Improving Compost Process Efficiency by Leachates Inoculation and Shredding of the Organic Fraction of Municipal Solid Waste at Bordo Poniente Composting Plant,Mexico City

Management of MSW(Municipal Solid Waste)is a major downside in most of the biggest cities.The composting of the organic fraction of MSW is one of the oldest and simplest ways of organic waste stabilization.It is a self-heating biological conversion that generates appropriate finished merchandise such as soil conditioner or fertilizers.Mexico City generates about 12,500 ton/day of MSW,44%of it is food scraps and yard trimmings which are the OFMSW(Organic Fraction of Municipal Solid Waste),2,500 ton/day of it is composted at the BPCP(Bordo Poniente Composting Plant)yielding 500 ton/day of compost.The purpose of this study was to evaluate three treatments to accelerate the composting process,so eventually the city could increase the amount of the OFMSW at BPCP.We compared three different treatments;one of them showed a significant reduction in time of the composting process(p≤0.05)i.e.,it took less time to reach the thermophilic stage,maturity and stabilization phases.Maturity was achieved at 35 days and 60 days to stabilize.We conclude that shredding the feedstock plus leachate inoculum addition at the beginning of the process,reduces the composting time in about 61%with respect to the time it takes at the BPCP,where lasted 90 days.

Release of volatile organic compounds during bio-drying of municipal solid waste

Three treatments were tested to investigate the release concentrations of volatile organic compounds （VOCs） during the bio-drying of municipal solid waste （MSW） by the aerobic and combined hydrolytic-aerobic processes.Results showed that VOCs were largely released in the first 4 days of bio-drying and the dominant components were：dimethyl disulfide,dimethyl sulfide,benzene,2-butanone,limonene and methylene chloride.Thus,the combined hydrolytic-aerobic process was suggested for MSW bio-drying due to fewer aeration quantities in this phase when compared with the aerobic process,and the treatment strategies should base on the key properties of these prominent components.Malodorous sulfur compounds and terpenes were mainly released in the early phase of bio-drying,whereas,two peaks of release concentrations appeared for aromatics and ketones during bio-drying.Notably,for the combined hydrolytic-aerobic processes there were also high concentrations of released aromatics in the shift from hydrolytic to aerobic stages.High concentrations of released chlorinateds were observed in the later phase.For the VOCs produced during MSW bio-drying,i.e.,malodorous sulfur compounds,terpenes and chlorinateds,their release concentrations were mainly determined by production rates;for the VOCs presented initially in MSW,such as aromatics,their transfer and transport in MSW mainly determined the release concentrations.

Influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste

A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste (MOSW). Heating failure was simulated by decreasing temperature suddenly from 55 °C to 20 °C suddenly; 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/(L·d) and 15 d respectively for MOSW load and retention time, following results were noted: (1) biogas production almost stopped and VFA (volatile fatty acid) accumulated rapidly, accompanied by pH decrease; (2) with low temperature (20 °C) duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation; (3) the longer the low temperature interval lasted, the more the methanogenic bacteria would decay; hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation; (4) the thermophilic microorganisms were highly resilient to temperature fluctuation.

Characterisation of Municipal Solid Waste Compost (MSWC) from Selected Indian Cities—A Case Study for Its Sustainable Utilisation

Utilisation of Municipal Solid Waste is important to curb the ever rising demand of scarce land for its disposal. Changing life style patterns, particularly in urban areas, has led to increase in generation of MSW. Municipal solid waste from Indian cities estimated to have 40% - 60% organic matter, which could be recycled as compost. The most suitable way to recycle it with low investment is aerobic composting using windrow method. With the compliance of Municipal Solid Waste (Management and Handling) Rules 2000, many cities in India are making compost with organic portion of MSW. Before applying MSWC for agricultural uses, it is important to inventories heavy metals in compost to assess its toxicity. In the present study the compost samples were quantified for its toxicity from three highly populated cities of India, i.e., Delhi (Capital of India), Ahmedabad (Gujarat) and Bangalore (Karnataka). The MSWC samples were analysed for total heavy metals and in extractable fractions. Few samples were found with higher concentration of metals then the prescribed limits for its application as compost in Indian MSW rules, whereas, samples have not showed significant heavy metals concentration in extractable fractions. Therefore, studied MSW compost samples had demonstrated its suitability to use as green compost.

The Use of Organic Waste as an Eco-Efficient Energy Source in Ghana

The problem of municipal solid waste (MSW) management has been an issue of global concern in recent times and has engaged governments and local authorities in their quest to manage solid waste in a sustained manner. One proposition which has the potential of solving three problems at the same time is the use of the biodegradable component of MSW as a source of energy to augment energy supply. This research therefore assessed the use of the organic fraction of MSW as an eco-efficient energy source in Ghana. A study of Ghana’s solid waste profile was undertaken and the fraction of biodegradable component was found to be approximately 60%, with a heating value of 17 MJ/kg and a moisture content of 50%. Moreover, it was established that 0.5 kg of solid waste is generated daily by each Ghanaian, meaning that about 5610 tons of the organic fraction could be made available every day to generate energy to the national grid. It was also established that waste disposal in Ghana is largely by way of open dumping as primary collection of waste from households in Ghana is limited to high-income communities which represent only 11% of the population, whereas secondary collection from transfer points to the disposal facilities is inefficient. With representative power output of 1.66 MWh/tonne a total of 3320 GWh of energy can be produced annually from the 4 proposed plants, generating net revenue of about $111,600,000. As an optimizing step, a waste incineration scheme was suggested in which the off-gases produced from organic waste combustion could be used to produce electrical power with steam in a multi-stage heat exchanger-steam turbine configuration, and the off gases again used for pre-drying of the organic waste in a cycle. A state-of-the art waste incineration technology was used as a model and adapted to suit Ghana’s tropical conditions. MSW combustion releases less CO2 for the same power output (837 Ib/MWh) than any of the other conventional fuels do, and is therefore a good fuel for the fight against climate change.

Method for C/N ratio estimation using Mask R-CNN and a depth camera for organic fraction of municipal solid wastes

Fast assessment of the initial carbon to nitrogen ratio(C/N)of organic fraction of municipal solid waste(OFMSW)is an important prerequisite for automatic composting control to improve efficiency and stability of the bioconversion process.In this study,a novel approach was proposed to estimate the C/N of OFMSW,where an instance segmentation model was applied to predict the masks for the waste images.Then,by combining the instance segmentation model with the depth-camera-based volume calculation algorithm,the volumes occupied by each type of waste were obtained,therefore the C/N could be estimated based on the properties of each type of waste.First,an instance segmentation dataset including three common classes of OFMSW was built to train mask region-based convolutional neural networks(Mask R-CNN)model.Second,a volume measurement algorithm was proposed,where the measurement result of the object was derived by accumulating the volumes of small rectangular cuboids whose bottom area was calculated with the projection property.Then the calculated volume was corrected with linear regression models.The results showed that the trained instance segmentation model performed well with average precision scores AP_(50)=82.9,AP_(75)=72.5,and mask intersection over unit(Mask IoU)=45.1.A high correlation was found between the estimated C/N and the ground truth with a coefficient of determination R2=0.97 and root mean square error RMSE=0.10.The relative average error was 0.42%and the maximum error was only 1.71%,which indicated this approach has potential for practical applications.

Cr(Ⅵ) reduction capability of humic acid extracted from the organic component of municipal solid waste

The capacity of humic acid extracted from organic waste （HAw） to reduce Cr（Ⅵ） was tested at pH 2.5,4 and 6 and compared with coal-derived humic acid （HAc）.HAw was more effective than HAc in reducing Cr（Ⅵ）.The kinetics of Cr（Ⅵ） reductions depended strongly on pH.The calculation of the apparent rate coefficients indicated that HAw was more efficient at reducing Cr（Ⅵ） than HAc,but was also more efficient than HAs from soil and peat.The reduction capability of HAs depends on the type of functional groups （i.e.,thiols and phenols） present,rather than the free radicals.HAw was more efficient at reducing Cr（Ⅵ） than HAc because more reactive phenols were present,i.e.,methoxy-and methyl-phenols.

Effective incineration technology with a new-type rotary waste incinerator

The technology of steady combustion in a new type of rotary incinerator is firstly discussed. The formation and control of HCl,NOx and SO_(2) during the incineration of sampled municipal organic solid waste are studied with the incinerator. Results showed that the new model of rotary incinerator can effectively control and reduce the pollutant formations by post combustion.

VOCs released from municipal solid waste at the initial decomposition stage: Emission characteristics and an odor impact assessment

The nuisance from odor caused by municipal solid waste(MSW) is resulting in a growing number of public complaints and concerns. Odor pollution occurs in the initial decomposition stage of MSW, including waste collection, transportation and early pre-treatment. Furthermore, decomposition takes place in waste facilities that are often close to living areas, which can result in odor impacts on local inhabitants. However, this aspect of odor impact from MSW has not been well studied. In the current study, lab-scale waste cells were designed to simulate MSW storage conditions in the early stage. The characteristics of VOCs emissions with different waste compositions were analyzed. The odor concentration( CO, non-dimensional) method and odor intensity were used for the assessment of odor. Ethanol was the substance with highest emission rate. The release rate of VOCs increased with the growth easily biodegradable waste(EBW). VOCs emissions was reduced by 25% when the proportion of EBW decreased from 60% to 45%. Methyl sulfide, ethanol, dimethyl disulfide and ethyl acetate were identified as typical odorants. The EBW proportion in waste is the main factor significantly influencing odor pollution. The CO was 244.51 for the 60% EBW condition, which was only 61.46 for 15% EBW condition. These study results provide important information for the implementation of a garbage sorting policy and the monitoring of odor pollution from waste management.

生活垃圾填埋场黄土覆盖层的甲烷氧化能力现场测试和评估

采用静态箱和激光甲烷检测仪等设备开展了50组地表甲烷通量测试,分析了不同龄期垃圾堆体上部土质覆盖层的甲烷氧化能力,并修正了评估现场土质覆盖层甲烷氧化速率和甲烷氧化率的计算方法.结果表明:80%测试点的地表甲烷通量低于澳大利亚CFI(澳洲碳农业倡议)规定限值60g/(m^(2)·d),导气竖井附近20m范围内存在甲烷通量超过CFI规定的排放热点.填埋龄期3~7a堆体的地表甲烷通量从1.13g/(m^(2)·d)下降到0.53g/(m^(2)·d),7~10a的地表甲烷通量基本保持稳定.甲烷氧化速率和覆盖层底部甲烷通量具有正相关性,现场测得的土质覆盖层最高甲烷氧化速率为63.30g/(m^(2)·d),对应的底部甲烷通量为75.95g/(m^(2)·d).每一龄期堆体上部黄土覆盖层的平均甲烷氧化率均超过90%.

填埋场地下水溶解性有机物时空分布特征分析:以四川红层区某生活垃圾填埋场为例

溶解性有机物(DOM)是生活垃圾填埋场地下水的主要污染物之一,但红层区填埋场地下水中DOM的特征尚不明晰.因此,为了探究红层区填埋场地下水中DOM组成及时空分布特征,本文运用三维荧光光谱技术,对我国典型红层区某生活垃圾填埋场地下水进行现场调研,结果表明:①调查区域地下水导排层监测井(DP17)、污染扩散监测井(KS2~KS6)和水产源监测井(SC8)地下水中COD_(Mn)的Psi(表示i评价指标相对于GB/T 14848—2017《地下水质量标准》Ⅲ类值的污染指数)介于1.323~5.392之间,水产源监测井(SC8)地下水中Mn^(2+)的Psi为1.140,所有监测井地下水中TN、TP、Fe、Cd、Hg和Cr的Psi介于0.001~0.587之间,其浓度均未超过GB/T 14848—2017《地下水质量标准》Ⅲ类标准限值;但相对于背景井(BJ1),各污染物的Pbi(表示i评价指标相对于背景值的污染指数)均介于0.703~142.991之间,说明调查区已受到不同污染源的影响.②填埋场渗滤液及附近地下水中DOM包括类胡敏酸(C1)和类富里酸(C2)等腐殖质类物质,以及类色氨酸(C3)蛋白质类物质.③填埋场地下水中DOM污染主要集中在填埋场附近,对周围地下水无明显影响.④地下水中DOM的腐殖化程度在丰水期[平均HIX(腐殖化指数)为3.99]和枯水期(平均HIX为10.69)具有显著性差异.⑤地下水导排层监测井中类胡敏酸(C1)和类富里酸(C2)的荧光强度分别是其他污染源的3.1~11.9倍和1.9~8.3倍,可作为填埋场地下水DOM污染的指示性指标.研究显示,调查区填埋场渗滤液及地下水有机质腐殖化程度高,对地下水的影响只局限在填埋场附近,对周围地下水未造成严重影响,填埋场趋于稳定.

城市固废焚烧过程数据驱动建模与自组织控制

城市固废焚烧(Municipal solid waste incineration,MSWI)是处置城市固废(Municipal solid waste,MSW)的主要手段之一.中国MSW来源范围广、组分复杂、热值波动大,其焚烧过程通常依靠人工干预,这导致MSWI过程智能化水平较低且难以满足日益提升的控制需求.MSWI具有多变量耦合、工况漂移等诸多不确定性特征,因而难以建立其被控对象模型并设计在线控制器.针对以上问题,提出了一种面向MSWI过程的数据驱动建模与自组织控制方法.首先,构建了基于多输入多输出Takagi Sugeno模糊神经网络(Multi-input multi-output Takagi Sugeno fuzzy neural network,MIMO-TSFNN)的被控对象模型;然后,设计了基于多任务学习的自组织模糊神经网络控制器(Multi-task learning selforganizing fuzzy neural network controller,MTL-SOFNNC)用于同步控制炉膛温度与烟气含氧量,其通过计算神经元的相似度与多任务学习(Multi-task learning,MTL)能力对控制器结构进行自组织调整;接着,通过Lyapunov定理对MTLSOFNNC稳定性进行了证明;最后,通过北京市某MSWI厂的过程数据验证了模型与控制器的有效性.

填埋场陈腐垃圾物化性质及资源化利用——以四川某中龄期填埋场为例

生活垃圾填埋场中的陈腐垃圾具有丰富的资源,而我国垃圾填埋量已超数十亿吨。将四川某12 a填埋龄垃圾与浙江某30 a填埋龄垃圾的物化性质进行对比研究,发现中龄期垃圾填埋场陈腐垃圾已具有稳定性,原始垃圾特征已消失,在物质组成上主要是部分大颗粒无机物和轻质可燃物及颗粒较小的腐殖土。其中,筛分后产生的轻质可燃物可焚烧发电或制造燃料,腐殖土可用于园林和废弃矿山等绿地绿化。

城市生活垃圾外源微生物堆肥对有机酸变化及堆肥腐熟度的影响

利用外源微生物(美商复合菌,MS;中加发酵菌,ZJ)进行城市生活垃圾工厂化堆肥,在堆肥过程中,分析了小分子有机酸及大分子腐殖酸动态变化.结果表明,接种外源微生物可明显提高堆肥前期小分子有机酸含量,在堆肥后期又呈明显的降低趋势.而腐殖酸与胡敏酸则呈现先降低而后增加的趋势.通过对堆肥过程中有机酸、腐殖化指数分析表明,接种外源微生物可明显提高堆肥的腐熟度,并且ZJ发酵菌优于MS复合菌,而2种外源菌混合接种具有协同促进作用.

城市生活有机垃圾各组分的厌氧消化产甲烷能力

通过生化产甲烷能力(BMP)测定实验确定了葡萄糖、大米、蔬菜、纸张、动物油、植物油和瘦肉等7种城市生活有机垃圾(BOFMSW)组分的生化产甲烷能力,并研究了抑制动物油、植物油和瘦肉厌氧消化过程的影响因素.实验结果表明,葡萄糖、大米、蔬菜和纸张在发酵过程中没有消化抑制发生,4种原料的生化产甲烷能力分别为241、210、147和244mL.g-1,相应地占理论产甲烷能力的64.5%、56.3%、32.6%和67.9%.瘦肉的厌氧消化过程停止产气后,消化液的总挥发性脂肪酸(VFAs)浓度为15800mg·mL-1,其中丙酸浓度为2509mg·mL-1;消化液中氨氮浓度为13892mg·mL-1;较高的VFAs和氨氮浓度共同作用形成消化过程的"抑制型稳态",抑制了产甲烷菌的产甲烷代谢,导致酸化率较高而生物气转化率却很低.猪油和花生油等脂类原料的厌氧消化,由于水解和酸化细菌受到长链脂肪酸(LCFAs)的抑制而影响了原料的降解和酸化,酸化率仅分别为11.5%和10.0%.

UASB反应器处理城镇有机垃圾浸出液的研究

采用UASB反应器处理城镇有机垃圾经两相厌氧消化产生的浸出液.在水温为28～35℃时,采用处理城镇有机垃圾的单级厌氧消化反应器的消化污泥进行接种,38 d内便完成了UASB反应器的启动.在运行期间,当进水COD为10 100～11100mg/L、负荷为8.5～9.5kgCOD/（m^3·d）时,对COD的去除率为88%～95%,出水COD浓度为575～1 609 mg/L;UASB系统运行稳定,具有较强的酸、碱缓冲能力,未出现氨氮与脂肪酸的积累和抑制现象;产气量为0.19～0.44L/gCOD,CH4含量可达75%以上,具有较高的利用价值.

城市有机生活垃圾厌氧发酵处理研究

在适当的PH值和搅拌条件下,研究了反应温度、总固体含量、pH值、碳氮比、碳磷比以及接种物量对有机生活垃圾厌氧发酵产沼气的影响。实验结果表明:有机生活垃圾厌氧消化产沼气的适宜条件是:反应温度50～55℃,总固体含量23%～28%,pH=6.8～7.4,w(C)/w(N)=(20～30),w(C)/w(P)=50,接种物量为25%～30%。在厌氧的条件下,可以制取含甲烷60%～75%的生物气,可实现能量回收;发酵剩余物可制有机肥,实现物质再利用。有机生活垃圾在厌氧消化反应器的停留时间为15～20d。

生活垃圾堆肥过程中腐殖质及有机态氮组分的变化

利用实际城市生活垃圾,采用工厂化工艺进行堆肥试验,探讨在堆肥过程中腐殖质及有机态氮组分的动态变化.结果表明,随着堆肥的进行,有机碳、富里酸、全氮、酸水解性有机氮含量均有不同程度的降低,与堆肥前相比,降低幅度分别为53.00%、64.73%、21.78%、22.80%.而腐殖质、胡敏酸、氨基酸态氮则分别在堆肥的第35d达到最低点,而后呈逐渐增加的趋势.酰胺态氮、氨基糖态氮在堆肥的第21d达到最高峰.堆肥过程中,腐殖质与胡敏酸、酸水解有机态氮与全氮含量显著相关.胡敏酸的红外光谱分析结果表明,堆肥后胡敏酸分子的芳构化程度明显增强.

利用热等离子体熔融垃圾焚烧飞灰

为了评价垃圾焚烧飞灰的热等离子体熔融处理效果,研究SiO2和CaO对重金属固化效果和重金属毒性浸出特性的影响.在飞灰中添加一定比例的SiO2和CaO,配置成不同的配灰样品,利用纯氩热等离子体在1 400～1 500℃下,对飞灰及配灰进行熔融玻璃化的实验研究,分别利用X射线能量色散谱仪(EDX)、场发射扫描电子显微镜(FSEM)、X射线衍射仪(XRD)和毒性浸出方法(TCLP)分析飞灰和熔渣的化学组成、微观结构、晶相组成和重金属毒性浸出特性.结果表明,热等离子体熔融所得熔渣为无定形的玻璃体,重金属浸出质量浓度均远低于毒性标准.SiO2和CaO的添加都可以改善重金属固化效果,CaO比SiO2对Cu、Zn、Cd和Pb挥发的抑制效果更好.SiO2的添加可以改善熔渣中重金属的浸出特性,而CaO的作用与之相反.