the raw liquid 11 is passed through a normal aeration pipe (porous diffuser, disk user, etc.).
An aeration device 7 having a larger oxygen supply capacity than the sludge is attached to supply air 8, and the sludge flows into a reaction tank 2 in which a non-dilution reaction process using highly concentrated activated sludge is performed. The aeration device 7 used here disperses and atomizes the compressed air supplied from the blower.
It is a high-speed rotating body with a cylindrical shape (however, the top is blank, which is similar to an upside-down tip). Although the interior is hollow, the supplied air is supplied into the rotating body, overflows, and forms fine bubbles on the external side wall due to friction with the liquid.
Therefore, in actual use, the oxygen supply rate can be adjusted by changing the rotational speed of this rotating body and the amount of supplied air. To increase the oxygen delivery rate,
To increase the number of revolutions and the amount of air, and conversely to decrease the oxygen supply rate, reduce the number of revolutions and the amount of air. In this reaction tank 2, the removal of BOD in the stock solution 11, the oxidation of organic nitrogen and ammonia nitrogen, and further reduction to _N2 are performed simultaneously. The reaction situation is as follows. (Equations 1 to 4) Nitrification treatment (NH ₄ -N→NO ₂ -N→NO ₃ -N) NH ₄ ⁺ +1.5O ₂ →NO ₂ ^- +H ₂ O+2H ^-
...1st formula NO ₂ ^- +0.5O ₂ →NO ₃ ^- ...2nd formula Denitrification treatment 2NO ₃ ^- +10H→N ₂ ↑+4H ₂ O+20H ^-
...3rd formula 2NO ₂ ^- +6H→N ₂ ↑+2H ₂ O+20H ^-
...Equation 4 In this treatment reaction step, an organic carbon source 12 necessary for reducing nitrous acid and nitrate nitrogen generated by oxidation of organic nitrogen and ammonia nitrogen is externally supplied to line 9 (for example, methanol, acetic acid, etc.). Inject from. The reason why the aeration device 7 with a large oxygen supply capacity is provided is as follows. In other words, this is because the O ₂ consumption rate per unit reaction tank capacity is high and the concentration level is high, resulting in a high reaction rate. By injected air 8 and organic carbon source 12, stock solution 11
After being efficiently nitrified and denitrified in reaction tank 2,
The reaction tank discharge liquid 13 is led to the downstream separation tank 3 through a line 14, where solid-liquid separation and sludge concentration are performed. A part of the treated water 15 is recycled from line 10 to line 1, and the remaining treated water 15 is discharged outside the system. On the other hand, a part of the sludge in the separation tank 3 is continuously circulated from line 6 to line 1 as return sludge 16, and excess sludge 17 is pulled out from line 5. This surplus sludge 17 is sent to a sludge treatment facility (not shown). EXPERIMENTAL EXAMPLE Next, the results of continuous tests on the process shown in FIG. 1 will be shown. The test conditions are as follows. (1) Raw solution 11 Human waste after sediment removal, decanter separated liquid of crushed raw human waste procured from a certain treatment plant (2) Number of processing days (reaction tank capacity / raw solution (undiluted human waste)
Flow rate)...2 days (3) Sludge concentration in tank...(10000 to 13000 (ppm)) (4) Dilution ratio...No dilution (5) Sludge return rate (return sludge amount/undiluted solution flow rate) x 100%
...200~300% (6) Dissolved oxygen (DO) concentration in reaction tank 2...3~
4.5 (ppm) (7) Aeration equipment High-performance aeration equipment (aeration equipment shown in Figure 1) (8) Organic carbon content... CH ₃ OH for N/Kg
The results of the 2Kg experiment are shown in Table 1.

[Table] In this way, the present invention provides a method for treating high concentration waste liquid with activated sludge without dilution or at a low dilution rate, by providing an aeration device with a large oxygen supply capacity for the high concentration waste liquid and increasing the activated sludge in the tank. The high concentration waste liquid is led to a single reaction tank where the concentration is maintained, an organic carbon source is injected into the reaction tank, the high concentration waste liquid is subjected to nitrification and denitrification treatment, and the treated liquid is then led to a precipitation tank to perform solid-liquid separation. The following effects can be obtained. When an organic carbon source is not injected, the TN removal rate A in this step has an irresistible limit as shown in equation 5 depending on the stock solution BOD/TN. That is, since the undiluted solution BOD is only used as an organic carbon source, when the inflow amount of the undiluted solution BOD decreases, the TN removal rate A is suppressed and a limit occurs. A=L ₀ /a×N ₀ (5th formula) where, L ₀ : BOD concentration in stock solution (Kg/m ³ ) N ₀ : TN concentration in stock solution (Kg/m ³ ) a: NO ₂ - N or NO ₃ - Amount of BOD required for N1Kg ring formation (Kg) However, if an organic carbon source is injected from outside as in the present invention, the organic carbon source increases, so the upper limit of the TN removal rate A is will further increase. In the no-dilution reaction process of highly concentrated wastewater, the influent ammonia nitrogen is oxidized only to nitrite nitrogen, which is biotoxic and thus limits the ability to remove ammonia nitrogen. By injecting an organic carbon source from the outside, the concentration level of nitrite nitrogen is reduced, the ammonia nitrogen removal ability is improved, and a highly efficient TN removal rate can be achieved. Note that the efficiency described above can be further improved if the present invention is carried out under the following conditions. (1) Increase sludge concentration as much as possible. (2) Apply an aeration device with a larger oxygen supply capacity than a general aeration pipe. (3) Target high concentration wastewater shall be treated at a dilution rate of 3 times or less.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the basic process flow of the present invention. 2... Reaction tank, 7... Aeration device with large oxygen supply capacity, 8... Air, 9... Organic carbon source, 11... Stock solution.

Claims (1)

[Claims] 1. In a method of treating high concentration waste liquid with activated sludge without dilution or at a low dilution ratio, a single reaction tank is provided with an aeration device having a large oxygen supply capacity and the activated sludge in the tank is maintained at a high concentration. A method for treating a high concentration waste liquid, comprising: injecting an organic carbon source into the reaction tank to subject the high concentration waste liquid to nitrification and denitrification treatment, and then introducing the treated liquid to a precipitation tank to perform solid-liquid separation. .