生物脱氮除磷与BNR系统污泥膨胀的关系及其控制研究
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摘要
活性污泥工艺一直占据污水处理的核心地位,然而由于污泥膨胀导致的泥水难以分离使处理不达标、甚至系统容易崩溃等,严重困扰着活性污泥工艺的运行。防止污泥膨胀一直是活性污泥工艺运行控制的重点。污泥膨胀不仅在传统的活性污泥运行工艺(CAS系统)中发生,也在脱氮除磷工艺(BNR系统)运行中经常出现。由于目前脱氮除磷工艺已经广泛应用于我国城市污水处理实践中,脱氮除磷工艺中具有一些与CAS系统不同的特征,因此CAS系统污泥膨胀机理及控制措施难以适用于BNR系统。国内外对于BNR系统中污泥沉降特性的研究尚不多、也不够深入。因此迫切需要探明脱氮除磷中这种交替环境对污泥沉降性的影响,并提出控制污泥膨胀的对策。
本试验(1)采取两套分别以醋酸钠(1~#)和淀粉(2~#)为碳源平行运行的SBR反应器,研究了反应总时间为480min、进水COD浓度为400mg/l下,三种缺氧和好氧时间配比模式(45min:325min、144min:226min和76min:294 min)和三种不同硝氮浓度(112、45.67和26.61mg/l)下,污泥沉降性能的变化;(2)在不同厌氧/好氧时间配比(1:8.3(30:260min),1:1.42(120:170min),1:0.81(160:130min)),在以醋酸盐(1~#)和淀粉(2~#)为基质的两个SBR反应器中研究了污泥的沉降性变化;(3)在固定厌氧/好氧水力停留时间为1:1.42(120:170min),1~#反应器以醋酸钠为基质下,研究了不同COD/P配比(40/1(400:10),20/1(400:20),10/1(400:40 mg/l))和不同COD浓度(180,250,400,550mg/l),以及不同VFAs配比(丙酸盐:醋酸盐1:0(350:0),1:1(175:175),1:3(87:263 mg/l))下SBR反应器中的污泥沉淀性能;(4)在2~#反应器考察了原水基质依次为葡萄糖,葡萄糖和醋酸钠,淀粉和葡萄糖,淀粉和醋酸钠时污泥沉降性变化,以及磷为限制条件下交替环境中污泥的沉降性。考察了BNR系统在不同环境条件下污泥膨胀情况,探讨了BNR系统污泥膨胀机理并提出了控制措施。
本试验研究结果表明:
(1)以淀粉为碳源的2~#反应器在缺氧段基本不发生反硝化脱氮作用,但在好氧段磷浓度有明显的降低。伴随着磷去除,系统内污泥浓度明显增加。试验结果表明这种缺氧-好氧交替环境下发生的磷去除是一种生物作用的结果,初步判定为一种新型生物除磷现象。
(2)在缺氧/好氧交替脱氮系统中,低C/N比(400:112mg/l)导致污泥膨胀。对污泥膨胀的“缺氧代谢抑制”作用不明显,并且不同缺氧-好氧时间的组合对污泥膨胀的发生没有太大影响;硝氮浓度降低至45.67 mg/l后,1~#反应器脱氮效果和污泥的沉降性有所改善;硝氮浓度降低至26.61 mg/l后,COD未被彻底氧化完,发生污泥膨胀;以淀粉为基质的2~#反应器,污泥的沉降性要优于1~#,表明原水中大分子基质较易利用的小分子基质能更好地防止缺氧/好氧交替环境下引发的污泥膨胀。
(3)在厌氧/好氧交替除磷系统中,基质浓度梯度大于92mg/l,并且厌氧期结束后水中残留15～22mg/l的COD,没有污泥膨胀现象发生。相对葡萄糖和醋酸钠等可溶性的中小分子基质,大分子基质淀粉更容易引起污泥膨胀。供给小分子基质时,厌氧反应结束时反应器的SVI值略低于好氧完毕时。供给大分子基质时,厌氧反应结束时反应器的SVI值略大于好氧完毕时。当供给小分子和大分子混合基质时,厌氧反应结束时反应器的SVI值和好氧完毕时基本一样;“对磷的去除→提高污泥无机分含量→增加污泥比重”这条途径不会改善污泥的沉降性。因此提高系统除磷效果,并不能实现改善污泥沉降性的目的;过高的负荷或过低负荷都没能引发污泥膨胀;设定磷为受限制营养条件下([P]≤2mg/L),反应器污泥沉降性很好,没有出现高粘性污泥膨胀。
Activated sludge process has been widely applied in the wastewater treatment plants(WWTPs)all over the world,but sludge bulking becomes one of the big problems of this process that have to deal with.Recently more and more activated sludge system with biological nutrient removal(BNR)has been introduced in our country,and sludge bulking frequently breaks out in the system.Because of some new characters of the sludge that differ from that of conventional activated sludge system (CAS).Mechanism and measures known from previous studies can not be adapted to sludge bulking in the BNR systems.Additionally the scarce of the related database enhanced the importance of research on sludge bulking in the BNR system.
Research explored the sludge settlebility in alternating anoxic/aerobic and anaerobic/aerobic systems individually,(1)In the alternating anoxic/aerobic nitrogen removal systems the effects of retention time of anoxic to aerobic (45min:324min,144min:227min,76min:294min)and ratios of COD to NO_3~--N (3.57:1(400:112mg/l),8.76:1(400:45.67mg/l)),15.03:1(400:26.61mg/l))on sludge settleability in two SBRs fed with synthetic wastewater with acetate and starch as carbon resource respectively in reactor No.1 and No.2 were studied.(2)In the alternating anaerobic/aerobic phosphorus removal systems the effects of retention time of anaerobic to aerobic(1:8.3(30:260min),1:1.42(120:170min),1:0.81 (160:130min))on sludge settleability in two SBRs fed with synthetic wastewater with acetate and starch as carbon resource respectively in reactor No.1(acetate)and No.2(starch)were studied(3).Then influence of other factors such as COD/P ratios (40/1(400:10mg/l),20/1(400:20mg/l),10/1(400:40mg/l)),influent COD concentrations(180,250,400,550 mg/l),different pationic/acetate ratios (pationic:acetate 1:0(350:0mg/l),1:1(175:175 mg/l),1:3(87:263 mg/l)) were studied in reactor NO 1;(4)substrates,phosphorus limitation et al on sludge settleability in biological phosphorus removal system were also studied in reactor NO 2。
The results showed that(1)in the alternating anoxic/aerobic nitrogen removal systems lower COD/NO_3~--N ratio(400:112mg/l)resulted in sludge bulking in both reactors;Anoxic to aerobic retention time had no concern with sludge settleability; Both nitrogen removal efficiency and sludge settleability improved in the run of COD/ NO_3~--N ratio of 8.76:1;COD residual in aerobic phase was detrimental to the sludge settlebility at COD/NO_3~--N ratio of 15.03:1;Better sludge settling ability achieved in reactor No.2 suggested filamentous bulking in the systems could be overcomed successfully by the adoption of feeding SBCOD,such as starch,possible mechanisms of eccentric discovery that lower phosphorus in effluent without anaerobic phosphorus release were analyzed.
(2)The results in the alternating anaerobic/aerobic phosphorus removal systems showed that:COD after anaerobic stage around 15～22mg/l was suitable;big molecule substrate,such as starch could improve sludge settleability over SBCOD;Contrast to influent with big molecule substrate,sludge settleability in aerobic stage was better than anaerobic stage when small molecule substance adopted, while there was no difference on influent with mixed substrate;Relation among efficiency of phosphorus removal、VSS/TSS and SVI showed addition of inorganic P was not the key factor to lower SVI;There was not absolute relation between sludge settleability and F/M ratio;Good settleability was observed through phosphorus limitation in influent.
本试验(1)采取两套分别以醋酸钠(1~#)和淀粉(2~#)为碳源平行运行的SBR反应器,研究了反应总时间为480min、进水COD浓度为400mg/l下,三种缺氧和好氧时间配比模式(45min:325min、144min:226min和76min:294 min)和三种不同硝氮浓度(112、45.67和26.61mg/l)下,污泥沉降性能的变化;(2)在不同厌氧/好氧时间配比(1:8.3(30:260min),1:1.42(120:170min),1:0.81(160:130min)),在以醋酸盐(1~#)和淀粉(2~#)为基质的两个SBR反应器中研究了污泥的沉降性变化;(3)在固定厌氧/好氧水力停留时间为1:1.42(120:170min),1~#反应器以醋酸钠为基质下,研究了不同COD/P配比(40/1(400:10),20/1(400:20),10/1(400:40 mg/l))和不同COD浓度(180,250,400,550mg/l),以及不同VFAs配比(丙酸盐:醋酸盐1:0(350:0),1:1(175:175),1:3(87:263 mg/l))下SBR反应器中的污泥沉淀性能;(4)在2~#反应器考察了原水基质依次为葡萄糖,葡萄糖和醋酸钠,淀粉和葡萄糖,淀粉和醋酸钠时污泥沉降性变化,以及磷为限制条件下交替环境中污泥的沉降性。考察了BNR系统在不同环境条件下污泥膨胀情况,探讨了BNR系统污泥膨胀机理并提出了控制措施。
本试验研究结果表明:
(1)以淀粉为碳源的2~#反应器在缺氧段基本不发生反硝化脱氮作用,但在好氧段磷浓度有明显的降低。伴随着磷去除,系统内污泥浓度明显增加。试验结果表明这种缺氧-好氧交替环境下发生的磷去除是一种生物作用的结果,初步判定为一种新型生物除磷现象。
(2)在缺氧/好氧交替脱氮系统中,低C/N比(400:112mg/l)导致污泥膨胀。对污泥膨胀的“缺氧代谢抑制”作用不明显,并且不同缺氧-好氧时间的组合对污泥膨胀的发生没有太大影响;硝氮浓度降低至45.67 mg/l后,1~#反应器脱氮效果和污泥的沉降性有所改善;硝氮浓度降低至26.61 mg/l后,COD未被彻底氧化完,发生污泥膨胀;以淀粉为基质的2~#反应器,污泥的沉降性要优于1~#,表明原水中大分子基质较易利用的小分子基质能更好地防止缺氧/好氧交替环境下引发的污泥膨胀。
(3)在厌氧/好氧交替除磷系统中,基质浓度梯度大于92mg/l,并且厌氧期结束后水中残留15～22mg/l的COD,没有污泥膨胀现象发生。相对葡萄糖和醋酸钠等可溶性的中小分子基质,大分子基质淀粉更容易引起污泥膨胀。供给小分子基质时,厌氧反应结束时反应器的SVI值略低于好氧完毕时。供给大分子基质时,厌氧反应结束时反应器的SVI值略大于好氧完毕时。当供给小分子和大分子混合基质时,厌氧反应结束时反应器的SVI值和好氧完毕时基本一样;“对磷的去除→提高污泥无机分含量→增加污泥比重”这条途径不会改善污泥的沉降性。因此提高系统除磷效果,并不能实现改善污泥沉降性的目的;过高的负荷或过低负荷都没能引发污泥膨胀;设定磷为受限制营养条件下([P]≤2mg/L),反应器污泥沉降性很好,没有出现高粘性污泥膨胀。
Activated sludge process has been widely applied in the wastewater treatment plants(WWTPs)all over the world,but sludge bulking becomes one of the big problems of this process that have to deal with.Recently more and more activated sludge system with biological nutrient removal(BNR)has been introduced in our country,and sludge bulking frequently breaks out in the system.Because of some new characters of the sludge that differ from that of conventional activated sludge system (CAS).Mechanism and measures known from previous studies can not be adapted to sludge bulking in the BNR systems.Additionally the scarce of the related database enhanced the importance of research on sludge bulking in the BNR system.
Research explored the sludge settlebility in alternating anoxic/aerobic and anaerobic/aerobic systems individually,(1)In the alternating anoxic/aerobic nitrogen removal systems the effects of retention time of anoxic to aerobic (45min:324min,144min:227min,76min:294min)and ratios of COD to NO_3~--N (3.57:1(400:112mg/l),8.76:1(400:45.67mg/l)),15.03:1(400:26.61mg/l))on sludge settleability in two SBRs fed with synthetic wastewater with acetate and starch as carbon resource respectively in reactor No.1 and No.2 were studied.(2)In the alternating anaerobic/aerobic phosphorus removal systems the effects of retention time of anaerobic to aerobic(1:8.3(30:260min),1:1.42(120:170min),1:0.81 (160:130min))on sludge settleability in two SBRs fed with synthetic wastewater with acetate and starch as carbon resource respectively in reactor No.1(acetate)and No.2(starch)were studied(3).Then influence of other factors such as COD/P ratios (40/1(400:10mg/l),20/1(400:20mg/l),10/1(400:40mg/l)),influent COD concentrations(180,250,400,550 mg/l),different pationic/acetate ratios (pationic:acetate 1:0(350:0mg/l),1:1(175:175 mg/l),1:3(87:263 mg/l)) were studied in reactor NO 1;(4)substrates,phosphorus limitation et al on sludge settleability in biological phosphorus removal system were also studied in reactor NO 2。
The results showed that(1)in the alternating anoxic/aerobic nitrogen removal systems lower COD/NO_3~--N ratio(400:112mg/l)resulted in sludge bulking in both reactors;Anoxic to aerobic retention time had no concern with sludge settleability; Both nitrogen removal efficiency and sludge settleability improved in the run of COD/ NO_3~--N ratio of 8.76:1;COD residual in aerobic phase was detrimental to the sludge settlebility at COD/NO_3~--N ratio of 15.03:1;Better sludge settling ability achieved in reactor No.2 suggested filamentous bulking in the systems could be overcomed successfully by the adoption of feeding SBCOD,such as starch,possible mechanisms of eccentric discovery that lower phosphorus in effluent without anaerobic phosphorus release were analyzed.
(2)The results in the alternating anaerobic/aerobic phosphorus removal systems showed that:COD after anaerobic stage around 15～22mg/l was suitable;big molecule substrate,such as starch could improve sludge settleability over SBCOD;Contrast to influent with big molecule substrate,sludge settleability in aerobic stage was better than anaerobic stage when small molecule substance adopted, while there was no difference on influent with mixed substrate;Relation among efficiency of phosphorus removal、VSS/TSS and SVI showed addition of inorganic P was not the key factor to lower SVI;There was not absolute relation between sludge settleability and F/M ratio;Good settleability was observed through phosphorus limitation in influent.
引文
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