【作者】 端允；

【导师】 李亚新；

【作者基本信息】 太原理工大学 ， 环境工程， 2010， 博士

【摘要】 厌氧序批式反应器(ASBR)因其能够形成颗粒污泥,有较大的进水浓度适应范围和灵活的操作方式,在国内外被逐步广泛应用到各种废水的处理中。然而,由于该反应器内优势菌群不稳定,出水还需好氧后续处理,其经济潜能尚未充分发挥。针对ASBR工艺中存在的缺陷,本文研究开发了一种新型废水处理工艺——吸附—生物降解厌氧序批式反应器(AB-ASBR)。对AB-ASBR的启动及其运行模式和工艺参数的研究得出如下结论:1. AB-ASBR工艺A段运行模式为“进水—吸附—沉降—排水—再生”,B段运行模式为“进水—反应—沉降—排水”。A段反应器和B段反应器中污泥颗粒化后,在AB-ASBR工艺模式下运行一段时间,可以实现两段反应器中甲烷菌群优化。由半饱和常数计算结果:A段反应器Ks(1.83mmol)远远大于B段反应器Ks(0.05mmol);结合颗粒污泥扫描电镜照片和A、B两段反应器中颗粒污泥的革兰氏染色结果,都说明:A段反应器以甲烷八叠球菌为优势菌;B段反应器以甲烷丝菌为优势菌。两段反应器中甲烷菌群的优化将有利于AB-ASBR工艺进水负荷的增加和出水水质的提高。2.以奶粉为基质配置废水,通过对反应过程中COD、VFA和产气量及反应器内MLSS和MLVSS的测定,考察了较低有机物浓度条件下(进水中COD浓度分别为1000mg/L、1333mg/L和2000mg/L)AB-ASBR工艺的运行效果。结果表明:反应器内生物量随着进水浓度的提高逐渐增加,且随着运行周期的增加,生物活性也越来越高。三种进水COD浓度条件下,A段反应器最佳吸附时间为20min,再生时间为6h;而B段反应器生物降解时间为2.5~4h。此时两个反应器内COD浓度均已低于100mg/L。由此可以确定:在A段反应器再生结束后,B段反应器生物降解过程已经完成。为了取得更好处理效果可以将B段反应器反应时间适当延长。如果考虑到反应器容积利用率,可以缩小B段反应器容积或者增加A段反应器容积,使得A段反应器再生结束,B段反应器恰好完成生物降解反应。产气量测定结果表明:气体中以H2和CH4为主,CH4所占比例72%~76%。3.实现AB-ASBR模式稳定运行后,逐步提高反应器有机负荷(进水浓度从3000mg/L至7500mg/L),并研究在不同负荷条件下,反应器内颗粒污泥对有机物初期吸附性能与生物量的关系。研究结果表明:随着进水有机物浓度的提高,达到最大吸附平衡所需时间由20min缩短至5min,由此表明:进水有机物浓度越高,反应器内生物量就越多,达到平衡所需时间也越短。污泥负荷和吸附量存在正相关关系,污泥负荷越高,其传质推动力越大,颗粒污泥吸附量也越大。在一定范围内(0.3~0.5gCOD/(gMLSS·d)),颗粒污泥吸附率随污泥负荷增大而增高(67%~90%),之后基本稳定在90%以上。在7500mg/L的有机物浓度条件下,由于反应器内污泥活性较好,采用连续搅拌、间歇搅拌和不搅拌都能迅速达到最大吸附效果,5min完成吸附反应,其最大吸附率分别为67%、65.7%和65.7%。若为节约能源,可采用不搅拌方式,进水5min后出水。再生能够提高厌氧颗粒污泥的吸附性能,随着厌氧颗粒污泥再生时间增加,厌氧颗粒污泥的吸附量与吸附率也逐渐提高,但超过6h后,厌氧颗粒污泥的吸附量与吸附率基本保持不变。适当的闲置会使最大吸附率有所增加,但闲置时间过长会引起微生物内源呼吸,生物量减少。相对于整个反应周期,3h的闲置时间虽使最大吸附率有所上升,却使反应器容积利用率下降。因此,断流时可以考虑适当的闲置,但要控制在一定时间之内。4.研究了进水COD浓度为2000mg/L的条件下,A段进水时间、出水前停留时间(TA)、进水水质及有机负荷(OLR)等因素对AB-ASBR工艺运行效果的影响。结果表明:进水时间不同,反应器在吸附期内COD达到最大吸附量的时间不同,其吸附率也不同。在研究的几种条件下,进水时间≤15min,其最大吸附出现在进水后25min。继续增加进水时间至45min,最大吸附出现在30min。而COD最大吸附去除率为15min的进水条件,为89.2%。此时反应器内VFA也达到最低值,为84mg/L。出水前A段停留时间(TA)不同,其出水水质也随之发生变化。TA为30min时,相对于初始进水COD去除率最好,达到96.8%;TA为60min时,在整个反应期,B段反应器内VFA值最低,这有利于防止高负荷运行时产生酸化现象。进水水质所含胶体比例越高,达到最大吸附所需时间越长,初期吸附去除的COD量也越多。试验中CODcol/CODt比例由30%增至50%,A段达到最大吸附时间由25min增至45min;COD去除率由86.8%增至89.1%。而B段生物降解所需反应时间也随胶体比例有所增加。出水均可达到100mg/L以下。在一定范围内,随OLR增加,COD总去除率逐渐升高。说明该工艺对负荷改变有较好的适应能力,但反应时间相应增加。5.对于以颗粒污泥为主要生物形态的高速厌氧生物反应器,由于颗粒污泥沉降性能良好,容易在反应器底部沉积,不利于固液接触、液相传质。搅拌可以使底物和生物体充分接触,缩短反应时间,提高系统处理效率,同时防止反应器内局部挥发酸大量积累,产生酸化结果。反应期内保持较低的VFA浓度,也可降低对碱度投加量的需求。通过对反应器内COD、VFA、生物量及生物相的分析,研究了进水浓度为16500mg/L,在搅拌时间相同(每小时总搅拌时间为6min)、搅拌方式不同的三种条件下,反应器运行性能和生物量的变化,结果表明:随搅拌强度增加,反应器内颗粒污泥逐步减小(由2~3mm最终变为0.5mm左右)。结合颗粒污泥扫描电镜照片,搅拌作用过强会使颗粒污泥结构破坏,大颗粒逐渐变为小颗粒。实验最终选定:在进水COD为16500mg/L的高浓度有机物条件下,3min/30min为最佳搅拌条件。此时对于颗粒污泥尺寸和结构的维持,以及反应器良好运行,均可达到最佳效果。6.通过反应器内吸附、再生和生物降解过程中COD浓度的变化,得出结论:在厌氧颗粒污泥吸附过程中,主要限速阶段是膜传质阶段,可用伪二级反应方程描述厌氧颗粒污泥吸附动力学。7.对比了ASBR工艺和AB-ASBR工艺的运行效果。在相同进水COD浓度(2000mg/L)条件下,ASBR工艺运行中进行着吸附、水解、酸化、产甲烷等间歇性发酵。反应器中颗粒污泥是由水解菌、产酸菌和产甲烷等共同组成的混合菌群体,即使延长反应时间COD也只能降至400mg/L左右。而AB-ASBR工艺中B段反应器在低负荷条件下运行,形成的颗粒污泥以甲烷丝菌为主体,所以能较为彻底去除残余有机物,B段出水COD可以降至100mg/L以下,达到《城镇污水处理厂污染物排放标准》GB18918-2002规定的二级标准(COD≤100mg/L),显著提高了出水水质。无论是通过本试验对较低进水COD浓度条件下两种工艺的对比研究,还是通过本试验较高进水COD浓度条件下的试验结果与文献中ASBR工艺相关试验结果的对比,都表明:AB-ASBR工艺处理效果显著优于ASBR工艺,且水力停留时间短。因此,AB-ASBR工艺既能取得良好的处理效果,又能提高反应器容积利用率,可以大大节约成本。更多还原

【Abstract】 ASBR has gradually been adopted widely both in the domestic and overseas in treating many kinds of wastewater owing to the abilities of granulation, adaptation to large wastewater concentration range and flexible operation. Since the dominant biomass in the reactor has no stabilization, the effluent from ASBR always needed to treat by aerobic method sequentially. Thus, ASBR still has economic potential to bring into play. Here, a new anaerobic technology in treating wastewater—Adsorption-Biodegradation Anaerobic Sequencing Batch Reactor (AB-ASBR) has been developed aiming at overcoming these limitations. The study of its start-up, operation mode and appropriate process conditions was concluded as follows:1. During the adsorption duration, the operation mode of AB-ASBR was fill-adsorb-drain-settle-regenerate. While during the biodegradation duration, the operation mode was fill-react-settle-drain. When the sludge in the reactor granulated, the different preponderant biomass began to predominate in each column of the reactor under AB-ASBR operation mode for some time. The semi-saturation constants (KS) of each column were calculated. The KS of column A was 1.83mmol, which was much larger than the KS of column B, 0.05mmol. Combining with the results of scanning electron micrograph(SEM) and Gram stain pictures, it was demonstrated that in adsorption column (column A), Methanosarcina was the predominated bacteria, while, in the biodegradation column (column B) Methanothrix was the predominated bacteria. The optimization of biomass populations will be propitious to enhance OLR and the drainage quality.2.Using milk powder as substrate, changes of COD, VFA, biogas, MLSS and MLVSS during the reaction process were monitored at low COD inflow concentrations (1000mg/L,1333mg/L and 2000mg/L). The results showed that the biomass gradually increased with the enhancement of COD concentration, at the same time, the activity of the granular sludge improved with the increasing times of AB-ASBR operation.The optimal adsorption duration under the three concentrations was all 20min. The regeneration duration was 6h, and the biodegradation duration was 2.5~4h, when the concentrations of COD in each column were below 100mg/L. It could be confirmed that when the regeneration duration ended in column A, the biodegradation reaction has completed already. In order to acquire better result, the reaction duration could prolong befittingly. Considering the cubage utilization ratio, the dimension of column B should be reduced or the column A be augmented. Thus, the regeneration will finish at the moment of the completion of biodegradation.The determining results showed that the main gases were H2 and CH4 in the biogas produced, and CH4 accounted for 72%~76%.3. OLR was enhanced step by step when AB-ASBR operated steadily. The COD concentrations in the inflow were increased ranging from 3000mg/L to 7500mg/L. The adsorption characteristic of the granular sludge and its relation with the amount of biomass were investigated. It was indicated with the enhancement of COD concentration, the maximum adsorption time shortened ranging from 20min to 5min. That was to say when the organic substrate concentration increased, the amount of biomass in the reactor manifold correspondingly, so the adsorption duration shortened.SLR has positive correlativity with the adsorption amount. When SLR was higher, the impetus of mass transfer larger, and the adsorption amount of the granular sludge lager. Within certain SLR (range from 0.3gCOD/(gMLSS·d) to 0.5gCOD/(gMLSS·d)), the adsorption ratios of the granular sludge increased with the enhancement of SLR (ranging from 67% to 90%). After that, the ratio was kept at more than 90% level constantly.At concentration of 7500mg/L, the maximum adsorption effect could obtain rapidly at 5min no matter whether the reactor was stirred by the biogas continuously, intermittently or without agitation at all because of the fine activity of the granular sludge, and the maximum adsorption ratios were 67%,65.7% and 65.7%, respectively. In order to save energy, draining could take place at 5min after the filling of wastewater with no agitation.The adsorption characteristic of the granular sludge could improve with regeneration. The longer of the regeneration duration, the larger of the adsorption amount and ratios of the granular sludge obtained. But they wouldn’t change any more after 6h.The maximum adsorption ratio of the granular sludge would also improve with proper idle. But the biomass decreased with too long idle duration because of the occurring of endogenesis respiration. Although the adsorption ratios ascended, 3 hours’idle was too long to the whole reaction cycle and could cause the reactor’s cubage utilization ratio descended. Therefore, in case of wastewater flow breaking down, proper idle duration controlled within certain range should be noticed.4. The influences of such factors as filling duration, stay duration before draining(TA), wastewater quality and OLR on the performance of AB-ASBR were investigated. The results were as follows:Different filling duration caused different maximum adsorption time and adsorption ratios. When the filling duration was no more than 15min, the maximum adsorption time appeared at 25min with the largest COD removal ratio (89.2%) and lowest VFA value (84mg/L). When the filling duration was prolonged to 45min, the maximum adsorption time appeared at 30min.The drainage quality varied with the wastewater stay duration before draining. The best COD removal ratio (96.8%) has been obtained when TA was 30min. But the lowest VFA value has been observed when TA was 60min, which was in favor of preventing acidification when AB-ASBR operated under much higher OLR.The higher the ratio of colloid substance in the inflow, the longer the time to arrive to maximum adsorption and the larger COD removal amount having been got. When the colloid substance ratios (CODcol/CODt) increased from 30% to 50%, the maximum adsorption time prolonged from 25min to 45min, and the COD removal ratios improved from 86.8% to 89.1%. The biodegradation duration in column B prolonged accordingly with colloid ratio’s enhancement. The COD concentrations in the drainage were all less than 100mg/L.The COD removal ratio increased with the enhancement of OLR within certain range, which indicated that AB-ASBR has good adaptation ability, although the reaction duration would augment.5. The granular sludge has good sedimentation performance in high speed reactors in which the sludge was granulation, which could cause sediment in the reactor’s bottom. This has no good for the solid–liquid mass transfer and the mass transfer in liquid phase. Agitation will benefit to the contact between substrate and biomass, shorten reaction duration and prevent the accumulating of the volatile acid in local reactor.According to the analysis of COD、VFA、MLSS、MLVSS and photographs, the effects of three agitation manners within the same stirring duration on AB-ASBR were investigated, which was stirred by the biogas produced itself and fed with the synthetic wastewater with the chemical oxygen demand (COD) concentration of 16500mg/L. It was indicated that the size of the granular sludge reduced from 2~3mm to 0.5mm with the increasing mixing intension. According to SEM, too much agitating intension could destroy the structure of the granular sludge, which caused the large granules to become into small ones. The condition of 3min/30min was chosen as the optimal agitation intension, which could maintain the granular sludge appropriate dimension and configuration and get best operation effect.6. According to the changes of COD concentration during adsorption, regeneration and biodegradation duration, it was concluded that during the granular sludge adsorption process, the membrane transfer mass was the limit speed step. The adsorption process could be described with pseudo-second-order model.7. The two technologies ASBR and AB-ASBR were contrasted.Dispending on the same COD concentration (2000mg/L) in inflow, all the intermittent fermentation reactions such as adsorption, hydrolysis, and acidification and so on happened in ASBR, in which the granular sludge was made up of hydrolytic bacteria, acidogenic bacteria and methanogenic bacteria. Thus, no matter how long the reaction duration prolonged, the COD value could only decrease to about 400mg/L at most. However, Methanothrix was the optimal biomass in column B of AB-ASBR, which could benefit to remove organic substance drastically. COD in the drainage from column B was below 100mg/L, which measured up the 2nd standard of the contamination let criterion of town sewage plant (GB18918-2002) (COD≤100mg/L). The drainage quality was enhanced remarkably.Under both low concentration experiment and high concentration comparing with the literature reported, AB-ASBR testified to have better wastewater-treating effect and shorter HRT, which could improve the reactor’s cubage utilization ratio. Thus the cost could be saved observably.更多还原