同じような効果が得られる方式として、例えば、好気槽３、無酸素槽２、再曝気槽、沈殿池４の順で窒素含有排水を通水する内生硝化脱窒法もある。この場合、好気槽３では、散気装置１２から供給される酸素によりアンモニア性窒素が硝化され、無酸素槽２では、活性汚泥中に吸着蓄積された有機物成分を水素供与体として脱窒が行われる。排水中の有機物濃度が低い場合、もしくは排水が無機性の場合は、外部から無酸素槽２に水素供与体を添加することにより脱窒が進められる。
また、窒素とリンを含有する排水の場合には、窒素、リン同時除去方法が用いられる。 例えば、嫌気槽、無酸素槽２、好気槽３の順で窒素含有排水を通水する嫌気―無酸素―好気法などである。
これらの窒素含有排水を生物学的に処理する施設では、窒素含有排水中に含まれるアンモニア性窒素を硝化するために、好気槽３において酸素含有気体の曝気を行っており、曝気風量は、曝気風量一定制御、もしくは流入水量比例制御、又は溶存酸素濃度（以下、ＤＯと称す）一定制御などによって制御されているのが一般的である。
As a method similar effect can be obtained, for example, the aerobic tank 3, anoxic tank 2, re-aeration tank, there is also a raw nitrification denitrification among you passed through a nitrogen-containing waste water in the order of settling tank 4. In this case, in the aerobic tank 3, ammonia nitrogen is nitrified by oxygen supplied from the air diffuser 12, and in the anoxic tank 2, denitrification is performed using the organic component adsorbed and accumulated in the activated sludge as a hydrogen donor. Done. When the concentration of organic matter in the wastewater is low or the wastewater is inorganic, denitrification proceeds by adding a hydrogen donor to the anoxic tank 2 from the outside.
In the case of wastewater containing nitrogen and phosphorus, a simultaneous nitrogen and phosphorus removal method is used. For example, anaerobic tank, anoxic tank 2, anaerobic you passed through a nitrogen-containing waste water in the order of the aerobic tank 3 - and the like aerobic method - anoxic.
In a facility for biologically treating these nitrogen-containing wastewater, oxygen-containing gas is aerated in the aerobic tank 3 in order to nitrify ammonia nitrogen contained in the nitrogen-containing wastewater, It is generally controlled by aeration air volume constant control, inflow water volume proportional control, or dissolved oxygen concentration (hereinafter referred to as DO) constant control.
好気槽へ流入する流入水のアンモニア性窒素濃度（Ｃ１）と、好気槽最後部区画における目標アンモニア性窒素濃度（ＳＶＮＨ４）から前述の（５）式を用いて、好気槽最後部区画における目標アンモニア性窒素濃度（ＳＶＮＨ４）を実現するために必要な目標硝化速度（ＳＶｄＳＮＨ４／ｄｔ）を求める。
計算した目標硝化速度（ＳＶｄＳＮＨ４／ｄｔ）、定数Ｋの値、目標アンモニア性窒素濃度（ＳＶＳ ＮＨ４）を前述の（６）式に代入し、ＳＶＤＯを求める。
以上の計算を溶存酸素・曝気風量演算装置２２にて行い、目標アンモニア性窒素濃度を実現するために必要なＤＯ設定制御のＳＶＤＯもしくは曝気風量を演算し、演算されたＳＶＤＯもしくは曝気風量から求められる制御信号を、ＳＶＤＯよりも測定されたＤＯが高い場合には曝気風量を減らし、低い場合には曝気風量を増やす制御を行う溶存酸素制御手段１４へ送る。
硝化速度演算装置２１と溶存酸素・曝気風量演算装置２２と溶存酸素制御手段１４により、ＤＯ設定制御手段が構築されており、計算されたＳＶＤＯに基づき、好気槽３のＤＯは制御される。
From the ammonia nitrogen concentration (C1) of the inflow water flowing into the aerobic tank and the target ammonia nitrogen concentration (SV NH4 ) in the last section of the aerobic tank, using the above formula (5), the last part of the aerobic tank A target nitrification rate (SVdS NH4 / dt) necessary to achieve the target ammoniacal nitrogen concentration (SV NH4 ) in the compartment is determined.
The calculated target nitrification rate (SVdS NH4 / dt), the value of the constant K, and the target ammonia nitrogen concentration (SV S NH4 ) are substituted into the aforementioned equation (6) to obtain SVDO.
The above calculation is performed by the dissolved oxygen / aeration air volume calculation device 22, and the DODO control SVDO or aeration air volume necessary for realizing the target ammoniacal nitrogen concentration is calculated and obtained from the calculated SVDO or aeration air volume. The control signal is sent to the dissolved oxygen control means 14 that performs control to reduce the aeration air volume when the measured DO is higher than the SVDO, and to increase the aeration air volume when the DO is low.
The DO setting control means is constructed by the nitrification speed calculating device 21, the dissolved oxygen / aeration air amount calculating device 22, and the dissolved oxygen control means 14, and the DO of the aerobic tank 3 is controlled based on the calculated SVDO.
以下に本発明を用いて施設を制御した例を示す。
実施例１
嫌気−無酸素−好気法のパイロットプラントにおける実施例を示す。本実施例は、本発明の方法にて制御した結果である。
図６及び図７に水温条件の異なる時期での制御状況を示す。
本処理設備は、嫌気槽１槽（０．６５ｍ３）、無酸素槽２槽（０．９６ｍ３×２）、好気槽３槽（０．９６ｍ３×３）からなり、流入水量８．２５ｍ３／ｄ、硝化液循環率は流入水量に対して１５０％、汚泥返送率は流入水量に対して５０％で運転されているＨＲＴ１５．９時間の嫌気−無酸素−好気法のパイロットプラントである。
図７の６／１５ １０：００を例にとって計算する。無酸素槽２区画目のアンモニア性窒素濃度が４．８ｍｇ／Ｌ、好気槽１区画目のアンモニア性窒素濃度が３．６ｍｇ／Ｌのとき、好気槽１区画目の滞留時間は０．９３ｈｒであった。（１）式により、好気槽１区画目の硝化速度は１．３ｍｇ／Ｌ・ｈｒとなった。このとき、好気槽１区画目のＤＯは、０．１２ｍｇ／Ｌであった。前述の（４）式の溶存酸素の飽和定数Ｋｏ２を０．６０、アンモニア性窒素の飽和定数を０．４５としたとき、（４）式により定数Ｋは８．８ｈｒ−１と計算される。
Examples of controlling facilities using the present invention are shown below.
Example 1
The Example in the pilot plant of an anaerobic-anoxic-aerobic method is shown. This example is the result of control by the method of the present invention.
6 and 7 show the control status at different times of the water temperature condition.
This treatment equipment consists of 1 anaerobic tank (0.65 m 3 ), 2 anaerobic tanks (0.96 m 3 × 2) and 3 aerobic tanks (0.96 m 3 × 3). HRT 15.9 hours anaerobic-anoxic-aerobic pilot plant operating at 25 m 3 / d, nitrifying liquid circulation rate of 150% with respect to inflow water, sludge return rate with 50% of inflow water It is.
The calculation is performed using 6/15 10:00 in FIG. 7 as an example. When the ammoniacal nitrogen concentration in the second section of the anaerobic tank is 4.8 mg / L and the ammoniacal nitrogen concentration in the first section of the aerobic tank is 3.6 mg / L, the residence time in the first section of the aerobic tank is 0.8. It was 93 hr. According to the formula (1), the nitrification rate in the first compartment of the aerobic tank was 1.3 mg / L · hr. At this time, the DO in the first compartment of the aerobic tank was 0.12 mg / L. When the saturation constant Ko 2 of dissolved oxygen in the above equation (4) is 0.60 and the saturation constant of ammoniacal nitrogen is 0.45, the constant K is calculated as 8.8 hr −1 according to the equation (4). .
処理水の目標アンモニア性窒素濃度を０．５ｍｇ／Ｌとすると、（５）式に無酸素槽２区画目のアンモニア性窒素濃度４．８ｍｇ／Ｌと目標アンモニア性窒素濃度０．５ｍｇ／Ｌと好気槽全体の滞留時間２．８ｈｒを代入して目標硝化速度１．５ｍｇ／Ｌ・ｈｒが計算される。計算された目標硝化速度を（６）式に代入し、目標溶存酸素濃度ＳＶＤＯ０．３ｍｇ／Ｌを得て、ＳＶＤＯを溶存酸素の制御値として制御を行った。なお、実験ではＤＯの制御下限を０．５ｍｇ／Ｌとしたため、実際にはＤＯは０．５ｍｇ／Ｌとして制御されている。これを１時間毎に繰り返した結果を図６及び図７に示す。
本パイロットプラントでは、本発明のＤＯ設定制御（実験系）とＤＯ一定制御（対照系）を比較した。図６のように、水温が１８℃の条件でＤＯは１．０ｍｇ／Ｌを中心に制御され、処理水ＮＨ４−Ｎ濃度も一時的に１．１ｍｇ／Ｌまで上昇するも、ほぼ０．４〜０．５ｍｇ／Ｌであった。このとき曝気風量はＤＯ一定制御（１．５ｍｇ／Ｌ）における日平均風量が８．８ｍ３／ｈだったのに対して、本発明のＤＯ設定制御を実施した場合には７．９ｍ３／ｈであり、本発明のＤＯ設定制御を実施することで、ＤＯ一定制御を実施したときよりも１０％程度曝気風量を低減することができた。
When the target ammonia nitrogen concentration of the treated water is 0.5 mg / L, the ammonia nitrogen concentration in the second section of the oxygen-free tank is 4.8 mg / L and the target ammonia nitrogen concentration is 0.5 mg / L in equation (5). The target nitrification rate of 1.5 mg / L · hr is calculated by substituting the residence time of the entire aerobic tank of 2.8 hr . The calculated target nitrification rate was substituted into equation (6) to obtain a target dissolved oxygen concentration SVDO 0.3 mg / L, and control was performed using SVDO as a control value of dissolved oxygen. In the experiment, since the lower control limit of DO was set to 0.5 mg / L, the DO is actually controlled to be 0.5 mg / L. The results of repeating this every hour are shown in FIGS.
In this pilot plant, the DO setting control (experimental system) of the present invention and the DO constant control (control system) were compared. As shown in FIG. 6, DO is controlled around 1.0 mg / L under the condition where the water temperature is 18 ° C., and the concentration of treated water NH 4 -N temporarily rises to 1.1 mg / L. It was 4 to 0.5 mg / L. While the daily average air flow in this case aeration amount DO constant control (1.5 mg / L) was 8.8 m 3 / h, when the DO setting control of the present invention was carried out in 7.9 m 3 / h, and by performing the DO setting control of the present invention, it was possible to reduce the aeration air volume by about 10% compared to when the DO constant control was performed.
実施例２
次に、実施例１と同じ施設において、本発明の別の方法にて制御した結果を示す。
図８に制御状況を示す。
図８の、６／１２ １３：００を例にとって計算する。好気槽１区画目のアンモニア性窒素濃度が３．６ｍｇ／Ｌ、好気槽２区画目のアンモニア性窒素濃度が１．９ｍｇ／Ｌのとき、好気槽２区画目の滞留時間は０．９３ｈｒであった。（１）式により、好気槽２区画目の硝化速度は１．８ｍｇ／Ｌ・ｈｒとなった。このとき、好気槽２区画目のＤＯは０．２６ｍｇ／Ｌであった。前述の（４）式の溶存酸素の飽和定数Ｋｏ２を０．６０、アンモニア性窒素の飽和定数を０．４５としたとき、（４）式により定数Ｋは７．５ｈｒ−１と計算される。
Example 2
Next, the results of control by another method of the present invention in the same facility as in Example 1 are shown.
FIG. 8 shows the control status.
The calculation is performed using 6/12 13:00 in FIG. 8 as an example. When the ammoniacal nitrogen concentration in the first compartment of the aerobic tank is 3.6 mg / L and the ammoniacal nitrogen concentration in the second compartment of the aerobic tank is 1.9 mg / L, the residence time in the second compartment of the aerobic tank is 0.00. It was 93 hr. According to the formula (1), the nitrification rate in the second compartment of the aerobic tank was 1.8 mg / L · hr. At this time, the DO in the second compartment of the aerobic tank was 0.26 mg / L. When the saturation constant Ko 2 of dissolved oxygen in the above equation (4) is 0.60 and the saturation constant of ammoniacal nitrogen is 0.45, the constant K is calculated as 7.5 hr −1 according to the equation (4). .
処理水の目標アンモニア性窒素濃度を０．５ｍｇ／Ｌとすると、（５）式に、好気槽１区画目のアンモニア性窒素濃度３．６ｍｇ／Ｌと、目標アンモニア性窒素濃度０．５ｍｇ／Ｌと、好気槽全体の滞留時間２．８ｈｒを代入して、目標硝化速度１．１ｍｇ／Ｌ・ｈｒが計算される。計算された目標硝化速度を（６）式に代入し、目標溶存酸素濃度ＳＶＤＯ０．２３ｍｇ／Ｌを得て、ＳＶＤＯを溶存酸素の制御値として制御を行った。これを１時間毎に繰り返した結果を図８に示す。
本処理施設では、本発明のＤＯ設定制御（実験系）とＤＯ一定制御（対照系）を比較した。
図８に示すように、水温２３℃の条件で、ＤＯは０．５〜１．０ｍｇ／Ｌで制御され、処理水ＮＨ４−Ｎも０．１〜０．６ｍｇ／Ｌで制御されており、曝気風量もＤＯ一定制御の場合が日平均７．２ｍ３／ｈ、本発明のＤＯ設定制御の場合が５．９ｍ３／ｈであり、ＤＯ一定制御を実施したときに比べて１８％程度低減できた。表２にその結果を示す。
When the target ammonia nitrogen concentration of the treated water is 0.5 mg / L, the ammonia nitrogen concentration 3.6 mg / L in the first section of the aerobic tank and the target ammonia nitrogen concentration 0.5 mg / L A target nitrification rate of 1.1 mg / L · hr is calculated by substituting L and the residence time of the entire aerobic tank of 2.8 hr . The calculated target nitrification rate was substituted into equation (6) to obtain a target dissolved oxygen concentration SVDO 0.23 mg / L, and control was performed using SVDO as a control value of dissolved oxygen. The result of repeating this every hour is shown in FIG.
In this treatment facility, the DO setting control (experimental system) of the present invention was compared with the DO constant control (control system).
As shown in FIG. 8, under the condition of a water temperature of 23 ° C., DO is controlled at 0.5 to 1.0 mg / L, and treated water NH 4 -N is also controlled at 0.1 to 0.6 mg / L. In addition, the aeration air volume is 7.2 m 3 / h daily in the case of DO constant control, and 5.9 m 3 / h in the case of DO setting control of the present invention, which is about 18% compared to when DO constant control is performed. Reduced. Table 2 shows the results.
１：流入水路、２：無酸素槽、３：好気槽、４：最終沈殿池、５：返送汚泥水路、６：返送汚泥ポンプ、７：循環水路、８：循環ポンプ、９：ブロア、１０：曝気空気管、１１：曝気風量調整弁、１２：散気装置、１３：ＤＯ測定手段、１４：溶存酸素制御手段、１５：余剰汚泥ポンプ、１６：攪拌装置、１７：水温測定手段、１８：アンモニア性窒素濃度測定手段、１９：水量測定手段、２０：流量演算手段、２１：硝化速度演算手段、２２：溶存酸素・曝気風量演算手段、２３：凝集剤添加手段、２５：嫌気槽、２６：再曝気槽、２７：アルカリ剤添加手段
1: Inflow water channel, 2: Anoxic tank, 3: Aerobic tank, 4: Final sedimentation tank, 5: Return sludge water channel, 6: Return sludge pump, 7: Circulation water channel, 8: Circulation pump, 9: Blower, 10 : Aeration air pipe, 11: aeration air volume adjusting valve, 12: aeration device, 13: DO measurement means, 14: dissolved oxygen control means, 15: surplus sludge pump, 16: stirring device, 17: water temperature measurement means, 18: Ammonia nitrogen concentration measuring means, 19: water amount measuring means, 20: flow rate calculating means, 21: nitrification rate calculating means, 22: dissolved oxygen / aeration air volume calculating means, 23: flocculant adding means, 2 5 : anaerobic tank, 2 6 : Re-aeration tank, 2 7 : Means for adding alkali agent