Microbial community dynamics in mesophilic anaerobic co-digestion of mixed waste

This paper identifies key components of the microbial community involved in the mesophilic anaerobic co-digestion (AD) of mixed waste at Rayong Biogas Plant, Thailand. The AD process is separated into three stages: front end treatment (FET); feed holding tank and the main anaerobic digester. The study examines how the microbial community structure was affected by the different stages and found that seeding the waste at the beginning of the process (FET) resulted in community stability. Also, co-digestion of mixed waste supported different bacterial and methanogenic pathways. Typically, acetoclastic methanogenesis was the major pathway catalysed by Methanosaeta but hydrogenotrophs were also supported. Finally, the three-stage AD process means that hydrolysis and acidogenesis is initiated prior to entering the main digester which helps improve the bioconversion efficiency. This paper demonstrates that both resource availability (different waste streams) and environmental factors are key drivers of microbial community dynamics in mesophilic, anaerobic co-digestion.     

不同有机废弃物改良新复垦耕地的综合效果评价

由废弃地整理复垦形成的耕地存在土壤有机质和有效养分低、土壤板结、微生物活性弱和土壤耕作性状不良等问题,快速、有效地提高土壤肥力质量是全面提升该类耕地质量和生产性能的重要组成部分.本文通过田间小区试验研究了城郊有机废弃物对新复垦耕地土壤培肥的综合效果,并比较了不同类型城郊有机废弃物在培育耕地质量方面的差异.试验设置了施用等量猪粪、鸡粪、水稻秸秆、蔬菜收获残留物、城市污泥、沼渣、猪粪/水稻秸秆堆肥、生活垃圾堆肥和对照（不施有机肥）9个处理（年用量30 t·hm^-2）,连续进行3年的定点试验.结果表明： 施用任何有机物对改善土壤肥力均有明显的作用.其中,提升土壤碳库管理指数以施用猪粪、鸡粪、猪粪/水稻秸秆堆肥、水稻秸秆和沼渣的效果最为显著;增加土壤水稳定性团聚体和降低土壤容重以施用猪粪/水稻秸秆堆肥和沼渣的效果最佳;施用污泥、猪粪/水稻秸秆堆肥和生活垃圾堆肥可增强土壤保蓄能力;施用猪粪、鸡粪和猪粪/水稻秸秆堆肥对增加土壤有效态养分的效果最为明显;各类有机物均显著提高了土壤微生物数量和酶活性.长期施用污泥、生活垃圾堆肥及畜禽粪存在着土壤重金属污染的风险,但短期施用对土壤环境质量影响不明显.总体上,对土壤肥力的改善效果由大至小依次为：猪粪/水稻秸秆堆肥>鸡粪>猪粪>沼渣>生活垃圾堆肥>水稻秸秆>城市污泥>蔬菜收获残留物;对土壤的相对污染程度由大至小为：城市污泥>生活垃圾堆肥>猪粪>鸡粪>沼渣>猪粪/水稻秸秆堆肥>蔬菜收获残留物>水稻秸秆.     

High rate algal pond operating strategies for urban wastewater nitrogen removal

Two experimental high rate algal ponds (HRAPs) (1.5m², 570 L per unit), each with a secondaryclarifier for algal biomass separation (0.025 m²,without recirculation), were fed with urban wastewaterfor a one-year period (June 1993 to July 1994). TheHRAPs were installed on the roof of the Department ofHydraulic, Coastal and Environmental Engineering ofthe Technical University of Catalonia, Barcelona,Spain (lat. 41^° 24 42 N; long. 2^° 742 E). Nitrogen removal efficiency and changes intotal nitrogen, total organic nitrogen,NH₄ ⁺-N, and oxidized nitrogen underdifferent hydraulic retention times (HRTs) werecompared. HRAP A was always operated at a higherHRT than HRAP B. Both HRAPs were subjected to thesame environmental conditions of solar radiation, airtemperature and influent water quality. Grab samplesof influent, effluent of the HRAP (mixed liquor) andfinal effluent from the clarifiers were taken once aweek. The annual average nitrogen removal was 73% forHRAP A, and 57% for HRAP B. Higher removal in HRAP Awas due to a lower inorganic nitrogen concentration inits effluent. Significant differences (p> 0.05) inthe relative proportions of nitrogen forms between thetwo HRAPs were observed only in autumn and winter.This was mainly because HRAP B did not achieve a highlevel of NH₄ ⁺-N removal by stripping andalgal uptake, as observed in HRAP A. NH₄ ⁺-Nstripping was the most important mechanism fornitrogen removal (mean efficiency of 47% and 32% inHRAP A and B, respectively) followed by algal uptake,and subsequent algal separation in the clarifiers(mean efficiency of 26% and 25% in HRAP A and Brespectively). The conclusion of this study is thatHRT determines both the nitrogen removal efficiencyand the distribution of nitrogen forms in the effluentof a HRAP. The nitrogen removal level can becontrolled through suitable HRT operating strategies.By operating at a HRT of 4 days in spring and summer,and 10 days in autumn and winter, nitrogenconcentration in the effluent of a HRAP system can bereduced to less than 15 mg L^-1 N.     

酒色着色菌利用产酸克雷伯氏菌发酵废液产氢

研究了酒色着色菌(Chromatium vinosum DSM185)利用产酸克雷伯氏菌（Klebsiella oxytoca HP1）发酵产氢废液进行光发酵和暗发酵产氢的可行性,以达到对产氢底物的充分利用和对产氢废液的进一步处理。研究结果表明C.vinosum可以利用K.oxytoca的发酵废液进行光发酵产氢和暗发酵产氢。C.vinosum发酵产氢后废液中残余还原糖和主要有机酸（丁酸）的含量明显降低,发酵产氢的最佳pH为6.5,添加0.1%(W/W)NH₄Cl能促进产氢。在光照条件下丁酸利用率可达54.38%,产氢量达36.97 mL/mg;在黑暗条件下丁酸利用率可达36.01%,产氢量达37.50mL/mg。     

添加厨余垃圾对剩余污泥厌氧消化产沼气过程的影响

为提高剩余污泥厌氧消化的沼气产量和甲烷含量,研究了厨余垃圾的不同添加量对剩余污泥厌氧消化性能的影响。结果表明,在35℃下,随着剩余污泥中厨余垃圾添加量的增加,厌氧消化系统中碳氮质量比（C／N）、胞外多聚物（EPS）等生理生化指标均有不同程度的改善。其中当剩余污泥与厨余垃圾质量比为2：1时,混合有机废弃物中沼气产量和甲烷含量均达到最大值,每克挥发性固体（VS）产生了156．56mL沼气,甲烷体积分数为67．52％,分别比剩余污泥单独厌氧消化时的产气量提高了5倍和1．5倍。     

The anaerobic filtration of dairy waste: Results of a pilot trial

Results are presented from a pilot scale (4·3 m³) upflow anaerobic filter for the treatment of the wastewater from ice-cream manufacture. The reactor was completely mixed by gas production but the solids or sludge held within the reactor were shown to be affected by the liquid velocities. The reactor was subject to a number of organic and hydraulic shocks and this reduced the consistency of COD removal. Daily loading rates varied from 0 to 18 kg COD/m³/day but with an average load of 5·5 kg/m³/day the mean COD removal was 70%. This was compared with previous work and shown to be a typical performance for an anaerobic filter. Alkalinity and carboxylic acid data are also presented and were within the normal, stable, operating range. Previous research on the anaerobic treatment of industrial effluents has shown alkalinity to be the most important factor controlling reliability.     

Anaerobic degradation of solid material: importance of initiation centers for methanogenesis, mixing intensity, and 2D distributed model

Batch anaerobic codigestion of municipal household solid waste (MHSW) and digested manure in mesophilic conditions was carried out. The different waste-to-biomass ratios and intensity of mixing were studied theoretically and experimentally. The experiments showed that when organic loading was high, intensive mixing resulted in acidification and failure of the process, while low mixing intensity was crucial for successful digestion. However, when loading was low, mixing intensity had no significant effect on the process. We hypothesized that mixing was preventing establishment of methanogenic zones in the reactor space. The methanogenic zones are important to withstand inhibition due to development of acids formed during acidogenesis. The 2D distributed models of symmetrical cylinder reactor are presented based on the hypothesis of the necessity of a minimum size of methanogenic zones that can propagate and establish a good methanogenic environment. The model showed that at high organic loading rate spatial separation of the initial methanogenic centers from active acidogenic areas is the key factor for efficient conversion of solids to methane. The initial level of methanogenic biomass in the initiation centers is a critical factor for the survival of these centers. At low mixing, most of the initiation methanogenic centers survive and expand over the reactor volume. However, at vigorous mixing the initial methanogenic centers are reduced in size, averaged over the reactor volume, and finally dissipate. Using fluorescence in situ hybridization, large irregular cocci of microorganisms were observed in the case with minimal mixing, while in the case with high stirring mainly dead cells were found.     

瘤胃微生物在有机废物处理中的应用研究

综述了瘤胃微生物在处理农业残余废物、城市有机垃圾和一些有毒物质方面的研究情况,并对影响其降解的环境条件、工艺条件和反应促进因素做了介绍,认为结合现代厌氧消化技术和瘤胃发酵技术,瘤胃微生物可以在有机废物处理中发挥较大作用.     

微生物菌剂对草坪植物高羊茅生长与土壤酶活性的影响

从生活垃圾堆肥中分离出放线菌、枯草芽孢杆菌和苏云金芽孢杆菌,通过形态学和染色鉴定,分别以微生物单菌剂施入到草坪土壤基质中,研究了几种微生物菌剂对高羊茅生长与土壤酶活性的影响。结果表明:3种微生物菌剂处理可以显著提高高羊茅株高、生物量和叶绿素含量(P0.01或P0.05),促进了高羊茅的生长。同时,施加不同的微生物菌剂对于土壤蔗糖酶、脲酶、过氧化氢酶、多酚氧化酶和过氧化物酶活性均有显著的增强作用,其中放线菌处理土壤脲酶和多酚氧化酶分别是对照的8.38倍和20.6倍。因此,从堆肥中得到的3种微生物菌剂均可有效提高土壤酶活性,改善植物根际微生态环境,提高了土壤肥力和养分的利用率,促进了草坪植物生长,改善草坪质量。该研究可为微生物菌剂在草坪建植体系中的应用提供依据。     

Chemical composition of fresh and composted urban waste

Chemical, spectroscopic (IR and NMR), and molecular characteristics of humus extracted from urban waste before and after compositing are reported. The main differences are in the contents of acidic groups and straight aliphatic chains which diminish in the composted material. In comparing humus characteristics of composted urban waste and soils, the only real difference was found in the elution curves on Sephadex G-100, where the ratio of 100,000 and 1,300 peaks was higher in the compost than in the soil curve. The finding suggests that this ratio is a parameter that could enable us, even if in a semiquantitative manner, to follow the humification process of the compost when its addition to the soil is not less than the autochthonous organic matter content.Research work supported by CNR, Italy, Special grant I.P.R.A.-Sub-project 1. Paper N. 1531.