Effect of ammonia concentration on hythane (H2 and CH4) production in two-phase anaerobic digestion

Co-production of hydrogen and methane by two-phase anaerobic digestion (AD) may offer a sustainable solution for the centralized treatment of food waste (FW), while ammonia accumulation is potentially encountered. A mesophilic two-phase AD was investigated for hydrogen and methane production from FW at varying ammonia concentrations. The process achieved a hydrogen yield of 47.7 mL/g VS and a methane yield of 335 mL/g VS by optimizing the organic loading rate (OLR) and recirculation ratio. Total ammonia nitrogen (TAN) concentration of 4044 mg/L corresponded to a threshold in the hydrogen reactor, above which ammonia would initiate inhibition of hydrogenogenesis and acidogenesis. Methane yield was recovered in the methane reactor after acute inhibiting effects of TAN below 5800 mg/L, while TAN above 6200 mg/L caused chronic inhibition of methanogens. Adjusting hydraulic retention time (HRT) and recirculation ratio in hydrogen and methane reactors reduced TAN to 960 and 2105 mg/L respectively, resulting in successful recovery was achieved in the hydrogen reactor but not in the methane reactor. The two-phase AD for methane and hydrogen production can be a promising solution for ammonia accumulation in AD from FW.     

低温低有机物浓度下EGSB反应器的运行特性

在10℃左右的低温、100～500 mg/L的低有机物浓度下,考察了EGSB反应器的运行效果,并分析了液体上升流速、HRT和有机负荷率等运行参数的影响.结果表明:在温度为10℃左右、COD为100～500 mg/L、HRT为1.7 h、液体上升流速为2.8 m/h的条件下,EGSB反应器能够获得70.33%～86.67%的COD去除率;液体上升流速明显影响着EGSB反应器的运行效果,在不同的运行条件下,EGSB反应器均存在着最佳的液体上升流速;在温度为10℃左右、COD为400 mg/L的条件下,EGSB反应器的最佳HRT为1.7 h、进水有机负荷为10～15 kgCOD/(m3·d),此时对COD的去除率高达81.84%～85.70%.     

AO工艺同步脱氮除磷效能的研究

采用A／O同步脱氮除磷工艺处理模拟污水,调整DO、HRT、内回流、进水污染物的浓度等影响因素,考察了该工艺单位活性污泥处理污水中TN、TP的能力。结果表明,当好氧区DO控制在0．6mg／L左右,HRT控制在10h,内回流比控制在1：1时,单位活性污泥处理污水TN、TP的能力最强,单位活性污泥TN去除速率达到14×10^-3mg／（L·mg MLVSS·h）,单位活性污泥TP去除速率达到0．14×10^-3mg／（L·mg MLVSS·h）,AO系统实现了同步硝化反硝化和反硝化除磷。     

影响添加反硝化聚磷菌的SBR脱氮除磷主要因素

以添加反硝化聚磷菌株后获得稳定生物脱氮除磷效果的SBR装置为研究对象,探讨各种因素对其脱氮除磷效果的影响.结果表明,最适温度为25℃,系统出水COD、氨氮和磷的去除率分别达到90.3%、88.1%和96.2%;进水pH为7.0时,释磷率达到8.1 mg·L-1·h-1,系统脱氛除磷效果最好;系统最佳HRT为厌氧2 h,缺氧4 h;系统污泥龄为10 d时,系统污泥含量和性能正常,厌氧释磷能力较强,运行效果最好.     

Selection of metabolic pathways for continuous hydrogen production under thermophilic and mesophilic temperature conditions in anaerobic fluidized bed reactors

This study evaluated the influence of hydraulic retention time (HRT) on hydrogen (H₂) production in anaerobic fluidized bed reactors at mesophilic (30 °C, AFBR-M) and thermophilic (55 °C, AFBR-T) temperatures. Reactors were fed sucrose-based synthetic wastewater (5000 mg chemical oxygen demand·L^?1) in the HRT of 8, 6, 4, 2, or 1 h. H₂ production rate increased from 67.8 ± 14.8 to 194.9 ± 57.0 ml H₂·h^?1 L^?1 (AFBR-T) and from 72.0 ± 10.0 to 344.4 ± 74.0 mL H₂·h^?1·l^?1 (AFBR-M) when HRT decreased from 8 to 1 h. Maximum H₂ yields for AFBR-T and AFBR-M were 1.93 ± 0.21 and 2.68 ± 0.48 mol H₂·mol^?1 sucrose, respectively. The main metabolites were acetic acid (31.3%–41.5%) and butyric acid (10.2%–20.7%) (AFBR-M) and acetate (20.1%–39.3%) and ethanol (14.3%–29.9%) (AFBR-T). Denaturing gradient gel electrophoresis profiles revealed selective enrichment of microbial populations responsible for H₂ production by the aceto-butyric route (AFBR-M) and ethanol-type fermentation (AFBR-T).     

Exploring optimal conditions for thermophilic fermentative hydrogen production from cassava stillage

This study investigated the effects of seed sludges, alkalinity and HRT on the thermophilic fermentative hydrogen production from cassava stillage. Five different kinds of sludges were used as inocula without any pretreatment. Though batch experiments showed that mesophilic anaerobic sludge was the best inoculum, the hydrogen yields with different seed sludges were quite similar in continuous experiments in the range of 82.9–92.3 ml H₂/gVS without significant differences which could be attributed to the establishment of Uncultured Thermoanaerobacteriaceae bacterium-dominant microbial communities in all reactors. It is indicated that results obtained from batch experiments are not consistent with those from continuous experiments and all the tested seed sludges are good sources for continuous thermophilic hydrogen production from cassava stillage. The influent alkalinity of 6 g NaHCO₃/L and HRT 24 h were optimal for hydrogen production with hydrogen yield of 76 ml H₂/gVS and hydrogen production rate of 3215 ml H₂/L/d. Butyrate was the predominant metabolite in all experiments. With the increase in alkalinity of more than 6 g/L, the concentration of VFA/ethanol increased while hydrogen yield decreased due to the higher concentration of acetate and propionate. The decrease in HRT resulted in the higher hydrogen production rate but lower hydrogen yield. Variation of hydrogen yields were quite correlated with butyrate/acetate (B/A) ratio with different influent alkalinities, however, butyrate was important parameter to justify the hydrogen yields with various HRTs.     

The use of acidified palm oil mill effluent for thermophilic biomethane production by changing the hydraulic retention time in anaerobic sequencing batch reactor

The feasibility of thermophilic biomethane production from acidified palm oil mill effluent (POME) was assessed in a 5 L anaerobic sequencing batch reactor (ASBR). The effects of various hydraulic retention time (HRT) (10-1 d) on methane production performance and the stability of ASBR in treating acidified POME were evaluated herein. It was found that the highest methane productivity of 5.65 L CH₄/L/d could be attained at HRT of 2 d. However, the removal of chemical oxygen demand (COD) and volatile fatty acid (VFA) at this HRT is rather low (65-62%) hence making it inefficient to operate at HRT 2 d since most of the contaminants remained in the liquid streams. Thus the most recommended HRT was 3 d with maximum methane productivity of 3.96 L CH₄/L/d with corresponding methane yield of 260.3 L CH₄/kgCOD_removed. The COD removal efficiency at 3 d HRT was 71%, and the VFA consumption was more than 80%. The correlation of total VFA: total alkalinity (TVFA: TA) at HRT of 3 d was found to be 0.1. This recommended HRT of 3 is equally shorter than any previously reported application of POME as a substrate for thermophilic biomethane.     

Influence of the temperature and hydraulic retention time in bioelectrochemical anaerobic digestion of sewage sludge

At ambient temperature (25 °C), bioelectrochemical anaerobic digestion of sewage sludge was investigated with a hydraulic retention time (HRT) of 10 days and compared to that at a mesophilic condition (35 °C). The methane production and methane content in the biogas at ambient temperature were 612.8 mL/L·d and 73.3%, respectively, which were not significantly lower than that of the mesophilic condition. Additionally, the VS removal was 54.5% which was similar for both temperature conditions. However, for a HRT of 20 days, the bioelectrochemical anaerobic digestion at ambient temperature became more stable, and the VS removal improved up to 65.0%. For the HRT of 10 days, the net energy production at ambient temperature was about 168 kJ/L·d, which was similar to the mesophilic condition; however, the apparent energy efficiency at ambient temperature was 249.2% which was significantly higher than 197.7% at the mesophilic condition. The bioelectrochemical anaerobic digestion that can save the thermal energy input at ambient temperature is recommended for the treatment of organic waste including sewage sludge in moderate and cold climate regions.     

DO和HRT对MBR同步硝化反硝化影响研究

通过连续运行MBR研究了DO和HRT对同步硝化反硝化的影响,同时对好氧反应器中实现SND的机理进行了探讨.试验结果表明:COD在250 mg/L左右,C/N为10∶1,MLSS为3500 mg/L,HRT为8.5h的相对稳定条件下,当DO为0.6~0.8 mg/L时,总氮去除率达66.7%,取得了最好的TN去除效果,DO过高或过低都会影响同步硝化反硝化的进行;控制DO在1.0 mg/L左右,其他操作条件相同,HRT为5 h,TN去除率达到最高为60%以上,随HRT的延长,同步硝化反硝化效果反而下降;研究结果还表明由于好氧反应器中缺氧区的存在,控制操作条件可以实现SND,同时也存在着短程SND的现象,实现SND可能是几种作用机制的共同结果.     

高效包埋硝化活性填料硝化特性及应用研究

为考察市政污水条件下高效包埋填料的硝化特性,采用聚乙烯醇对硝化细菌进行固定化处理。实验室恢复培养后实验考察了包埋填料对水力停留时间、温度等因素的适应性变化以及包埋填料在市政污水中的应用。结果表明,恢复后的填料实现了氨氧化速率93.20 mg·(L·h)^-1的高表达。在常温条件下,水力停留时间对包埋填料硝化速率影响较小;温度对硝化速率影响显著,当水温为12℃时,氨氧化速率最高为30.70 mg·(L·h)^-1。在市政污水低温和常温条件下,当水力停留时间分别为3 h和1 h时,进水氨氮基本完全去除,表明包埋填料用于市政污水硝化是完全可行的。扫描电镜结果显示填料内部有良好的孔隙度,网状结构明显;荧光定量PCR结果表明细菌大量增殖,说明填料为微生物提供了良好的生长微环境。