pH值对玉米秸秆厌氧消化产气的影响

采用批式实验,研究了(35±0.5)℃、搅拌速度65 r/min的厌氧消化体系中,pH值对玉米秸秆厌氧消化产甲烷的影响,分析了消化液相及固相特性的变化.结果表明,厌氧消化第7～9天时各系统VFA浓度均达到最大值,pH值为7和9时,挥发性脂肪酸(VFA)浓度显著高于其他系统,SCOD向VFA的转化效率较高.pH值为9时累积产气量增加速度最快,最大累计产气量达到134.33 mL/g VS.pH值为7时累计产气量最大,高达149.2 mL/g VS,是pH值为5和11系统的3.23和6.71倍.pH值为7和9时,沼气中甲烷的平均含量分别为64.1％和62.5％,比pH值为5和11的系统提高了约10％.pH值为7和9时VS去除率达到67.68％和58.87％,显著高于其他系统.控制厌氧消化pH值在7～9范围内可以有效提高木质纤维素生物质的产气效率.     

中国挥发性有机物污染防治政策及对监测技术的管理需求

本文通过梳理现行的挥发性有机物污染防治政策法规和方法标准,结合国外经验,提出了现阶段挥发性有机物污染防治政策体系。尽管起步较晚,但陆续实施的挥发性有机物排污收费和总量控制机制,已经对污染物监测提出了明确的管理需求。虽然离线检测技术具有良好的灵敏度和响应度,但使用FID和NDIR法的在线和便携仪器响应时间短、数据连续,可以实现对挥发性有机物污染的实时追踪,更好地满足污染预警、应急执法等环境管理新需求。     

构建开放监督型工业源挥发性有机物排污申报平台的建议

工业源挥发性有机物(VOCs)以无组织排放为主,其排放量的确定和申报对现行的以有组织排放管理为主的环境管理模式提出挑战。为顺利实施VOCs排污收费、总量控制、环境影响评价、污染防治管理,切实降低环保部门收集信息、监督管理的成本,促进环境信息的真实性和有效性,我国迫切需要在国家层面结合环境信息公开和公众参与对VOCs排污申报管理模式进行研究和构建。在研究国内外排污申报平台的基础上,提出以VOCs管控为契机,整合环境统计、排污费征收等要求,建立面向企业的唯一开放监督型VOCs排污申报平台,采取数据联审制度,推行信息公开和开放型监督。通过申报功能、试算功能、监督审核功能、决策支持功能、减排技术评价功能、信息公开功能、资料和文件功能、培训和试报功能等平台八大功能的有机融合,建立公众、企业和政府相互监督、制约的三级VOCs排放监督管理新机制,为我国环境管理模式的更新升级提供参考。     

真菌降解挥发性有机化合物的研究进展

挥发性有机化合物(VOCs)是一类重要的大气污染物,生物降解法是近年来兴起的VOCs治理技术,它具有费用低、净化效率高、无二次污染等特点。目前,有关生物降解污染物的研究大部分都以细菌作为优势微生物,而对于真菌的研究起步相对较晚。真菌具有耐干燥、耐弱酸等特性,使得其在处理疏水性VOCs上具有明显优势。分析了真菌的降解特征及优势,总结了已分离到的可降解VOCs的真菌及其善于降解的污染物,重点探讨了影响真菌生物反应器VOCs降解性能的主要因素和相关动力学研究,并对今后真菌降解VOCs的研究方向进行了展望。     

Long-term thermophilic mono-digestion of rendering wastes and co-digestion with potato pulp

In this study, mono-digestion of rendering wastes and co-digestion of rendering wastes with potato pulp were studied for the first time in continuous stirred tank reactor (CSTR) experiments at 55 °C. Rendering wastes have high protein and lipid contents and are considered good substrates for methane production. However, accumulation of digestion intermediate products viz., volatile fatty acids (VFAs), long chain fatty acids (LCFAs) and ammonia nitrogen (NH₄-N and/or free NH₃) can cause process imbalance during the digestion. Mono-digestion of rendering wastes at an organic loading rate (OLR) of 1.5 kg volatile solids (VS)/m³ d and hydraulic retention time (HRT) of 50 d was unstable and resulted in methane yields of 450 dm³/kg VS_fed. On the other hand, co-digestion of rendering wastes with potato pulp (60% wet weight, WW) at the same OLR and HRT improved the process stability and increased methane yields (500–680 dm³/kg VS_fed). Thus, it can be concluded that co-digestion of rendering wastes with potato pulp could improve the process stability and methane yields from these difficult to treat industrial waste materials.     

Application of an early warning indicator and CaO to maximize the time–space-yield of an completely mixed waste digester using rape seed oil as co-substrate

In order to increase the organic loading rate (OLR) and hereby the performance of biogas plants an early warning indicator (EWI-VFA/Ca) was applied in a laboratory-scale biogas digester to control process stability and to steer additive dosing. As soon as the EWI-VFA/Ca indicated the change from stable to instable process conditions, calcium oxide was charged as a countermeasure to raise the pH and to bind long-chain fatty acids (LCFAs) by formation of aggregates. An interval of eight days between two increases of the OLR, which corresponded to 38% of the hydraulic residence time (HRT), was sufficient for process adaptation. An OLR increase by a factor of three within six weeks was successfully used for biogas production. The OLR was increased to 9.5 kg volatile solids (VS) m^?3 d^?1 with up to 87% of fat. The high loading rates affected neither the microbial community negatively nor the biogas production process. Despite the increase of the organic load to high rates, methane production yielded almost its optimum, amounting to 0.9 m³ (kg VS)^?1. Beneath several uncharacterized members of the phylum Firmicutes mostly belonging to the family Clostridiaceae, a Syntrophomonas-like organism was identified that is known to live in a syntrophic relationship to methanogenic archaea. Within the methanogenic group, microorganisms affiliated to Methanosarcina, Methanoculleus and Methanobacterium dominated the community.     

聚丙烯中空纤维膜生物反应器净化复合芳香族VOCs

采用中空纤维膜生物反应器(HFMBR)去除气态复合苯系物。挂膜后期,生物反应器的去除效率可以稳定达到80%左右(去除能力(EC)≥225 g/(m3.h))。研究了中空纤维膜生物反应器处理对于单一二甲苯以及混合二甲苯的性能,并且发现HFMBR对于去除单一二甲苯和混合二甲苯都有明显的效果,去除效率均达到90%以上;表明二甲苯之间竞争效应带来的相互抑制作用小。在低浓度的情况下,单一二甲苯和混合二甲苯的去除能力呈线性增加,在高浓度阶段,去除能力增加变缓。比较了混合二甲苯与甲苯联合降解,发现两者之间存在相互抑制作用,但相比传统生物反应器有明显的改善。与传统生物过滤系统比较而言,膜生物反应器有着很好的应用前景。     

中空纤维膜吸收甲苯气体

采用疏水性聚偏氟乙烯(PDVF)中空纤维膜为气液接触膜,n-甲酰吗啉(NFM)水溶液为吸收剂,研究了膜吸收技术分离甲苯/空气混合气的性能。考察了进气气体浓度、气体停留时间、吸收液体积分数和吸收液流量等诸因素对分离性能的影响。研究结果表明,膜吸收技术可以有效地分离甲苯/空气混合气,甲苯去除率可达90%;提高NFM吸收液的浓度和流量可同时增加甲苯的去除效率η和总传质系数K;气体停留时间的减小导致η降低,K反而增大;进气甲苯浓度的增加导致η下降,同时降低总传质系数K。     

自制ZSM-5分子筛对甲苯气体的吸附-脱附性能

考察了自制ZSM-5分子筛对甲苯气体的吸附-脱附性能,并与市售MCM-22分子筛进行了对比实验。实验结果表明:在吸附温度为25℃、进口甲苯质量浓度为840mg/m3、吸附气体流速为0.016m/s、床层高度为15cm的条件下,出口甲苯质量浓度达到0.8mg/m3时的穿透时间为82min,吸附效率为4.26mg/g;在脱附温度为80℃、脱附气体流速为0.016m/s的条件下,脱附35min时出口甲苯质量浓度达到最大,为1220mg/m3。自制ZSM-5分子筛的吸附-脱附性能优于市售MCM-22分子筛。     

Biodegradation behavior of agricultural pesticides in anaerobic batch reactors

This study explored the biodegradation potential of two agricultural pesticides (2,4-D and isoproturon) as well as their effect on the performance of the anaerobic digestion process. Three 3.5 L batch reactors were used, having the same initial isoproturon concentration (25 mg/L) and different 2,4-D concentrations (i.e. 0, 100, or 300 mg/L, respectively). All systems were fed with equal amounts of primary sludge and digested sludge and operated at the low mesophilic range (32 ± 2°C). Following an acclimation period of approximately 30 days, complete 2,4-D removal was achieved, whereas isoproturon biodegradation was practically negligible. The presence of 2,4-D did not have a direct effect on acidogenesis since soluble organic carbon [expressed either as volatile fatty acids (VFAs) or as total organic carbon (TOC)] peaked within the first 10 days of operation in all bioreactors. Utilization of VFAs however appeared to follow two distinct patterns: one pattern was represented by acetate and butyrate (i.e. no acid accumulation) while the other was followed by propionate, isobuturate, valerate and isovalerate (i.e. acid accumulation, duration of which was related to the initial 2,4-D concentration). On the whole, all reactors exhibited a successful digestion performance demonstrated by complete VFAs utilization, considerable gas production (containing 45 to 65% methane by volume), substantial volatile suspended solids (VSS) reduction (42 to 50%), as well as pH and alkalinity recovery.