Effect of four crop straws on transformation of organic matter during sewage sludge composting

A 45-d laboratory experiment was conducted to compare the effect of four crop straws on the transformations of organic matter （OM） during composting of sewage sludge. The four crop straws included rape straw, wheat straw, maize straw and rice straw. The following parameters such as temperature, OM, humic-like substances （HS）, fulvic-like acids （FA） and humic-like acids （HA） were determined. The degradation of OM and the formation of HS and HA could be described well by the first-order kinetic model, while the FA content fluctuated during composting. The maximal degradation rates of OM in the compost piles added with rape straw, wheat straw, maize straw and rice straw were 34.7, 46.9, 54.7 and 52.8%, respectively, and the final contents of HS were 118, 128, 141 and 134 g kg-1, respectively, while the humification indices were higher in the compost piles added with maize straw and wheat straw than in those with rice straw and rape straw. The results indicate that a higher hemicellulose content and a lower C/N ratio in crop straw can result in a higher rate of OM degradation and higher contents of HS, while a higher content of lignin can lead to a higher polymerization degree of humic substances in compost piles. The final compost piles added with maize straw has the highest contents of OM, total nitrogen and humus substance as well as the highest values of polymerization degree, while compost piles with rape straw have the highest potassium content and those with rice straw have the highest pH values.

Changes of Cu, Zn, and Cd speciation in sewage sludge during composting

The potential toxicity risks from heavy metals depend on their chemical speciation. The four stages of the Tessier sequential extraction method were employed to investigate changes in heavy metal speciation （Cu, Zn, and Cd） of sewage sludge during forced aeration composting, and then to identify whether the composting process would reduce or enhance their toxicities. Throughout the composting process, the exchangeable, carbonate-bound, Fe-Mn oxide-bound, and organic matter-bound fractions of Cu were converted to the residual Cu fraction. The organic matter-bound Cu fraction greatly contributed to this transformation. Residual Zn fraction was transformed to the Fe-Mn oxide-bound and organic matter-bound fractions after composting. The residual Zn fraction was a major contributor to the organic matter-bound Zn fraction. The availability of Cu and Zn was reduced by composting such that the risk of heavy metal toxicity decreased with prolonged treatment times. Additionally, attention should be paid to the increased availability of Cd in sewage sludge after composting treatment.

Changes of Cu, Zn, and Ni chemical speciation in sewage sludge co-composted with sodium sulfide and lime

A batch composting study was performed to evaluate the feasibility of co-composting sewage sludge with sodium sulfide and lime （SSL） mixture （Na2S/CaO= 1：1）, aiming at reducing the availability of heavy metals in the sludge compost. Sewage sludge with sawdust as a bulking agent was amended with SSL at 3% （w/w, dw）, and composted for 15 d in laboratory batch reactors. The four stages of the Tessier sequential extraction method was employed to investigate changes in heavy metal fractions of Cu, Zn, and Ni in sewage sludge composted with SSL. For all the three metals, the mobile fractions, such as, exchangeable and carbonate bound were mainly transformed into low availability fractions （organic matter and sulfide, Fe-Mn oxides bound and residual forms）, and the addition of SSL enhanced this transformation. Therefore, SSL is a suitable material to co-compost with sewage sludge to reduce the availability of heavy metals. According to the cabbage seed germination test, a SSL amendment of ≤3% （w/w, dw） is recommended to co-compost with sewage sludge.

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.

Evolution of Heavy Metal Speciation During a Large-scale Sewage Sludge Composting

The evolution of metal species during sludge composting in aerobic reactor has been widely investigated,but little is known in large scale.In this study,the transformations of heavy metals speciation(Zn,Cu,Pb and Cd)in the process of sludge composting were studied in a bunker.Physico-chemical parameters,such as pH,moisture content(MC),organic matter(OM),humic acids(HA)and fulvic acids(FA)contents,were determined to evaluate their impacts on the redistribution of Zn,Cu,Pb and Cd in sludge compost.During the composting process,the contents of Cu,Pb,Zn and Cd in oxidizable and residual forms increased,whereas the contents of the exchangeable Cu,Pb,Zn and Cd decreased,with a slight increase in the total heavy metal contents.The contents of Cu,Zn and Cd in carbonate form and the reducible Cu,Zn and Pb falled;however,the content of Pb in carbonate formed and the reducible Cd increased.The results indicated that heavy metals(Zn,Cu,Pb and Cd)in sewage sludge could be passivated during composting process.The heavy metals speciation in the compost correlated with the physico-chemical parameters.In addition,linear regression analysis indicated that the content of mobile Pb could predict the total content of Pb.The contents of the residue fraction for Pb,Zn and Cd were decreased,but those for Ni and Cr were increased;the Cu residue fraction was almost constant.The contents of the total mobile fractions(including fractions 1-4)for Zn and Pb were significantly increased,but the increase of those for Cu and Ni were not so remarkable.There were significant degrees of correlation between heavy metal fractions and changes of some selected parameters(for example,pH,composting temperature and OM content).Only the content of the total mobile fractions for Cu could be predictable from its total content.For the prediction of the total mobile fractions of Zn,Ni,Cd and Cr,the R2 value was significantly increased by the inclusion of other variables such as pH,temperature and OM content.

Ambient air temperature effects on the temperature of sewage sludge composting process

Using data obtained with a full-scale sewage sludge composting facility, this paper studied the effects of ambient air temperature on the composting temperature with varying volume ratios of sewage sludge and recycled compost to bulking agent. Two volume ratios were examined experimentally, 1 ： 0 ： 1 and 3 ： 1 ： 2. The results show that composting temperature was influenced by ambient air temperature and the influence was more significant when composting was in the temperature rising process： composting temperature changed 2.4-6.5℃ when ambient air temperature changed 13℃. On the other hand, the influence was not significant when composting was in the high-temperature and/or temperature falling process： composting temperature changed 0.75-1.3℃ when ambient air temperature changed 8-15℃. Hysteresis effect was observed in composting temperature＇s responses to ambient air temperature. When the ventilation capability of pile was excellent（at a volume ratio of 1：0：1）, the hysteresis time was short and ranging 1.1-1.2 h. On the contrary, when the proportion of added bulking agent was low, therefore less porosity in the substrate（at a volume ratio of 3：1：2）, the hysteresis time was IonQ and ranging 1.9-3.1 h.

Selecting and optimizing of the heavy metal inactivator in sewage sludge composting

In sewage sludge composting, adding ash from stove （FA20） inactivated active Cu effectively and the results were significantly better than control. For Zn, Mn, Pb and Cd, satisfying results was,achieved by adding ash from stove and phosphorite powder （FA20, PR10）, phosphorite powder and lime （PR15, CL10）, ash from stove and phosphorite powder （FA10, PR10）, and ash from stove and peat （FA20, PT 10）. Based on their effects of inactivating available forms of heavy metals, ash from stove, phosphorite powder and peat were supposed to be effective inactivators with optimum percentages of 20%, 15% and 10% （FA20, PR15, PT10）.

Biodegradation of triclosan and triclocarban in sewage sludge during composting under three ventilation strategies

Triclosan (TCS) and triclocarban (TCC) are widely used in home and personal care products as antimicrobial agents. After these products are used, TCS and TCC enter the terrestrial environment and pose a great risk to humans and animals. In this research, the biodegradation of TCS and TCC was investigated during sewage sludge composting with ventilation rates of 10& 92, and 79 m^3/min. TCS and TCC were mainly biodegraded in the mesophilic and thermophilic phases, and the biodegradation rates improved with an increase in ventilation. After sewage sludge was composted for 16 days with forced ventilation (108 m^3/min), the concentration of TCS decreased from 497.4 to 214.5 μg/kg, and the concentration of TCC decreased from 823.2 to 172.7 μg/kg. The biodegradation rates of TCS and TCC were 65.2% and 83.1%, respectively. However, after the sewage sludge was stacked for 16 days, the biodegradation rates of TCS and TCC were only 17.0% and 18.2%, respectively. The environmental risks of TCS and TCC in the sewage sludge piles significantly decreased after composting. In the sludge pile with a ventilation rate of 108 m/min, the RQ values of TCS and TCC decreased from 8.29 and 20.58 to 3.58 and 4.32 after composting for 16 days, respectively. There is still a high risk if the sludge compost is directly used as a culture substrate. Nevertheless, the environmental risk could be decreased distinctly if a reasonable quantity of sludge compost is applied to land to ensure an RQ of< 1 for TCS and TCC.

Sewage sludge composting simulation as carbon/nitrogen concentration change

Available composting models do not describe accurately the dynamics of composting processes.Difficulty in modeling composting processes is attributed mainly to the unpredicted change in process rate caused by change in activation energy value （E）.This article presented the results of an attempt made to utilize patterns of change in carbon,nitrogen and temperature profiles to model sewage sludge composting process as a multi-stage process.Results of controlled sewage sludge composting experiments were used in the study.All the experiments were carried out as batch experiments in a 300-liter Horizontal Drum Bioreactor （HDB）.Analysis of the profiles of carbon,nitrogen and temperature has indicated that there were clear patterns that could be used to develop simple models of the process,the initial C/N ratio was between 7–8 and the final C/N ratio of the compost in most experiments were found to be around 15.0,indicating the compost was fully matured and could be used safely for agricultural purpose.Electrical conductivity of composting material decreased from 1.83 to 1.67 dS/m,after a period,it increased gradually from 2.01 to 2.23 dS/m and remained at around 2.33 dS/m till the end of composting.It is found that change in the concentration of total carbon can reasonably be described by three constant process rate coefficients （k 1,k 2,k 3 ）.It is found that the process starts with a certain process rate coefficient （k 1 ） and continues until peak temperature is reached,then it reaches lower process （k 2 ） in the declining phase of the thermophilic stage,and finally it proceeds with a faster process rate （k 3 ） when maturation is reached.Change in the concentration of total nitrogen has shown to have the same patterns of change as carbon.

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.

长期大量施用污泥堆肥显著提升华北地区粮食作物产量和土壤碳汇效应

【目的】阐明长期不同用量质量达标的污泥堆肥配施化肥对华北地区冬小麦-夏玉米轮作体系作物产量,以及耕层土壤有机碳储量(SOCS)和全氮(TN)、全磷(TP)、全钾(TK)含量的影响,为污泥高效资源化利用及农业绿色可持续发展提供理论依据。【方法】于北京市昌平区,开展污泥堆肥(SW)与化肥配施定位试验(2008—2020年),种植制度为冬小麦-夏玉米轮作,试验设置5个处理:100%尿素(N)、50%WS+50%尿素(0.5SW+0.5N)、100%SW+50%尿素(SW+0.5N)、200%SW+50%尿素(2SW+0.5N)、400%SW+50%尿素(4SW+0.5N)处理。小麦、玉米收获后,调查籽粒和秸秆产量,0—20 cm土层土壤有机质和氮磷钾含量,并计算土壤固碳效率。【结果】随着污泥堆肥用量的增加,小麦和玉米籽粒和秸秆产量逐渐增加,与N处理相比,0.5SW+0.5N处理小麦、玉米籽粒和秸秆多年平均产量无显著差异,SW+0.5N、2SW+0.5N和4SW+0.5N处理下小麦籽粒产量分别增加了6.97%、14.88%和17.94%,玉米籽粒产量分别增加了8.43%、11.77%和15.38%。土壤中有机碳储量、全氮、全磷、全钾含量在0.5SW+0.5N、SW+0.5N、2SW+0.5N和4SW+0.5N处理下较N处理明显提升。同时,土壤中有机碳储量、全氮、全磷和全钾含量随污泥堆肥用量的增加而显著增加(P<0.05)。N、0.5SW+0.5N、SW+0.5N、2SW+0.5N和4SW+0.5N处理下,土壤全氮含量多年平均值分别为1.07、1.26、1.56、1.93和2.73 g/kg,全磷含量分别为1.19、1.67、2.37、3.27、4.11 g/kg,全钾含量分别为18.60、19.06、19.85、20.07、21.19 g/kg。【结论】与单施尿素相比,以质量达标的污泥堆肥替代50%尿素(0.5SW+0.5N)不会影响小麦、玉米籽粒和秸秆产量,而且可以提升土壤肥力。在尿素用量减半条件下,增加污泥堆肥用量可显著提高小麦、玉米籽粒产量和土壤肥力,特别是在污泥堆肥氮用量为尿素氮用量的4倍时,小麦和玉米可稳定增产15%~18%,并且由于高量污泥堆肥的长期施用极大地提升了土壤中有机碳、全氮、全磷和全钾的储量,保证了产量的可持续性和土壤的碳汇效应。

厌氧消化和好氧堆肥对城市污泥中新污染物的削减

城镇污水处理规模的扩大使得城市污泥的产生量增加,而药物及个人护理品(PPCPs)、生物性污染物、微塑料(MPs)和雌激素等新污染物在污泥中的检出率也呈增加趋势。污泥厌氧消化制沼气、好氧堆肥制土壤改良剂具有削减污染物、回收有价值组分、降低环境风险等多重功效,然而它们对新污染物的削减效果尚待考察。以上述4种新污染物为例,比较了它们在不同国家城市污泥中的存在状况,综述了厌氧消化、好氧堆肥、厌氧消化和好氧堆肥结合以及与物化措施联合对新污染物的削减情况及存在的问题。针对污泥中多种新污染物并存的状况,提出未来应开发针对多种新污染物的去除技术,同时强化新污染物削减机制的研究,以保障城市污泥的安全利用。

施用堆肥污泥对土壤肥力及植物生长的影响

土地利用有望成为市政污泥处置的主要途径。本研究以好氧堆肥的市政污泥为研究对象,通过田间试验,设置不同堆肥污泥施用量:0%、30%、50%、70%、100%(堆肥污泥与土壤体积配比),研究堆肥污泥施用对土壤肥力、植物生长以及土壤重金属含量的影响。结果表明:堆肥污泥施用未造成土壤酸碱化,土壤肥力等级由三级一般土壤提升为二级肥沃土壤,土壤主要营养组分含量随污泥施用量的增加均显著提高,其中堆肥污泥添加比例为50%时土壤有机质增加1.9倍、碱解氮增加3.0倍、有效磷增加9.5倍、速效钾增加3.7倍。堆肥污泥添加比例为50%时木春菊组长势最好,添加比例为30%时鼠尾草组和高羊茅&黑麦草组长势最佳,但是不同添加比例下早樱组生长并无显著差异。尽管施用堆肥污泥会导致试验区土壤重金属含量略有升高,但远低于《城镇污水处理厂污泥处置林地用泥质》(CJ/T 362-2011)所规定的污染物指标及其限值,未造成土壤重金属污染。本研究将为堆肥污泥的土地利用提供理论依据和数据支撑。

外源菌剂对餐厨垃圾和污泥联合堆肥酶活性及微生物的影响

以餐厨垃圾和污泥(质量比1∶1)混合物为底物,以不接种微生物为对照,以添加外源菌剂和腐熟堆肥为两个处理,研究外源菌剂对联合堆肥过程中酶活性和腐熟期微生物的影响。结果表明,外源菌剂可促进堆体升温并延长高温期,可显著提高纤维素酶、过氧化氢酶、脲酶、蛋白酶的活性,4种酶的峰值分别为377.294 U/g、83.107 mL/(g·h)、0.763 mg/(g·d)和147.411 U/g。采用高通量测序技术分析发现,添加外源菌剂降低了腐熟期细菌、真菌的群落多样性,但提高了真菌群落丰富度。门水平上,各堆体细菌和真菌的优势群落种类差异较小,仅相对丰度变化较大;属水平上,添加外源菌剂使堆体中优势细菌占比更均匀,优势真菌主要为土壤伊萨酵母菌(Issatchenkia)、念珠菌(Candida)、未分类真菌(Unclassified Fungi)等。采用FAPROTAX工具对细菌功能分组,各堆体相对丰度较高的功能菌以化能异养、有氧化能异养、硝酸盐还原等为主,然而添加外源菌剂和腐熟堆肥使芳香族化合物的降解功能菌相对丰度分别提高了8.0倍、7.4倍。

不同基质配比对孔雀草生长发育的影响

以草本花卉孔雀草为试材,采用盆栽试验方法研究了用污泥堆肥、菇渣和河沙配制成不同配比的栽培基质对孔雀草生长发育的影响。结果表明:5种基质配比的物理性状均优于CK(园土);污泥堆肥和菇渣可促进孔雀草的生长发育,以T1处理(污泥堆肥40%、菇渣40%、河沙20%)和T2处理(污泥堆肥50%、菇渣30%、河沙20%)的孔雀草营养生长最好,T2处理的开花性状最优,其单株花朵数是CK的189%,花朵直径达5.53 cm,单朵花期为17.32 d,观赏期长达115 d。综合考虑基质的物理性状、孔雀草的营养生长及开花情况,T2和T1处理是适合孔雀草生长发育的较优基质,用其栽培孔雀草时花朵大且花期长,观赏期也较长。

间歇通风对污泥好氧堆肥过程中腐殖质电子转移能力的影响

选取连续通风和间歇通风两种不同的供氧方式进行好氧堆肥,分析污泥堆肥腐殖质富里酸(FA)和胡敏酸(HA)光谱特征和还原容量不同时期的变化.结果表明:与连续通风处理相比,间歇通风处理促进了类蛋白质的分解和类腐殖质的形成,增加了电子转移能力;间歇通风FA的本底还原容量(NRC)、化学还原容量(CRC)提高了194.33,127.97μmol e-/(g C),HA的NRC、CRC提高了168.26,203.81μmol e-/(g C).相关性分析和主成分结果显示,C3、C4是FA电子转移能力主要控制因子,而SUVA254、SUVA280是HA的电子转移能力主要控制因子.

污泥堆肥部分替代化肥对铬污染耕地玉米生长的影响

为探索污泥堆肥在铬污染耕地上的资源化合理利用,本研究通过田间试验,设置了空白对照、常规施肥、单施污泥堆肥以及不同比例污泥堆肥替代化肥配施处理,并将其与有机肥替代化肥进行效果对比,从玉米生物量、铬吸收、土壤铬含量及其有效性等方面探讨污泥堆肥施用对作物生长和土壤铬累积的影响。结果表明:相比于对照,不同用量污泥堆肥均能促进玉米生长,显著提高玉米产量,增产范围为15.24%~36.65%,其中污泥堆肥替代20%化肥配施对玉米的增产效果最好,相较于常规施肥增产了7.16%。各替代化肥处理下玉米籽粒中重金属铬含量均低于《食品安全国家标准食品中污染物限量》(GB 2762—2022)中的限值,其中污泥堆肥30%替代化肥处理玉米籽粒降铬效果最好。污泥堆肥施用量在750~1 500 kg·hm^(-2)时玉米地上部分对铬的携出量大于污泥铬的携入量。当季施用污泥堆肥对土壤总铬含量无显著影响,且各替代化肥处理下土壤有效态铬含量相较对照降幅为5.59%~12.68%。施用污泥堆肥不会对作物产生盐害并且能够缓解土壤酸化、提高土壤有机质、全氮以及速效氮磷钾含量。综合来看,在铬污染耕地,污泥堆肥替代化肥施用不仅有利于提高玉米产量,还能显著降低籽粒铬含量,并且施用量为1 500 kg·hm^(-2)时即能保障玉米安全、高产,且不会对土壤造成富集铬的风险,并能有效提高土壤各养分指标。

添加剂对污泥堆肥过程中气体排放和酶活性的影响

针对市政污泥与秸秆混合在传统堆肥过程中温室气体排放量与氮损失量较高的问题,采用玉米秸秆生物炭(CSB)与煤矸石基沸石(ZL)联合堆肥,为减少堆肥过程中CH_(4)、NH_(3)、N_(2)O气体排放.将10%的CSB与0%、10%、20%、30%的ZL混合(百分比为添加剂与污泥秸秆混合物质量之比),同时,无添加剂作为对照组,结果表明,与对照组相比,CSB与ZL联合添加(记为10%CSB+ZL)显著提高了堆肥过程中温度和pH值,增加了堆肥有机质降解,且降解速率高于对照组和10%CSB处理.两种添加剂联合添加降低了堆肥过程中氮损失,10%CSB+10%ZL、10%CSB+20%ZL、10%CSB+30%ZL处理中CH_(4)、NH_(3)、N_(2)O累积排放量比对照组分别降低87.81%~90.87%、41.61%~57.45%、85.01%~94.92%,CO_(2)累积排放量比对照组提高55.45%~86.55%;同时,在堆肥过程中脱氢酶、蛋白酶、木聚糖酶、磷酸酶活性增强.生物炭作为膨松剂,提高堆肥孔隙率促进微生物生长和相关酶活性提高,煤矸石基沸石通过吸附减少气体排放,10%CSB+20%ZL处理通过减少堆肥过程中CH_(4)、NH_(3)、N_(2)O排放速率实现降低氮损失的效果最佳.

Nitrogen transformations during co-composting of herbal residues,spent mushrooms,and sludge

Sewage sludge composting is an important environmental measure. The reduction of nitrogen loss is a critical aim of compost maturation, and the addition of spent mushrooms (SMs) and herbal residues (HRs) may be helpful. To evaluate the nitrogen transformations during co-composting of sewage sludge, SMs, and HRs, windrows were constructed in a residual processing plant. Dewatered sewage sludge and sawdust were mixed with SMs and HRs at two proportions on a fresh weight basis, 3:1:1 (sewage sludge:sawdust:SMs or HRs) and 3:1:2 (sewage sludge:sawdust:SMs or HRs). The mixture was then composted for 40 d. Changes in the physicochemical charac- teristic of sewage sludge during composting were recorded and analyzed. Addition of SMs and HRs accelerated the temperature rise, mediating a quicker composting maturation time compared to control. The addition also resulted in lower nitrogen losses and higher nitrate nitrogen levels in the compost products. Among the windrows, SM and HR addition improved the nitrogen status. The total nitrogen (TN) and nitrogen losses for SM and HR treatments ranged from 22.45 to 24.99 g/kg and from 10.2% to 22.4% over the control values (18.66-21.57 g/kg and 40.5%-64.2%, respectively). The pile with the highest proportion of SMs (3:1:2 (sewage sludge:sawdust:SMs)) had the highest TN level and the lowest nitrogen loss. The germination index (GI) values for all samples at maturity were above 80%, demonstrating optimal maturity. The addition of SMs and HRs augments sewage composting.