JP2012236122A - Method for denitrification treatment of ammonium nitrogen and calcium-containing wastewater, and treatment apparatus for the same - Google Patents
Method for denitrification treatment of ammonium nitrogen and calcium-containing wastewater, and treatment apparatus for the same Download PDFInfo
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Abstract
Description
本発明は、アンモニア性窒素及びカルシウム含有廃水の脱窒処理方法、及びその処理装置に関するものであり、詳しくは、アンモニア性窒素含有の有機性及び無機性廃液の窒素除去に関するもので、カルシウムや窒素濃度の高いごみ浸出水、半導体工場や化学工場排水の窒素除去に関するものである。 The present invention relates to a denitrification method and treatment apparatus for ammonia nitrogen and calcium-containing wastewater, and more particularly to nitrogen removal from ammonia and nitrogen-containing organic and inorganic waste liquids. It is related to nitrogen removal from waste leachate with high concentration, wastewater from semiconductor factories and chemical factories.
一般的に浸出水の特徴としてNH4−Nが高く、BOD等の有機物濃度が低い。従来、このような浸出水の窒素除去方式として、一般的に生物学的硝化脱窒法がよく用いられる。生物学的硝化脱窒法では、通常硝化プロセス及び脱窒プロセスより構成される。第1プロセスの硝化プロセスでは、原水中のアンモニア性窒素を好気状態の反応槽、通称硝化槽において先ずアンモニア酸化菌により亜硝酸性窒素に酸化し、続いて亜硝酸酸化菌により亜硝酸性窒素を硝酸性窒素に酸化する。硝化プロセス後段の脱窒プロセスではこの硝化槽からの処理液(硝化液)を嫌気状態の反応槽、通称脱窒槽に導入して、硝化液中の硝酸性窒素及び亜硝酸性窒素を従属栄養性の脱窒菌により、電子供与体により、無害の窒素ガスに還元される。この電子供与体は通常処理対象液中の有機物が利用される。有機物の少ない場合、外部からメタノールを電子供与体として添加する必要がある。 Generally, NH 4 -N is high as a feature of leachate, and the concentration of organic substances such as BOD is low. Conventionally, a biological nitrification denitrification method is often used as a nitrogen removal method for such leachate. The biological nitrification denitrification method is usually composed of a nitrification process and a denitrification process. In the nitrification process of the first process, ammoniacal nitrogen in raw water is first oxidized to nitrite nitrogen by ammonia-oxidizing bacteria in an aerobic reaction tank, commonly called a nitrification tank, and then nitrite-nitrogen by nitrite-oxidizing bacteria. Is oxidized to nitrate nitrogen. In the denitrification process after the nitrification process, the treatment liquid (nitrification liquid) from this nitrification tank is introduced into an anaerobic reaction tank, commonly known as a denitrification tank, and nitrate nitrogen and nitrite nitrogen in the nitrification liquid are heterotrophic. The denitrifying bacteria are reduced to harmless nitrogen gas by the electron donor. As this electron donor, an organic substance in the liquid to be treated is usually used. When the amount of organic substances is small, it is necessary to add methanol as an electron donor from the outside.
この生物学的硝化脱窒処理では、流入原水中のアンモニア性窒素を硝化槽に対し、亜硝酸性窒素を経て最終的に硝酸性窒素に酸化する。このため、硝化槽にアンモニア性窒素酸化に必要な酸素を供給する必要がある。酸素必要量は原水アンモニア性窒素の4.57倍と高く、その供給動力が無視できない。また、脱窒槽では、硝酸性窒素が電子受容体となる従属脱窒反応において、電子供与体となる有機物が必要となる。原水中に有機物が少ない場合、脱窒に必要な電子供与体となるメタノールを添加することが必要となる。安定した脱窒性能を得るため、メタノール添加量は通常、脱窒槽に流入する硝酸性窒素量の2.5〜3倍程度必要となる。このように硝化プロセスの曝気動力及び脱窒プロセスのメタノール添加量は莫大であり、ランニングコストが高い。これらの低減が硝化脱窒プロセスを普及させるために解決しなければいけない大きな課題となっている。 In this biological nitrification denitrification treatment, ammonia nitrogen in the inflow raw water is finally oxidized into nitrate nitrogen via nitrite nitrogen in the nitrification tank. For this reason, it is necessary to supply oxygen necessary for ammoniacal nitrogen oxidation to the nitrification tank. The required amount of oxygen is 4.57 times higher than that of raw water ammonia nitrogen, and the supply power cannot be ignored. Further, in the denitrification tank, an organic substance that becomes an electron donor is required in a dependent denitrification reaction in which nitrate nitrogen becomes an electron acceptor. When the organic water is small in the raw water, it is necessary to add methanol as an electron donor necessary for denitrification. In order to obtain stable denitrification performance, the amount of methanol added is usually required to be about 2.5 to 3 times the amount of nitrate nitrogen flowing into the denitrification tank. Thus, the aeration power of the nitrification process and the amount of methanol added in the denitrification process are enormous, and the running cost is high. These reductions are a major issue that must be solved to disseminate the nitrification denitrification process.
近年、上記従属栄養脱窒菌による従来の脱窒機構と全く異なる独立栄養脱窒菌による脱窒処理法が開示されている(例えば、特許文献1)。これはアンモニア性窒素を電子供与体とし、亜硝酸性窒素を電子受容体とする独立栄養性微生物を利用し、アンモニア性窒素と亜硝酸性窒素を嫌気状態において反応させて窒素ガスに変換する嫌気性アンモニア酸化処理法(Anaerobic Ammonium Oxidation Process)、所謂ANAMMOX反応による窒素除去方法、またはアンモニア脱窒処理法である。下記式(1)はアンモニア脱窒の反応式を示す。式(1)に示すようにはアンモニア脱窒の場合、アンモニア性窒素と亜硝酸性窒素が直接反応するため、メタノール等の有機物添加が不要であり、薬品代が大きく低下する。また、脱窒反応ではNH4−N 1モルに対し、NO2−N 1.32モルの比率で反応するため、処理対象原水中アンモニア性窒素を従来の硝化プロセスのように全部亜硝酸性及び硝酸性窒素に酸化する必要が無く、その一部を亜硝酸性窒素に酸化すればよいこととなる。アンモニア脱窒反応から、原水NH4−Nの57%を亜硝酸性窒素に酸化すれば、アンモニア脱窒原水のNO2−N/NH4−N比が1.32となり、式(1)に示すような反応が得られ、処理水にNH4−N及びNO2−Nがともになくなることが可能である。
1NH4 ++1.32NO2 −+0.066HCO3 −+0.13H+→1.02N2+0.26NO3 −+0.066CH2O0.5N0.15+2.03H2O (1)
In recent years, a denitrification treatment method using an autotrophic denitrifying bacterium that is completely different from the conventional denitrifying mechanism using the heterotrophic denitrifying bacterium has been disclosed (for example, Patent Document 1). This uses an autotrophic microorganism that uses ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, and reacts ammonia nitrogen and nitrite nitrogen in an anaerobic state to convert them into nitrogen gas. And an ammonia ammonia oxidation process, a nitrogen removal method using a so-called ANAMX reaction, or an ammonia denitrification method. The following formula (1) shows a reaction formula of ammonia denitrification. As shown in the formula (1), in the case of ammonia denitrification, ammonia nitrogen and nitrite nitrogen directly react with each other, so that addition of organic substances such as methanol is unnecessary, and the chemical cost is greatly reduced. In addition, since the denitrification reaction is performed at a ratio of 1.32 mol of NO 2 -N to 1 mol of NH 4 -N, the ammonia nitrogen in the raw water to be treated is completely nitrite-like as in the conventional nitrification process. There is no need to oxidize to nitrate nitrogen, and a part of it may be oxidized to nitrite nitrogen. If 57% of the raw water NH 4 —N is oxidized to nitrite nitrogen from the ammonia denitrification reaction, the NO 2 —N / NH 4 —N ratio of the ammonia denitrified raw water becomes 1.32. A reaction as shown is obtained, and it is possible to eliminate both NH 4 —N and NO 2 —N in the treated water.
1NH 4 + + 1.32NO 2 − + 0.066HCO 3 − + 0.13H + → 1.02N 2 + 0.26NO 3 − + 0.066CH 2 O 0 . 5 N 0 . 15 + 2.03H 2 O (1)
上記のようにアンモニア脱窒を用いた脱窒処理として、先ず流入原水中のアンモニア性窒素の一部を硝化プロセスにおいて亜硝酸性窒素に酸化する必要がある。アンモニア脱窒反応で高率な脱窒性能を得るために、原水NH4−Nの57%をNO2−Nにし、43%のNH4−Nを残留させておくことが望まれる。この場合、亜硝酸化処理水のNO2−N/NH4−N比が1.32となり、式(1)に示すアンモニア脱窒反応に必要なNO2−N/NH4−N比に一致する。 As described above, as a denitrification process using ammonia denitrification, it is necessary to first oxidize a part of ammonia nitrogen in the inflow raw water to nitrite nitrogen in the nitrification process. In order to obtain a high rate of denitrification performance by the ammonia denitrification reaction, it is desired that 57% of the raw water NH 4 —N is changed to NO 2 —N and 43% NH 4 —N is left. In this case, the NO 2 —N / NH 4 —N ratio of nitrite-treated water is 1.32, which matches the NO 2 —N / NH 4 —N ratio required for the ammonia denitrification reaction shown in Formula (1). To do.
原水中のNH4−NがNO2−Nに酸化されることに伴い、M−アルカリ度が消費される。1mg/L NH4−Nの硝化で消費されるM−アルカリ度が7.1mg/Lとなる。原水のNH4−Nに対するM−アルカリ度比率が低い場合、原水NH4−Nの硝化比率が少なく、処理水NO2−N/NH4−N比が目標値の1.3を大きく下回ることとなる。逆に原水のNH4−Nに対するM−アルカリ度が高い場合、硝化が進行し、処理水NH4−N残留が少なくなり、処理水NO2−N/NH4−N比が目標値の1.3を大きく超えることとなる。従って、原水中のM−アルカリ度/NH4−N比を予め適切な値にしておく必要がある。通常、M−アルカリ度/NH4−Nが3.7〜4.4になるように調製しておくことが重要である。 As NH 4 —N in raw water is oxidized to NO 2 —N, M-alkalinity is consumed. The M-alkalinity consumed by nitrification of 1 mg / L NH 4 -N is 7.1 mg / L. If M- alkalinity ratio NH 4 -N raw water is low, the raw water NH 4 -N is low nitrification ratio of the treated water NO 2 -N / NH 4 -N ratio well below the 1.3 target value It becomes. Conversely, when the M-alkalinity of the raw water with respect to NH 4 -N is high, nitrification proceeds, the residual amount of the treated water NH 4 -N decreases, and the treated water NO 2 -N / NH 4 -N ratio is a target value of 1 .3 will be greatly exceeded. Therefore, it is necessary to set the M-alkalinity / NH 4 -N ratio in the raw water to an appropriate value in advance. Usually, it is important to prepare such that M-alkalinity / NH 4 —N is 3.7 to 4.4.
一方、近年、埋立処分場に埋め立てられる廃棄物の内、焼却灰や焼却残渣の比率が高くなっている。これに伴い、浸出水中のカルシウム濃度(Ca濃度)が増加している。Ca濃度が高いと浸出水中の炭酸イオン(CO3 2−)との反応で不溶性のCaCO3として析出する。水処理施設ではこの不溶性CaCO3析出により、処理水配管の閉塞や散気装置の目詰まり等を引起し、装置トラブルの大きな要因となる。これに対応するため、Ca濃度の高い浸出水に対し、一般的に予めCaを除去する軟化処理装置を設けている。 On the other hand, in recent years, the ratio of incineration ash and incineration residue among the waste landfilled in the landfill site has increased. Along with this, the calcium concentration (Ca concentration) in the leachate is increasing. If the Ca concentration is high, it precipitates as insoluble CaCO 3 due to the reaction with carbonate ions (CO 3 2− ) in the leachate. In water treatment facilities, this insoluble CaCO 3 precipitation causes clogging of the treated water piping, clogging of the diffuser, and the like, which is a major cause of equipment trouble. In order to cope with this, generally, a softening treatment device for removing Ca in advance is provided for leachate having a high Ca concentration.
Ca除去の軟化処理方法は一般的に被処理水に炭酸ナトリウム(Na2CO3)を添加し、アルカリ添加により、pHを約10以上に高くすることで被処理水中のCaイオンを不溶性のCaCO3汚泥として除去するものである。この軟化処理においてNa2CO3の添加量は反応式(2)に示すように理論的に被処理液Ca濃度に対し、2.65倍のNa2CO3が必要となる。一般的に処理水Ca濃度が100mg/L以下となれば、Caスケール析出が抑制されるので、軟化処理の処理水Ca濃度目標値を100mg/L以下とすることが多い。なお、実際の処理では処理水のCa濃度を100mg/L以下とするためには、Na2CO3添加量を理論値の1.05〜1.1倍、即ち被処理水Ca濃度の2.8〜2.9倍の添加が必要となる。
Ca2++Na2CO3=CaCO3↓+2Na+ (2)
The softening treatment method for removing Ca generally includes adding sodium carbonate (Na 2 CO 3 ) to the water to be treated, and increasing the pH to about 10 or more by adding an alkali, so that Ca ions in the water to be treated are insoluble CaCO. 3 Remove as sludge. In this softening treatment, the added amount of Na 2 CO 3 theoretically requires 2.65 times Na 2 CO 3 with respect to the concentration of the liquid Ca to be treated as shown in the reaction formula (2). Generally, when the treated water Ca concentration is 100 mg / L or less, Ca scale precipitation is suppressed, and therefore, the target value of the treated water Ca concentration for the softening treatment is often set to 100 mg / L or less. In the actual treatment, in order to make the Ca concentration of treated water 100 mg / L or less, the amount of Na 2 CO 3 added is 1.05 to 1.1 times the theoretical value, that is, 2. Addition of 8 to 2.9 times is required.
Ca 2+ + Na 2 CO 3 = CaCO 3 ↓ + 2Na + (2)
Ca及び窒素の高い被処理水に対し、従来のCa及び窒素除去方法としてCa除去の軟化処理→硝化脱窒の順で行うことが開示されている。特許文献2の図1に開示されているように被処理水に対し、前処理槽において炭酸塩を添加し、CO3 2−が被処理水中のCa2+と反応して不溶性のCaCO3として析出されることが明示されている。さらにCa除去後の上澄水を中和処理し、後段の生物硝化脱窒槽に導入して従来の生物学的脱窒処理で窒素除去を行うことが開示されている。
It is disclosed that, as a conventional Ca and nitrogen removal method, water removal treatment with high Ca and nitrogen is performed in the order of softening treatment of Ca removal → nitrification denitrification. As disclosed in FIG. 1 of
近年、Ca除去+窒素除去において 従来の窒素除去に替わり、前記の独立栄養脱窒菌による脱窒、即ちANAMMOX方式による脱窒を適用する処理法が開示されている。 In recent years, instead of conventional nitrogen removal in Ca removal + nitrogen removal, a treatment method has been disclosed that applies denitrification by the above-mentioned autotrophic denitrifying bacteria, that is, denitrification by the ANAMMOX method.
特許文献3では、図1に示すように被処理水に対し、Ca除去装置+亜硝酸化反応槽+ANAMMOX反応槽の順でCa及び窒素除去を行っている。 In Patent Document 3, as shown in FIG. 1, Ca and nitrogen are removed from the water to be treated in the order of a Ca removal device + a nitritation reaction tank + an ANMOX reaction tank.
一方、亜硝酸化処理プロセスにおいて、近年、硝化菌の付着できる生物担体を亜硝酸化槽に添加した担体方式が開示されている(例えば、特許文献4)。 On the other hand, in the nitritation treatment process, a carrier system in which a biological carrier to which nitrifying bacteria can adhere has been recently added to a nitritation tank (for example, Patent Document 4).
Ca除去の軟化処理方法において、実機の場合、被処理水Caの測定を通常頻繁にせず、Na2CO3添加量は計画値のCa濃度に基いて添加量を決めることが多い。また、浸出水の場合、降雨量によりCa濃度が変化する。Na2CO3添加量が過剰の場合、軟化処理水のM−アルカリ度が高くなる。これらのことから、当初計画値のCa濃度に対して所定量Na2CO3を添加していることが多く、過剰添加の場合が多い。Na2CO3添加量が過剰の場合、軟化処理水のM−アルカリ度が高くなる。軟化処理水に炭酸源が多く残留し、必要に応じて酸添加による脱炭酸を行うため、ランコスの増加要因となるという問題があった。 In the case of an actual machine, in the Ca removal softening treatment method, measurement of the water to be treated Ca is not usually performed frequently, and the amount of Na 2 CO 3 added is often determined based on the planned Ca concentration. In the case of leachate, the Ca concentration varies depending on the amount of rainfall. When the amount of Na 2 CO 3 added is excessive, the M-alkalinity of the softened water is increased. For these reasons, a predetermined amount of Na 2 CO 3 is often added to the initially planned Ca concentration, and excessive addition is often the case. When the amount of Na 2 CO 3 added is excessive, the M-alkalinity of the softened water is increased. There is a problem that a large amount of carbonic acid remains in the softened water, and decarboxylation by acid addition is performed as necessary, which increases Lancos.
さらに浸出水のM−アルカリ度が通常高いことから、浸出水中M−アルカリ度由来の炭酸源も高pH領域においてCaと反応して不溶性のCaCO3となることから、浸出水中のM−アルカリ度、即ち炭酸源を考慮しないでNa2CO3必要量を添加すると、添加量がさらに過剰になり、ランコス増となるという問題があった。 Further, since the M-alkalinity of leachate is usually high, the carbonate source derived from the M-alkalinity of leachate also reacts with Ca in the high pH region to become insoluble CaCO 3. That is, when the required amount of Na 2 CO 3 was added without considering the carbonic acid source, there was a problem that the amount added was further excessive, resulting in an increase in Lancos.
また、上記従来技術では、Ca除去手段の一つとして炭酸塩である炭酸ナトリウムや重炭酸ナトリウムの添加で不溶性のCaCO3として析出させて除去する方法が示されている。また、処理水Ca濃度を100mg/L以下とすることでCaによるスケール析出がなく、安定した処理が得られるとしている。しかし、炭酸塩の添加量については原水Ca等の濃度変動に対応できる適切な注入方法は示されていない。従って、炭酸塩の添加量が過剰となれば、処理水に炭酸塩が残留し、M−アルカリ度の増加となる。特に浸出水中にもM−アルカリ度に代表されるように溶存炭酸塩が多く存在していることから、浸出水中Ca除去において、M−アルカリ度由来の炭酸源を考慮しないで必要量の炭酸塩を添加すると処理水中の炭酸塩が大幅に残留して、M−アルカリ度の増加となるという問題があった。 In the above prior art, as one of the Ca removing means, a method of depositing and removing insoluble CaCO 3 by adding sodium carbonate or sodium bicarbonate as a carbonate is shown. In addition, by setting the treated water Ca concentration to 100 mg / L or less, there is no scale deposition due to Ca, and stable treatment is obtained. However, an appropriate injection method that can cope with the concentration fluctuation of raw water Ca or the like is not shown for the amount of carbonate added. Therefore, if the amount of carbonate added is excessive, the carbonate remains in the treated water, resulting in an increase in M-alkalinity. In particular, since there are many dissolved carbonates as typified by M-alkalinity in the leachate, a necessary amount of carbonate is taken into account in removing Ca from the leachate without considering the carbonate source derived from M-alkalinity. There was a problem that the carbonate in the treated water remained largely and the M-alkalinity increased.
一方、Ca除去後の軟化処理水を対象とした亜硝酸化処理では、処理水のNO2−N/NH4−N比を後段のアンモニア脱窒反応に最適な1.32とするためには、軟化処理水のM−アルカリ度濃度がNH4−N濃度に対して3.7〜4.4倍となるように調整することが必要である。従って、軟化処理水に炭酸塩の残留が多く、M−アルカリ度が高くなると調整に必要な酸添加量が増加することとなるという問題もあった。 On the other hand, in the nitritation treatment for the softened water after removing Ca, in order to set the NO 2 —N / NH 4 —N ratio of the treated water to 1.32 which is optimal for the ammonia denitrification reaction in the subsequent stage. It is necessary to adjust the M-alkalinity concentration of the softened treated water to be 3.7 to 4.4 times the NH 4 -N concentration. Therefore, there is also a problem that the amount of acid addition necessary for adjustment increases as the amount of carbonate remaining in the softened water increases and the M-alkalinity increases.
また、硝化槽に担体を添加し、担体表面に付着する硝化菌による硝化において、硝化性能は担体表面の付着硝化菌量に左右される。発明者らは担体と活性汚泥を混合した硝化槽において、Ca濃度の高い原水が硝化槽に流入した場合、活性汚泥において硝化菌の増殖が認められる一方、CaCO3析出による硝化菌比率が低下し、さらに担体においては硝化菌の付着が殆ど認められないという問題を見出した。 In addition, the nitrification performance depends on the amount of adhering nitrifying bacteria on the surface of the carrier when a carrier is added to the nitrification tank and nitrifying bacteria adhere to the surface of the carrier. In the nitrification tank in which the carrier and the activated sludge are mixed, the inventors found that when raw water with a high Ca concentration flows into the nitrification tank, the nitrifying bacteria are increased in the activated sludge, while the nitrifying bacteria ratio due to CaCO 3 precipitation decreases. Further, the present inventors have found a problem that nitrifying bacteria are hardly adhered to the carrier.
本発明は、上記問題を解消するためになされたものであり、その課題は、担体に安定してアンモニア酸化菌を付着固定させることができ、かつ安定した亜硝酸化処理ができるアンモニア性窒素及びカルシウム含有廃水の脱窒処理方法及びその装置を提供することにある。 The present invention has been made in order to solve the above problems, and the problem is that ammonia nitrogen capable of stably adhering and fixing ammonia-oxidizing bacteria to a carrier and stable nitritation treatment and An object of the present invention is to provide a denitrification method and apparatus for calcium-containing wastewater.
1)以下の工程を含む、アンモニア性窒素及びカルシウム含有廃水の脱窒処理方法。
カルシウム濃度制御工程:アンモニア性窒素及びカルシウム含有廃水中のカルシウム濃度を亜硝酸化工程の運転条件に応じて制御する工程
亜硝酸化工程:カルシウム濃度制御工程で得られた廃水存在下、担体にアンモニア酸化菌を固定化するとともに該廃水を亜硝酸化する工程
脱窒工程:亜硝酸化工程で得られた亜硝酸及びアンモニア性窒素を含む廃水を脱窒処理する工程
2)上記1)のアンモニア性窒素及びカルシウム含有廃水の脱窒処理方法を実施する装置であって、前記カルシウム濃度制御工程に用いられる装置は、該廃水のカルシウム濃度を測定する装置、カルシウムを除去する装置、M−アルカリ度濃度、及びNH4−N濃度を測定する装置を備えた槽を含み、前記亜硝酸化工程に用いられる装置は、前記M−アルカリ度濃度、及びNH4−N濃度を測定する装置と連絡した中和剤添加量制御装置、及び該中和剤添加量制御装置に連絡した中和剤注入装置を備えた亜硝酸化槽を含み、前記脱窒工程に用いられる装置は、脱窒槽を含む、アンモニア性窒素及びカルシウム含有廃水の脱窒処理装置。
1) A denitrification method for wastewater containing ammoniacal nitrogen and calcium, comprising the following steps.
Calcium concentration control process: A process for controlling the calcium concentration in ammonia nitrogen and calcium-containing wastewater according to the operating conditions of the nitritation process. Nitrite process: Ammonia in the carrier in the presence of wastewater obtained in the calcium concentration control process. A process of immobilizing oxidizing bacteria and nitrifying the wastewater Denitrification process: A process of denitrifying wastewater containing nitrous acid and ammonia nitrogen obtained in the nitritation process 2) Ammonia of 1) above An apparatus for performing a denitrification method of nitrogen and calcium-containing wastewater, the apparatus used in the calcium concentration control step is an apparatus for measuring the calcium concentration of the wastewater, an apparatus for removing calcium, and an M-alkalinity concentration , And a tank equipped with a device for measuring the NH 4 -N concentration, and the device used for the nitritation step comprises the M-alkaliness concentration, And a neutralizing agent addition amount control device in communication with a device for measuring the NH 4 -N concentration, and a nitrification tank equipped with a neutralizing agent injection device in communication with the neutralizing agent addition amount control device. The apparatus used in the nitriding process is a denitrification apparatus for wastewater containing ammonia nitrogen and calcium, including a denitrification tank.
本発明は、アンモニア性窒素(NH4−N)及びカルシウム含有廃水中のカルシウム濃度(Ca濃度)を、アンモニア酸化菌を固定化する担体を用いる亜硝酸化工程の運転条件に応じて制御するカルシウム濃度制御工程を設けたことを最大の特徴とする。
上記担体に硝化菌付着ができない原因の一つとしては、担体表面にCaCO3析出で硝化菌の付着を困難にしたことによるものであることを見出した。特に亜硝酸化槽において、立上げ運転時、アンモニア酸化菌を優占的に増殖させるには、Ca濃度を低くすればCaCO3析出の恐れがほぼなく、担体表面においてアンモニア酸化菌が安定して付着することができることを見出した。
一方、担体にアンモニア酸化菌が付着固定し、硝化が亜硝酸型硝化となった定常運転後、亜硝酸化槽において、Ca濃度が高くなっても、担体にCa析出がなく、アンモニア酸化菌が安定して付着できていることが実験的に確認できたものである。
The present invention controls calcium concentration (Ca concentration) in ammoniacal nitrogen (NH 4 -N) and calcium-containing wastewater according to the operating conditions of the nitritation process using a carrier that immobilizes ammonia oxidizing bacteria. The greatest feature is that a concentration control step is provided.
It has been found that one of the reasons why nitrifying bacteria cannot adhere to the carrier is that nitrifying bacteria are difficult to adhere due to CaCO 3 deposition on the surface of the carrier. Particularly in a nitrification tank, in order to proliferate ammonia-oxidizing bacteria preferentially during start-up operation, if the Ca concentration is lowered, there is almost no risk of CaCO 3 precipitation, and the ammonia-oxidizing bacteria stabilize on the surface of the carrier. It was found that it can adhere.
On the other hand, after steady operation where ammonia-oxidizing bacteria adhered and fixed to the carrier and nitrification became nitrite-type nitrification, even if the Ca concentration increased in the nitrite tank, there was no Ca precipitation on the carrier, and ammonia-oxidizing bacteria were not It was confirmed experimentally that it was stably adhered.
本発明によれば、Ca及びアンモニア性窒素含有の被処理水に対し、担体を用いた亜硝酸化処理とアンモニア脱窒処理を組み合わせた処理プロセスによる窒素除去を行う場合において、被処理水に対して、予めCaを除去すれば、亜硝酸化槽内の担体にアンモニア酸化菌が短期間で付着固定でき、安定した部分亜硝酸化性能が得られる。また、Ca除去の軟化処理において、被処理水中の炭酸塩濃度を考慮した炭酸塩必要量の添加を行うことにより、炭酸塩の添加量が低減できる。炭酸塩添加量の適正化により、軟化処理水中に炭酸塩残留によるM−アルカリ度の増加がなく、該処理水のM−アルカリ度/NH4−N比率を安定して部分亜硝酸化処理に必要な数値範囲に設定できるので、部分亜硝酸化処理が安定して得られる。さらに担体にアンモニア酸化菌が付着固定し、部分亜硝酸化型硝化に移行した後、M−アルカリ度律速による亜硝酸化処理条件において、軟化処理水のCa濃度を高く設定しても、担体表面にCaCO3析出によるスケール生成がなく、アンモニア酸化菌が安定して付着固定できることから、軟化処理に伴う薬品添加量及び汚泥発生量が大幅に低減できる。 According to the present invention, when water to be treated containing Ca and ammonia nitrogen is subjected to nitrogen removal by a treatment process that combines nitritation treatment using a carrier and ammonia denitrification treatment, If Ca is removed in advance, ammonia oxidizing bacteria can adhere and be fixed to the carrier in the nitritation tank in a short period of time, and stable partial nitritation performance can be obtained. In addition, in the Ca removal softening treatment, the amount of carbonate added can be reduced by adding the necessary amount of carbonate in consideration of the carbonate concentration in the water to be treated. By optimizing the amount of carbonate added, there is no increase in M-alkalinity due to residual carbonate in the softened treated water, and the M-alkalinity / NH 4 -N ratio of the treated water is stabilized for partial nitritation treatment. Since it can be set within the required numerical range, partial nitritation treatment can be obtained stably. Furthermore, after ammonia-oxidizing bacteria adhere and fix to the carrier and shift to partial nitritation type nitrification, even if the Ca concentration of the softening water is set high under the nitritation treatment conditions based on the M-alkali degree, the carrier surface In addition, there is no scale generation due to CaCO 3 precipitation, and ammonia oxidizing bacteria can be stably adhered and fixed, so that the amount of chemical addition and sludge generation accompanying the softening treatment can be greatly reduced.
以下、本発明を詳細に説明する。
初めに、Ca濃度制御工程について説明する。
Ca濃度制御工程は、アンモニア性窒素及びカルシウム含有廃水(以下、単に原水ともいう)中のCa濃度を亜硝酸化工程の運転条件に応じて制御する工程である。
ここで、Ca濃度は、(株)共立理化学研究所製カルシウム分析用パックテスト、電極式Ca濃度計、キレート敵定法、フレーム原子吸光法、ICP発光分光分析法の何れかにより測定される値を意味する。
本工程では、測定されたCa濃度及び亜硝酸化工程の運転条件に応じてCa濃度が制御される。本発明において、該制御は、原水のCa濃度の測定のみをも包含するものであり、測定値が所定以下の場合には、軟化処理の必要はない。本工程で処理された原水を軟化処理水ともいう。ただし、原水に軟化処理を施してないものも便宜上、軟化処理水に含める。
該運転条件が、亜硝酸化工程の立ち上げ運転工程の場合には、Ca濃度が低くなるように制御する。Ca濃度が所定値以下の場合は、軟化処理の必要はない。一方、亜硝酸化工程の定常運転工程では、Ca濃度を高く維持でき、軟化処理の負荷を低減できる。
該軟化処理としては、Ca濃度を低くする制御手段を用いるのであれば、特に制限はない。例えば、凝集沈殿、凝集−膜分離、晶析、イオン交換、電気脱塩、電気泳動、等が挙げられる。
Hereinafter, the present invention will be described in detail.
First, the Ca concentration control process will be described.
The Ca concentration control step is a step of controlling the Ca concentration in the ammoniacal nitrogen and calcium-containing waste water (hereinafter also simply referred to as raw water) according to the operating conditions of the nitritation step.
Here, the Ca concentration is a value measured by any one of a calcium analysis pack test, an electrode-type Ca concentration meter, a chelate enemy method, a flame atomic absorption method, and an ICP emission spectroscopic method manufactured by Kyoritsu Riken. means.
In this step, the Ca concentration is controlled according to the measured Ca concentration and the operating conditions of the nitritation step. In the present invention, the control includes only measurement of the Ca concentration of the raw water, and there is no need for softening treatment when the measured value is not more than a predetermined value. The raw water treated in this step is also called softened treated water. However, the raw water that has not been softened is also included in the softened water for convenience.
When the operation condition is a start-up operation process of the nitritation process, control is performed so that the Ca concentration is lowered. When the Ca concentration is less than or equal to a predetermined value, there is no need for softening treatment. On the other hand, in the steady operation step of the nitritation step, the Ca concentration can be kept high and the load of the softening treatment can be reduced.
The softening treatment is not particularly limited as long as a control means for lowering the Ca concentration is used. For example, aggregation precipitation, aggregation-membrane separation, crystallization, ion exchange, electrodeionization, electrophoresis and the like can be mentioned.
本発明では、軟化処理は、Na2CO3添加量C0(mg/L)を下記式(3)より算出して原水に添加して炭酸カルシウムの凝集沈殿を行い、原水のCa濃度を制御する処理が好ましい。
C0=(Cin−Cout)×a−C2/1.06 (3)
ここで、Cin(mg/L):原水のCa濃度、Cout(mg/L):原水の目標Ca濃度(例えば、立ち上げ運転工程、定常運転工程)、C2(mg/L):原水のM−アルカリ度濃度、aは係数である。本発明において、M−アルカリ度濃度は、pH4.8でのアルカリ消費量を求める滴定法により測定される値を意味する。
この軟化処理は、原水中の炭酸塩をCa除去に有効利用することが可能である。発明者らは浸出水のM−アルカリ度と添加炭酸塩(Na2CO3換算)濃度の関係を実験的に検討した結果、上式(3)に示す関係式が得られることを明らかにできた。
係数aは軟化処理のpHによって若干異なるが、Ca除去の好適なpHは9〜10、好ましくは9.0〜9.5である。係数aはpH9.0〜10.0において2.6〜2.9、pH9.0〜9.5においては2.8〜2.9とすることで安定したCa濃度制御を行うことができ、安定した目標水質が得られる。
In the present invention, in the softening treatment, Na 2 CO 3 addition amount C 0 (mg / L) is calculated from the following formula (3) and added to the raw water to perform coagulation precipitation of calcium carbonate to control the Ca concentration of the raw water. The treatment is preferably
C 0 = (C in -C out ) ×
Here, C in (mg / L): raw water Ca concentration, C out (mg / L): raw water target Ca concentration (for example, start-up operation step, steady operation step), C 2 (mg / L): M-alkalinity concentration of raw water, a is a coefficient. In the present invention, the M-alkalinity concentration means a value measured by a titration method for determining alkali consumption at pH 4.8.
This softening treatment can effectively use carbonate in raw water for Ca removal. As a result of experimentally examining the relationship between the M-alkalinity of leachate and the concentration of added carbonate (converted to Na 2 CO 3 ), the inventors were able to clarify that the relational expression shown in the above equation (3) can be obtained. It was.
The coefficient a is slightly different depending on the pH of the softening treatment, but a suitable pH for removing Ca is 9 to 10, preferably 9.0 to 9.5. The coefficient a is 2.6 to 2.9 at pH 9.0 to 10.0, and 2.8 to 2.9 at pH 9.0 to 9.5, so that stable Ca concentration control can be performed. Stable target water quality can be obtained.
該軟化処理は、Ca濃度を100mg/L以下、又は100mg以上500mg/L以下に制御することが好ましい。Ca濃度を100mg/L以下に制御すると亜硝酸化工程の立ち上げ運転工程でのアンモニア酸化菌の担体への付着固定を促進することができる。また、100mg以上500mg/L以下に制御することにより、亜硝酸化工程の定常運転工程を安定して行うことができるとともに軟化処理の薬剤を低減できる。 In the softening treatment, the Ca concentration is preferably controlled to 100 mg / L or less, or from 100 mg to 500 mg / L. When the Ca concentration is controlled to 100 mg / L or less, it is possible to promote adhesion and fixation of ammonia-oxidizing bacteria to the carrier in the start-up operation process of the nitritation process. Moreover, by controlling to 100 mg or more and 500 mg / L or less, the steady operation process of a nitritation process can be performed stably, and the chemical | medical agent of a softening process can be reduced.
本発明のCa濃度制御工程に用いられる装置は、原水のCa濃度を測定する装置、カルシウムを除去する装置、M−アルカリ度濃度、及びNH4−N濃度を測定する装置を備えた槽を含む。上記各装置は、制御装置と連絡させることができる。本発明において、NH4−N濃度は、(株)共立理化学研究所製アンモニウム態窒素想定用パックテスト、NH4−N電極測定法、中和滴定法の何れかにより測定される値を意味する。
該Ca濃度制御工程に用いられる装置は、Ca濃度測定及び軟化処理を行う槽とM−アルカリ度濃度、及びNH4−N濃度を測定するための槽を独立に設けてもよいし、同一の槽としてもよい。後者の場合、M−アルカリ度濃度及びNH4−N濃度の測定は、軟化処理の後に行うことが好ましい。
カルシウムを除去する装置は、軟化処理を行う槽と兼用され、かつカルシウムを炭酸カルシウムとして沈殿させるための薬品を槽へ注入するための注入装置を備えることができる。また、該注入装置は、Ca濃度を測定する装置と連絡した制御装置に連絡させてもよい。例えば、上記式(3)を用いて制御装置にて該薬品量を計算した結果を、注入装置に連絡し、注入装置から槽へ同量を投入するように構成することができる。
The apparatus used for the Ca concentration control process of the present invention includes a tank equipped with an apparatus for measuring the Ca concentration of raw water, an apparatus for removing calcium, an M-alkalinity concentration, and an apparatus for measuring NH 4 -N concentration. . Each of the above devices can be in communication with a control device. In the present invention, the NH 4 -N concentration means a value measured by any of the pack test for assumption of ammonium nitrogen, NH 4 -N electrode measurement method, and neutralization titration method manufactured by Kyoritsu Riken. .
The apparatus used for the Ca concentration control step may be independently provided with a tank for measuring Ca concentration and softening treatment, and a tank for measuring M-alkalinity concentration and NH 4 -N concentration. It is good also as a tank. In the latter case, the measurement of M-alkalinity concentration and NH 4 -N concentration is preferably performed after the softening treatment.
The device for removing calcium can be equipped with an injection device that is used also as a tank for performing the softening treatment and injects a chemical for precipitating calcium as calcium carbonate into the tank. Moreover, you may make this injection | pouring apparatus contact the control apparatus connected with the apparatus which measures Ca density | concentration. For example, the result of calculating the chemical amount by the control device using the above formula (3) can be communicated to the injection device, and the same amount can be put into the tank from the injection device.
次に亜硝酸化工程について説明する。
亜硝酸化工程は、カルシウム濃度制御工程で得られた廃水存在下(即ち、Ca濃度制御工程で得られた軟化処理水存在下)、担体にアンモニア酸化菌を固定化するとともに軟化処理水を亜硝酸化する工程である。ここで、Ca濃度制御工程で得られた軟化処理水とは、上記軟化処理を施されて得られる処理水、又は上記軟化処理を施されないままのものをいう。また、この亜硝酸化工程で得られた処理水を亜硝酸化処理水ともいう。
亜硝酸化工程は、立ち上げ運転工程、及び定常運転工程を含むことが好ましく、軟化処理水のCa濃度は上述のように制御されたものである。
また、亜硝酸化工程は、軟化処理水のM−アルカリ度/NH4−N比を3.7〜4.4に制御することが好ましい。
Next, the nitritation step will be described.
In the nitrification step, ammonia-oxidizing bacteria are immobilized on the carrier in the presence of the waste water obtained in the calcium concentration control step (that is, in the presence of the softening treatment water obtained in the Ca concentration control step), and the softened treatment water is sublimated. This is the step of nitrating. Here, the softened water obtained in the Ca concentration control step refers to treated water obtained by performing the softening treatment, or water that has not been subjected to the softening treatment. Moreover, the treated water obtained in this nitritation process is also called nitritation treated water.
The nitritation step preferably includes a start-up operation step and a steady operation step, and the Ca concentration of the softened treated water is controlled as described above.
Moreover, nitrous acid step, it is preferable to control the M- alkalinity / NH 4 -N ratio of softening treatment water from 3.7 to 4.4.
立ち上げ運転工程において、通常、アンモニア酸化菌を担体に付着固定させるためには反応槽内pHを高くし、遊離NH3(以下FA)濃度を高く維持する。通常、亜硝酸化槽内のFAを1〜10mg/L、好ましくは2〜10mg/Lに維持すれば、短期間で担体にアンモニア酸化菌が優占的に付着固定するので安定した亜硝酸化処理が得られる。FAは反応槽のpH、NH4−N濃度、水温の変化に大きく左右される。FAはpHが高いほど高くなるため、立ち上げ運転工程初期においてpHを最大8程度に高くすることがある。この条件において、Ca濃度を100mg/L以下にすればCaCO3析出の恐れがほぼなく、担体表面においてアンモニア酸化菌が安定して付着することができる。 In the start-up operation process, in order to adhere and fix ammonia oxidizing bacteria on the carrier, the pH in the reaction tank is generally increased and the free NH 3 (hereinafter referred to as FA) concentration is maintained high. Usually, if the FA in the nitrification tank is maintained at 1 to 10 mg / L, preferably 2 to 10 mg / L, ammonia oxidizing bacteria preferentially adhere and fix to the carrier in a short period of time, so stable nitritation Processing is obtained. FA greatly depends on changes in pH, NH 4 -N concentration, and water temperature in the reaction vessel. Since FA increases as pH increases, the pH may be increased to about 8 at the initial stage of the start-up operation process. Under these conditions, if the Ca concentration is 100 mg / L or less, there is almost no fear of CaCO 3 precipitation, and ammonia oxidizing bacteria can adhere stably on the surface of the carrier.
一方、担体にアンモニア酸化菌が付着固定し、硝化が亜硝酸型硝化となった定常運転工程では、亜硝酸化槽において、M−アルカリ度律速による部分亜硝酸化処理が進行し、pHが7付近、若しくは7以下に低下する。この条件では亜硝酸化槽内のCa濃度が最大500mg/Lとなっても、担体にCa析出がなく、アンモニア酸化菌が安定して担体に付着し、維持される。 On the other hand, in a steady operation process in which ammonia-oxidizing bacteria adhere and fix to the carrier and nitrification becomes nitrite-type nitrification, partial nitritation treatment with M-alkalinity rate control proceeds in the nitritation tank, and the pH is 7 Near or below 7 Under these conditions, even when the Ca concentration in the nitritation tank reaches 500 mg / L at the maximum, there is no Ca precipitation on the carrier, and ammonia oxidizing bacteria adhere to the carrier stably and are maintained.
上記のように担体を用いた亜硝酸処理では、担体にアンモニア酸化菌が付着固定するまでの立ち上げ運転工程においては軟化処理水Ca濃度を例えば、100mg/L以下とすれば、FA濃度が高く維持できるpH8前後でも担体の表面にCaCO3析出によるスケール付着がなく、アンモニア酸化菌が安定して付着固定できる。アンモニア酸化菌が一旦付着固定し、亜硝酸型硝化に進行した場合には、定常運転工程となり、M−アルカリ律速に伴い、亜硝酸化槽pHが7前後に低下する。このpH条件では亜硝酸化槽内のCa濃度を最大500mg/LとしてもCaCO3析出の可能性がほとんどない。即ち、Ca除去の軟化処理プロセスにおいて、式(3)に示すように炭酸塩添加量が大幅に低減できる上、CaCO3析出の汚泥量も大幅に減少する。 In the nitrous acid treatment using the carrier as described above, the FA concentration is high if the softened water Ca concentration is, for example, 100 mg / L or less in the start-up operation process until the ammonia-oxidizing bacteria adhere and fix to the carrier. Even at a pH of about 8 that can be maintained, there is no scale adhesion due to CaCO 3 precipitation on the surface of the carrier, and ammonia oxidizing bacteria can be stably adhered and fixed. When ammonia-oxidizing bacteria once adhere and fix and proceed to nitrite type nitrification, it becomes a steady operation step, and the pH of the nitrite tank decreases to around 7 with M-alkali rate control. Under this pH condition, there is almost no possibility of CaCO 3 precipitation even when the maximum Ca concentration in the nitritation tank is 500 mg / L. That is, in the Ca removal softening treatment process, the amount of carbonate added can be greatly reduced as shown in the equation (3), and the amount of sludge deposited on CaCO 3 is also greatly reduced.
本発明の亜硝酸化工程に用いられる装置は、軟化処理水のM−アルカリ度濃度、及びNH4−N濃度を測定する装置と連絡した中和剤添加量制御装置、及び該中和剤添加量制御装置に連絡した中和剤注入装置を備えた亜硝酸化槽を含む。中和剤添加量制御装置は、該軟化処理水のM−アルカリ度及びNH4−N濃度の情報を処理して亜硝酸化槽への中和剤添加量を計算するとともにその計算結果を中和剤注入装置に連絡し、同注入装置から同中和剤添加量を同槽へ注入させる機能を有するように構成できる。 The apparatus used for the nitritation process of the present invention includes a neutralizer addition amount control apparatus in communication with an apparatus for measuring the M-alkaliness concentration and NH 4 -N concentration of softened treated water, and the neutralizer addition It includes a nitritation tank equipped with a neutralizing agent injection device in communication with a volume control device. The neutralizer addition amount control device processes the information on the M-alkalinity and NH 4 -N concentration of the softened treated water to calculate the amount of neutralizer added to the nitritation tank, It can be configured to communicate with the sump injection device and to have the function of injecting the same neutralizing agent addition amount into the same tank from the injection device.
また、本発明では、亜硝酸化工程は、PO4−P濃度を0.1〜1mg/Lに制御することが好ましい。
例えば、浸出水や工場廃水の場合、原水中にリン含有が少ない場合には、微生物増殖に必要となるリンを亜硝酸化槽に添加することが好ましい。亜硝酸化槽においてリン濃度が低いと担体にアンモニア酸化菌の付着固定が困難な傾向にある。
発明者らの実験検討結果では、軟化処理水のリン濃度をPO4−Pとして0.1mg/L以上、好ましくは0.2mg/L以上とすれば、担体に付着固定するアンモニア酸化菌量及び活性の何れも安定することを確認できた。一方、処理水においてCa濃度が100mg/L程度存在するので、PO4−Pが高いとpHの高い領域でCaとPO4−Pとの反応でハイドロキシルアパタイト(以下HAP)主体とされる不溶性固形物が析出し、担体に付着し、アンモニア酸化菌の安定付着を阻害する。このため、リン添加量を適値に調製することが求められる。軟化処理水をPO4−Pとして1mg/L以下、好ましくは、0.5mg/L以下とすれば、長期においてHAP析出は全くなく、安定した亜硝酸化処理性能が得られる。
In the present invention, nitrous acid step, it is preferable to control the PO 4 -P concentration 0.1 to 1 mg / L.
For example, in the case of leachate or factory wastewater, if the raw water contains little phosphorus, it is preferable to add phosphorus necessary for microbial growth to the nitritation tank. When the phosphorus concentration is low in the nitritation tank, it tends to be difficult to attach and fix ammonia oxidizing bacteria to the carrier.
According to the results of the experimental study by the inventors, if the phosphorus concentration of the softened water is 0.1 mg / L or more, preferably 0.2 mg / L or more as PO 4 -P, It was confirmed that all of the activities were stable. On the other hand, since the Ca concentration is about 100 mg / L in the treated water, when PO 4 -P is high, the insoluble water is mainly composed of hydroxyapatite (hereinafter referred to as HAP) due to the reaction between Ca and PO 4 -P in the high pH region. Solid matter precipitates and adheres to the carrier, which inhibits stable adhesion of ammonia-oxidizing bacteria. For this reason, it is calculated | required to adjust phosphorus addition amount to an appropriate value. If the softened water is 1 mg / L or less, preferably 0.5 mg / L or less as PO 4 -P, there is no HAP precipitation in the long term, and stable nitritation treatment performance can be obtained.
亜硝酸化処理水のPO4−P濃度を0.1〜1mg/Lに制御する手段としては、亜硝酸化処理工程に、又は同工程から脱窒工程前までの間に亜硝酸化処理水のPO4−P濃度を測定する装置を設け、上記と同様にこの装置をリン注入装置及び制御装置と連絡させることができる。例えば、制御装置にて該PO4−P濃度を連絡し、注入装置から所定のPO4−P濃度となるリン物質を軟化処理水または亜硝酸化槽に投入するように構成することができる。 As means for controlling the PO 4 -P concentration of nitrite-treated water to 0.1 to 1 mg / L, nitrite-treated water is used in the nitrite treatment step or before the denitrification step. A device for measuring the concentration of PO 4 -P can be provided and communicated with the phosphorus infusion device and control device in the same manner as described above. For example, the PO 4 -P concentration can be communicated by the control device, and a phosphorous substance having a predetermined PO 4 -P concentration can be supplied from the injection device to the softened water or nitritation tank.
次に脱窒工程について説明する。
本発明の脱窒工程は、亜硝酸化工程で得られた亜硝酸及びアンモニア性窒素を含む廃水(即ち、亜硝酸化処理水)を脱窒処理する工程である。
亜硝酸化処理水は、亜硝酸化処理水中のNH4−Nが電子供与体、NO2−Nが電子受容体となり、アンモニア脱窒菌により脱窒処理される。この脱窒処理により得られた処理水をアンモニア脱窒処理水ともいう。
脱窒工程に用いられる装置は、亜硝酸化処理水を脱窒処理するための脱窒槽を含むことが好ましい。
Next, the denitrification process will be described.
The denitrification step of the present invention is a step of denitrifying waste water containing nitrous acid and ammonia nitrogen obtained in the nitritation step (ie, nitritation water).
In the nitrite-treated water, NH 4 -N in the nitrite-treated water becomes an electron donor and NO 2 -N becomes an electron acceptor, and is denitrified by ammonia denitrifying bacteria. The treated water obtained by this denitrification treatment is also called ammonia denitrification treatment water.
It is preferable that the apparatus used for the denitrification step includes a denitrification tank for denitrifying the nitritation water.
以下に本発明を、実施態様の一例を示す図面を用いて詳細に説明する。ただし、本発明はこれのみに限定されるものではない。
図1に廃棄物埋立最終処分場の浸出水を原水として、この原水に対して本発明による処理を実施する一例をフローシートにて説明する。
図1に示す如く、原水1が軟化処理槽2に導入されて、前記式(3)を用いてCaの除去を行う。軟化処理槽にはCa除去に必要な炭酸塩やアルカリ及び凝集用ポリマー等の添加薬品3を順次添加して原水中のCaを不溶のCaCO3を含む汚泥として沈降濃縮させて濃縮汚泥を排出汚泥4として系外に排出する。
後述の実施例1の軟化処理は一つの軟化処理槽で凝集と混和反応及び固液分離を順に行うバッチ式であったが、一般的に炭酸塩添加とpH調製で凝集反応を行う軟化処理槽とポリマー添加で汚泥フロックを形成する混和槽、そして固液分離を行う沈殿池の順に連続処理しても同様な効果が得られる。
軟化処理槽2には、添加薬品3を原水1に注入する注入装置21、添加薬品3を原水1に混合、攪拌するための攪拌装置2b、原水のpHを測定するためのpH測定装置2c、Ca濃度、M−アルカリ度濃度等を測定するための濃度測定装置等を備えることができる。
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an example of an embodiment. However, the present invention is not limited to this.
FIG. 1 is a flow sheet illustrating an example in which leachate from a landfill final disposal site is used as raw water, and the raw water is treated according to the present invention.
As shown in FIG. 1, raw water 1 is introduced into a softening
The softening treatment of Example 1 described later was a batch type in which agglomeration, mixing reaction and solid-liquid separation were sequentially performed in one softening treatment tank, but generally a softening treatment tank in which agglomeration reaction was performed by adding carbonate and adjusting pH. The same effect can be obtained by continuous treatment in the order of a mixing tank for forming sludge flocs by addition of a polymer and a sedimentation tank for solid-liquid separation.
In the
軟化処理槽2からの上澄液は軟化処理水5として原水槽6に導入される。この軟化処理水5は亜硝酸化槽原水7として亜硝酸化槽8に導入される。原水槽6は必ずしも必要ではなく、原水の水質変動が少ない場合や安定した流入量が得られる場合、特に原水槽を設けなくても良い。また、軟化処理水のpHが通常、高いので、必要に応じて酸を添加してpH調製することが望ましい。
原水槽6は、M−アルカリ度濃度、及びNH4−N濃度を測定する装置6a、並びに所望の添加薬品を軟化処理水5に混合するための攪拌装置6bを備える。
The supernatant from the softening
The raw water tank 6 includes a device 6 a for measuring the M-alkaliness concentration and the NH 4 -N concentration, and a stirring device 6 b for mixing a desired additive chemical into the softened water 5.
亜硝酸化槽8に添加直後の担体はアンモニア酸化菌が全く付着固定していないことから、硝化菌含有の種汚泥を添加した状態で原水7を供給して、ブロワー8d1及び散気管8d2を備えた散気装置8dにより曝気処理し、アンモニア酸化菌を付着固定させる立上げ運転を行う。この立上げ運転において亜硝酸化槽8に流入する原水7、即ち、軟化処理水5のCaを100mg/L以下に制御すれば、亜硝酸化槽内pH、水温が大きく変動してもCaCO3析出が全くなく、担体表面に短期間でアンモニア酸化菌を安定して付着固定することができる。この立上げ運転ではFA濃度を1〜10mg/Lと高くするために、水温20℃以上、好ましくは25℃〜40℃とすれば、アンモニア酸化菌が数日間で付着する。また、pHを7.0以上、好ましくは7.5〜8.5に設定すれば、アンモニア酸化菌が優占的に増殖して担体に付着固定できる。これにより、硝化が亜硝酸型となり、NO3−Nの生成がほぼ無くなる。上記のような立上げ運転条件で数日程度、最大2週間程度の通水処理を行うと担体にほぼ定常状態に近いアンモニア酸化菌が付着できる。
The carrier immediately after addition to the nitrification tank 8 has no ammonia-oxidizing bacteria attached and fixed, so the raw water 7 is supplied in a state where seed sludge containing nitrifying bacteria is added, and is provided with a blower 8d1 and an air diffuser 8d2. The aeration operation is performed by the
アンモニア酸化菌が安定して付着すると硝化速度が上昇し、亜硝酸化槽8へ流入する原水7のアンモニア性窒素がアンモニア酸化菌の働きでNO2−Nに変換される。それに伴って、M−アルカリ度が消費されてpHが低下する。該原水7のM−アルカリ度/NH4−N比を予め3.7〜4.4に調製したことから、M−アルカリ度が100mg/L以下に低下しても亜硝酸化処理水NO2−N/NH4−Nがほぼ1.0〜1.5となる。M−アルカリ度の残留が少ないことから、これ以上硝化がほとんど進行せず、NO2−N/NH4−Nがほぼ1.0〜1.5のままとなる。
このように部分亜硝酸型硝化が安定して進行した場合、亜硝酸化槽pH低下とともにNO2−Nも増加するので亜硝酸化槽内の遊離亜硝酸(以下FNA)濃度が増加する。FNAが高いほどアンモニア酸化菌が優占的に増殖するのでpHが7.5以下、好ましくは6.0〜7.2と制御されることでアンモニア酸化菌の優占増殖が維持される。
When ammonia-oxidizing bacteria adhere stably, the nitrification rate increases, and ammonia nitrogen in the raw water 7 flowing into the nitritation tank 8 is converted to NO 2 -N by the action of the ammonia-oxidizing bacteria. Along with that, M-alkalinity is consumed and pH is lowered. Since the M-alkalinity / NH 4 -N ratio of the raw water 7 was adjusted to 3.7 to 4.4 in advance, even if the M-alkalinity decreased to 100 mg / L or less, nitrite-treated water NO 2 the -N / NH 4 -N approximately 1.0 to 1.5. Since there is little residue of M-alkalinity, nitrification hardly proceeds any more, and NO 2 —N / NH 4 —N remains approximately 1.0 to 1.5.
Thus, when the partial nitrite type nitrification proceeded stably, since NO 2 -N also increases with nitritation bath pH lowered free nitrous acid (hereinafter FNA) Concentration of nitrite reduction vessel increases. The higher the FNA, the more ammonia-oxidizing bacteria grow. Therefore, the dominant growth of the ammonia-oxidizing bacteria is maintained by controlling the pH to 7.5 or lower, preferably 6.0 to 7.2.
上述の亜硝酸化型硝化の立上げ運転が完了すると、次いで、例えば、以下のような定常運転に移行される。M−アルカリ度律速によりpHが7.5以下に低下した処理段階において、軟化処理水Ca濃度を立上げ運転時の100mg/L以下から100〜500mg/L、特に亜硝酸化槽8のpH6.0〜7.2の場合、軟化処理水のCa濃度を300〜500mg/Lとしても、CaCO3生成がないことから、担体にCaスケール付着による硝化性能低下がなく、安定した処理が得られる。これにより、軟化処理での炭酸塩添加量及びCaCO3析出による汚泥発生量が大幅に減少し、処理コストの低減となる。 When the start-up operation of the above-described nitrite-type nitrification is completed, then, for example, the following steady operation is performed. In the treatment stage in which the pH is lowered to 7.5 or less due to the rate of M-alkalinity, the softened treated water Ca concentration is increased from 100 mg / L or less to 100 to 500 mg / L during the start-up operation, particularly pH 6 of the nitritation tank 8. In the case of 0 to 7.2, even if the Ca concentration of the softened treated water is set to 300 to 500 mg / L, there is no CaCO 3 generation, so that the nitrification performance does not deteriorate due to Ca scale adhesion to the carrier, and a stable treatment can be obtained. As a result, the amount of carbonate added in the softening treatment and the amount of sludge generated due to CaCO 3 precipitation are greatly reduced, resulting in a reduction in treatment costs.
上述のように、亜硝酸化槽8に導入される原水7のM−アルカリ度/NH4−N比率が部分亜硝酸化処理に必要な3.7〜4.4となるように予め制御、調製することが望ましい。軟化処理では原水のCa及びM−アルカリ度に対応した炭酸塩量の添加を行っているため、M−アルカリ度の過剰がほぼ無いことから、一般的にM−アルカリ度不足による中和剤9を添加するケースが生じる。この方法として原水槽に所定量の中和剤9を添加しても、直接、亜硝酸化槽に添加しても同様な効果が得られる。
中和剤の添加量は、軟化処理水のM−アルカリ度濃度にもよるが、M−アルカリ度換算で通常、2000mg/L以下である。
中和剤9として、重炭酸ナトリウム、炭酸ナトリウム、水酸化ナトリウムを用いることができる。また、必要に応じて硫酸、塩酸等の酸添加による調整も可能である。
亜硝酸化槽8は、原水槽6に備えた軟化処理水のM−アルカリ度濃度、及びNH4−N濃度を測定する装置6aと連絡した中和剤添加量制御装置8a、及び該中和剤添加量制御装置8aに連絡した中和剤注入装置8bを備えている。中和剤添加量制御装置8aは、該軟化処理水のM−アルカリ度及びNH4−N濃度の情報を処理して亜硝酸化槽への中和剤9の添加量を計算するとともにその計算結果を中和剤注入装置8bに連絡し、同注入装置から同中和剤9の添加量を同槽8へ注入させる機能を有する。この中和剤注入装置8bは、ポンプと中和剤溶液槽等から構成することができる。また、亜硝酸化槽は、槽内の溶存酸素(DO)量を測定するための装置8e、槽内のpHを測定するための装置8fを備えることができる。
As described above, the M-alkalinity / NH 4 -N ratio of the raw water 7 introduced into the nitritation tank 8 is controlled in advance so as to be 3.7 to 4.4 necessary for the partial nitritation treatment. It is desirable to prepare. Since the amount of carbonate corresponding to the Ca and M-alkalinity of raw water is added in the softening treatment, there is almost no excess of M-alkalinity. In some cases. The same effect can be obtained by adding a predetermined amount of the neutralizing agent 9 to the raw water tank or directly adding it to the nitritation tank.
The addition amount of the neutralizing agent is usually 2000 mg / L or less in terms of M-alkalinity although it depends on the M-alkalinity concentration of the softened water.
As the neutralizing agent 9, sodium bicarbonate, sodium carbonate, or sodium hydroxide can be used. Further, adjustment by adding an acid such as sulfuric acid or hydrochloric acid is also possible as required.
The nitritation tank 8 includes a neutralizer addition
亜硝酸化槽8では、同槽内のアンモニア酸化菌付着の担体10及び活性汚泥中のアンモニア酸化菌の働きで流入NH4−Nの一部がNO2−Nに酸化される。処理後の亜硝酸化槽内混合液が亜硝酸化槽分離スクリーン8cにて担体が分離されて亜硝酸化槽混合液8gが沈殿池11に流入し、汚泥沈降分離後、上澄液が亜硝酸化処理水12として得られる。また、沈殿池からの濃縮汚泥11aの一部は返送汚泥11bとして亜硝酸化槽に戻され、残余は余剰汚泥11cとする。
In the nitritation tank 8, a part of the inflow NH 4 -N is oxidized to NO 2 -N by the action of the ammonia oxidizing
亜硝酸化処理水12は直接、アンモニア脱窒槽13に導入してもよいが、水量やpH調製、さらにアンモニア脱窒に必要な炭酸源や栄養剤を添加するために中間調整槽14を設けて、添加薬品15を同注入装置14aより亜硝酸化処理水に添加混合すると水量及び水質が一層均一化される。
The nitrite-treated water 12 may be directly introduced into the ammonia denitrification tank 13, but an
この中間調整槽14からの流出水をアンモニア脱窒原水16としてアンモニア脱窒槽13に導入されると担体17に付着、固定したアンモニア脱窒菌により流入原水のNH4−Nが電子供与体、NO2−Nが電子受容体となり、脱窒処理される。脱窒処理後の混合液が分離スクリーン131により担体17が分離された処理液がアンモニア脱窒処理水18となる。
また、アンモニア脱窒槽13は、槽内の酸化還元電位(orp)量を測定するための装置13b、槽内のpHを測定するための装置13c、攪拌装置13d、添加薬品注入装置13eを備えることができる。
When the effluent water from the
The ammonia denitrification tank 13 includes a
亜硝酸化槽8にアンモニア酸化菌を付着固定できる担体10として、高分子担体を充填すれば、アンモニア酸化菌を安定して付着できることから、亜硝酸化槽において安定した亜硝酸化性能が得られる。亜硝酸化槽に充填する高分子担体としては、ポリエチレングリコール(PEG)やポリビニルアルコール(PVA)、ポリアクリルアミド、光硬化性樹脂等の合成高分子、カラギーナン、アルギン酸ソーダ等の高分子を用いたゲル担体、ポリエチレンやポリウレタン、ポリポロピレン等からなる流動担体が挙げられる。
該担体の形状としては球形、四角形、円筒形の何れも使用可能、有効径は曝気槽出口のスクリーンより安定して分離できる3〜10mmが好ましい。担体比重は曝気状態において均一に流動可能となる1.01〜1.05であるものが好ましい。また、担体充填量は均一に混合流動可能となる10〜30容量%(V%)であることが望ましい。
As the
As the shape of the carrier, any of a spherical shape, a square shape and a cylindrical shape can be used, and the effective diameter is preferably 3 to 10 mm which can be stably separated from the screen at the outlet of the aeration tank. The specific gravity of the carrier is preferably 1.01 to 1.05, which allows the carrier to flow uniformly in the aerated state. Further, it is desirable that the carrier filling amount is 10 to 30% by volume (V%) that enables uniform mixing and flow.
アンモニア脱窒槽13にアンモニア脱窒菌を付着固定できる担体17として、高分子担体を充填すれば、アンモニア脱窒菌を安定して付着できることから、アンモニア脱窒槽13において安定した脱窒性能が得られる。アンモニア脱窒槽に充填する高分子担体としては、亜硝酸化に用いられるものと同様の材料の流動担体が挙げられる。
担体の形状としては球形、四角形、円筒形の何れも使用可能、有効径は脱窒槽出口のスクリーンより安定して分離できる3〜10mmが好ましい。担体として表面に微細孔径を多く有するもの、内部中空であるスポンジ、表面に無数の凹凸を有するものがアンモニア脱窒菌の付着固定が速く、短期間で高い脱窒性能が得られる。さらに長期間、脱窒槽内アンモニア脱窒菌を高濃度に維持できることから、安定した脱窒性能が得られる。
担体比重は嫌気状態において撹拌より均一流動できる1.01〜1.10であるものが好ましい。担体充填量は脱窒槽内において局部堆積のないように10〜30V%とすることが望ましい。
As the
As the shape of the carrier, any of a spherical shape, a square shape and a cylindrical shape can be used, and the effective diameter is preferably 3 to 10 mm which can be stably separated from the screen at the denitrification tank outlet. A carrier having a large number of fine pores on the surface, a sponge having a hollow inside, and a material having innumerable irregularities on the surface can quickly attach and fix ammonia denitrifying bacteria, and high denitrification performance can be obtained in a short period of time. Furthermore, since the ammonia denitrifying bacteria in the denitrification tank can be maintained at a high concentration for a long period of time, stable denitrification performance can be obtained.
The specific gravity of the carrier is preferably 1.01 to 1.10 which can flow uniformly by stirring in an anaerobic state. The carrier filling amount is desirably 10 to 30 V% so as not to cause local deposition in the denitrification tank.
以下、本発明の実施例を説明するが、以下に制限されない。
(実施例1)
図1に示した方法及び装置構成に準じてアンモニア性窒素及びカルシウム含有廃水の脱窒処理を行った。
表1に本実施例1における軟化処理の条件を示す。上述のように軟化処理は一つの軟化処理槽で凝集と混和反応及び固液分離を順に行うバッチ式で行った。
Examples of the present invention will be described below, but are not limited to the following.
Example 1
Denitrification treatment of ammonia nitrogen and calcium containing wastewater was performed according to the method and apparatus configuration shown in FIG.
Table 1 shows the conditions for the softening treatment in Example 1. As described above, the softening treatment was performed by a batch method in which aggregation, mixing reaction, and solid-liquid separation were sequentially performed in one softening treatment tank.
軟化処理の条件は後段の亜硝酸化処理の立上げ運転期間と定常運転期間に対応した条件とした。表1は各期間の平均値を示した。
軟化処理のpH及びHRTはそれぞれ、9.0と20分であり、いずれの処理期間においても同じとした。立上げ運転期間では、軟化処理水Ca濃度目標値を100mg/Lとし、前記式(3)より求めたNa2CO3添加量を2040mg/Lとした。一方、亜硝酸化処理が立上げ運転後の定常運転期間では、軟化処理水のCa濃度目標値を300mg/Lに変更したため、Na2CO3添加量が1480mg/Lとなり、立上げ運転時より560mg/L少なくなった。
The conditions for the softening treatment corresponded to the start-up operation period and the steady operation period of the subsequent nitritation treatment. Table 1 shows the average value of each period.
The pH and HRT for the softening treatment were 9.0 and 20 minutes, respectively, and were the same for any treatment period. In the start-up operation period, the target value of the softened treated water Ca concentration was 100 mg / L, and the amount of Na 2 CO 3 added obtained from the above equation (3) was 2040 mg / L. On the other hand, in the steady operation period after nitritation treatment start-up operation, the Ca concentration target value of softened water is changed to 300 mg / L, so the amount of Na 2 CO 3 added is 1480 mg / L, which is higher than that during start-up operation. Reduced by 560 mg / L.
表2は亜硝酸化処理槽の条件を示す。また、表3はアンモニア脱窒の処理条件を示す。
亜硝酸化処理の立上げ運転では、水温30℃、pH7.5〜8.0でNH4−N負荷を平均1.0kg/m3/dとし、15日間の連続通水を行った。
立上げ運転後の定常運転期間では水温20〜30℃、pH6.0〜7.5、NH4−N負荷を平均2.5kg/m3/dとし、180日間の連続通水処理を行った。
Table 2 shows the conditions of the nitritation tank. Table 3 shows the treatment conditions for ammonia denitrification.
In the start-up operation of the nitritation treatment, the water temperature was 30 ° C., the pH was 7.5 to 8.0, the NH 4 —N load was averaged 1.0 kg / m 3 / d, and continuous water flow was performed for 15 days.
During the steady operation period after the start-up operation, the water temperature was 20 to 30 ° C., the pH was 6.0 to 7.5, the NH 4 —N load was 2.5 kg / m 3 / d on average, and continuous water treatment was performed for 180 days. .
亜硝酸化処理槽には平均粒径4.2mmのPEG担体を20V%充填した。原水7(軟化処理水)に対し、予めM−アルカリ度/NH4−N比を求め、M−アルカリ度/NH4−Nが約4.0となるように所定量のNaOH水溶液を亜硝酸化槽に注入した。亜硝酸化槽内DOが4mg/L以上となるようにブロワーの出力調整を行った。
アンモニア脱窒槽に対し、pHが7.5以下となるように硫酸注入による制御を行った。脱窒槽には平均粒径4mmのPVA担体を20V%充填した。また、アンモニア脱窒槽に流入する亜硝酸化処理水の無機炭素がほとんど無かったため、無機炭素源としてNa2CO3約250mg/Lを亜硝酸化処理水に添加した。
表4に実施例1において、亜硝酸化処理立上げ運転後の180日定常運転期間中、原水、軟化処理水、亜硝酸化処理水及びアンモニア脱窒処理水質の一例を示す。
The nitrite treatment tank was filled with 20 V% of a PEG carrier having an average particle size of 4.2 mm. M-alkalinity / NH 4 -N ratio is determined in advance for raw water 7 (softening-treated water), and a predetermined amount of NaOH aqueous solution is added to nitrous acid so that M-alkalinity / NH 4 -N is about 4.0. It was injected into the chemical bath. The output of the blower was adjusted so that the DO in the nitritation tank was 4 mg / L or more.
The ammonia denitrification tank was controlled by injecting sulfuric acid so that the pH was 7.5 or less. The denitrification tank was filled with 20 V% of a PVA carrier having an average particle diameter of 4 mm. Further, since inorganic carbon nitrite treatment water flowing into the ammonia denitrification had little, was added Na 2 CO 3 to about 250 mg / L nitrite treatment water as an inorganic carbon source.
Table 4 shows an example of the quality of raw water, softened water, nitrified water, and ammonia denitrification water during the 180-day steady operation period after the nitritation treatment start-up operation in Example 1.
軟化処理では、表1及び表2に示す立上げ運転期間において、亜硝酸化槽のPEG担体にアンモニア酸化菌が既に付着したことから、軟化処理水のCa濃度は目標値300mg/L以下の250mg/Lとなった。
亜硝酸化処理では、軟化処理水のM−アルカリ度/NH4−N比を4.0となるように亜硝酸化槽にNaOH注入による調整を行ったことから、NH4−Nの約56%が亜硝酸化され、亜硝酸化処理水のNO2−Nが140mg/Lとなり、NO2−N/NH4−N比が1.22とアンモニア脱窒必要量1.32に近い値が得られた。亜硝酸化処理水のNOX−Nに対するNO2−N比が98.6%となり、安定した亜硝酸化処理が得られた。
In the softening treatment, ammonia oxidizing bacteria had already adhered to the PEG carrier in the nitritation tank during the start-up operation period shown in Tables 1 and 2, and therefore the Ca concentration of the softening treated water was 250 mg, which is a target value of 300 mg / L or less. / L.
In the nitritation treatment, since the M-alkalinity / NH 4 -N ratio of the softened water was adjusted to 4.0 by NaOH injection into the nitritation tank, about 56 NH 4 -N was obtained. % Is nitritized, NO 2 —N of nitrite-treated water is 140 mg / L, and the NO 2 —N / NH 4 —N ratio is 1.22, which is close to the ammonia denitrification required amount of 1.32. Obtained. The NO 2 —N ratio to NO X —N of the nitritation water was 98.6%, and a stable nitritation treatment was obtained.
アンモニア脱窒処理において、亜硝酸化処理水のNO2−N/NH4−Nが1.22とアンモニア脱窒反応に必要な比率にほぼ近い。その結果、脱窒処理水NH4−N及びNO2−Nがそれぞれ、12.3mg/L、8.9mg/Lといずれも低い。T−Nが52.2mg/Lとなり、原水T−Nに対する除去率が83.3%得られた。 In the ammonia denitrification treatment, the NO 2 —N / NH 4 —N ratio of nitrite-treated water is 1.22, which is close to the ratio required for the ammonia denitrification reaction. As a result, the denitrification treated water NH 4 -N and NO 2 -N are both low at 12.3 mg / L and 8.9 mg / L, respectively. TN became 52.2 mg / L and the removal rate with respect to raw | natural water TN was obtained 83.3%.
実施例1では、原水の不足M−アルカリ度を補給するため、亜硝酸化槽8に所定量のアルカリ剤を連続添加した。なお、アルカリ剤を原水槽6に直接添加しても同様な効果が得られる。また、アルカリ剤としてNaOHやNa2CO3及びNaHCO3等何れを用いても同様な効果が得られる。また、この実施例では、亜硝酸化処理水を一旦中間調整槽に導入して水量やpH調製、さらにアンモニア脱窒に必要な炭酸源や栄養剤を添加混合後、アンモニア脱窒に導入したが、直接、アンモニア脱窒槽に導入しても同様な効果が得られる。 In Example 1, a predetermined amount of alkaline agent was continuously added to the nitritation tank 8 in order to replenish the insufficient M-alkalinity of raw water. Note that the same effect can be obtained by adding an alkali agent directly to the raw water tank 6. The same effect can be obtained by using any one of NaOH, Na 2 CO 3 and NaHCO 3 as the alkali agent. In this example, the nitrite-treated water was once introduced into the intermediate adjustment tank, the water amount and pH were adjusted, and the carbonic acid source and nutrients necessary for ammonia denitrification were added and mixed, and then introduced into ammonia denitrification. Even if it is directly introduced into the ammonia denitrification tank, the same effect can be obtained.
(比較例1)
実施例1と同一の原水を用い、Ca除去の軟化処理を行わず、直接、亜硝酸化処理、アンモニア脱窒処理の順に処理を行った。処理水量は表2に示す実施例1の定常運転期間と同様な水量で540L/dとし、NH4−N負荷も同じく2.5kg/m3/dとなった。
表5に比較例1の原水及び処理水水質結果の一例を示す。
表5に示すように原水に対するCa除去がないため、亜硝酸化処理では流入原水Caが1200mg/Lと高く、亜硝酸化処理水Caが1050mg/Lとなり、原水より約150mg/L低下した。これは亜硝酸化槽においてCaCO3が生成したことによるものであり、担体表面にCaCO3由来のスケール付着が見られた。この結果、亜硝酸化処理水のNH4−Nが230mg/Lと高く、NO2−N/NH4−N比率が0.2と低く、亜硝酸化処理能力が低いことが示された。
上記のように亜硝酸化槽において安定した亜硝酸化処理ができず、亜硝酸化処理水のNH4−Nが高く、硝化性能が低いことから、アンモニア脱窒槽ではアンモニア脱窒処理水のNH4−Nが205mg/Lと高く、同処理水T−Nも242mg/Lと原水T−Nとほぼ同程度となり、窒素除去率が僅か18%程度であった。
(Comparative Example 1)
The same raw water as in Example 1 was used, and the treatment was performed directly in the order of nitritation treatment and ammonia denitrification treatment without performing Ca softening treatment. The amount of treated water was 540 L / d with the same amount of water as in the steady operation period of Example 1 shown in Table 2, and the NH 4 —N load was also 2.5 kg / m 3 / d.
Table 5 shows an example of the raw water and treated water quality results of Comparative Example 1.
As shown in Table 5, since there was no Ca removal from the raw water, the inflow raw water Ca was as high as 1200 mg / L and the nitrite-treated water Ca was 1050 mg / L, which was about 150 mg / L lower than the raw water. This is due to the formation of CaCO 3 in the nitritation tank, and scale deposition derived from CaCO 3 was observed on the surface of the support. As a result, NH 4 —N of nitritation water was as high as 230 mg / L, and the NO 2 —N / NH 4 —N ratio was as low as 0.2, indicating that the nitritation capacity was low.
As described above, stable nitritation treatment cannot be performed in the nitritation tank, NH 4 -N of nitritation water is high, and nitrification performance is low. 4- N was as high as 205 mg / L, and the treated water TN was 242 mg / L, almost the same as the raw water TN, and the nitrogen removal rate was only about 18%.
(比較例2)
原水は実施例1と同様なものを用いた。本比較例では、軟化処理において原水中のM−アルカリ度由来の炭酸源を考慮せず、Ca濃度に対し約2.8倍の炭酸ナトリウム(Na2CO3)を添加した。他の処理条件は実施例1と同一とした。
表6は軟化処理での原水及び軟化処理水の水質の一例を示す。
軟化処理のNa2CO3添加量が3360mg/Lとなり、実施例1の1480mg/Lより1880mg/L多くなっている。その結果、処理水Caが50mg/Lと低くなったが、M−アルカリ度が1850mg/Lと高く、炭酸塩が多く残留した。M−アルカリ度/NH4−N比が6.1倍となり、部分亜硝酸化処理に必要となる4.0に調整するためには多量の酸添加が必要となった。また、これに伴うCaCO3を含む汚泥の発生量は実施例1より500mg/L多い。
(Comparative Example 2)
The raw water was the same as in Example 1. In this comparative example, the carbonate source derived from the M-alkalinity in the raw water was not considered in the softening treatment, and about 2.8 times as much sodium carbonate (Na 2 CO 3 ) as Ca concentration was added. Other processing conditions were the same as in Example 1.
Table 6 shows an example of the quality of raw water and softened water in the softening treatment.
The amount of added Na 2 CO 3 for the softening treatment is 3360 mg / L, which is 1880 mg / L higher than 1480 mg / L in Example 1. As a result, the treated water Ca was as low as 50 mg / L, but the M-alkalinity was as high as 1850 mg / L and a large amount of carbonate remained. The M-alkalinity / NH 4 -N ratio was 6.1 times, and a large amount of acid was required to adjust to 4.0, which is necessary for the partial nitritation treatment. In addition, the amount of sludge containing CaCO 3 is 500 mg / L higher than that in Example 1.
(実施例2)
実施例1と同一な原水を用い、図1に示す実施例1と同様な処理フローで処理を行った。実施例2ではリンがほとんど無い軟化処理水に対し、PO4−Pが約0.8mg/Lとなるように添加して徐々に亜硝酸化処理の立ち上げを行った。表7には亜硝酸化処理立ち上げ後、定常運転時の原水及び処理水の一例を示す。
表7に示すように軟化処理水に対し、リン酸の添加でPO4−Pを約0.8mg/Lに調整し、亜硝酸化処理液PO4−Pが0.6mg/Lとなった。その結果、亜硝酸化槽PEG担体に安定したアンモニア酸化菌が付着できたことから、亜硝酸化処理水のNH4−Nが140mg/Lに低下し、NO2−Nが171mg/Lに増加した。NO2−N/NH4−N比が1.22とアンモニア脱窒に最適値の1.32に近い値となった。さらにアンモニア脱窒処理水でNH4−N及びNO2−Nがそれぞれ、12.3mg/Lと8.9mg/Lに低下し、T−Nが52.2mg/Lとなり、良好な脱窒性能が得られた。
(Example 2)
The same raw water as in Example 1 was used, and processing was performed in the same processing flow as in Example 1 shown in FIG. In Example 2, the nitritation treatment was gradually started by adding PO 4 -P to about 0.8 mg / L with respect to softening-treated water having almost no phosphorus. Table 7 shows an example of raw water and treated water during steady operation after the start of nitritation treatment.
As shown in Table 7, with respect to softened treated water, PO 4 -P was adjusted to about 0.8 mg / L by adding phosphoric acid, and the nitrite treating solution PO 4 -P became 0.6 mg / L. . As a result, stable ammonia-oxidizing bacteria could adhere to the nitrification tank PEG carrier, so that NH 4 -N of nitrite-treated water decreased to 140 mg / L and NO 2 -N increased to 171 mg / L. did. The NO 2 —N / NH 4 —N ratio was 1.22, which was close to the optimum value of 1.32 for ammonia denitrification. Further, NH 4 -N and NO 2 -N decreased to 12.3 mg / L and 8.9 mg / L, respectively, and TN became 52.2 mg / L in ammonia denitrification treated water, and good denitrification performance was gotten.
(比較例3)
比較例3では、実施例2と同一な原水及び処理フローを用いた。だだし、実施例2と異なるのは軟化処理水に添加する燐酸濃度が実施例2より高く、PO4−Pとして約3.0mg/Lとなった。表8に比較例3の原水及び各種処理水の水質の一例を示す。
軟化処理水に添加するPO4−Pが3.0mg/Lと高く、Ca残留や高pHの影響により亜硝酸化処理槽のPEG担体にはHAP主体と思われるスケールが生成した。この結果、良好な亜硝酸化処理性能が得られず、処理水NH4−Nが240mg/Lと高く、NO2−Nが45mg/Lと低い。これによりアンモニア脱窒処理水のNH4−Nが205mg/Lと高く、T−Nが244mg/Lの残留となった。
(Comparative Example 3)
In Comparative Example 3, the same raw water and treatment flow as in Example 2 were used. However, the difference from Example 2 was that the concentration of phosphoric acid added to the softened water was higher than that of Example 2 and was about 3.0 mg / L as PO 4 -P. Table 8 shows an example of the quality of raw water and various treated water in Comparative Example 3.
The PO 4 -P added to the softened water was as high as 3.0 mg / L, and a scale that seems to be mainly HAP was generated on the PEG carrier in the nitrite treatment tank due to the influence of Ca residue and high pH. As a result, good nitritation treatment performance cannot be obtained, the treated water NH 4 —N is as high as 240 mg / L, and the NO 2 —N is as low as 45 mg / L. As a result, NH 4 —N of ammonia denitrification treated water was as high as 205 mg / L, and TN was 244 mg / L.
Ca濃度制御工程で予め軟化処理水中のM−アルカリ度及びNH4−N濃度を知ることで、亜硝酸化工程における軟化処理水への中和剤の添量を適切に制御することができる。 By knowing the M-alkaliness and NH 4 —N concentration in the softened water in advance in the Ca concentration control step, it is possible to appropriately control the amount of neutralizing agent added to the softened water in the nitritation step.
1…原水、2…軟化処理槽、2a…注入装置、2b…攪拌装置、2c…pH測定装置、3…添加薬品、4…排出汚泥、5…軟化処理水、6…原水槽、6a…M−アルカリ度濃度、及びNH4−N濃度を測定する装置、6b…攪拌装置、7…亜硝酸化槽原水、8…亜硝酸化槽、8a…中和剤添量制御装置、8b…中和剤注入装置、8c…分離スクリーン、8d…散気装置、8d1…ブロワー、8d2…散気管、8e…DO測定装置、8f…pH測定装置、8g…亜硝酸化槽混合液、9…中和剤、10…担体、11…沈殿池、11a…濃縮汚泥、11b…返送汚泥、11c…余剰汚泥、12…亜硝酸化処理水、13…アンモニア脱窒槽、13a…分離スクリーン、13b…orp量測定装置、13c…pH測定装置、13d…攪拌装置、13e…添加薬品注入装置、14…中間調整槽、14a…添加薬品注入装置、15…添加薬品、16…アンモニア脱窒原水、17…担体、18…アンモニア脱窒処理水。
DESCRIPTION OF SYMBOLS 1 ... Raw water, 2 ... Softening processing tank, 2a ... Injection | pouring apparatus, 2b ... Stirring apparatus, 2c ... pH measuring device, 3 ... Additive chemical, 4 ... Discharged sludge, 5 ... Softening processing water, 6 ... Raw water tank, 6a ... M -Apparatus for measuring alkalinity concentration and NH 4 -N concentration, 6b ... Stirrer, 7 ... Raw water for nitritation tank, 8 ... Nitrite tank, 8a ... Control device for adding neutralizing agent, 8b ... Neutralization Agent injection device, 8c ... separation screen, 8d ... aeration device, 8d1 ... blower, 8d2 ... aeration tube, 8e ... DO measurement device, 8f ... pH measurement device, 8g ... mixed liquid of nitritation tank, 9 ... neutralizing agent DESCRIPTION OF
Claims (7)
カルシウム濃度制御工程:アンモニア性窒素及びカルシウム含有廃水中のカルシウム濃度を亜硝酸化工程の運転条件に応じて制御する工程
亜硝酸化工程:カルシウム濃度制御工程で得られた廃水存在下、担体にアンモニア酸化菌を固定化するとともに該廃水を亜硝酸化する工程
脱窒工程:亜硝酸化工程で得られた亜硝酸及びアンモニア性窒素を含む廃水を脱窒処理する工程 A denitrification method for wastewater containing ammoniacal nitrogen and calcium, comprising the following steps.
Calcium concentration control process: A process for controlling the calcium concentration in ammonia nitrogen and calcium-containing wastewater according to the operating conditions of the nitritation process. Nitrite process: Ammonia in the carrier in the presence of wastewater obtained in the calcium concentration control process. A process of immobilizing oxidizing bacteria and nitrifying the wastewater Denitrification process: A process of denitrifying wastewater containing nitrous acid and ammonia nitrogen obtained in the nitritation process
C0=(Cin−Cout)×a−C2/1.06
ここで、Cin(mg/L):該廃水のカルシウム濃度、Cout(mg/L):該廃水の目標カルシウム濃度、C2(mg/L):該廃水のM−アルカリ度濃度、aは係数である。 The denitrification treatment of ammonia nitrogen and calcium-containing wastewater according to claim 1 or 2, wherein the calcium concentration control step calculates the amount of Na 2 CO 3 addition C 0 (mg / L) from the following formula and adds it to the waste water. Method.
C 0 = (C in -C out ) × a-C 2 /1.06
Here, C in (mg / L): Calcium concentration of the waste water, C out (mg / L): Target calcium concentration of the waste water, C 2 (mg / L): M-alkalinity concentration of the waste water, a Is a coefficient.
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