Short‐time estimation of biogas and methane potentials from municipal solid wastes

Biogas (GB) and methane (BMP) potentials are important parameters for the energy potential of the anaerobic digestion of municipal solid wastes (MSW) and to design full‐scale facilities. However, no standard protocol has been defined for this measure. Several samples of mixed MSW and the source‐selected organic fraction of municipal solid waste (OFMSW) obtained at different stages of their mechanical‐biological treatment were analyzed. GB and BMP values obtained at different times were correlated. Biogas potentials calculated at 3, 4, 5, 6, 7, 14, 21, 50 and 100 days correlated well for the OFMSW samples. In the case of the MSW samples, only GB values obtained at times of 14 or more days correlated well with the ultimate biogas production (considered at 100 days). The biogas potential analyzed at 21 days (as proposed in some standard methods) accounted for 77% of the total biogas potential in OFMSW samples and for 71% in the MSW samples. These results are useful for the correct design and operation of anaerobic digestion plants in terms of retention time estimation and expected biogas and methane production. Copyright © 2011 Society of Chemical Industry     

Biogas generation from bagasse-based paper mills by anaerobic digestion

Bagasse-based paper mills in developing countries do not have sophisticated waste water treatment technology to combat water pollution released by these mills. This paper presents an overview of bagasse handling and sources of waste generation, the seriousness of pollution discharge, and treatment options available to tackle the waste water derived from bagasse-based paper mills. Extensive laboratory treatability studies indicate that anaerobic digestion for biogas generation is a viable method for handling bagasse-based paper mill wastes. The waste water was treated at an organic loading of 0.8 kg BOD m^?3 day^?1 and 1.6 kg COD m^?3 day^?1 and a detention time of 10 days, achieving 90% reduction in BOD and COD without supplementation of any nutrients. With a yield coefficient of 0.5, the average quantity of cells produced per day was calculated to be 1.683 kg day^?1 or 0.25 kg cells produced kg^?1 BOD removed. Intermittent checking on excess alkalinity in the anerobic system is necessary for achieving maximum treatment efficiency.     

Laboratory simulation of municipal solid waste fermentation with leachate recycle

Municipal solid waste fermentation, simulating landfill conditions, was studied using five test cells operated at different temperatures. The digestion was carried out under enhanced conditions. Leachate recycle was set up in all the test cells. Depending on temperature, the digestion was complete (more than 90% biodegradable matter converted) in a period of 25 to 57 days. Optimum operating temperatures were in the range of 34 to 38°C. Two kinetic models were fitted to experimental data. Their kinetic constants were related to temperature using an Arrhenius expression. Landfill life operated under the studied conditions could be reduced to less than 2 years.     

Dry anaerobic batch digestion of the organic fraction of municipal solid waste

Anaerobic digestion at high solid concentrations (dry anaerobic digestion) is an attractive method for the stabilization of solid organic wastes. A new concept for dry anaerobic batch digestion (BIOCEL) of the organic fraction of municipal solid waste is presented. The start up of a BIOCEL reactor was studied with several methods of process set up and operation. Dry anaerobic digestion of the pure undiluted organic fraction obtained from a shredding/separation process was not accelerated by partial spatial separation of substrate and methanogenic inoculum (granular sludge) or leachate recycle, or both. With these three methods after 30 days the high organic acids concentration and low pH in the reactor indicated a sour reactor, unable to establish significant methane production. When the organic fraction was digested in combination with compost addition (40% (w/w) of the initial solids) and leachate recycle, the stabilization rate increased significantly. Leachate recycling in combination with partial spatial separation of the substrate/compost mixture and the inoculum showed the shortest lag phase in the methane production and the shortest digestion time. When the digested residue of a completed digestion was applied as the methanogenic inoculum (40% (w/w) of the initial total solids) the digestion time was slightly shorter. It is concluded that dilution with compost had a positive effect on the start up of the dry anaerobic digestion and compensated for a suboptimal amount of initial methanogenic biomass. During the start up of dry anaerobic batch digestion of municipal solid waste the rapid recovery of methane formation from an initial overloading was observed and was found to be the result of a population shift in the methanogenic biomass and the existence of zones in the reactor with more optimal conditions (higher p H, lower organic acids concentration). The observed digestion time was 36 days. Recommendations are given to shorten the period needed, for complete digestion.     

沼液余热回收对高温发酵沼气工程净产气率的影响

以瑞典Alviksgården养猪场高温发酵沼气工程为分析对象,通过传热模型计算发酵罐加热负荷,通过与江苏金坛永康农牧养猪场同等规模的中温发酵沼气工程对比,讨论高温发酵的容积产气率和余热回收对沼气工程净产气率的影响。结果表明虽然瑞典Alviksgården养猪场高温发酵沼气工程的加热能耗是江苏金坛永康农牧养猪场中温发酵沼气工程的2.1倍,但由于产气速率达到2.3 m³·m^-3·d^-1,增产的沼气量远远大于增温的能耗;若进一步在瑞典Alviksgården养猪场沼气工程中增加余热回收,可将沼气净产气率从82%提高至90%。相对于提高容积产气率,采用余热回收技术对降低高温发酵沼气工程的增温能耗、提高净产气率效果更加显著。     

豆腐渣厌氧消化产沼气的试验研究

本试验以新鲜豆腐渣为沼气发酵原料,控制厌氧消化温度35±2℃的条件下,采用一次性投料,进行厌氧消化产沼气试验,结果表明:豆腐渣是良好的沼气发酵原料,通过分析消化系统pH值、挥发性脂肪酸(VFA)、日产气量和气体成分的变化可知,在投料比(渣泥质量比)为1∶5、1∶2、1∶1时消化系统的变化是一个正常的水解酸化过程,其单位产气率分别为0.87 L/g TS、1.43 L/g TS、0.93 L/g TS。其中投料比为1∶5的消化系统产生的甲烷含量最高可达81.03%,平均甲烷含量为49.95%。而投料比为2∶1、5∶1的消化系统均出现了酸抑制现象,系统不能顺利进入产甲烷阶段。     

微波预处理剩余污泥的研究进展

介绍了微波预处理污泥的作用机理及作用过程,包括污泥絮体破解、污泥细胞破碎及有机物的释放、有机物水解、美拉德反应等,总结了微波预处理污泥的作用效果（物理特性、化学特性、生物特性）、影响微波预处理效果的因素（污泥特性、处理条件）和微波预处理污泥对其后续厌氧消化的影响。指出了目前研究中存在的主要问题是试验规模偏小,预处理方式为间歇处理,在对污泥中有毒有害有机物和病原微生物的去除研究方面还需加强。提出今后应重点开展微波组合工艺对污泥中有毒有害有机物和病原微生物去除的基础研究,同时积极开发相关设备,开展微波预处理污泥的连续和中试研究,推动微波技术在污泥资源化、减量化和无害化处理中的应用。     

不同反应温度的城市生活垃圾厌氧发酵研究

通过对城市生活垃圾厌氧消化进行批量实验,研究了温度对厌氧消化过程的影响,探讨了不同消化温度对产气量、发酵启动时间、不同固含量的消化程度的影响以及温度突变对厌氧反应器产气量的影响,同时对温度的影响机理进行了初步探讨。实验结果表明,城市生活垃圾厌氧处理的较佳温度为55℃,消化程度比较彻底,沼气中的甲烷含量较高。     

水热耦合厌氧消化技术处理餐厨垃圾沼渣沼液及工艺能耗分析

以水热与厌氧消化耦合工艺作为餐厨垃圾沼渣沼液（digestate of food waste,DFW）的处理过程,探究了DFW处理前后的脱水性能及固、液两相产物的特性,分析了工艺过程中的物质流动、能量输入/输出,并评估了能量平衡的影响因素。结果表明,水热处理改善了DFW脱水性能,降低了脱水后的泥饼产量和含水率。温度是影响水热处理效果的主要因素,处理效果随温度的升高明显提升。当水热温度为200℃时,离心后泥饼的产量和含水率降低最为显著,分别从最初的71.83kg/t DFW和88.43%减小至22.11kg/t DFW和76.30%。此外,水热过程促进了DFW有机物质从固相向液相的转移,通过耦合厌氧消化处理工艺生产甲烷,可以有效地回收液相能量。本研究对整个处理工艺进行了全面的物质和能量衡算。水热处理温度的提高增加了加热能量的输入,但减少了后续热干化过程的能量输入,并增加了DFW液相产物的产甲烷潜力。当水热温度为160℃、保温时间为60min时,水热与厌氧消化耦合工艺净能量输入最少（30.75MJ/t DFW）,相比于不采用水热技术处理节省106.48MJ/t DFW。水热过程热能的回收率、脱水后泥饼的含水率、液相产物的产甲烷潜势是影响工艺过程能量净消耗的主要因素,是工艺优化的主要方向。     

餐厨垃圾厌氧消化技术研究进展

综合评述了厌氧消化技术研究进展。从脂肪及离子含量、温度、固含率及稀释率、接种物和接种量等方面对餐厨垃圾厌氧消化技术进行了介绍。     

PTA污水处理技术综述

系统总结了PTA污水的特点和目前PTA污水处理技术,重点介绍了几种PTA污水处理方法,并对PTA污水处理的发展趋势进行了展望。厌氧PTA污水处理技术朝着高级厌氧反应器方向发展。     

Anaerobic digestion of Aegean olive mill effluents with and without pretreatment

BACKGROUND: Olive oil production is an important economical activity in the Aegean region of Turkey. However, the effluents of the olive oil producing mills with their high organic loads and toxic compounds are causing serious environmental problems. The anaerobic biological treatment of olive mill wastewater (OMWW) using the treatment plants of the regional industries could be a method of choice and within the scope of this study floccular and granular sludges were investigated in batch mode for their success in the treatment of OMWW while producing biogas. The major limitation of this treatment is the inhibition of methanogenic bacteria by the phenolic compounds in OMWW. Thus an integrated solution was suggested in which a pre‐treatment step (dephenolization) was also introduced before biological step. RESULTS: The effluents of 27 olive mills out of 47 were found to have total phenolics (TP) less than 3 g L^?1 and could be treated anaerobically after simple dilution. The biogas production for the untreated OMWW was higher for floccular sludge than for the granular sludge (68.5 mL and 45.7 mL respectively). Combined pre‐treatment experiments, first coagulation with polyaluminum chloride, followed by flocculation with cationic polyelectrolyte and finally Fenton's oxidation, could remove 80% of TP and 95% of the total suspended solids. CONCLUSION: OMWW having TP values less than 3 g L^?1 can be treated anaerobically using floccular sludge after simple dilution and biogas can be produced. For OMWW samples having higher TP values pre‐treatment is necessary and the pre‐treatment given in this study may be used effectively. Copyright © 2010 Society of Chemical Industry