Prevalence of asbestos in composted waste from 26 communities in the United States

Composting of yard waste, sewage sludge and municipal solid waste (MSW) for subsequent application to soils in agricultural, horticultural and recreational areas is being promoted nationwide. Since asbestos is a common contaminant in sewage sludge, an analytical survey was conducted for the presence of asbestos in composts collected from 26 communities nationwide resulting from sludge as well as yard waste and municipal solid waste. Asbestos was detected in 12 of the 26 composts or 46%. Asbestos was most consistently present in compost resulting from source material containing MSW and to a lesser extent sewage sludge rather than yard waste. The possible origins of asbestos in the compost source material, the mechanisms by which humans may be exposed, and the health significance are discussed.     

Composition of toxicants and other constituents in yard or sludge composts from the same community as a function of time-of-waste-collection

Samples of yard waste compost and sewage sludge compost were analyzed for toxic and nutrient elements and PCBs to assess variations in their concentrations as a function of the time of delivery of the initial organic material to the same composting site. In general, the variations in composition found were remarkably small. Generally, the samples of sludge compost were higher in Ca, Cd, Cu, Fe, Hg, Mo, Na, P, Pb, S, Se, Zn, and PCBs than those of the yard waste compost. The latter was higher in Cr, Ni, K, Mg, and Si. Possible factors affecting compost composition are discussed.     

A novel challenge test incorporating irradiation (60Co) of compost sub-samples to validate thermal lethality towards pathogenic bacteria

Maturing compost heaps normally attaining temperatures ranging from 55 to 65 degrees C is generally regarded to conform to recommended biological risks and sanitation standards for composts stipulated by either EU or US-EPA. Composted products derived from animal sources are further required by EU biohazard safety regulatory legislation that such composts either attain 70 degrees C for over 3h during maturation or via treatment at 70 degrees C for 1h before being considered for dispensation on land. The setting of the upper limit of thermal lethality at 70 degrees C/1h for achieving biosecurity of the animal waste composted products (e.g. pelleted fertilizer formulations) is not properly substantiated by specific validation tests, comprising a 'wipe-out' step (usually via autoclaving) followed by inoculation of a prescribed bacterium, exposure to 70 degrees C/1h and the lethality determined. Pelleted formulations of composts are not amenable for wet methods (autoclaving) for wipe-out sterilization step as this is detrimental to the pellet and compromises sample integrity. This study describes a laboratory method involving the employment of ((60)Co) irradiation 'wipe-out' step to: (a) compost sub-samples drawn from compost formulation heaps and (b) pelleted products derived from composted animal products while determining the thermal lethality of a given time/temperature (70 degrees C/1h) treatment process and by challenging the irradiated sample (not just with one bacterium but), out with 10 potential food-poisoning organisms from the bacterial genera (Campylobacter, Escherichia, Listeria, Salmonella, Yersinia) frequently detected in pig and poultry farm wastes. This challenge test on compost sub-samples can be a useful intervention ploy for 'inspection and validation' technique for composters during the compost maturity process, whose attainment of temperatures of 55-65 degrees C is presumed sufficient for attainment of sanitation. Stringent measures are further required by law for composted products arising from rural industrialists producing pelleted fertilizers from re-composted animal agriculture wastes comprising pig slurry solids, poultry litter and spent mushroom compost, which carry residual food-borne pathogens with implications to the food chain including humans. Environmentally, sustainable means of recycling farm wastes require that final composted products are free of pathogens in compliance with environmental safety legislation before their release to the market. This test developed provides a science-based risk characterization tool for sustainably managing environmental safety by 'validating' thermal lethality of a given composting process or their derivatives achieved without compromising the sample integrity or ambiguity attached to microbiological validation involving steam sterilization or autoclaving procedures and helps audit the resurgent bacterial populations from surviving non-pathogenic organisms in the end-products of animal waste compost formulations.     

模糊数学法在堆肥腐熟度评价中的应用

根据常见物料的自身特征及国内外评价堆肥腐熟度的相关标准,提出以堆肥高温期持续时间、C／N降解速率、NH3-N／NO3-N、种子发芽指数、NH3-N降解速率5个指标作为堆肥腐熟度的判别指标,并基于模糊数学方法建立腐熟程度的综合判别模型,然后利用该模型验证了分别以污水污泥和生活垃圾为物料的3种堆肥样品的腐熟度。结果表明,利用这5个指标,通过综合判别模型可以作为污泥（C／N初≥C／N终）、生活垃圾高温好氧堆肥腐熟程度通用的判别方法．判别结果合理且较符合实际。     

Effects of Composting Process and Fly Ash Amendment on Phytotoxicity of Sewage Sludge

With the increasingly growing global production of sewage sludge, evaluation of its applicability in agriculture and land restoration is essential. This study assessed the potential effects of composting process and fly ash amendment on soil-ameliorating properties of sewage sludge. The metal availability and phytotoxicity of ash-amended sludge compost (AS, mature sewage sludge compost mixed with fresh lagoon ash) and sludge-ash co-compost (SA, co-composted mixture of sewage sludge and lagoon ash) were compared. The results of this work suggested that both composts favored the applicability of sewage sludge for land application by reducing Cd, Cu, Pb, and Zn availability. The SA co-compost stimulated seed germination at ash amendment rates of ≤10%, whereas various treatments of AS compost inhibited germination at an extract dilution of 50%. Amendment of lagoon ash before or after sludge composting increased electrical conductivity (EC) and volatilization of NH₄-N, but lowered availability of PO₄-P. Together with the results of phytotoxicity, an optimal ash amendment rate of 5% for AS and 10% for SA were most desirable. Alkaline amendment prior to sludge composting was recommended, because it could be more effective in reducing soluble and plant-available metal concentrations through the composting process. Received: 1 October 1999/Accepted: 31 May 2000     

Analytical survey of elements and other constituents in Central New York state sewage sludges

Thirty-nine elements, polychlorinated biphenyls (PCBs), volatile N-nitrosamines and gamma emission were determined by several instrumental methods in sewage sludges from 24 communities in Central New York. Relatively high concentrations of certain elements or PCBs were found in sludges from specific communities. For example, antimony and certain rare earth elements used in glass manufacture were found at elevated levels in sludge from Corning, New York. Various volatile N-nitrosamines were found in all of the sludges in trace amounts. Gamma emission levels were relatively low in all sludges. One-third of the sludges would be classified as unsuitable for agricultural land application based on presently suggested federal guidelines for acceptable heavy metal or PCB concentrations in sludges. The question of the application of sludge to agricultural land is discussed.     

Trace metal distribution in soluble organic matter from municipal solid waste compost determined by size-exclusion chromatography

Municipal solid waste (MSW) composts carry high amounts of trace metals and organic complexing agents that may influence metal bioavailability and mobility after application to soils. In order to assess the degree of organic complexation of trace metals in the solution phase of MSW compost and the relevance of organic ligand type, size exclusion chromatography (SEC) was applied to compost-extracted organic ligands. Adjustment of the elution conditions minimized the interaction with the gel matrix for compost humic substances and dissolved organic matter (DOM) fractions. The SEC was then used to separate the aqueous compost extract into samples with distinct differences in chemical constituents. The highest quantities of Cu, Zn, Ni, Mn, and Cd were found to coelute with the main peak of the SEC elution curve, which, as observed by Fourier-transformed infrared (FTIR) spectroscopy, also had the highest density of carboxyl groups. The ratio of aromatic to aliphatic structures was higher for eluates with low retention times, and cations such as Al, Cr, and Fe were preferably associated with these larger organic molecules. All trace metals in the compost solution phase were bound mostly to DOM rather than forming inorganic complexes.     

Quality monitoring of composting processes of wastewater sludge in Alexandria

There are two wastewater primary treatment plants in Alexandria (west and east). The produced primary sludge is mechanically dewatered and transported to sludge disposal site 9N where composting is carried out. However, prior to 1970, composting played a very minor role in sludge or solid wastes treatment because of greatly unfavorable balance between its economics and those of the principal competing option, namely landfill disposal. This study aims at monitoring and evaluating the composting process of demitted sludge produced from Alexandria wastewater treatment plants. Ten batches of sludge were composted. During the composting process the batches were been investigated and followed up to 3 months. Representative samples (10 for each batch) were taken from these batches at the start of windrowing and after each turning (4-15 days) and were analyzed for physical; chemical; bacteriological; and parasitological characteristics, heavy metals, and plant nutrients. Results revealed that C/N ratio of the final compost product comply with the decree of the Minister of Agriculture No. 100 11967, while moisture, C%, and TKN did not. Heavy metals, faecal coliforms, and helminthes complied with the decree No. 222/2002 for the Minister of Housing, Utilities, and Urban Communities. Moisture had positive correlation with both C and VS and negative correlation with pH. Temperature had negative correlation with TKN. Both total and faecal coliforms had negative correlation with temperature and positive correlation with C, N, and VS. It is recommended to optimize the quality of the produced sludge compost by use bulking agent rich in carbon and nitrogen as Hay or Rice straw, instead of the matured sludge compost.     

Phytotoxicity of municipal sewage sludge composts related to physico-chemical properties, PAHs and heavy metals

The aim of the study was to determine the influence of the composting on the phytotoxicity of sewage sludge in relation to their physical-chemical properties, heavy metals and polycyclic aromatic hydrocarbons content. Four municipal sewage sludges were composted for 76 days. A Phytotoxkit Test and pot experiment with Lepidium sativum were used for bioassay. The total PAH content in sludges ranged from 3674.1 to 11236.3 microg kg(-1). Heavy metals content was in the range Cd (1.9-76 mg kg(-1)), Cr (27.6-120 mg kg(-1)), Cu (156-335 mg kg(-1)), Pb (37.5-59.5 mg kg(-1)), Ni (21.7-155 mg kg(-1)) and Zn (1015-1385 mg kg(-1)). The results showed a varied toxicity of sewage sludge in relation to the plant tested. In the case of two sludges a 100% inhibition of seed germination were noted. Sludge composting limited their negative influence on most of the phytotoxicity parameters. Only chlorophyll concentration was often lower than in the plant bred on compost obtained from sludge.     

Feeding inhibition in the soil collembolan Folsomia candida as an endpoint for the estimation of organic waste ecotoxicity

Despite the increasing quantities of organic wastes that are being reused in soils, there are few studies that focus on the selection of bioassays for the ecotoxicological risk assessment of organic wastes to soils. In the present study, differences in feeding inhibition in the soil collembolan Folsomia candida were evaluated as an ecotoxicological endpoint for the assessment of risk to soils amended with polluted organic wastes. Seven organic wastes (dewatered sewage sludges, thermally dried sewage sludges, composted sewage sludges, and a thermally dried pig slurry) were tested. These wastes had different origins, treatments, and pollutant burdens, and were selected as a representative sample of the wide variety of wastes currently generated. A clear dose response was observed for this parameter, with an increase in percentage of individual feeding inhibition with increased doses of organic wastes. More significantly, feeding inhibition correlated highly with mortality and reproduction inhibition in the different wastes. Composted sludges displayed the lowest toxicity, followed by thermally dried sludge and dewatered sludge. Thermally dried pig slurry showed the highest toxicity for feeding, with lower median effective concentration (EC50) values than the lowest dose tested. Among waste physicochemical parameters and pollutants, low organic matter stability appeared to be the main predictor of potential adverse effects on soil fauna, because it correlated significantly with feeding inhibition and mortality. Furthermore, feeding inhibition tests were run over a short exposure time (less than 7 d), which, together with the results obtained, makes this bioassay a good screening tool for organic waste toxicity.     

Reduction of mercury,copper, nickel,cadmium, and zinc levels in solution by competitive adsorption onto peanut hulls,and raw and aged bark

Summary The competitive adsorption of common heavy metal ions by peanut hulls, raw bark, and composted bark was studied. These solid wastes were found to adsorb significant amounts of one or more of the heavy metals (Hg, Cu, Ni, Cd, Zn) commonly found in municipal sludge and wastewater.     

Mutagens,toxicants, and other constituents in small city siudges in New York State

An analytical survey was conducted of sewage sludges from 15 small cities in New York State for mutagens, forty-four elements, polychlorinated biphenyls (PCBs) and radioactivity. Low levels of mutagenicity were detected in several of the samples. PCBs were very high in only one sample. A number of toxic elements were found at elevated concentrations in specific sludges but it is not possible to relate these to specific industrial sources with certainty. The concentrations of specific toxicants in five city sludges were above presently suggested federal guidelines for their suitability for land application. Gamma emission was comparatively low in all samples. The problems of analytical sampling and possible sources of specific constituents in sludge are discussed.     

Ecotoxicological characterization of hazardous wastes

In Europe hazardous wastes are classified by 14 criteria including ecotoxicity (H 14). Standardized methods originally developed for chemical and soil testing were adapted for the ecotoxicological characterization of wastes including leachate and solid phase tests. A consensus on which tests should be recommended as mandatory is still missing. Up to now, only a guidance on how to proceed with the preparation of waste materials has been standardized by CEN as EN 14735. In this study, tests including higher plants, earthworms, collembolans, microorganisms, duckweed and luminescent bacteria were selected to characterize the ecotoxicological potential of a boiler slag, a dried sewage sludge, a thin sludge and a waste petrol. In general, the instructions given in EN 14735 were suitable for all wastes used. The evaluation of the different test systems by determining the LC/EC₅₀ or NOEC-values revealed that the collembolan reproduction and the duckweed frond numbers were the most sensitive endpoints. For a final classification and ranking of wastes the Toxicity Classification System (TCS) using EC/LC₅₀ values seems to be appropriate.     

National survey of elements and other constituents in municipal sewage sludges

Fifty-nine elements, poly chlorinated biphenyls, volatile N-nitrosamines and gamma emission were determined in 30 sewage sludges from 23 American cities using several analytical methods. Relatively high concentrations of toxic metals were found in sludges from specific municipal plants. The pH and levels of calcium and iron in certain of the sludges appeared to reflect the addition of lime, ferric chloride and/or spent pickle liquor during sewage treatment. Of 15 sludges analyzed, the carcinogen, N-nitrosodimethylamine was detected in 14 and various other N-nitrosamines in 12 of them. Based on present federal guidelines, only 7 of the 30 municipal sludges analyzed would be considered suitable for land application owing to their elevated content of one or more heavy metals.     

Waste-related cadmium cycle in Switzerland

The anthropogenic contribution to the global cadmium flux exceeds natural sources by a factor of three. The most important pathway is the atmosphere; therefore, high cadmium concentrations can be found even in remote areas. On a local level, the increase in cadmium consumption can be observed in increasing concentrations in the soil, plants, and food. The question arises as to what extent the soil-plant-man-waste-soil cycle can be loaded with cadmium in order to function without negative impact on the environment. In Switzerland, 120 tons (t) of cadmium are consumed per year. Of this amount, 25 t end up in municipal solid waste, 3 t in wastewater, and 19 t in precipitation and dry fallout. As a consequence of today's waste management practice (75% incineration, 20% sanitary landfill, 5% composting; 75% of all sewage is purified), the annual input to the soil is 40 t: 18 t concentrated in landfills, 19 t dissipated via the atmosphere, and 3 t directly spread via sewage sludge, compost, and fertilizer on agricultural land. If even distribution were possible, the cadmium content of the soil would theoretically double in 150 years. The accumulation in the soil will increase the cadmium content of plants grown on such a soil. According to a simple model, the level of 3 ppm cadmium in soils should not be surpassed. At such concentrations, plants are likely to contain greater than 0.4 mg Cd/kg, a concentration which can cause toxic effects in long-term experiments. The safe level in food might be even lower. In reality, cadmium is not evenly distributed over Switzerland. According to today's practice, it must be assumed that in only 14 years the use of compost will have enriched soils to such an extent that its cadmium content will prohibit the production of food for human consumption. For sewage sludge, this timespan is 130 years. If heavy metal limits in food are to be observed, the input of such metals to the soil has to be limited. In a steady state, the cadmium input to the soil should be equal to its output via plants, leachate, and erosion. This implies that today's dissipative use of cadmium must be stopped.     

施用城市污泥对土壤中重金属积累和迁移的影响

目的 了解城市污泥农用后土壤重金属的积累和迁移。方法 于1998年分不同季节，从苏州、无锡、常州3个城市污水处理厂采集污泥样本，用原子吸收光谱仪分析样本中重金属(Pb、Zn、Cu、Cd、Hg、As)含量和不同形态含量，分析污泥农用后土壤重金属积累及迁移特性。结果 城市污泥重金属含量远高于土壤背景值，3城市污泥中Zn含量均超标，分别达到1199，00、784．00、1216．00mg／kg。长期施用能导致土壤重金属积累。污泥中重金属具有一定的活性和潜在迁移性。结论 城市污泥农用可能会导致土壤和生物体重金属积累，存在着一定的环境重金属积累风险。     

城市污泥堆肥土地修复利用研究进展

综述了城市污泥堆肥在园林绿地、农田土壤、土地修复等领域的应用现状，分析了土地利用中存在的土壤重金属积累、臭气污染、养分含量低、肥效慢等主要问题，探讨了相应的对策。     

延安市污水处理厂各工段重金属元素的含量分析

采取延安市污水处理厂各工段污水,利用电感耦合等离子体发射光谱法(ICP-AES),对其中Zn、Cu、Pb、Mn和Cr 5种重金属元素的总量进行测定,结果表明部分活性污泥回流到厌氧池后,几种重金属元素在厌氧池和氧化沟中的去除率都较高。     

Environmental problems from the disposal of sewage sludge in Greece

The current situation on the quantities and disposal methods of sewage sludge in European Union is discussed, together with the trends up to 2005 and the future sludge disposal possibilities. The problems relating to the methods currently used in Greece and the requirement for land suitable for the safe agricultural application of sewage sludge are evaluated. This concept will be important to the decision-makers for the purpose of the disposal of sewage sludge in the future. Soil measurements in lands used for sludge disposal in western and southern Greece show that some soils have been already polluted by heavy metals and should be abandoned while others need careful monitoring until their saturation.     

污水厂污泥在天津滨海地区盐渍土改良上的应用前景分析

根据天津滨海地区盐渍土的特点,对比不同的材料后认为,城市污泥堆肥是用于盐渍土改良的理想材料。分析了天津经济技术开发区污水厂污泥堆肥在开发区内盐渍土改良的可行性,并对可能产生的问题提出了相应的对策。