Microbial activity in a combined UASB-activated sludge reactor system

A combined upflow anaerobic sludge bed-activated sludge (UASB-AS) reactor system with consistently wasting of excess biomass was used to treat suspended-solids pre-settled piggery wastewater (COD=2000 mg l(-1), total Kjeldahl nitrogen TKN=400 mg l(-1), suspended solids=250-400 mg l(-1)). Thus, the activity of nitrogen-related microbial groups in each individual bioreactor was investigated. When the granules retention time (GRT) of 20-50 d in the UASB reactor, the solids retention time (SRT) of 10-25 d in the AS reactor and the recycle-to-influent ratio (Re) of 1 were maintained, the combined system removed 95-97% of chemical oxygen demand (COD), 100% of TKN and 54-55% of total nitrogen (TN). Denitrification and methanogenesis occurred in the UASB reactor so that both biochemical processes contributed to most of the COD removal and, complete nitrification (most of the TKN removal) occurred in the AS reactor. Compact granules with good settling abilities developed in the UASB reactor, and rapid rates of granulation of break-up granules in the UASB reactor were confirmed by experiments. The activity of nitrifiers and denitrifiers (an=0.68-0.87; adn=0.55-0.70) and the calculated specific nitrification and denitrification rates (qn=0.26-0.47 mg NH4+ -N mg VSS(-1)d(-1); qdn=0.046-0.076 mg NOx- -N mg VSS(-1)d(-1)) significantly increased with decreasing SRT and GRT, respectively. Accordingly, the combined UASB-AS reactor system should be regarded a promising alternative for the removal of organic carbon and nitrogen from piggery wastewater.     

牡蛎壳粉末投加UASB反应器的运行特性

采用牡蛎壳粉末作为UASB反应器的辅助介质,探讨了牡蛎壳钙盐的溶出特性,系统考察了运行期中牡蛎壳粉末添加方式、进水有机负荷、水力停留时间等因素对反应器出水COD、碱度与pH的影响,分析了污泥比产甲烷活性变化。结果表明,当初始pH从5到9变化时,牡蛎壳粉末溶出Ca2+浓度为40~65 mg/L,平衡pH稳定在7.7~8.0;当进水COD负荷从3.4 kg/(m3·d)逐渐增至7.0 kg/(m3·d)、牡蛎壳粉末投加量从1.5 g/d逐渐增至3.2 g/d时,与未投加的反应器相比,投加牡蛎壳粉末反应器的启动周期缩短了10%左右,COD去除率与比产甲烷活性分别提高了13.3%和22%。投加牡蛎壳粉末可有效提供碱度,加快污泥的颗粒化进程。     

Effect of recycle-to-influent ratio on activities of nitrifiers and denitrifiers in a combined UASB-activated sludge reactor system

A laboratory study using a combined upflow anaerobic sludge bed (UASB)-activated sludge (AS) reactor system was undertaken to explore the effect of recycle-to-influent ratio (R(e)=1, 2, and 3) on the activities of nitrifiers and denitrifiers. Suspended-solids pre-settled piggery wastewater was used as the substrate-feed wastewater. At the R(e) of 1-3, the combined reactor system achieved efficient removal of COD (96-97%), TKN (100%) and total nitrogen TN (54-77%). Methanogenesis occurred with nearly-complete denitrification in the UASB reactor, whereas complete nitrification took place in the AS reactor. A higher R(e) (i.e., accompanied with a shorter solids retention time) resulted in a larger amount of high-activity denitrifiers and thereby achieved a higher TN removal efficiency. Compact granules and a high biomass concentration in the UASB reactor were observed. At the R(e) of 1-3, the maximum specific reaction rate of nitrifiers (0.45-0.49 NH(4)(+)-NmgVSS(-1)d(-1)) and the specific nitrification rates of mixed culture (0.18-0.22mg NH(4)(+)-NmgVSS(-1)d(-1)) in the AS reactor varied slightly; whereas the maximum specific reaction rate of denitrifiers (0.18-0.27mg NO(x)(-)-NmgVSS(-1)d(-1)) and the specific denitrification and COD removal rates of mixed culture (0.025-0.050mg NO(x)(-)-NmgVSS(-1)d(-1); 0.24-0.31mgCODmgVSS(-1)d(-1)) in the UASB reactor increased with increasing R(e). The primary finding of the study is that the combined UASB-AS reactor system should be operated at a higher R(e) to maintain high-activity denitrifiers to remove organic materials and nitrogen from piggery wastewater.     

UASB反应器处理链霉素废水启动及运行性能

采用上流式厌氧污泥床(UASB)反应器处理链霉素生产废水,研究了中温条件下反应器启动和稳定运行中废水处理性能及厌氧污泥颗粒化过程。结果表明,通过逐步提高链霉素废水进水比例和负荷,可以实现UASB反应器的启动和稳定运行,并对高浓度链霉素实际废水具有良好的处理性能,COD去除率稳定在80%以上,COD去除负荷达7.2 kg/(m3·d),CH4产生量达到6.2 L/d。UASB反应器启动运行过程中,链霉素废水对污泥活性具有抑制影响,造成短期反应器运行性能明显下降,而后很快恢复。同时高负荷链霉素废水造成甲烷产率降低。污泥性状变化显著,污泥形态逐渐转变为颗粒态,污泥粒径增大,出现大量0.5~1.0 mm颗粒污泥,污泥VSS/SS比值升高,污泥沉降性明显增强,比产甲烷活性显著升高,表明污泥开始实现颗粒化。     

Treatment of carbofuran-bearing synthetic wastewater using UASB process

In the present study, fate of carbofuran in anaerobic environments and the adverse effects of carbofuran on conventional anaerobic systems were evaluated. Carbofuran degradation studies were carried out in batch reactors with varying carbofuran concentrations of 0 to 270.73 mg/L corresponding to a sludge-loading rate (SLR) of 2.12 x 10(-6) to 3.83 x 10(-3) g of carbofuran/g of volatile suspended solids (VSS)/d. Carbofuran concentration was reduced to undetectable levels at the end of 8 and 13 days in the batch reactors operated with a SLR of 2.12 x 10(-6) and 3.33 x 10(-5) g of carbofuran/g of VSS/d, respectively. Performances of two anaerobic reactors i.e. upflow anaerobic sludge blanket (UASB) and modified UASB (with tube settlers) were evaluated in the presence and absence of carbofuran using synthetic wastewater. In the absence of carbofuran, the soluble chemical oxygen demand (COD) removal efficiency in the conventional UASB reactor at 8 h and 6 h hydraulic retention time (HRT) was nearly 88% and 76%, respectively, whereas in modified UASB reactor it was increased to 90% at 8 h HRT and 78% at 6 h HRT. When 28 mg/L (SLR of 1.19 x 10(-2) g of carbofuran/g of VSS/d) of carbofuran was introduced in the reactors, the COD removal efficiency was reduced to 41% and 44% in conventional and modified UASB reactors respectively. However, the reactor could maintain around 80% COD removal efficiency at a carbofuran concentration of 7.84 mg/L (SLR of 3.64 x 10(-3) g of carbofuran/g of VSS/d). The reactor efficiency was also measured in terms of specific acetoclastic methanogenic activity (SMA). The toxic effect of carbofuran was reversible to a certain extent. Carbofuran removal efficiency in the conventional UASB reactor at carbofuran concentrations of 7, 13 and 28 mg/L were 40 +/- 3%, 27 +/- 3%, and 11 +/- 3%, respectively. In modified UASB reactor, carbofuran removal efficiency was almost uniform at 7 and 13 mg/L but it was reduced nearly by 56% at 28 mg/L. The major metabolite of carbofuran i.e. 3-keto carbofuran was found in all the reactors.     

Characteristics of granular sludge developed in an upflow anaerobic sludge fixed-film bioreactor treating palm oil mill effluent.

In the present study, characteristics of the granular sludge (including physical characteristics under stable conditions and process shocks arising from suspended solid overload, soluble organic overload, and high temperature; biological activity; and sludge kinetic evaluation in a batch experiment) developed in an upflow anaerobic sludge blanket fixed-film reactor for palm oil mill effluent (POME) treatment was investigated. The main aim of this work was to provide suitable understanding of POME anaerobic digestion using such a granular sludge reactor, particularly with respect to granule structure at various operating conditions. The morphological changes in granular sludge resulting from various operational conditions was studied using scanning electron microscopy and transmission electron microscopy images. It was shown that the developed granules consisted of densely packed rod- (Methanosaeta-like microorganism; predominant) and cocci- (Methanosarsina) shaped microorganisms. Methanosaeta aggregates functioned as nucleation centers that initiated granule development of POME-degrading granules. Under the suspended solid overload condition, most of the granules were covered with a thin layer of fiberlike suspended solids, so that the granule color changed to brown and the sludge volume index also increased to 24.5 from 12 to 15 mL/g, which caused a large amount of sludge washout. Some of the granules were disintegrated because of an acidified environment, which originated from acidogenesis of high influent organic load (29 g chemical oxygen demand [COD]/L d). At 60 degrees C, the rate of biomass washout increased, as a result of disintegration of the outer layer of the granules. In the biological activity test, approximately 95% COD removal was achieved within 72 hours, with an initial COD removal rate of 3.5 g COD/L d. During POME digestion, 275 mg calcium carbonate/L bicarbonate alkalinity was produced per 1000 mg COD(removed)/ L. A consecutive reaction kinetic model was used to simulate the data obtained from the sludge activity in the batch experiment. The mathematical model gave a good fit with the experimental results (R2 > 0.93). The slowest step was modeled to be the acidification step, with a rate constant between 0.015 and 0.083 hours(-1), while the rate constant for the methanogenic step was obtained to be between 0.218 and 0.361 hours(-1).     

Formation and instability of aerobic granules under high organic loading conditions

The cultivation and instability of aerobic granular sludge in a sequencing batch reactor under high loading conditions were investigated. Compact bacteria-dominated aerobic granules with a mean diameter of 1 mm were formed at a chemical oxygen demand (COD) loading rate of 6.0 kg m(-3) d(-1) within 30 d. However, the compact bacteria-dominated aerobic granules were not stable and transited to large-sized filamentous ones gradually. With the formation of bacteria-dominated granules, the hydrophobicity and specific gravity of the sludge increased. When the granules were transited to filamentous ones, the hydrophobicity and specific gravity decreased. Both granules had a high COD removal efficiency, excellent settling ability and showed a clear, regular round-shaped outline. After the filamentous granules reached a diameter of 16 mm, due to the mass transfer limitation and the possible presence of anaerobes in the inner part of the granules, they began to disintegrate and be washed out of the reactor, follow by failure of the reactor.     

厌氧序批式反应器中丝状颗粒污泥的形成

以葡萄糖为基质,研究浮动盖式ASBR中颗粒污泥的形成。实验结果表明,污泥在120 d时完全颗粒化,颗粒污泥具有良好的沉降性能(25 m/h)及良好的产甲烷活性,甲酸、乙酸、丙酸及丁酸最大代谢活性分别达到0.216、0.825、0.237和0.796 g COD/(g VSS.d)。电镜扫描(SEM)发现,整个污泥结构均一,均由丝状菌构成。     

Oily wastewater treatment using a novel hybrid PBR-UASB system

In this study, anaerobic treatability of oily wastewater was investigated in a hybrid reactor system consisting of a packed bed reactor (PBR) followed by an upflow anaerobic sludge blanket (UASB) reactor at 35 degrees C. The system was operated using real pet food wastewater at different hydraulic retention times and loading rates for 165 d. The PBR was packed with sol-gel/alginate beads containing immobilized enzyme which hydrolyzed the oil and grease (O&G) into free long chain fatty acids, that were biodegraded by the UASB. The hybrid system was operated up to an oil loading rate of 4.9 kg O&Gm(-3)d(-1) (to the PBR) without any operational problems for a period of 100 d, with COD and O&G removal efficiencies above 90% and no sludge flotation was observed in the UASB. Beads supplement to the PBR was less than 2 g d(-1) and the relative activity was about 70%. Further increment in O&G loading to 18.7 kg O&Gm(-3)d(-1) caused destabilization of the system with 0.35% (v float/v feed) sludge float removed from the UASB.     

UASB处理硫酸盐有机废水的启动

为了考察上流式厌氧污泥床反应器(UASB)处理含硫酸盐有机废水的特性,采用有效容积为10 L的UASB,研究了启动运行过程中COD和SO2-4降解情况、出水VFA和pH值、产气量及颗粒污泥比产甲烷活性(SMA)变化状况。结果表明,接种厌氧颗粒污泥,保持进水COD为1 500 mg/L,SO2-4浓度为100 mg/L,将HRT由24 h缩短至12 h以提高负荷,经历55 d成功启动了UASB反应器;当HRT为12 h,进水COD和SO2-4负荷为3.0 kg/(m3·d)和0.20 kg/(m3·d),COD和SO2-4的去除率分别达到80%和89%,出水VFA为3 mmol/L,产气量达9.5 L/d,颗粒污泥的SMA为86.4 mL/(g VSS·d)。     

Improvement of upflow anaerobic sludge bed performance using chitosan.

Chitosan, with a degree of deacetylation of 85% and a molecular weight of 2.5 x 10(5) Da, yielding high flocculation efficiency (85 to 100% flocculation) and a broad flocculation region (2 to 45 mg/g suspended solids), was selected for accelerating granulation in a 30-L upflow anaerobic sludge bed (UASB) used to treat wastewater from a tropical fruit-processing industry. Compared with other studies, smaller amounts of chitosan were applied (two injections with 2 mg chitosan/g suspended solids in the reactor at each injection). Comparison with the UASB without chitosan addition, the UASB had a 24 to 37% larger particle size and a 6 to 41% longer solids retention time. In addition, the reactor performances were also enhanced. The UASB with chitosan addition had a 9 to 59% lower effluent chemical oxygen demand (COD), 4 to 10% higher COD removal, up to 35% higher biogas production rate, and a 16 to 68% lower biomass washout. The paired t-test analysis indicated that these performance parameters were significantly different (P < 0.05).     

Effect of limited aeration on the anaerobic treatment of evaporator condensate from a sulfite pulp mill

Serious inhibition was found in the regular up-flow anaerobic sludge blanket (UASB) reactor in treating the evaporator condensate from a sulfite pulp mill, which contained high strength sulfur compounds. After applying the direct limited aeration in the UASB, the inhibition was alleviated gradually and the activity of the microorganisms was recovered. The COD removal rate increased from 40% to 80% at the organic loading rate of 8kgCODm(-3)d(-1) and a hydraulic retention time of 12h. Limited aeration caused no oxygen inhibition to the anaerobic microorganisms but instigated sulfide oxidization and H(2)S removal, which was beneficial to the methanogens. The experiment confirmed the feasibility of applying limited aeration in the anaerobic reactor to alleviate the sulfide inhibition. It also proved that the anaerobic system was actually aerotolerant. SEM observation showed that the predominant microorganisms partly changed from rod-shaped methanogens to cocci after the UASB reactor was aerated.     

外循环式UASB反应器处理槟榔废水

在中温（35±2℃）条件下,利用外循环式UASB反应器处理中高有机浓度的槟榔加工废水,并着重探讨了水力停留时间（HRT）对厌氧消化的影响。研究表明,当反应器稳定运行,水力停留时间为1 d,进水COD浓度5 000 mg/L左右,容积负荷在2.53-5.25 kg COD/（m3·d）时,COD去除率在38%以上,出水COD〈3 000 mg/L,平均产气率为0.41 m3/kg COD;若水力停留时间延长至4 d,容积负荷为1.26-1.30 kg COD/（m3·d）,COD去除率可以达到79%,出水COD〈1 200 mg/L,出水可生化性下降,BOD5/COD平均为0.28,实验取得了良好的处理效果,为利用厌氧技术处理槟榔加工废水提供了设计依据。     

常温下IC反应器启动过程中的颗粒污泥性能研究

在常温下用自配葡萄糖废水启动IC反应器,研究了厌氧颗粒污泥的形成过程和特性。IC反应器进水浓度为3 000 mg COD/L,水温为14.5～26℃,25 d内形成了颗粒污泥。结果表明,随着运行时间和容积负荷的增加,颗粒污泥粒径逐渐增大。反应器启动完成后,反应器中2 mm的颗粒污泥增加到6.6%,0.3 mm的颗粒从57.7%减少到39.4%;VSS浓度从24.7 g/L上升到48.2 g/L;VSS/SS从34.4%增加到72.8%。颗粒污泥的沉降速度与颗粒粒径成正比,0.3～3 mm的颗粒污泥的沉降速度介于34.05～109.75 m/h之间,具有良好的沉降性能。初始接种污泥几乎没有产甲烷活性,与第30 d的初期颗粒污泥相比,成熟的颗粒污泥的产甲烷活性提高了46.7%。     

颗粒化序列间歇式活性污泥反应器工艺处理化粪池污水

在序列间歇式活性污泥反应器(SBR)中成功培养出适应化粪池污水水质的好氧颗粒污泥.并将其应用于化粪池污水的处理.在好氧颗粒污泥培养的第15天左右,SBR中开始出现细小的颗粒,然后微生物在其上繁殖生长使颗粒逐渐增大而成熟;在第24天时,SBR中絮状活性污泥已基本实现了颗粒化.培养出的好氧颗粒污泥对化粪池污水有稳定的处理效果,在进水完全为化粪池污水时,COD、NH_4~+-N、TN的平均去除率分别为77%、61%、47%.但是,由于化粪池污水COD较低,因此无法维持较高的生物量,在后期的稳定运行过程中MLSS始终维持在2 500 mg/L左右.好氧颗粒污泥的同步硝化反硝化作用是其稳定脱氮的保证.     

Comparative granule characteristics and biokinetics of sucrose-fed and phenol-fed UASB reactors

Two upflow anaerobic sludge bed (UASB) reactors were fed with a non-inhibitory substrate sucrose and an inhibitory substrate phenol, respectively, to compare granule characteristics and biokinetics. The average size of biomass granules in the sucrose-fed UASB reactor was slightly larger than that of the phenol-fed reactor. The average microbial density was significantly higher in the phenol-fed reactor. The intrinsic biokinetics of sucrose-acidogenesis and phenol-acidogenesis followed Monod and Haldane kinetics, respectively. By comparing half-saturation constants for sucrose and phenol (Ks1,s; Ks1,p), the affinity of phenol to the granule should be much higher. The mass fraction of methanogens (f) in the sucrose-fed reactor decreased with increasing volumetric loading rate (VLR) because of the accumulation of volatile fatty acids (VFAs); the f of the phenol-fed reactor decreased with increasing VLR because acidogenesis was the rate-limiting step. The mass transfer resistance in overall substrate removal in the sucrose-fed reactor was greater than that in the phenol-fed reactor.     

Enhanced sludge granulation in upflow anaerobic sludge blanket (UASB) reactors by aluminum chloride.

Two upflow anaerobic sludge blanket (UASB) reactors were concurrently operated for 146 days to examine the effects of aluminum chloride (AlCl3) on the sludge granulation process during start-up. Sludge granulation (defined as that over 10% of granules were larger than 2.0 mm) was achieved in the control reactor (R1) in approximate three months. Introduction of Al3+ at a concentration of 300 mg/l reduced the sludge granulation time by approximate one month. Throughout the experiment the AlCl3-added reactor (R2) had a higher biomass concentration, e.g., 13.8 g-MLVSS/l versus 12.8 g-MLVSS/l on Day 146. Granules became visible earlier in R2 compared with R1 (35 days versus 65 days). The average size of granules from R2 was larger than that from R1. The results demonstrated that AlCl3 enhanced the sludge granulation process in the UASB reactors.     

印染废水水解酸化处理中填料式反应器与UASB反应器的比较

根据印染废水的特点和印染废水处理工程实例,从适用性、与其他工艺的衔接、工程造价、运行费用及水解效果等方面对UASB水解酸化反应器和填料式水解酸化反应器进行比较研究。研究表明,UASB水解酸化反应器在适用性和工程造价两个方面具有一定的缺陷;但是UASB水解酸化反应器对印染废水中COD、SS和色度去除率能够分别达到50%、73%和75%,明显高于填料式水解酸化反应器;且UASB水解酸化反应器每降解1 kg COD所需电量为(0.23±0.05)kW·h,优于填料式水解酸化反应器。     

印染废水水解酸化处理中填料式反应器与UASB反应器的比较

根据印染废水的特点和印染废水处理工程实例，从适用性、与其他工艺的衔接、工程造价、运行费用及水解效果等方面对UASB水解酸化反应器和填料式水解酸化反应器进行比较研究。研究表明，UASB水解酸化反应器在适用性和工程造价两个方面具有一定的缺陷；但是UASB水解酸化反应器对印染废水中COD、SS和色度去除率能够分别达到50％、73％和75％，明显高于填料式水解酸化反应器；且UASB水解酸化反应器每降解1kgCOD所需电量为（0．23±0．05）kW·h，优于填料式水解酸化反应器。     

外循环式UASB反应器处理高浓度酒精废水

利用改进型上流式厌氧污泥床反应器在中温条件下处理高浓度酒精废水,研究反应器的启动影响因素及颗粒污泥形成过程,分析反应器运行特性。在容积负荷为10.39 kg COD/(m3.d),COD去除率达90.2%,VFA在300 mg/L以下,平均产气率为0.328 m3/kg COD,取得最佳的运行效果,为高浓度酒精废水的处理应用提供科学依据。