The Hydrochar Characters of Municipal Sewage Sludge Under Different Hydrothermal Temperatures and Durations

Innovative measure is a urgent requirement for managing the huge volume of municipal sewage sludge. The hydrothermal carbonation(HTC) shows some potential advantages for using hydrochar as a soil conditioner. The aim of this work was to investigate the properties of hydrochars, by means of the HTC of municipal sewage sludge under different temperatures(190 and 260°C) and reaction hours(1, 6, 12, 18 and 24 h). The HTC led to the decreases of N, O and H contents by more than 54.6, 37.9 and 10.0%, respectively, and slight changes of C content. The Py-GC-MS analysis showed that a large proportion of fatty acids, in particular hexadecanoic acid, transferred into alkenes, olefins and aromatic compounds. The 13C-NMR and fourier transform infrared spectra(FTIR) confirmed the transformation and changes in chemical structure in which hydrochar contained lower oxygen-containing organic C of O-alkyl, carboxylic and carbonyl C and aliphaticity, but higher aromatic C and aromaticity. The rich hydrophobic functions induced in high positive charges in the charred sludge. The HTC facilitated the pore structure development, proved by higher specific surface area and specific pore volume, with a maximum of 17.30 and 0.83 cm3 g-1, respectively. The availabilities of N, P and K markedly reduced during HTC treatment. The activities of most heavy metals were depressed though they accumulated in the hydrochar. Further work is required to investigate the values and risk of the charred sludge amended to soil.

Static aerobic composting of municipal sewage sludge with forced ventilation:Using matured compost as bulking conditioner

Static aerobic composting of municipal sewage sludge with forced ventilation or air ventilation using matured compost as bulking conditioner was investigated.Physical and chemical parameters,e.g.,temperature,moisture content,VSS,CODcr,pH,and germination index(GI),were analyzed to characterize the composting process.Fermentation starts quickly in both forced and air ventilation compost heaps and reaches high-temperature stage after 2 d,owing to the bulking function of matured compost.Compared to air ventilation,however,forced ventilation enables the high-temperature stage to last longer for approximately 7 d.The moisture content of both compost bodies decreases from 62% to about 50% as a result of evaporation,and it decreases slightly faster in forced ventilation compost heap after 13 d due to the higher temperature and better ventilation condition.Although no obvious differences of VSS and pH are observed between both compost heaps,the soluble CODCr and GI show differences during the second half period of fermentation.In forced ventilation compost,the soluble CODCr has a small rebound after 13 d,and GI decreases from 46% to 35% but then increases.These results show that in general,the matured compost is a good conditioner and force ventilation with a proper air supply strategy can be more efficient than air ventilation.

Effects of Municipal Sewage Sludge on Fixation of Cr,Ni,Cu,and Zn during Co-processing of Heavy Metal-containing Waste in Cement Kilns

Cement raw meal with MSS and different heavy metals was blended to examine the fixation ratios, chemical species, and cement crystalline phases in clinkers. The results showed that blending MSS could decrease the fixation ratio of Cr, Ni, Cu, and Zn in the produced clinker by 5% to 25%. And Cr, Cu, and Zn were mainly incorporated into clinkers as metal silicates, Ni was mainly solubilized in Mg O to form magnesium nickel oxides, and the transition phases were mainly metal aluminum oxides as indicated by X-ray diffraction. The reduction of fixation ratios was likely attributed to the presence of impure elements, such as sodium and phosphorus in MSS. In addition, high concentrations(eg, 1.7 wt%) of chlorine in MSS led to metal chloride formation that could vaporize Cu, Cr, Ni, and Zn. To summarize, introducing MSS would decrease the fixation ratios of heavy metals due to the presence of impure elements, such as sodium and phosphorus and chlorine.

Development of a novel modified EGSB reactor for municipal sewage treatment at ambient temperatures

A novel modified expanded granular sludge bed(EGSBm) reactor was developed for anaerobic treatment of municipal sewage with mixed liquid recirculation instead of effluent recirculation commonly adopted by a conventional EGSB(EGSBc) reactor.Performances of these two reactors were compared in treating municipal sewage at ambient temperatures ranging from 8 to 26 ℃.At an upflow liquid velocity(Vup) of 10.3 m/h,the mean concentrations of filtrated COD(CODfilt) and COD of the EGSBm effluent were determined to be 59.4 and 95.9 mg/L,respectively,which were significantly lower than those of the EGSBc effluent operated under identical experimental conditions.When the organic loading rate was suddenly increased from 1.2 to 7.2 kg COD/(m3·d),the EGSBm regained the removal efficiency of previous operation phase in 10 d.Hydrodynamic characteristics of the reactors were compared using the residence time distribution(RTD) model.It was found that the treatment efficiency of EGSBm kept increasing as the Vup increased.The polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis(PCR-DGGE) technique was used to analyze the microbial diversity in EGSBm.Fingerprinting pattern indicated that some species in the inoculating sludge were still reserved in the granular sludge of EGSBm,moreover,several new species occurred.

Kinetics of municipal sewage degradation in EGSB and UASB reactors at 10 ℃

Kinetics of municipal sewage degradation in Expanded Granular Sludge Bed(EGSB)and Up-flow Anaerobic Sludge Blanket(UASB)reactors at 10℃ were investigated via continuous experimental equipments.The results indicated that the whole reaction process can be simulated by the first-order dynamic equation model.Dynamic parameters such as k,Vmax and Ks of UASB in hydrolysis acidification stage were 1.08 d-1,2.8 d-1 and 372 mg/L comparing to those of 1.18 d-1,3.5 d-1 and 112 mg/L in the methanogenesis stage respectively.The EGSB's k,Vmax and Ks were 2.91 d-1,14.3 d-1 and 470 mg/L in the hydrolysis acidification stage comparing to those of 1.68 d-1,6.6 d-1 and 103 mg/L in the methanogenesis stage respectively.Comparison of k values of the two stages in UASB and EGSB indicates that hydrolysis acidification stage is the controlling step for the whole reaction process of UASB,while methanogenesis stage is the controlling step in EGSB.Compared with UASB,municipal sewage treatment by EGSB at 10 ℃ can reach the same effluent requirement with lower retention time due to its effluent recirculation.

Influence of dissolved organic matter on methylmercury transformation during aerobic composting of municipal sewage sludge under different C/N ratios

Current knowledge about the transformation of total mercury and methylmercury(Me Hg) in aerobic composting process is limited. In this study, the composition and transformation of mercury and dissovled organic matter(DOM) in aerobic composting process of municipal sewage sludge were were comprehensively characterized, and the differences among the three C/N ratio(20, 26 and 30) were investigated. The main form of mercury in C/N 20 and 26 was organo-chelated Hg(F3, 46%-60%);while the main form of mercury in C/N 30 was mercuric sulfide(F5, 64%-70%). The main component of DOM in C/N 20 and 26 were tyrosine-like substance(C1, 53%-76%) while the main fractions in C/N 30 were tyrosine-like substance(C1, 28%-37%) and fulvic-like substance(C2, 17%-39%). The mercury and DOM varied significantly during the 9 days composting process. Compared to C/N 20 and 26, C/N 30 produced the less Me Hg after aerobic composting process, with values of 658%(C/N 20), 1400%(C/N 26) and 139%(C/N 30) of the initial, respectively. Meanwhile, C/N 30 produced the best compost showed greater degree of DOM molecular condensation and humification. Hg fraction had been altered by DOM, as indicated by a significant correlation between mercury species and DOM components. Notably, C/N 30 should be used as an appropriate C/N ratio to control the methylation processes of mercury and degration of DOM.

Sewage sludge ditch for recovering heavy metals can improve crop yield and soil environmental quality

The treatment and disposal of municipal sewage sludge(MSS)is an urgent problem to be resolved in many countries.Safely using the nutrients within MSS to increase crop yield and enhance the fertility of poor soil could contribute to achieving sustainable development.An indirect use of MSS in ditches alongside Pennisetum hybridum plants was studied in field plots for 30 months and the contents of heavy metals and macronutrients were monitored in soil,sludge and plant samples.We found that the yield of P.hybridum was significantly increased by 2.39 to 2.80 times and the treated plants had higher N content compared with no sludge.In addition,the organic matter(OM)and N contents in the planted soil increased significantly compared with the initial soil.The OM content in the planted soil of the MSS treatment was 2.9 to 5.2 times higher than that with no sludge,and N increased by 2.0 to 3.8 times.However,MSS had no significant effect on the N,P and K contents in the soil at the bottom of the MSS ditch,and the content of heavy metals(Cd,Pb,Cu and Zn)were also within the safe range.Moreover,the moisture content and phytotoxicity of MSS after this indirect use were reduced and the heavy metal contents changed little,which is favorable to the further disposal of recovered MSS.Therefore,this indirect use of MSS is beneficial to agricultural production,soil quality and environmental sustainability.

市政污泥热化学处置中磷元素形态转变与回收利用研究进展

我国市政污泥产量即将突破9000万吨,无害化、减量化和资源化处置非常迫切。干污泥中磷元素含量占2%~6%,回收磷资源的潜力巨大,其可以减少有限磷矿的消耗,缓解全球磷危机。本文从污泥处置技术、脱水污泥中磷元素含量与形态、热化学(热解、焚烧、气化和水热炭化)处理中磷元素形态转变、污泥灰/炭中磷元素回收方法和含磷矿物的植物可吸收性五个方面对污泥中磷资源回收与利用展开论述,详细对比分析了温度、添加剂成分、掺混燃料种类等因素对热处理产物中磷元素形态的影响。最后,归纳分析了热处理产物中磷元素的回收工艺和不同因素的影响以及含磷矿物的植物可吸收性,以期为我国未来污泥资源化利用提供参考。

“双碳”背景下市政污泥热解资源化利用研究进展

随着我国对污泥处理的环保要求越来越严格,热解作为一种新兴的污泥无害化资源化处理技术,得到了越来越多的关注。本文分析了我国市政污泥的基本特性,总结了国内外市政污泥热解技术的研究进展,阐述了污泥热解技术的基本原理及主要影响因素、热解产物特性和资源化利用途径,并对比分析了不同类型的污泥热解装置,指出了污泥热解资源化利用的进一步发展方向,以期为我国市政污泥高值资源化处置提供参考和思路。

市政污泥的高温热解处理及产物特性研究

针对我国市政污泥资源化处理处置的发展需求,本文针对市政污泥的高温热解处理及其热解产物特性开展实验研究。通过分析不同来源的市政污泥的水分、可燃分和灰分以及热失重特性,发现不同的预脱水工艺对市政污泥中有机组分含量影响较为明显。而通过污泥高温(600~900℃)热解实验,发现热解温度对于三相产物产率、热解气组分的影响显著,且产物中热解气富含高附加值的合成气(占比达到60.5%~81.5%),表明市政污泥高温热解处理具有较好的资源化技术优势。

污泥焚烧灰免烧轻质骨料性能及重金属固化效果研究

焚烧技术能有效减少城市污泥(以下简称污泥)的有机污染物、细菌含量和污泥体积等,污泥焚烧后产生的污泥焚烧灰(SSA)大多采用填埋的方式处理,给生态环境和土地资源利用带来严峻挑战。以碱性激发剂制备SSA免烧轻质骨料(以下简称骨料),并探究了矿渣掺量对骨料物理力学性能的影响规律。结果表明:骨料的粒径主要集中在4.75~9.50 mm;骨料的密度等级和筒压强度分别介于700~900与1.86~4.20 MPa,符合《结构性轻骨料混凝土指南》(ACI-213R-03)和《轻集料及其试验方法第1部分:轻集料》(GB/T 17431.1—2010)要求;扫描电子显微镜(SEM)、能量弥散X射线分析仪(EDS)、X射线衍射仪(XRD)、全自动压汞仪(MIP)和电感耦合等离子体发射光谱仪(ICP-OES)测试结果表明,矿渣发生地质聚合反应生成的地质聚合物凝胶能包裹SSA颗粒,并相互黏结形成球状颗粒骨料,增加矿渣掺量能有效减少骨料中的有害孔隙,达到增强骨料结构致密性的效果;SSA中的离子态Mn浸出值超出了非危险固体废弃物排放限值(3 mg/L),而骨料中的重金属离子浸出值均满足要求。上述研究成果能为SSA的资源化高效利用提供新途径。

生物炭基质人工湿地处理生活污水效能的实验研究

为考察生物炭基质对人工湿地处理污水效果的影响,建立了以沸石、白云石、市政污泥生物炭为基质的三种人工湿地装置,测试各组人工湿地对生活污水中COD、BOD_(5)、NH^(+)_(4)-N、TN和TP的去除情况,考察其运行效能,并分析不同基质不同高度下的各组人工湿地微生物量差异、微生物群落及相对丰富度。结果表明:以剩余污泥为原料制备的生物炭基质构建人工湿地对生活污水的处理效果优于沸石和白云石基质人工湿地;生物炭基质人工湿地对COD、BOD_(5)、NH^(+)_(4)-N、TN和TP的去除率分别为(82.3±3.3)%、(87.3±0.9)%、(69.9±1.7)%、(64.5±1.2)%和(52.3±0.5)%;经微生物群落分析发现,Aeromonons Pseudomonos、Nitrobacter和Denitrobacter菌群是基质中分别负责有机物、氨氮和总氮去除的三类菌群。

某水质净化厂水质异常溯源调查

针对某水质净化厂长期以来污泥中重金属含量较高的情况,相关部门开展了重金属污染溯源调查。对水质净化厂服务片区范围的企业废水、生活污水、沟道污泥开展定点取样和监测分析。通过分析数据真实地反应出了各源头排口重金属含量,摸清了重金属污染来源。不但可以为公司下属的水质净化厂提质增效工作提供数据支撑和决策依据,还能为上游企业外排水是否合规排放提供判断依据,为公司污泥处置“减量化、稳定化、无害化、资源化”创造条件。

城市污泥农用资源化研究进展

污泥农用具有投资少、能耗低、运行费用低等优点,正在成为世界上各国主要的污泥处置方式,为此综述了城市污泥农用资源化方式的应用特点和发展状况,并通过对目前污泥农用资源化的方法进行分析和比较,认为超富集植物和低累积作物/富钾植物进行套种处理城市污泥同时进行农用资源化利用具有明显的优势,将为城市污泥的处理处置提供新的思路。

城市污水厂污泥快速好氧堆肥技术研究

以污泥静态堆肥工艺为基础,针对上海曲阳污水处理厂的脱水污泥进行动态好氧堆肥处理工艺研究,重点研究了控制参数和评价参数(温度、含水率、pH、水溶性有机碳和发芽指数等)变化规律.结果表明:污泥堆肥过程中,含水率、物料温度、水溶性有机碳、发芽指数等指标变化规律性强,效果指示性明显,均可选作堆肥腐熟度的表征参数或评价参数.在优化工艺条件下,通过添加适量的木屑和回流物料,控制物料初始含水率在60%±2%时,堆肥处理可以实现顺利升温并在>55℃维持4d,100%杀灭了病原菌;14d反应周期结束时,物料含水率显著降低,水溶性有机质降解50%左右,出料松散且无臭味,堆肥产品腐熟,卫生学指标达到了我国标准和美国EPA污泥产品A类标准.

利用皇竹草处理城市污泥生产植物产品

利用大生物量植物——皇竹草(Pennisetum hydridum),处理城市污泥高效生产有用的植物产品。通过小型田间试验,采用根兜分株移栽和直接扦插方式种植皇竹草,比较土壤、新鲜污泥、土壤+新鲜污泥等体积混合、植物处理后的污泥4种介质的适应性,测定了皇竹草的成活率和生长状况,以及污泥自身性质的变化;通过盆栽试验及田间试验进一步探讨育苗后移栽在新鲜污泥上的可行性。结果表明,新鲜污泥上直接扦插的皇竹草无一存活,即使是根兜分株移栽其成活率也仅为16.67%,生长较差。而对于土壤+污泥混合物或植物处理后的污泥,采用直接扦插方式,皇竹草的成活率也分别达58.33%、75.00%,两个月干草产量达22.20、19.80 t/hm2,为土壤上的5.11、4.55倍。皇竹草吸收K较明显,3个有污泥的处理皇竹草K含量接近40 g/kg干重,N、P2O5、K2O的总含量大于70 g/kg,可作为有机K肥原料;皇竹草重金属Cu、Zn、Pb、Cd含量均符合国家饲料卫生标准(GB 13078—2001),作为饲料是安全的。盆栽试验及田间试验表明,采用育苗后移栽的方式,皇竹草在新鲜污泥上的成活率达66.67%以上。因此,城市污泥直接种植皇竹草可以实现资源化利用。

城市污泥和煤混燃特性的热重分析法研究

利用热重分析法对某城市污泥和某煤种及其两者混合物的着火温度、活化能及综合燃烧特性等参数进行了研究。试验结果表明 ,混合试样和煤相比其活化性能得到了提高 ,着火温度提前 ,综合燃烧性能下降。在混燃过程中 ,煤和城市污泥基本上保持了各自的挥发分析出特性 ,煤的燃烧表现得更为明显。

城市污泥资源化利用现状及发展探讨

随着城市污泥产量连年增长,污泥处理问题迫在眉睫。由于用地日益紧张和潜在的环境污染问题,传统的处置方法如填埋已经不符合发展要求。作为污水处理厂的伴生产物,污泥含有大量有机物、氮、磷等营养物质,经过适当处理,可以变废为宝。因此,资源化利用是解决污泥问题的主要发展趋势。通过分析国内外城市污泥的处置现状,对污泥资源化技术进行了分类,并就污泥在土地利用、建材利用、能源利用和其他方面的应用进行了详细综述,同时还分析了资源化利用存在的问题,指出污泥资源化利用和发展需要因地制宜、合理开发,需要继续提高工艺水平,推进技术创新,完善政策法规。