JPH0131958B2 - - Google Patents
Info
- Publication number
- JPH0131958B2 JPH0131958B2 JP57146243A JP14624382A JPH0131958B2 JP H0131958 B2 JPH0131958 B2 JP H0131958B2 JP 57146243 A JP57146243 A JP 57146243A JP 14624382 A JP14624382 A JP 14624382A JP H0131958 B2 JPH0131958 B2 JP H0131958B2
- Authority
- JP
- Japan
- Prior art keywords
- denitrification
- sulfur
- tank
- aerobic
- anaerobic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 claims description 53
- RMGVZKRVHHSUIM-UHFFFAOYSA-N dithionic acid Chemical compound OS(=O)(=O)S(O)(=O)=O RMGVZKRVHHSUIM-UHFFFAOYSA-N 0.000 claims description 26
- 239000002351 wastewater Substances 0.000 claims description 22
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 21
- 229910052717 sulfur Inorganic materials 0.000 claims description 20
- 239000011593 sulfur Substances 0.000 claims description 20
- 239000010802 sludge Substances 0.000 claims description 14
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 12
- 239000002253 acid Substances 0.000 claims description 12
- 150000003464 sulfur compounds Chemical class 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000001556 precipitation Methods 0.000 claims description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 3
- RPAJSBKBKSSMLJ-DFWYDOINSA-N (2s)-2-aminopentanedioic acid;hydrochloride Chemical class Cl.OC(=O)[C@@H](N)CCC(O)=O RPAJSBKBKSSMLJ-DFWYDOINSA-N 0.000 claims description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 2
- 230000001590 oxidative effect Effects 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 2
- 229910052742 iron Inorganic materials 0.000 claims 1
- 229910052979 sodium sulfide Inorganic materials 0.000 claims 1
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims 1
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 27
- 239000003638 chemical reducing agent Substances 0.000 description 15
- 239000011734 sodium Substances 0.000 description 14
- 239000007788 liquid Substances 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 230000003647 oxidation Effects 0.000 description 9
- 238000007254 oxidation reaction Methods 0.000 description 9
- 241000894006 Bacteria Species 0.000 description 7
- 238000005273 aeration Methods 0.000 description 7
- 244000005700 microbiome Species 0.000 description 7
- 239000007789 gas Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000012530 fluid Substances 0.000 description 5
- 230000007935 neutral effect Effects 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000006477 desulfuration reaction Methods 0.000 description 4
- 230000023556 desulfurization Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002829 reductive effect Effects 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 229940075933 dithionate Drugs 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000010907 mechanical stirring Methods 0.000 description 2
- 230000000813 microbial effect Effects 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 230000001546 nitrifying effect Effects 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 description 1
- 230000001651 autotrophic effect Effects 0.000 description 1
- 238000009395 breeding Methods 0.000 description 1
- 230000001488 breeding effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- -1 methanol Chemical compound 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000035755 proliferation Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Landscapes
- Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
Description
本発明はジチオン酸、ポリチオン酸を含有する
廃水を生物学的に処理する方法に関するものであ
る。
排ガス中のSOxの脱硫、NOxの脱硝に際して
排出される廃水には高濃度のジチオン酸、ポリチ
オン酸、NH3、NOxが含有されている。排水中
のNH3、NOxは富栄養化の原因物質としてその
除去が望まれているが、生物学的な硝化脱窒法に
よつて比較的容易に除去される。しかしながら、
脱窒に際してNOxの還元剤となる有機炭素源が
多量に必要であり、運転経費の大部分を占るため
憂慮されている。
一方、ジチオン酸、ポリチオン酸はCODMｎの
成分となるためそれらの除去が望まれているが、
とりわけジチオン酸は生物学的にも物理化学的に
も難分解性のため、これまで種々の方法が鋭意検
討されている。この中でイオウ交換樹脂によつて
ジチオン酸を濃縮し、湿式燃焼する方法が実用段
階にあるが、コストが非常に高いという欠点があ
る。
本発明は、以上の諸欠点を合理的に解消し、廃
水の脱窒と廃水中のジチオン酸及び／又はポリチ
オン酸の酸化分解処理を的確に行うことができる
処理方法を提供することを目的とするものであ
る。
以下、本発明を完成するに至つた経過について
説明する。
本発明者らは、第１図に示す脱窒液循環方式の
生物学的硝化脱窒プロセス用いて、NH3を多量
に含有する火力発電所の脱硝脱硫廃水の窒素除去
を行い、極めて良い成績を得ることができた。
第１図の方式は廃水（脱硝脱硫廃水）１中の
NH3を好気的条件にある硝化槽２に導き、NH3
をNOx（NO2及び／又はNO3）にまで酸化したの
ち、嫌気的条件に保持した脱窒槽３に導き、脱窒
用の還元剤９としてメタノールを添加して脱窒菌
によりNOxをN2ガスにまで還元分解するもので
ある。硝化槽２ではNH3の硝化によつてPHを低
下するが、硝化菌の至適PHは中性範囲にあるの
で、アルカリ剤８を添加して硝化槽混合液のPHは
中性付近に維持される。第１図の方式では脱窒に
際して遊離したアルカリ分が硝化槽２に循環さ
れ、その分硝化槽２に添加するべきアルカリ剤８
が減少するように工夫されている。
この方式により処理水５のNH3−Ｎ、NOx−
Ｎをそれぞれ1ppm以下（廃水１のNH3−Ｎは
305ppm）にすることができたが、CODMｎの除
去率が極めて悪く、30〜35％程度の除去率しか得
られなかつた。そこで廃水１の水量負荷を生物学
的硝化脱窒に必要な1/5にしたり、硝化槽２の水
温、汚泥濃度を高めるなどの工夫を行つてみたが
CODMｎの除去率は向上しなかつた。この理由に
ついて調査したところ、脱硝脱硫廃水に多量に含
有されているジチオン酸（S2O- 6が生物処理にお
いて全く酸化されず、これがCODMｎの除去効率
の向上しない原因であることがわかつた。
処理水のCODMｎを低減するため、本発明者ら
は種々検討を加えた結果、脱窒槽３に添加する還
元剤９としてメタノールの代りにNa2S（硫化ソー
ダ）を用いることにより、脱窒槽３における
NOxの還元分解と、硝化槽２におけるジチオン
酸の酸化が可能になることを見い出した。
次にこの経過を人工廃水を用いた例について述
べる。
本発明者らは、還元剤９としてメタノールの代
りにNa2Sを、Na2Sを利用して脱窒する菌の増殖
用炭素源として炭酸ソーダ（Na2CO3）９′を脱
窒槽３にそれぞれ添加したところ、当初はNOx
の除去率が大幅に悪化し、大量のNOxが処理水
に残留したが、経日的にNOxの除去率が向上し、
約３週間後にはメタノール添加時と同等となつ
た。NOxの除去率の向上と並行してジチオン酸
のの酸化率も向上し、処理水のCODMｎも低減し
始めた。そこで、それまで過剰に添加していた
Na2Sを、次式に示す化学量論的に必要な量を過
不足なく添加するようにしたところ、Na2Sは、
嫌気的条件にある脱窒槽３で完全に消費され、そ
の結果返送汚泥６、循環液（脱窒液）７に随伴さ
れて硝化槽２で酸化されることがなくなつた。
15Na2S＋24NO- 3＋12H2O
→12N2＋15Na2SO4＋24OH- ……(1)
このようにNa2Sが好気的条件で酸化されるこ
とが完全になくなつても、硝化槽２におけるジチ
オン酸酸化能力は実験終了後の２ケ月まで劣化す
ることがなかつた。第１図のフローにおいて脱窒
槽３の活性汚泥は返送汚泥６、脱窒混合液の循環
によつて硝化槽２へ流入することから、嫌気的条
件下でNOxの酸素を利用してNa2Sを酸化し増殖
した微生物は、好気的条件にある硝化槽２でジチ
オン酸を酸化する能力のあることがわかる。な
お、第１図中４は沈殿槽、１０は再ばつ気槽であ
る。
一方、上記活性汚泥を用いて嫌気的条件下で、
Na2Sによるジチオン酸の還元分解を試みたとこ
ろ、ジチオン酸は殆ど分解されなかつた。
Na2Sは脱窒の還元剤としては高価なので、次
に比較的安価な粒子状イオウを脱窒槽に充填し、
脱窒混合液を循環しない第２図の装置によつて硝
化、脱窒およびジチオン酸の酸化を試みたところ
極めて良好な成績が得られた。
しかして本発明は、上記実験結果に基づいて完
成されたものであり、ジチオン酸、ポリチオン酸
の少なくとも一方および窒素分を含有する廃水を
好気的工程と嫌気的工程を有する生物処理工程で
処理する際に、嫌気的工程にイオウ、イオウ化合
物の少なくとも一方と炭酸ソーダを添加し、かつ
PH6.0以上に保つてNOxを生物学的に脱窒すると
共に該脱窒により微生物を増殖させ、該増殖した
微生物を好気的工程で廃水と接触せしめてジチオ
ン酸および／又はポリチオン酸を酸化することを
特徴とする廃水の処理方法である。
次に、本発明の一実施態様を２図に示す装置に
よる実験結果に基づいて説明する。
廃水１は返送汚泥６とともに硝化槽２に流入
し、NH3はNOxに硝化されジチオン酸およびポ
リチオン酸は硫酸に酸化される。硝化槽２では硝
化によつて酸が生成してPHが低下するため、アル
カリ剤８としてNa2CO3が添加されるが、その量
はPHコントローラ１１によつてPHが中性域になる
ように制御される。一方、ジチオン酸の酸化もPH
は中性域が最もよいので、硝化槽２のPHを中性域
に保つようにするとよい。
硝化が終了した混合物は脱窒槽３に流入し、
NOxは脱窒槽３内に充填されている還元剤９と
してのイオウ粒子と増殖用炭素源としての炭酸ソ
ーダ９′の存在下により脱窒される。イオウによ
る脱窒反応は化学量論的に次式で表わすことがで
きる。
5S＋6NaNO3＋2H2O
→3N2＋3Na2SO4＋2H2SO4 ……(2)
この式からわかるように脱窒に際しH2SO4が
副生するため、脱窒槽３混合液のPHが低下する。
脱窒菌の活性は硝化菌ほどPHに影響されないが、
PHが5.5以下になると活性が大幅に低下するので、
PHが6.0以上になるように制御する。
脱窒槽３のPHコントローラ用アルカリ剤８とし
てはNaOHよりもNa2CO3がよい。これはイオウ
を利用して脱窒する微生物が自栄養細菌であり、
増殖に必要な炭素源として無機炭素を必要とする
からである。
脱窒槽３内の混合液の撹拌は回転式撹拌機の如
き機械撹拌で行つてもよいが、第２図に示した如
く脱窒槽３気相部のガスを用いてブロワー１２に
よるガス撹拌を採用してもよい。
還元剤９としてのイオウは固定されているより
も混合液の撹拌によつて流動化するようにした方
が望ましい。また第２図の如く脱窒槽３中に特に
イオウの充填区域を設けず、脱窒槽３全体にイオ
ウ粒が分布するようにしてもよいが、この場合は
イオウ粒と混合液が均一に接触するように、散気
管あるいは散気板の数を多くし、撹拌ガス量を増
加することが望ましい。
脱窒槽３から流出する混合液は好気的条件にあ
る再ばつ気槽１０に流入し、嫌気的条件において
活性汚泥が溶出した有機物を酸化して処理水質を
向上させ、さらに微生物フロツクに付着している
微細なN2気泡を大気開放下で除去し沈殿槽４に
おける微生物フロツクの浮上を防止する。再ばつ
気槽１０における有機物の酸化およびN2ガスの
脱気は短時間で終了するので、混合液の滞留時間
は１時間程度で充分である。再ばつ気液は沈殿槽
４で固液分離され、処理水５は放流され汚泥は硝
化槽２へ返送される。
上記還元剤９としてはNa2S、イオウ粒のほか
にイオウの粉末、硫化鉄あるいはその粉末を用い
てもよく、脱窒およびジチオン酸の酸化を同様に
効果的に行うことができる。
また脱窒槽３の代りに第３図に示すように脱窒
槽塔１３を使用し、イオウ粒または硫化鉄粒の固
定床あるいは流動床にすれば、ポンプ１４の押し
込み液流によつて塔内の混合液が撹拌されるの
で、機械撹拌あるいはガス撹拌の設備は不要とな
る。なお、第３図中１５は循環液、１６は流量調
節用の弁である。
本発明の方法では脱窒工程でアルカリの生成が
期待できないので、第１図のフローのような硝化
槽２のアルカリ分補給のための脱窒液循環は無駄
であるが、硝化槽２で高濃度のNO2が蓄積して
活性汚泥にとつて有害となる場合には、脱窒液を
循環してNO2濃度を低下させることは有効であ
る。
次に、本発明の実施例について、脱窒の還元剤
としてメタノールおよびエタノールを用いた例と
比較して記載する。実施に際しては第２図のフロ
ーを採用し、脱窒槽に還元剤を注入する方法と充
填する方法の二通りを行つた。
第１表に処理条件を、第２表に還元剤の使用条
件を、第３表に処理水の水質をそれぞれ示した。
The present invention relates to a method for biologically treating wastewater containing dithionic acid and polythionic acid. The wastewater discharged during desulfurization of SOx and denitrification of NOx in exhaust gas contains high concentrations of dithionic acid, polythionic acid, NH 3 , and NOx. NH 3 and NOx in wastewater are desired to be removed as substances that cause eutrophication, but they can be removed relatively easily by biological nitrification and denitrification methods. however,
Denitrification requires a large amount of organic carbon source, which acts as a NOx reducing agent, and is a cause for concern because it accounts for most of the operating costs. On the other hand, since dithionic acid and polythionic acid are components of COD M n, their removal is desired.
In particular, dithionic acid is difficult to decompose both biologically and physicochemically, so various methods have been intensively investigated. Among these methods, a method of concentrating dithionic acid using a sulfur exchange resin and performing wet combustion is currently in practical use, but it has the drawback of being extremely expensive. The purpose of the present invention is to provide a treatment method that can rationally eliminate the above-mentioned drawbacks and can accurately denitrify wastewater and oxidize and decompose dithionic acid and/or polythionic acid in wastewater. It is something to do. The progress that led to the completion of the present invention will be described below. The present inventors used a biological nitrification and denitrification process using the denitrification liquid circulation method shown in Figure 1 to remove nitrogen from denitrification and desulfurization wastewater from a thermal power plant that contains a large amount of NH3 , and achieved very good results. I was able to get The method shown in Figure 1 is based on wastewater (denitrification and desulfurization wastewater).
The NH 3 is introduced into the nitrification tank 2 under aerobic conditions, and the NH 3
After being oxidized to NOx (NO 2 and/or NO 3 ), it is led to a denitrification tank 3 maintained under anaerobic conditions, methanol is added as a reducing agent 9 for denitrification, and NOx is converted to N 2 gas by denitrifying bacteria. It is reduced and decomposed to the extent that In nitrification tank 2, the PH is lowered by nitrification of NH3 , but since the optimal PH for nitrifying bacteria is in the neutral range, alkaline agent 8 is added to maintain the PH of the nitrification tank mixture near neutral. be done. In the system shown in Fig. 1, the alkaline content liberated during denitrification is circulated to the nitrification tank 2, and the alkali agent 8 to be added to the nitrification tank 2
It has been devised to reduce the With this method, NH 3 −N, NOx− of treated water 5
1 ppm or less of each N (NH 3 −N of wastewater 1 is
305 ppm), but the removal rate of COD M n was extremely poor, and the removal rate was only about 30 to 35%. Therefore, we tried various measures such as reducing the water load of wastewater 1 to 1/5 of the amount required for biological nitrification and denitrification, and increasing the water temperature and sludge concentration in nitrification tank 2.
The removal rate of COD M n was not improved. When we investigated the reason for this, we found that dithionic acid (S 2 O - 6 , which is contained in large amounts in denitrification and desulfurization wastewater, is not oxidized at all during biological treatment, and that this is the reason why the removal efficiency of COD Mn does not improve. In order to reduce the COD M n of the treated water, the present inventors conducted various studies and found that by using Na 2 S (soda sulfide) instead of methanol as the reducing agent 9 added to the denitrification tank 3. , in denitrification tank 3
It has been found that the reductive decomposition of NOx and the oxidation of dithionic acid in the nitrification tank 2 become possible. Next, we will discuss this process using an example using artificial wastewater. The present inventors used Na 2 S instead of methanol as the reducing agent 9 and soda carbonate (Na 2 CO 3 ) 9' as a carbon source for the growth of bacteria that denitrify using Na 2 S in the denitrification tank 3. When added to each, initially NOx
However, the NOx removal rate improved over time, and a large amount of NOx remained in the treated water.
After about 3 weeks, it became the same as when methanol was added. In parallel with the improvement in the NOx removal rate, the dithionic acid oxidation rate also improved, and the COD Mn of the treated water began to decrease. Therefore, until then, excessive amounts of
When Na 2 S was added in the stoichiometrically required amount as shown in the following formula, Na 2 S was
It is completely consumed in the denitrification tank 3 under anaerobic conditions, and as a result, it is no longer oxidized in the nitrification tank 2 because it is accompanied by the return sludge 6 and circulating fluid (denitrification liquid) 7. 15Na 2 S + 24NO - 3 + 12H 2 O → 12N 2 + 15Na 2 SO 4 + 24OH - ... (1) Even if Na 2 S is completely oxidized under aerobic conditions, the The dithionate oxidation ability did not deteriorate until two months after the end of the experiment. In the flow shown in Figure 1, the activated sludge in the denitrification tank 3 flows into the nitrification tank 2 through the circulation of the return sludge 6 and the denitrification mixture, so that Na 2 S It can be seen that the microorganisms that oxidized and multiplied had the ability to oxidize dithionic acid in the nitrification tank 2 under aerobic conditions. In addition, 4 in FIG. 1 is a settling tank, and 10 is a re-aeration tank. On the other hand, under anaerobic conditions using the above activated sludge,
When we attempted reductive decomposition of dithionic acid with Na 2 S, dithionic acid was hardly decomposed. Since Na 2 S is expensive as a reducing agent for denitrification, we next filled the denitrification tank with relatively inexpensive particulate sulfur.
When nitrification, denitrification and oxidation of dithionic acid were attempted using the apparatus shown in FIG. 2 in which the denitrification mixture was not circulated, very good results were obtained. The present invention was completed based on the above experimental results, and is a method of treating wastewater containing at least one of dithionic acid and polythionic acid and nitrogen through a biological treatment process that includes an aerobic process and an anaerobic process. At least one of sulfur and sulfur compounds and soda carbonate are added to the anaerobic process, and
NO x is biologically denitrified by keeping the pH above 6.0, and microorganisms are grown by the denitrification, and the grown microorganisms are brought into contact with wastewater in an aerobic process to produce dithionic acid and/or polythionic acid. This is a method for treating wastewater characterized by oxidation. Next, one embodiment of the present invention will be described based on experimental results using the apparatus shown in FIG. The wastewater 1 flows into the nitrification tank 2 together with the return sludge 6, where NH3 is nitrified to NOx and dithionic acid and polythionic acid are oxidized to sulfuric acid. In the nitrification tank 2, nitrification produces acid and the pH decreases, so Na 2 CO 3 is added as an alkaline agent 8, but the amount is controlled by the PH controller 11 so that the PH is in the neutral range. controlled by. On the other hand, the oxidation of dithionic acid also
is best in the neutral range, so it is best to keep the pH of the nitrification tank 2 in the neutral range. The mixture after nitrification flows into the denitrification tank 3,
NOx is denitrified in the presence of sulfur particles as a reducing agent 9 and soda carbonate 9' as a breeding carbon source filled in the denitrification tank 3. The denitrification reaction due to sulfur can be expressed stoichiometrically by the following equation. 5S+6NaNO 3 +2H 2 O →3N 2 +3Na 2 SO 4 +2H 2 SO 4 ...(2) As can be seen from this equation, H 2 SO 4 is produced as a by-product during denitrification, so the PH of the mixed solution in denitrification tank 3 decreases. .
The activity of denitrifying bacteria is not as affected by pH as nitrifying bacteria, but
When the pH falls below 5.5, the activity decreases significantly, so
Control the pH to 6.0 or higher. As the alkaline agent 8 for the PH controller in the denitrification tank 3, Na 2 CO 3 is better than NaOH. This is because the microorganisms that denitrify using sulfur are autotrophic bacteria.
This is because inorganic carbon is required as a carbon source necessary for proliferation. The mixed liquid in the denitrification tank 3 may be stirred by mechanical stirring such as a rotary stirrer, but as shown in FIG. You may. It is preferable that the sulfur used as the reducing agent 9 be fluidized by stirring the mixed solution rather than being fixed. Further, as shown in Fig. 2, the sulfur particles may be distributed throughout the denitrification tank 3 without providing a special sulfur-filled area in the denitrification tank 3, but in this case, the sulfur particles and the mixed liquid are in uniform contact with each other. Therefore, it is desirable to increase the number of aeration tubes or aeration plates to increase the amount of stirring gas. The mixed liquid flowing out from the denitrification tank 3 flows into the re-aeration tank 10 which is under aerobic conditions, and under anaerobic conditions, the activated sludge oxidizes the organic matter eluted, improving the quality of the treated water, and further adhering to the microbial flocs. The microbial flocs in the sedimentation tank 4 are prevented from floating by removing fine N 2 bubbles in the atmosphere. Since the oxidation of the organic matter and the deaeration of the N 2 gas in the re-aeration tank 10 are completed in a short time, the residence time of the mixed liquid is approximately one hour. The rebacterated gas and liquid are separated into solid and liquid in the settling tank 4, the treated water 5 is discharged, and the sludge is returned to the nitrification tank 2. As the reducing agent 9, in addition to Na 2 S and sulfur particles, sulfur powder, iron sulfide, or powder thereof may be used, and denitrification and oxidation of dithionic acid can be similarly effectively performed. In addition, if a denitrification tank column 13 is used instead of the denitrification tank 3 as shown in FIG. 3, and a fixed bed or fluidized bed of sulfur grains or iron sulfide grains is used, the liquid flow pushed by the pump 14 will cause the denitrification tank tower 13 to be used. Since the mixed liquid is stirred, mechanical stirring or gas stirring equipment is not required. In addition, in FIG. 3, 15 is a circulating fluid, and 16 is a valve for adjusting the flow rate. In the method of the present invention, the generation of alkali cannot be expected in the denitrification process, so it is wasteful to circulate the denitrification liquid to replenish the alkali content in the nitrification tank 2, as shown in the flow shown in Figure 1. When concentrations of NO 2 accumulate and become harmful to activated sludge, it is effective to circulate the denitrification fluid to reduce the NO 2 concentration. Next, examples of the present invention will be described in comparison with examples using methanol and ethanol as reducing agents for denitrification. For implementation, the flow shown in Figure 2 was adopted, and two methods were used: one method was to inject the reducing agent into the denitrification tank, and the other method was to fill it. Table 1 shows the treatment conditions, Table 2 shows the conditions for using the reducing agent, and Table 3 shows the quality of the treated water.
【表】【table】
【表】【table】
【表】【table】
【表】
第２表および第３表からわかるように、従来の
ように還元剤としてメタノール、エタノールを用
いた場合、脱窒は良好に行われているが、ジチオ
ン酸は酸化されずCODMｎの除去率も悪かつた。
一方、イオウおよび硫化鉄を用いた場合には脱窒
もジチオン酸の除去も良好であつた。
なお、硫化鉄を用いた実施No.Ｆ、Ｇにおいて
NO3−Ｎが若干残留しているが、これは硫化鉄
が還元剤として利用しずらいか、あるいは馴養期
間（40日）が短かかつたことによると思われる。
しかしながら実施No.Ｆ、Ｇの活性汚泥は沈降性、
濃縮性が他の実施例よりはるかに優れていたの
で、実施例よりも高濃度のMLSSで運転すること
が可能であり、それによつてNO3の残留を防止
できると考えられる。
また第２表に示した実施例の他のメタノールと
Na2S、メタノールと粒状イオウを還元剤として
利用したところ、処理水の水質は第３表のＣ、
Ｄ、Ｅとほぼ同様の結果となり、S2O6 2-の除去
に有効であつた。
実施No.Ａ〜Ｇにおいて硝化槽のNOxはNO3で
あつたが、実施No.Ｅ、Ｇの活性汚泥を用いて
NO2（亜硝酸）を第２表の実施No.Ｅ、Ｇの方法で
脱窒させて活性汚泥を増殖したところ、活性汚泥
はNO3を脱窒したときと同等のジチオン酸酸化
能力を示した。また実施No.Ｅ、Ｇの活性汚泥を用
いて他のポリチオン酸例えばS32- 6、S4O2- 6を酸化
したところ極めて容易に酸化分解されることが判
明した。
上記二つの実施態様においては、好気的工程、
嫌気的工程、再ばつ気工程及び沈殿工程をこの順
序で組合わせることによつて生物学的硝化脱窒素
プロセスが構成されていたが、本発明方法はこれ
に限定されるものではない。
すなわち、イオウ又はイオウ化合物を使用して
行う生物学的脱窒工程で増殖した微生物の共存下
でジチオン酸等の酸化分解処理を行う好気的生物
処理工程とを有するプロセスであるならばどのよ
うなものでもよく、脱窒プロセスとしては第１図
に示すような脱窒液循環方式のほかに硝化液循環
方式を採用することもできる。また、上記好気的
工程としては硝化工程単独に限らず、BODを酸
化処理する工程を硝化工程の前段に設けたものを
採用することもできる。
以上述べたように本発明は、嫌気的工程にイオ
ウあるいはイオウ化合物を存在せしめることによ
つて、廃水の脱窒と同時にジチオン酸および他の
ポリチオン酸を好気的に酸化分解する能力のある
微生物を増殖し、該微生物を利用して廃水中のジ
チオン酸等を好気的工程で酸化分解すると共に、
前記嫌気的工程に炭酸ソーダを添加してPH6.0以
上に保つように構成したものであり、したがつ
て、従来方法では除去困難なジチオン酸等を簡便
なプロセス・装置により極めて高い除去率で除去
できるうえ、これまで脱窒に多量に消費されてい
たメタノールなどのアルコールも不要となり、イ
オウ等の消費量は嫌気的工程においてNOxを脱
窒処理するに足る量であればよく著しい省エネル
ギ化が可能となり、炭酸ソーダを脱窒菌の活性維
持及び増殖用とPH調整用に利用することができる
うえ、維持管理も容易であるなど、多大の効果が
得られるものである。[Table] As can be seen from Tables 2 and 3, when methanol and ethanol are used as reducing agents as in the past, denitrification is performed well, but dithionic acid is not oxidized and COD M n The removal rate was also poor.
On the other hand, when sulfur and iron sulfide were used, both denitrification and removal of dithionic acid were good. In addition, in implementation No. F and G using iron sulfide
A small amount of NO 3 -N remained, but this is probably because iron sulfide is difficult to use as a reducing agent or because the acclimatization period (40 days) was short.
However, the activated sludge of implementation Nos.F and G is sedimentable,
Since the enrichment performance was much better than in the other Examples, it is possible to operate with a higher concentration of MLSS than in the Examples, and it is thought that this can prevent NO 3 from remaining. In addition, other methanol in the examples shown in Table 2
When Na 2 S, methanol and granular sulfur were used as reducing agents, the quality of the treated water was C in Table 3.
The results were almost the same as D and E, and it was effective in removing S 2 O 6 2- . The NOx in the nitrification tank was NO 3 in practice Nos.
When activated sludge was grown by denitrifying NO 2 (nitrous acid) using the method of practice No. E and G in Table 2, the activated sludge showed the same ability to oxidize dithionate as when NO 3 was denitrified. Ta. Furthermore, when other polythionic acids such as S 32-6 and S 4 O 2-6 were oxidized using the activated sludges of Examples E and G, it was found that they were very easily oxidized and decomposed. In the above two embodiments, an aerobic step,
Although the biological nitrification and denitrification process was constructed by combining the anaerobic step, the re-aeration step, and the precipitation step in this order, the method of the present invention is not limited thereto. In other words, what if it is a process that includes an aerobic biological treatment process in which dithionic acid, etc. is oxidized and decomposed in the coexistence of microorganisms grown in the biological denitrification process using sulfur or sulfur compounds? In addition to the denitrification liquid circulation system shown in FIG. 1, a nitrification liquid circulation system can also be adopted as the denitrification process. Furthermore, the aerobic process is not limited to the nitrification process alone, but may also include a process in which a BOD oxidation process is provided before the nitrification process. As described above, the present invention provides microorganisms capable of aerobically oxidizing and decomposing dithionic acid and other polythionic acids while simultaneously denitrifying wastewater by allowing sulfur or sulfur compounds to be present in the anaerobic process. The microorganisms are used to oxidize and decompose dithionic acid, etc. in wastewater in an aerobic process.
This method is configured to add sodium carbonate to the anaerobic process to maintain the pH above 6.0. Therefore, dithionic acid, etc., which are difficult to remove using conventional methods, can be removed at an extremely high rate using simple processes and equipment. Not only can it be removed, but alcohol such as methanol, which was previously consumed in large quantities for denitrification, is no longer required, and the consumption of sulfur, etc. is only sufficient to denitrify NO x in the anaerobic process, resulting in significant energy savings. In addition to being able to use sodium carbonate to maintain the activity and propagation of denitrifying bacteria and to adjust the pH, it is also easy to maintain and manage, resulting in many benefits.
第１図は本発明の基礎実験の要領を示すフロー
シート、第２図及び第３図は本発明のそれぞれ異
なる実施態様を示すフロートシートである。
１……廃水、２……硝化槽、３……脱窒槽、４
……沈殿槽、５……処理水、６……返送汚泥、７
……循環液、８……アルカリ剤、９……還元剤、
９′……炭酸ソーダ、１０……再ばつ気槽、１１
……PHコントローラ、１２……ブロワー、１３…
…脱窒塔、１４……ポンプ、１５……循環液、１
６……弁。
FIG. 1 is a flow sheet showing basic experiment procedures of the present invention, and FIGS. 2 and 3 are float sheets showing different embodiments of the present invention. 1...Wastewater, 2...Nitrification tank, 3...Denitrification tank, 4
... Sedimentation tank, 5 ... Treated water, 6 ... Return sludge, 7
...Circulating fluid, 8...Alkaline agent, 9...Reducing agent,
9'... Soda carbonate, 10... Re-aeration tank, 11
...PH controller, 12...Blower, 13...
...Denitrification tower, 14...Pump, 15...Circulating fluid, 1
6... Valve.
Claims (1)
および窒素分を含有する廃水を好気的工程と嫌気
的工程を有する生物処理工程で処理する際に、 嫌気的工程にイオウ、イオウ化合物の少なくと
も一方と炭酸ソーダを添加し、かつPH6.0以上に
保つてNOxを生物学的に脱窒すると共に該脱窒
により微生物を増殖させ、該増殖した微生物を好
気的工程で廃水と接触せしめてジチオン酸およ
び／又はポリチオン酸を酸化することを特徴とす
る廃水の処理方法。 ２ 前記生物処理工程が前記好気的工程、前記嫌
気的工程、再曝気工程および沈殿工程より構成さ
れ、該沈殿工程による沈殿汚泥の一部を前記好気
的工程に返送して行われるものである特許請求の
範囲第１項記載の方法。 ３ 前記好気的工程が、生物学的硝化工程である
特許請求の範囲第１項又は第２項記載の方法。 ４ 前記嫌気的工程が、イオウ又はイオウ化合物
を廃水中に懸濁させて行われるものである特許請
求の範囲第１項、第２項又は第３項記載の方法。 ５ 前記嫌気的工程が、イオウ又はイオウ化合物
の充填層を用いて行われるものである特許請求の
範囲第１項、第２項又は第３項記載の方法。 ６ 前記好気的工程がアルカリ剤として炭酸ソー
ダを添加して行われるものである特許請求の範囲
第１項、第２項、第３項、第４項又は第５項記載
の方法。 ７ 前記イオウ化合物が、硫化ソーダ又は鉄系硫
化物である特許請求の範囲第１項、第２項、第３
項、第４項、第５項又は第６項記載の方法。[Claims] 1. When wastewater containing at least one of dithionic acid and polythionic acid and nitrogen is treated in a biological treatment process having an aerobic process and an anaerobic process, sulfur and sulfur compounds are added to the anaerobic process. and sodium carbonate, and maintain the pH at 6.0 or above to biologically denitrify NO A method for treating wastewater, comprising oxidizing dithionic acid and/or polythionic acid by contacting the same. 2. The biological treatment step is composed of the aerobic step, the anaerobic step, the reaeration step, and the precipitation step, and is carried out by returning a part of the settled sludge from the precipitation step to the aerobic step. A method according to claim 1. 3. The method according to claim 1 or 2, wherein the aerobic step is a biological nitrification step. 4. The method according to claim 1, 2 or 3, wherein the anaerobic step is carried out by suspending sulfur or a sulfur compound in wastewater. 5. The method according to claim 1, 2 or 3, wherein the anaerobic step is carried out using a packed bed of sulfur or a sulfur compound. 6. The method according to claim 1, 2, 3, 4, or 5, wherein the aerobic step is performed by adding soda carbonate as an alkaline agent. 7 Claims 1, 2, and 3, wherein the sulfur compound is sodium sulfide or iron-based sulfide.
4. The method according to paragraph 4, paragraph 5, or paragraph 6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14624382A JPS5936600A (en) | 1982-08-25 | 1982-08-25 | Treatment of waste water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14624382A JPS5936600A (en) | 1982-08-25 | 1982-08-25 | Treatment of waste water |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5936600A JPS5936600A (en) | 1984-02-28 |
| JPH0131958B2 true JPH0131958B2 (en) | 1989-06-28 |
Family
ID=15403328
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14624382A Granted JPS5936600A (en) | 1982-08-25 | 1982-08-25 | Treatment of waste water |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5936600A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000018694A1 (en) * | 1998-09-25 | 2000-04-06 | Nitchitsu Co, Ltd. | Denitrifying composition for removing nitrate nitrogen and process for producing the same |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100336483B1 (en) * | 1999-02-27 | 2002-05-15 | 조양호 | Method for removing nitrogen from waste water through sulfur-utilizing denitrification |
| KR100331943B1 (en) * | 1999-06-21 | 2002-04-10 | 김재모 | Water treatment system and water treatment method using the same |
| JP2006122771A (en) * | 2004-10-27 | 2006-05-18 | Chuden Kankyo Technos Co Ltd | Fluid treatment method and fluid treatment system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56124496A (en) * | 1979-09-29 | 1981-09-30 | Ebara Infilco Co Ltd | Treatment of waste water containing nitrogen in ammonia form and dithionates |
| JPS56144797A (en) * | 1980-04-15 | 1981-11-11 | Mitsui Miike Mach Co Ltd | Biological disposal of waste water containing nitrogen compound, sulfur compound and nitrogen-sulfur compound |
| JPS5712893A (en) * | 1980-06-26 | 1982-01-22 | Mitsubishi Heavy Ind Ltd | Disposal of waste water |
-
1982
- 1982-08-25 JP JP14624382A patent/JPS5936600A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56124496A (en) * | 1979-09-29 | 1981-09-30 | Ebara Infilco Co Ltd | Treatment of waste water containing nitrogen in ammonia form and dithionates |
| JPS56144797A (en) * | 1980-04-15 | 1981-11-11 | Mitsui Miike Mach Co Ltd | Biological disposal of waste water containing nitrogen compound, sulfur compound and nitrogen-sulfur compound |
| JPS5712893A (en) * | 1980-06-26 | 1982-01-22 | Mitsubishi Heavy Ind Ltd | Disposal of waste water |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000018694A1 (en) * | 1998-09-25 | 2000-04-06 | Nitchitsu Co, Ltd. | Denitrifying composition for removing nitrate nitrogen and process for producing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5936600A (en) | 1984-02-28 |
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