Effects of moisture content and initial pH in composting process on heavy metal removal characteristics of grass clipping compost used for stormwater filtration

Heavy metals are common contaminants in stormwater runoff. One of the devices that can be used to effectively and economically remove heavy metals from runoff is a yard waste compost stormwater filter. The primary goal of composting is to reduce waste volume rather than to produce stormwater filter media. Moisture content (MC) and initial pH, the two important parameters in composting, were studied for their effects on yard waste volume reduction and heavy metal adsorption performances of the compost. The main objective of this investigation was to examine whether the conditions that provided high yard waste volume reduction would also result in compost with good heavy metal removal performances. Manila grass was composted at different initial pHs (5–9) and MCs (30–70%) and the composts were used to adsorb cadmium, copper, lead and zinc from water. Results indicated that MC is more critical than initial pH for both volume reduction and production of compost with high metal adsorption performances. The most optimal conditions for the two attributes were not exactly the same but lower MCs of 30–40% and pH 7 or higher tended to satisfy both high volume reduction and effective metal adsorption.     

Heavy metal fractionation during the co-composting of biosolids,deinking paper fibre and green waste

Due to the introduction of the European Union Landfill Directive, composting has become a potentially viable disposal route for some organic wastes. As waste-derived compost is frequently added to soil to improve soil quality, it is important to quantify the environmental risk posed by potentially toxic elements contained within it. Here we used a sequential chemical extraction procedure to investigate the temporal dynamics of heavy metals (Cu, Zn, Pb and Ni) during the co-composting of biosolids, deinking paper fibre and green waste. Overall, composting over 26 weeks reduced the availability of Ni, had no effect on Pb and slightly increased the availability of Cu and Zn. We conclude that although the total Cu and Ni concentrations in the compost exceed legislative guidelines for land application, due to their recalcitrant nature within the compost, this compost posed very little threat to soil or plant quality if used in agriculture or land restoration.     

Effect of carbide sludge (lime) on bioavailability and leachability of heavy metals during rotary drum composting of water hyacinth

Abstract

The bioavailability and leachability of heavy metals play a major role in the toxicity of heavy metals in the compost applied for soil conditioning. A rotary drum composter was used for the study of heavy metal bioavailability and leachability during water hyacinth composting with a mixture of cattle manure, sawdust and lime. Lime was added in 1, 2 and 3% to the mixture of water hyacinth, cattle manure and sawdust at a ratio of 6:3:1 respectively. Influences of physico-chemical parameters on heavy metal bioavailability and leachability were studied during the process. The bioavailability of heavy metals solubility and diethylene triamine penta-acetic acid extractability was examined. The toxicity characteristics leaching procedure (TCLP) test was performed for assessing the hazardous properties of compost. The nutrients and the total concentration of heavy metals were increased during the composting process. The lime was very effective in reducing water solubility, plant availability and leachability of the selected heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during the process. The addition of lime provided a buffer against the decrease in pH and a sufficient amount of Ca that would improve the metabolic activity during composting. The addition of an excess amount of lime slowed the metabolic activity of the microbes due to its high alkalinity. The TCLP test confirms that the heavy metals concentrations in the control and in the lime-amended compost were below the threshold limits.     

Critical evaluation of municipal solid waste composting and potential compost markets

Mechanical biological treatment (MBT) of mixed waste streams is becoming increasingly popular as a method for treating municipal solid waste (MSW). Whilst this process can separate many recyclates from mixed waste, the resultant organic residue can contain high levels of heavy metals and physical and biological contaminants. This review assesses the potential end uses and sustainable markets for this organic residue. Critical evaluation reveals that the best option for using this organic resource is in land remediation and restoration schemes. For example, application of MSW-derived composts at acidic heavy metal contaminated sites has ameliorated soil pollution with minimal risk. We conclude that although MSW-derived composts are of low value, they still represent a valuable resource particularly for use in post-industrial environments. A holistic view should be taken when regulating the use of such composts, taking into account the specific situation of application and the environmental pitfalls of alternative disposal routes.     

Evaluating heavy metal contents in nine composts using four digestion methods

The production and application of compost potentially contaminate the environment with heavy metals. The heavy metal contents of composts must be exactly determined. Therefore, this study aims to understand the heavy metal contents in composts, using different digestion methods and to recommend the most appropriate digestion method making this measurement. Nine composts from different sources, including swine manure, poultry litter, food waste, municipal sewage sludge, soybean meal, wood residues, flesh-bone dust, fish-bone meal and guano, were selected to be digested by four methods to determine the contents of Cd, Cr, Cu, Mn, Ni, Pb and Zn by AAS. The four digestion methods were nitric acid, dry ashing, nitric-perchloric acid and sulfuric acid methods. Analytical results indicated that the nitric acid procedure was the most efficient for recovering Cd, Mn and Ni from most compost samples. The sulfuric acid procedure yielded the lowest recovery of Pb from the certified reference material (BCR 146) and the compost samples, especially from the composts with high pH and EC values potentially high in Ca. The nitric acid procedure was recommended as the method for digesting the composts herein, based on recovery analysis, cost and time taken. Dry ashing was recommended as a flexible method. Nitric-perchloric acid procedure was not recommended because perchloric acid is potentially hazardous during digestion and it recovers relatively little heavy metal.     

Composting of bio-waste, aerobic and anaerobic sludges--effect of feedstock on the process and quality of compost

In-vessel composting of three stocks with originally different degree of organic matter degradation was conducted for: (1) kitchen source-separated bio-waste (BW), (2) aerobic (AS) as well as (3) anaerobic sludges (AnS) from municipal wastewater treatment plant. Composting experiment lasted over a year. The highest activity of the process was in the BW compost. It was implied by the highest temperature, CO(2) release, ammonification and nitrification, intensive accumulation and removal of low-weight carboxylic acids (water- and NaOH-extractable). Between the sludges higher mineralization and CO2 release was in AnS, while ammonification and nitrification were higher in AS compost; no significant difference between sludge composts was noticed for dynamics of pH, conductivity, concentrations of LWCA, and some nutrient compounds and heavy metals. Nitrogen content of the final compost increased in BW, but decreased in AS and AnS. Phytotoxicity of Lepidium sativum was eliminated faster in sludge composts compared to BW compost.     

Ash in composting of source-separated catering waste

Our earlier experiments in small composters (220 l) indicated the favourable effect of ash from co-incineration of sorted dry waste on the composting of catering waste. The aim of this new study was to clarify further, at a scale of 10 m3, the feasibility of using similar ash as an additive in composting. Source-separated catering waste was mixed with bulking agent (peat and wood chips) and fuel ash from a small (4 MW) district heating power plant. Three compost mixes (CM) were obtained: CM I with 0%, CM II with 10% and CM III with 20 wt.% of fuel ash. These three different mixes were composted in a 10-m3 drum composter as three parallel experiments for 2 weeks each, from January to April 2000. After drum composting, masses were placed according to mixing proportions in separate curing piles. The catering waste fed to the drum was cold, sometimes icy. Even then the temperature rapidly increased to over 50 degrees C. In CM III, the temperature rose as high as 80 degrees C, and after the first week of composting the temperature was about 20 degrees C higher in the CMs II and III than in the CM I. It also improved the oxygen concentrations at the feeding end of the drum and obviously prevented the formation of H2S. No odour problems arose during the composting. Addition of ash increased the heavy metal contents of the composting masses, but the compost was suitable for cultivation or green area construction. Ash clearly decreased the loss of total nitrogen in a time span of 2 years. The lower amounts of nitrogen mean that the amounts applied per hectare can be greater than for normal composts. Measured by mineralization, the breaking down of the organic matter was more rapid in the CM III than in the CM I. Humic acid increased steadily during first 12 months composting, from the initial 39 mg/g organic matter to 115 and 137 mg/g in CMs II and III. Measured by temperature, mineralization and humification the addition of ash appeared to boost the composting. Ash had also other beneficial effects on composting it improved the availability of oxygen in compost mass during the drum composting phase and reduced the formation of odorous gases, especially H2S.     

好氧高温猪粪堆肥中重金属砷、铜、锌的形态变化及钝化剂的影响

采用连续提取法研究了猪粪好氧堆肥处理中重金属浓度和形态的变化以及添加不同比例的重金属钝化剂对其浓度和形态的影响.结果表明：经过堆肥处理后,猪粪中重金属As、Cu和Zn的总浓度均有所增加.从重金属结合形态的变化来看,可交换态As和Zn含量降低,残渣态As和Zn含量升高,表明As和Zn存在着向有效性相对较低的形态转化的趋势;重金属Cu则表现出不同的变化趋势,即可交换态与残渣态Cu含量下降,而碳酸盐结合态、铁锰结合态及有机结合态Cu含量有所增加,在今后的堆肥利用中应注意其可能带来的环境风险;3种重金属钝化剂及不同添加比例的处理中,5.0%的海泡石和2.5%的膨润土分别对重金属As、Zn表现出较好的钝化效果,堆肥后残渣态As和Zn的增幅分别达到79.8%和158.6%,均高于不加钝化剂处理.与对照相比,堆肥后7.5%的海泡石对残渣态Cu的降低幅度最小,为39.3%.猪粪堆肥中添加适量的重金属钝化剂,可以在一定程度上降低重金属的有效性以及猪粪堆肥利用中重金属污染的风险.     

堆肥对土壤重金属垂直分布的影响与污染评价

对不同畜禽粪便堆肥与土壤重金属垂直分布的关系进行了研究．结果表明,在畜禽粪便堆肥过程中,粪堆下土壤pH值和有机质显著增加,其pH和有机质含量的垂直分布表现为从表层到底层逐渐降低．各种畜禽粪便粪堆下土壤Zn、Cd含量明显增高,且从表层到底层呈逐渐减小的趋势．鸡粪和猪粪堆下土壤Cu含量随土层深度增加而降低;牛粪堆下土壤Cu含量随土层深度增加没有明显的变化．自然条件下Cd和Zn在土壤系统中的迁移能力大于Cu．各粪堆下的部分土层Cu、Zn、Cd含量超过我国土壤环境质量一级标准．应用地质积累指数法对各土层污染评价的结果表明,只有肉鸡粪堆下0～10cm土壤和蛋鸡粪堆下0～40cm土壤受到轻度Zn污染,其它粪堆下各土层均未受到Cu、Zn、Pb和Cd污染．     

Low pH as an inhibiting factor in the transition from mesophilic to thermophilic phase in composting

During composting of household waste, the acidity of the material affects the process during the initial phase of rising temperature. In this study, the effects of temperature (36-46 degrees C) and pH (4.6-9.2) on the respiration rate during the early phase of composting were investigated in two different composts. A respiration method where small compost samples were incubated at constant temperature was used. The respiration rate was strongly reduced at 46 degrees C and pH below 6, compared to composts with a higher pH or lower temperature. The combination of high temperature and low pH is a possible adverse factor in large-scale composting of food waste.     

Effect of the raw materials and mixing ratio of composted wastes on the dynamic of organic matter stabilization and nitrogen availability in composts of Sub-Saharan Africa

The effect of raw materials and their proportions in initial mixtures on organic matter (OM) stabilization and nitrogen (N) availability during pit composting in Sub-Saharan Africa was assessed using biochemical fractionation and laboratory incubations to characterize composts sampled throughout the composting process. Stabilization of OM occurred more rapidly in mixtures with slaughter-house wastes, it was progressive in mixture with household refuses while tree leaves compost remained unstable. Carbon mineralization from compost samples was positively correlated to water soluble and hemicellulose-like organic fractions. Mixtures containing large proportions of household refuses reached the highest stability and total N but available N remained weak. Slaughter-house wastes in the initial mixtures made possible to reach good OM stabilization and the largest N availability. The nature of initial mixing influenced composting parameters, OM stabilization and N availability. It is suggested mixing household refuses and slaughter-house wastes with tree leaves to reach better amending and fertilizer qualities of composts.     

Microbial diversity and activity are increased by compost amendment of metal-contaminated soil

Unlike organic pollutants, heavy metals cannot be degraded and can constitute a persistent environmental hazard. Here, we investigated the success of different remediation strategies in promoting microbial diversity and function with depth in an acidic soil heavily contaminated with Cu, Pb and Zn. Remediation involved the incorporation of either a high- or a low-quality compost or inorganic fertilizer into the topsoil and monitoring of microbial activity and diversity with soil depth over a 4-month period. While changes in topsoil microbial activity were expected, the possible effects on the subsurface microbial community due to the downward movement of metals, nutrients and/or soluble organic matter have not been examined previously. The results showed that both compost additions, especially the low-quality compost, resulted in significantly increased bacterial and fungal diversity (as assessed by terminal restriction fragment length polymorphism) and activity compared with the inorganic and control treatments in the topsoil. Although phospholipid fatty acid profiling indicated that compost addition had promoted enhanced microbial diversity in the subsoil, no concomitant increase in subsoil microbial activity was observed, suggesting that amelioration of the heavy metals remained localized in the topsoil. We conclude that although composts can successfully immobilize heavy metals and promote ecosystem diversity/function, surface incorporation had little remedial effect below the surface layer over the course of our short-term trial.     

Microbial Properties of Composts That Suppress Damping-Off and Root Rot of Creeping Bentgrass Caused by Pythium graminicola

Composts prepared from a variety of feedstocks were tested for their ability to suppress seedling and root diseases of creeping bentgrass caused by Pythium graminicola. Among the most suppressive materials in laboratory experiments were different batches of a brewery sludge compost and a biosolids compost from Endicott, N.Y. Batches of these composts that were initially not suppressive to Pythium damping-off became more suppressive with increasing compost age. Leaf, yard waste, food, and spent mushroom composts as well as certain biosolids, cow manure, chicken-cow manure, and leaf-chicken manure composts were not suppressive to Pythium damping-off. In some cases, turkey litter, chicken manure, chicken-leaf, and food waste composts were inhibitory to creeping bentgrass seed germination in laboratory experiments. Microbial populations varied among all of the composts tested. Bacterial populations were high in all composts except the turkey litter compost, in which populations were 1,000- to 10,000-fold lower than in the other composts tested. Among the highest populations of heterotrophic fungi and antibiotic-producing actinomycetes were those found in all batches of the brewery sludge compost, whereas the lowest populations were found in turkey litter, chicken manure, and food waste composts. Heat treatment of suppressive composts reduced populations of bacteria, fungi, and actinomycetes in all composts tested. Disease suppressiveness was also reduced or eliminated in heated composts. Amending heated composts with small amounts of nonheated compost restored suppressive properties and partially restored microbial populations to wild-type levels. A strong negative relationship between compost microbial activity (as measured by the hydrolysis of fluorescein diacetate) and Pythium damping-off severity was observed. When composts were applied to creeping bentgrass in field experiments, a significant level of suppressiveness was evident with some composts when disease pressure was high (i.e., disease ratings high in uninoculated plots). A 1991 batch of turkey litter compost and the 1990 batch of Endicott biosolids were consistently suppressive to foliar symptoms of Pythium root rot on creeping bentgrass. This study indicates that suppression of Pythium diseases of creeping bentgrass in batches of brewery sludge and Endicott biosolids composts, and possibly in other suppressive composts examined in less detail in this study, is related directly to the microbial activities in the composts. On the other hand, the mechanisms of Pythium suppression in turkey litter and perhaps other poultry-based composts is not related directly to the compost microbial activity. Although turkey litter showed a lack of suppressiveness in laboratory bioassays and low microbial populations and activity, it resulted in a significant and consistent level of suppressiveness in field experiments. Therefore, the microbiological properties of Pythium-suppressive composts may differ substantially, and measurements of microbial populations and activity may not be predictive of the level of disease suppression in all composts.     

Heavy metal bioavailability in a soil affected by mineral sulphides contamination following the mine spillage at Aznalcóllar (Spain)

A field experiment, lasting 14 months, was carried out in order to assess the effect of organic amendment and lime addition on the bioavailability of heavy metals in contaminated soils. The experiment took place in a soil affected by acid, highly toxic pyritic waste from the Aznalcóllar mine (Seville, Spain) in April 1998. The following treatments were applied (3 plots per treatment): cow manure, a mature compost, lime (to plots having pH < 4), and control without amendment. During the study two crops of Brassica juncea were grown, with two additions of each organic amendment. Throughout the study, the evolution of soil pH, total and available (DTPA-extractable) heavy metals content (Zn, Cu, Mn, Fe, Pb and Cd), electrical conductivity (EC), soluble sulphates and plant growth and heavy metal uptake were followed. The study indicates that: (1) soil acidification, due to the oxidation of metallic sulphides in the soil, increased heavy metal bioavailability; (2) liming succeeded in controlling the soil acidification; and (3) the organic materials generally promoted fixation of heavy metals in non-available soil fractions, with Cu bioavailability being particularly affected by the organic treatments.     

烟草废弃物在堆肥领域的研究进展

在烟草生产及加工过程中,通常会产生大量的烟草废弃物,如何有效利用这些废弃物以避免环境污染和资源浪费,已成为烟草行业亟需解决的问解。研究发现,烟草废弃物堆肥化处理是规模化利用废弃资源的有效途径之一,对烟草农业的绿色、低碳、循环、可持续发展具有重要意义。从有机肥堆肥制备技术、肥效研究等方面进行了系统综述,从整体上展示了烟草废弃物堆肥技术的发展现状,以期为国内烟草废弃物源堆肥未来技术的研发及产业化提供一定的参考。通过分析发现,在堆肥制备技术方面,主要有微生物菌剂添加技术、共堆肥技术和烟草材料预处理技术3种,此外还衍生出液态有机肥和厌氧发酵联产有机肥技术;在堆肥肥效研究方面,烟草废弃物堆肥可明显改善土壤的物性参数、化学参数以及生物学参数,显著钝化土壤重金属元素,进而提高作物的产量或品质,其中堆肥与化学肥料配施的效果相对较好;堆肥的多功能化是未来堆肥创新利用的重要途径。     

Effect of chitin waste-based composts produced by two-phase composting on two oomycete plant pathogens

Biphasic composts were prepared by first mixing peat moss and sawdust with a nitrogen-rich biomass such as chitinous waste or cow manure and composting them until termination of the thermophilic phase. These partially stabilized composts were then amended with shrimp waste inducing a second thermophilic phase. Filter-sterilized water extracts obtained from two mature biphasic composts (SP₂W₂+S and MPW+S) reduced the growth of two oomycete plant pathogens, Phytophthora fragariae var. rubi and Pythium ultimum. Both SP₂W₂+S and MPW+S composts significantly reduce the incidence of cucumber damping-off caused by Pythium ultimum as compared to a commercial brand of compost made from shrimp waste and peat moss. Hydrolysis products of chitin were unlikely to be responsible for growth inhibition since no oligomeric forms of chitin were detected in SP₂W₂+S. The shrimp waste amendment carried out after the first thermophilic phase modified the microbial populations of biphasic composts. Following the amendment, the proportion of branched-chain microbial fatty acids typical of Gram-positive bacteria increased considerably suggesting that this group of bacteria became more prevalent within the total microbial population. These data suggests that the two-phase composting process promotes the proliferation of Gram-positive bacteria antagonistic to oomycete plant pathogens.     

Factors influencing chemical quality of composted poultry waste

The need for organic recycling is justified in the case of poultry waste because after ensuring hygienization there is a chance of obtaining a compost with substantial fertilizer value. Organic recycling of slaughter waste has its justification in sustainable development and retardation of resources. In the research being described, composting of hydrated poultry slaughterhouse waste with maize straw was carried out. Combinations with fodder yeast and postcellulose lime were also introduced in order to modify chemical and physicochemical properties of the mixtures. The experiment was carried out within 110 days in 1.2 × 1.0 × 0.8 m laboratory reactors. Temperature of the biomass was recorded during composting, and the biomass was actively aerated through a perforated bottom.Composting of substrates selected in such a way caused losses of some elements in gaseous form, an increase in concentration of other elements, and changes in relationships between elements. The ability to select substrates influences compost quality. This ability is determined by chemical indicators. Among other things, compost evaluation based on carbon to nitrogen ratio shows the intensity of the composting process and possible nitrogen losses. The addition of slaughter waste to maize straw reduced the content of individual fractions of carbon in the composts, whereas the addition of postcellulose lime intensified that process. The addition of fodder yeast significantly increased the phosphorus content in the compost. Since iron compounds were used in the processing of poultry carcasses, composts that were based on this material had an elevated iron content. The applied postcellulose lime significantly increased the copper, zinc, chromium, nickel, and lead contents. Proper selection of substrates for composting of hydrated poultry slaughterhouse waste allows to obtain a compost with chemical properties that create favorable conditions for natural application of that compost. Addition of large quantities of postcellulose lime to the composting process leads to obtaining an organic-mineral substratum for cultivation or to obtaining an agent that improves soil properties.     

湿度对堆肥理化性质的影响

水分是堆肥微生物生命活动的基础 ,也是堆肥中重要的工艺控制参数。弄清湿度对堆肥微生物及理化性质的影响 ,对于优化堆肥工艺参数、提高堆肥效率、降低投资和运行成本具有重要意义。综述了堆肥湿度研究的动态 ,指出了当前研究中存在的问题 ,并提出了未来的研究方向。大量的研究表明 ,湿度低于 4 5 %或高于 6 5 %都不利于堆肥处理。湿度太高会导致堆料的压实度增加、FAS减少、透气性能降低 ,从而导致堆体内氧气供应不足、堆肥升温困难、有机物降解速率降低、堆肥周期延长。湿度过低 ,水分会限制堆肥微生物的新陈代谢 ,导致微生物活性下降、堆肥腐熟困难。由于鼓风、散热、水蒸发等会使堆体内存在湿度的空间变异 ,也会降低堆肥效率和堆肥产品的质量。另外 ,堆肥湿度还影响堆肥的保肥能力。由各文献得出结论 ,堆肥的最佳湿度范围一般为 5 0 %～ 6 0 %左右     

Enhancing the co-composting of olive mill wastes and sewage sludge by the addition of an industrial waste

In this work, the effect of incorporating an acidic ferrous sulphate waste (SF) over co-composting process of sewage sludge and olive mill solid wastes in a 1:2 v/v wet basis was investigated. The SF used was an industrial by-product of titanium oxide synthesis and its addition resulted in a chemical stabilisation of the wastes at low pH. The optimum dose of SF to enhance the composting of the studied biowastes was a 20% v/v (wet basis) and the best moment for the addition turned out to be whenever the composting piles had achieved the thermophilic range. The addition of SF over the composting process made possible a faster stabilisation, increasing the composting rate from 0.033 to 0.13 d(-1), and leading to a Fe and S rich compost. All composts obtained fulfilled the limits determined by current European and Spanish regulations and presented better characteristics for its use as soil amendment and organic fertilizer than the traditional composts without SF. The optimum dose of compost containing SF was determined through agronomic tests being its value about 18 Ton ha(-1).     

Long-term survival of pathogenic and sanitation indicator bacteria in experimental biowaste composts

For economic, agricultural, and environmental reasons, composting is frequently used for organic waste recycling. One approach to limiting the potential risk from bacterial food-borne illnesses is to ensure that soil amendments and organic fertilizers are disinfected. However, more knowledge concerning the microbiological safety of composted substrates other than sludge and manure is necessary. Experimental in-vessel biowaste composts were used to study the survival of seeded Listeria monocytogenes, Salmonella enterica subsp. enterica serotype Enteritidis, and Escherichia coli. Four organic waste mixtures, containing various proportions of paper and cardboard, fruits and vegetables, and green waste, were composted in laboratory reactors with forced aeration. The physicochemical and microbiological parameters were monitored for 12 weeks during composting. The survival of bacteria over a 3-month period at 25 degrees C was assessed with samples collected after different experimental composting times. Strain survival was also monitored in mature sterilized composts. Nonsterile composts did not support pathogen growth, but survival of seeded pathogens was observed. Salmonella serovar Enteritidis survived in all composts, and longer survival (3 months) was observed in mature composts (8 and 12 weeks of composting). Mature biowaste composts may support long-term survival of Salmonella serovar Enteritidis during storage at room temperature. E. coli and L. monocytogenes survival was observed only in 4-week-old composts and never in older composts. Proper composting may prevent long-term survival of E. coli and L. monocytogenes. These results suggest that like composted sewage sludge or manure, domestic waste composts may support pathogen survival. Survival was not related to the physicochemical characteristics of the composts.