Sludge wash-out as strategy for Anammox process start-up

In this study sludge wash-out was evaluated as a strategy to start-up the Anammox process in order to establish it in a shorter period of time. Sludge from a domestic wastewater treatment plant (WTP) was used to seed two (RI and RII) anaerobic sequencing batch reactors (ASBR). During the start-up period RI was operated as a continuous stirred tank reactor (CSTR) using a dilution rate of 0.2 d⁻¹, which promoted the sludge wash-out. After this period, the remaining sludge was retained in the reactor. The reactor RII was operated as an ASBR throughout the study period with a high cell retention. The performance of the two reactors in terms of nitrogen removal was compared over a period of 380 days. During the last RI operation phase the specific nitrogen removal rate increased exponentially, attaining values of 85 mg N/g TSS d. However, a rate of 190 mg N/g TSS d in the batch test under optimal conditions was achieved. The specific nitrogen removal rate remained almost constant for RII with a mean value of 6 mg N/g TSS d being observed during the operation period. The rate for the RII batch test was 20 mg N/g TSS d. These results confirm that the higher total suspended solids (TSS) in RII (reactor with high cell retention) was not effective in terms of N removal improvement. Anammox-like bacteria were found using fluorescence in situ hybridization (FISH) in reactor RI after 225 days and a new Anammox species was identified.     

Start-up of a two-stage bioaugmented anoxic–oxic (A/O) biofilm process treating petrochemical wastewater under different DO concentrations

The traditional two-stage anoxic–oxic (A/O) activated sludge process might be inefficient in pollutants removal and could not ensure the effluent quality. By installing polyurethane foams as carriers and inoculating specialized bacteria in the oxic compartments, the activated sludge systems could be transformed into bioaugmented biofilm processes to enhance the removal efficiency to recalcitrant pollutants. Optimal environment should be provided for the bioaugmented bacteria during systems’ start-up. In the present research, dissolved oxygen (DO) concentration was studied as a crucial environmental factor on the performances of the bioagumented systems. The results indicated that the system adopted lower DO concentration took less time to start-up, performed higher pollutants removal efficiency and stronger resistance to shock loadings compared to the system with higher DO level. This was the first attempt to evaluate the importance of DO concentration on the start-up of the two-stage bioaugmented A/O biofilm process.     

Ethanol addition as a strategy for start-up and acclimation of an AnSBBR for the treatment of landfill leachate

This study evaluated the ethanol addition as a strategy for start-up and acclimation of a pilot scale (1300 L) anaerobic sequencing batch biofilm reactor (AnSBBR) for the treatment of municipal landfill leachate with seasonal biodegradability variations. The treatment was carried out at ambient temperature (23.8 ± 2.1 °C) in the landfill area. In a first attempt, the leachate collected directly from landfill showed to be predominantly recalcitrant to anaerobic treatment and the acclimation was not possible. In a second attempt, adding ethanol to leachate, the reactor was successfully acclimated. After acclimation, without ethanol addition, the COD_Total influent ranged from 4970 to 13040 mg L^?1 and the removal efficiencies ranged from 12.1% to 70.7%. A final test was carried out increasing the ammonia and free-ammonia concentration from 2486 mgN L^?1 and 184 mgN L^?1 to 4519 mgN L^?1 and 634 mgN L^?1, respectively, with no expressive inhibition verified. The start-up strategy was found to be feasible, providing the acclimation of the biomass in the AnSBBR, and maintaining the biomass active even when the leachate was recalcitrant.     

Anammox反应器启动过程中颗粒污泥性状变化特性

以厌氧颗粒污泥作为接种物,通过185 d的运行,成功启动了上流式厌氧氨氧化污泥床(Upflow anaerobic sludge blanket,UASB)反应器。反应器的进水氨氮与亚硝氮浓度分别提升至224 mg/L和255 mg/L,容积氮去除速率提升至3.76 kg/(m3·d)。采用红外光谱、扫描电镜和透射电镜等对厌氧氨氧化颗粒污泥的性状进行观察,发现颗粒污泥在启动过程中经历了污泥颗粒裂解到污泥颗粒重组的过程,且厌氧氨氧化颗粒污泥表面含有丰富的官能团,说明厌氧氨氧化颗粒污泥可能具有良好的吸附性能。采用宏基因组测序的方法对启动前后颗粒污泥的生态结构进行分析,发现原接种污泥优势菌群(变形菌门、厚壁菌门、拟杆菌门)丰度大幅减少,厌氧氨氧化菌所属的浮霉状菌门丰度则由1.59%提升到23.24%。     

A next generation, pilot-scale continuous sterilization system for fermentation media

A new continuous sterilization system was designed, constructed, started up, and qualified for media sterilization for secondary metabolite cultivations, bioconversions, and enzyme production. An existing Honeywell Total Distributed Control 3000-based control system was extended using redundant High performance Process Manager controllers for 98 I/O (input/output) points. This new equipment was retrofitted into an industrial research fermentation pilot plant, designed and constructed in the early 1980s. Design strategies of this new continuous sterilizer system and the expanded control system are described and compared with the literature (including dairy and bio-waste inactivation applications) and the weaknesses of the prior installation for expected effectiveness. In addition, the reasoning behind selection of some of these improved features has been incorporated. Examples of enhancements adopted include sanitary heat exchanger (HEX) design, incorporation of a “flash” cooling HEX, on-line calculation of F _o and R _o, and use of field I/O modules located near the vessel to permit low-cost addition of new instrumentation. Sterilizer performance also was characterized over the expected range of operating conditions. Differences between design and observed temperature, pressure, and other profiles were quantified and investigated.     

Behavior of methanogens during start-up of farm-scale anaerobic digester treating swine wastewater

The aim of this study was to monitor the changes in methanogenic community structures in an anaerobic digester (250 m³ working volume) during start-up including prolonged starvation periods. Redundancy analysis was performed to investigate the correlations between environmental variables and microbial community structures. The anaerobic digester was operated for 591 days at alternating operating temperatures. In initial start-up period at stage I (35 °C), growth of various species of mesophilic aceticlastic methanogens (AMs) and hydrogenotrophic methanogens (HMs) was observed. Methanobacteriales species survived better than other methanogens under long-term starvation conditions. In stage II (50 °C), HMs became dominant over AMs as the operating temperature changed from mesophilic to thermophilic due to increase of ammonia inhibition. In stage III (35 °C), only the Methanomicrobiales population significantly increased during 50 days of HRT while Methanobacteriales dominated over 15 days of HRT. The influent pH negatively correlated with all methanogenic populations especially in stage II.     

Characterization of start-up performance and archaeal community shifts during anaerobic self-degradation of waste-activated sludge

Successful start-up strategy for anaerobic digestion of waste-activated sludge using internal inoculum and relationship between the shift of methanogenic community and the digester performance during start-up was investigated. Combination of TS control of inoculum and batch operation during early days enabled the successful start-up operation without serious volatile fatty acid accumulation, followed by the stable continuous operation. However, the propionate degradation was rate-limiting step during the batch operation. The results of real-time quantitative polymerase chain reaction analysis suggested that there was a correlation between the population of the genus Methanosarcina and the methane production rate coupled with acetate consumption during batch operation, and the results of terminal-restriction fragment length polymorphism (T-RFLP) revealed that the increasing intensity of T-RF peaks of hydrogenotrophic methanogens was associated with a decrease in the level of C3-acids.     

Research on soybean protein wastewater treatment by the integrated two-phase anaerobic reactor

The start-up tests of treating soybean protein wastewater by the integrated two-phase anaerobic reactor were studied. The results showed that the soybean protein wastewater could be successfully processed around 30 days when running under the situation of dosing seed sludge with the influent of approximately 2000 mg/L and an HRT of 40 h. When the start-up was finished, the removal rate of COD by the reactor was about 80%. In the zone I, biogas mainly revealed carbon dioxide (CO₂) and hydrogen (H₂). Methane was the main component in the zone 2 which ranged from 53% to 59% with an average of 55%. The methane content in biogas increased from the zone I to II. It indicated that the methane-producing capacity of the anaerobic sludge increased. It was found that the uniquely designed two-phase integrated anaerobic reactor played a key role in treating soybean protein wastewater. The acidogenic fermentation bacteria dominated in the zone I, while methanogen became dominant in the zone II. It realized the relatively effective separation of hydrolysis acidification and methanogenesis process in the reactor, which was benefit to promote a more reasonable space distribution of the microbial communities in the reactor. There were some differences between the activities of the sludge in the two reaction zones of the integrated two-phase anaerobic reactor. The activity of protease was higher in the reaction zone I. And the coenzyme F₄₂₀ in the reaction zone II was twice than that in the reaction zone I, which indicated that the activity of the methanogens was stronger in the reaction zone II.     

Fast start-up, performance and microbial community in a pilot-scale anammox reactor seeded with exotic mature granules

The possibility to introduce the exotic anammox sludge to seed the pilot-scale anammox granular reactor and its fast start-up for treating high nitrogen concentration wastewater were evaluated in this study. The reactor was started up successfully in two weeks; in addition, high nitrogen removal was achieved for a long period. Stoichiometry molar ratios of nitrite conversion and nitrate production to ammonium conversion were calculated to be 1.26 ± 0.02:1 and 0.26 ± 0.01:1, respectively. The Stover-Kincannon model which was first applied in granular anammox process indicated that the granular anammox reactor possessed high nitrogen removal potential of 27.8 kg/m³/d. The anammox granules in the reactor were characterized via microscope observation and fluorescence in situ hybridization technique. Moreover, the microbial community of the granules was quantified to be composed of 91.4-92.4% anammox bacteria by real-time polymerase chain reaction. This pilot study can elucidate further information for industrial granular anammox application.     

Start-up and inhibition analysis of the Anammox process seeded with anaerobic granular sludge

The longer start-up period of the Anammox process is due to the very low cellular yield and growth rates of Anammox bacteria. Nitrite inhibition is considered to be the key factor in the instability of the Anammox process during the operation. However, little attention was paid to the inhibitory effect of pH and free ammonia. This paper presents start-up and inhibition analysis of an Anammox biofilm reactor seeded with anaerobic granular sludge. Results showed that the start-up period could be divided into the sludge lysis phase, lag phase, propagation phase, stationary phase and inhibition phase. Optimization control could be implemented correspondingly to accelerate the start-up of Anammox bioreactors. Effluent pH increased to 8.7–9.1 when the nitrogen removal rate was higher than 1,200 mg l⁻¹ day⁻¹. The free ammonia concentration was accompanied with a higher level of 64–73 mg l⁻¹. Inhibitory effects of high pH and free ammonia on Anammox bacteria contributed to the destabilization of the Anammox bioreactor during the first 125 days with influent KHCO₃ of 0.5 g l⁻¹. Increasing the suffering capacity in the inlet by dosing 1.25 g KHCO₃ l⁻¹ effectively reduced the pH variation, and the nitrogen removal performance of the reactor was further developed.