Identification and cultivation of hydrogenotrophic methanogens from palm oil mill effluent for high methane production

By means of biorefinery, biogas production through anaerobic digestion is one of the most common treatments of wastewater in the palm oil industry. After biogas production, the treated palm oil mill effluent (POME) is generally discharged into the environment. However, certain level of hazardous compounds still exists in the treated wastewater, which can lead to the pollution of water bodies. In this study, we have investigated the dynamics of volatile organic acids dwelling in consecutive POME treatment lagoons as well as identified, and categorized, microbial species responsible for the treatment process. Bacteria and methanogens, both hydrogenotrophic and acetoclastic, related to methane production were identified using mcrA and 16S rRNA genes specific primers. Two hydrogenotrophic methanogens, Methanoculleus marisnigri and Methanoculleus chikugoensis, were found abundant in accordance with high formate concentration throughout the process of anaerobic digestion. This study has also isolated eight consortia of microbes that yielded different methane productions by utilizing formate as the substrate in the synthetic medium. The consortia of a group, containing M. marisnigri, M. chikugoensis, uncultured bacteria, Aminobacterium sp., and Ruminobacillus xylanolyticum, produced the highest methane yield of 259 mL/g COD after 25 days of incubation in the laboratory. The findings from this study are contributing to optimize and increase biogas production in POME, which will allow higher efficiency in palm oil mill wastewater treatment.     

Effects of size and autoclavation of fruit and vegetable wastes on biohydrogen production by dark dry anaerobic fermentation under mesophilic condition

Fermentative hydrogen production from fruit and vegetable wastes (FVWs) through Dry Fermentation Technology (DFT) was studied through three independent experiments in order to find out the effect of particle size and autoclaving pretreatment on bio-hydrogen production from FVWs and as follows: (1) autoclaved FVWs with sizes < 5 cm (experiment I); (2) raw FVWs with sizes < 5 cm (experiment II) and (3) autoclaved FVWs with sizes > 5 cm (experiment III). The assay with autoclaved waste yielded a higher percentage of hydrogen in the headspace of the dry fermenter reaching a maximum value of 44% in experiment I. However, the maximum hydrogen production was obtained in experiment III with 14573 NmL at a yield of 23.53 NmL H₂/gVS. Profiling of the microbial communities by denaturing gradient gel electrophoresis (DGGE) indicated that the most prominent species were the genera Clostridium, Bifidobacterium, and Lactobacillus.     

Strategies of valorization of sludge from wastewater treatment

Sludge is regarded as a potential source to achieve valorization via strategies such as resource recovery, sludge based adsorbents preparation, bioflucculants production, sludge manufacturing construction materials preparation, sludge composting and thermal valorization, which are currently common and effective strategies. Appropriate treatment strategies of sludge are of great importance worldwide for the fast growing population and rapidly increasing waste. This mini review summarized some widely used and effective strategies to achieve sludge valorization based on whether the strategy would utilize or reuse the potential of sludge to obtain valuable product and eliminate secondary pollution. Anaerobic digestion of sludge is perceived as a potentially cost‐effective method to achieve sludge reduction and resource recovery including carbon, nitrogen, phosphorus resource recovery coupled with other technologies. Utilizing sludge as raw material for preparation of valuable products including sludge based adsorbents, bioflocculants and construction materials is another aspect to achieve sludge valorization. Sludge composting and thermal valorization are also introduced in the mini review since the two strategies could also achieve sludge valorization. In addition, the strategies mentioned were discussed and analyzed in the mini review from environmental and economic aspects. © 2017 Society of Chemical Industry     

基于LabVIEW的甲烷产气量自动测量系统设计

针对实验室现有的厌氧发酵装置产气测量存在费时费力、人眼读数误差较大、自动化程度低等问题,设计一种基于LabVIEW的甲烷产气量自动测量系统。提出采用排水法与称重计量法结合的测量方法,以实现产气量自动测量。称重传感器获取发酵甲烷产气排水后得到水的质量,经换算得到排水体积即甲烷产气体积。利用LabVIEW编写软件平台,采用NI USB-6251数据采集卡对发酵过程中的关键参数如甲烷产气量、温度和pH值进行实时采集、处理、显示及存储,同时控制夹管阀和蠕动泵实现自动补充排水液的功能。利用微量注射器对自动测量系统开展性能验证实验。试验结果表明:该装置的测量平均相对误差最大值为1.10%。该系统可以满足发酵实验对甲烷气体的测量需求,不仅能够提高自动化水平还可以提高测量准确性。     

The anaerobic degradation of detergent range fatty alcohol ethoxylates. Studies with C-labelled model surfactants

The anaerobic degradation of fatty alcohol polyglycol ethers was studied in a model sludge digester employing stearyl alcohol ethoxylate which was ¹⁴C-labelled either in the alkyl or in the heptaglycol chain. After 4-weeks' incubation of the ¹⁴C-compounds at 35°C in the presence of raw sludge as additional digestible substrate more than 80% of the initial radioactivity was found as methane and carbon dioxide. In addition, the major part of radioactivity in the digested sludge, corresponding to nearly 10% of added ¹⁴C, was attributable to biomass so that ultimate degradation of the two model surfactants amounted to more than 90%. Analysis of the small fraction of radiolabelled metabolites in the sludge supernatant allowed conclusions with regard to the anaerobic degradation route of linear alcohol ethoxylates. After primary biodegradation of the surfactant molecule by scission into the alkyl and poly(ethylene glycol) moieties the further biodegradation of the latter seems to proceed as under aerobic conditions, i.e. via oxidative or hydrolytic depolymerization steps. Eventually, ultimate biodegradation of the obtained monomers (C₂-units) leads to the formation of the gaseous end products.     

Dynamic modelling of anaerobic digestion

The anaerobic digestion model presented here considers a two step process. First, acidogenic bacteria convert glucose into acetate then methanogenic bacteria convert this acid into methane and carbon dioxide. The biomass and metabolite production rates are described by distinct relations. Therefore, there is not a direct relationship between the growth and the energy production related to metabolite formation. The inhibitory effects of the unionized acid concentration on growth rate of both bacterial populations and the methane production from acetate were considered separately. The model was tested in batch cultures with two types of organic loads, i.e. pea bleaching wastewaters and a synthetic substrate containing sucrose and organic acid. The model allowed to simulate satisfactorily the methane production under very different operational conditions.     

厌氧塘加盖提高处理效率的试验研究

为了提高厌氧塘的处理效率,进行了厌氧塘加盖密闭试验。结果表明,加盖后的COD、BOD5 和SS去除率比加盖前分别提高了27%、19%和10%,出水BOD5 和SS基本达到了《污水综合排放标准》的一级标准。     

生物质能利用技术及研究进展

对生物质能的概念、利用生物质能的意义及生物质能的转化利用方式进行了介绍。生物质能转化方法分为生物化学转化(发酵和消化)、热化学转化(直接燃烧、气化、热解和液化)、机械萃取等。     

聚季胺盐投加方式对厌氧污泥颗粒化的影响研究

投加阳离子聚合物是加速厌氧污泥颗粒化的有效方法,根据静态试验得出的聚季胺盐投加总量,选定了聚季胺盐的几种投加方式（不同的投加量和投加时间间隔）,研究其对实验室规模下的厌氧序批式反应器（ASBR）中污泥颗粒化的影响.试验以污水厂的厌氧污泥为对象,以污泥颗粒的粒径、沉速及出水COD等作为评价污泥颗粒化进程的指标,分析了各投加方式对污泥颗粒化进程的影响,并挑选出适宜的絮凝剂投加方式.结果表明,不同投加方式对ASBR污泥颗粒化进程有不同影响,建议采用每次投加量为0.16～0.32 mg/gMLSS,投加时间间隔为2～5 d,分5～10次投加的方式.