Microbiological and chemical quality of sludges from domestic wastewater plants

Digested sludge samples from domestic wastewater treatment plants located in Northern Italy were tested as far as the presence of viruses (enteric viruses and coliphages), bacteria (faecal coliforms, salmonella) and helminth eggs is concerned. Heavy metals were also analysed. Escherichia coli bacteriophages and faecal coliforms were isolated from all samples, while salmonellae and helminth eggs were isolated only from four and three out of 27 total samples, respectively. The 66% of sludge samples, 46 and 82% of aerobic and anaerobic digested sludges respectively, showed the presence of enteric viruses (enteroviruses and reoviruses). The virus concentrations ranged from 0.6 to 123 MPNCU/g. Results of this study suggest that significant concentrations of pathogens such as enteric viruses can be present in digested sludge, which showed compliance with Italian legislation. As suggested by other authors, there is the need for surveillance and reference indications both in EU (European Union) and Italian regulations concerning the use of sludge in agriculture.     

Survey of toxicants and nutrients in composted waste materials

Currently, there is much activity in composting yard wastes (leaves, twigs, grass), sewage sludge and portions of municipal solid wastes (MSW) in the United States. The resultant compost is typically applied to agricultural or recreational land. A nationwide analytical survey was therefore conducted of 21 toxic and nutrient elements, polychlorinated biphenyls (PCBs) and gamma emission in 26 composts sampled nationwide in 1991. Those composts produced solely from sludge or MSW tended to be higher in metals such as Cd, Cu, Hg, and Zn as compared to totally yard waste compost. Molybdenum, P and Se were higher in composted sewage sludge and Na and Pb in composted MSW than in yard waste compost. PCBs and gamma emission were low or not detectable in most compost samples. Shards of metal and glass found particularly in MSW-containing composts would detract from its application especially in recreational areas. References dealing with the reactions of metals in composts and environmental effects of compost application to land are cited.     

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。     

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.     

静态好氧堆肥处理城市生活垃圾的工艺特性

生活垃圾堆肥装置——好氧静态立式发酵仓具有温度控制、通风自动控制系统。用该装置对城市生活垃圾进行了堆肥试验，对堆肥过程的温度、pH值、含水率、耗氧量和有机质等参数进行监测，表明堆肥过程能顺利进行，堆肥产品的卫生指标符合国家标准；堆肥过程中含水率和有机质VS含量明显减少；通过对堆肥的通风加热，能加快温度提升，加快堆肥过程。     

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     

有机固体废物处理行业臭气的产生与控制

针对目前主流的有机固体废物处理处置工艺,总结了各工艺的臭气成分和影响因素。恶臭物质NH3和H2S在污泥堆肥、污泥干化、餐厨垃圾好氧分解和生活垃圾填埋场中都有产生,但不同处理工艺的主要致臭物质不同。污泥堆肥工艺的主要致臭物质为含硫化合物,污泥干化工艺和垃圾填埋场的主要致臭物质为苯系物和萜烯类,餐厨垃圾好氧分解的主要致臭物质为含氧类化合物。提出了相应的恶臭防控措施。     

造纸污泥交替好氧厌氧堆肥中氮素的形态转变研究

通过交替式好氧厌氧堆肥处理造纸污泥试验,研究氮素的变化规律.结果表明:堆肥初始的中高温期,主要是堆体中的有机氮转化为氨氮;之后的降温期和腐熟期是硝态氮形成的主要阶段;总氮在整个堆肥阶段呈上升趋势.无机氮(NH3-N,NO-3-N)可以直接被作物吸收,是污泥堆肥中的主要氮素形态,因此减少堆肥初期氨氮的挥发,增加腐熟阶段NO-3-N的形成,以及降低滤液中无机氮的流失是提高造纸污泥堆肥肥效的关键.     

大港污水污泥兼性厌氧堆肥用于绿地的可行性研究

以天津市大港区污水处理厂的剩余污泥为研究对象,利用兼性厌氧堆肥装置,研究了污泥堆肥前后温度、含水率、有机质、氮、磷、钾以及pH等指标的变化。结果表明：采用污泥与锯末的体积比为1∶1的堆肥,控制初始含水率为65%左右,可顺利实现升温。堆肥15d后,物料的含水率、有机质明显降低;总氮、总磷及总钾的含量有不同程度的增加,符合绿地施用的要求。经计算得出由N决定的污泥堆肥年施用量为32.77t/hm2。     

污泥处置技术分析与探讨——以哈尔滨市为例

以哈尔滨污泥处置项目为背景,结合污泥处置工艺技术特点,对河道底泥和城市污泥进行了技术适应性分析。结果表明,哈尔滨市河道底泥采用单独填埋、城市污泥采用堆肥的工艺技术路线比较合适。     

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.     

Dilution effects on the quality of untreated wastewater used for irrigation along the USA-Mexico border

The Juarez Valley, located along the USA-Mexico border, currently relies on untreated municipal and industrial wastewater from nearby Ciudad Juarez (est. pop. 1.6 million) which has been diluted with water diverted from the Rio Bravo (Rio Grande), and groundwater from underlying aquifers, to irrigate 18000 hectares of crops. The results indicate that dilution does very little to reduce the risks associated with the use of untreated wastewater for irrigation as faecal coliforms levels remained high (> 10 7 cfu/100 ml). Concentrations of heavy metals were low in the raw wastewater and in the mixed waters. However, the practice of diluting raw wastewater seriously degrades significant volumes of high quality waters from the Rio Bravo and from the underlying aquifer, and thus is not an optimal use of the limited high-quality water available to this semi-arid region.     

Solidification as low cost technology prior to land filling of industrial hazardous waste sludge

The aim of this study is to stabilize and solidify two different treated industrial hazardous waste sludges, which were selected from factories situated close to Alexandria. They were selected to ensure their safe transportation and landfill disposal by reducing their potential leaching of hazardous elements, which represent significant threat to the environment, especially the quality of underground water. The selected waste sludges have been characterized. Ordinary Portland Cement (OPC), Cement Kiln Dust (CKD) from Alexandria Portland Cement Company, and Calcium Sulphate as a by-product from the dye industry were used as potential solidification additives to treat the selected treated waste sludges from tanning and dyes industry. Waste sludges as well as the solidified wastes have been leach-tested, using the General Acid Neutralization Capacity (GANC) procedure. Concentration of concerning metals in the leachates was determined to assess changes in the mobility of major contaminants. The treated tannery waste sludge has an acid neutralization capacity much higher than that of the treated dyes waste sludge. Experiment results demonstrated the industrial waste sludge solidification mix designs, and presented the reduction of contaminant leaching from two types of waste sludges. The main advantages of solidification are that it is simple and low cost processing which includes readily available low cost solidification additives that will convert industrial hazardous waste sludges into inert materials.     

生活垃圾的不同组分对堆肥腐熟度的影响

依托北京市南宫堆肥厂,研究了生活垃圾的不同物理组分对高温发酵阶段的堆肥腐熟度的影响。结果表明：从EC、Ed/E6、C／N、GI等指标来看,植物性垃圾对堆肥的腐熟度起主导性作用;纸类和木竹类也对堆肥的腐熟度有一定的促进作用。在8d的高温发酵阶段,以上类别的原垃圾均可以得到较充分的降解,基本达到了高温期间对腐熟度指标的要求。因此在堆肥的原料中适当增加植物性垃圾,如厨余垃圾的比例,可加快垃圾堆肥的腐熟速度。     

Pathogen destruction and solids decomposition in composting latrines: study of fundamental mechanisms and user operation in rural Panama

The relationship between temperature, high pH, desiccation, decomposition, pathogen destruction, and user operation in active double vault urine diverting (DVUD) composting latrines located in the Bocas del Toro region of Panama was assessed. Latrine samples were analyzed for temperature, pH, % moisture, carbon-to-nitrogen (C/N) ratio, and presence of specific pathogens. Surveys and visual inspections were used to verify use and type of dry material desiccant added. Measurements supported findings that compost latrines do not reach temperatures sufficient to destroy all pathogens. pH measurements showed that many latrines were operating within the range for ideal aerobic decomposition, a pH of 7.5–8.5, but only 17% of latrines measured pH 9 or above. Almost 100% of composting latrine users added sawdust and wood ash, to lower moisture level and provide carbon for decomposition. However, the recommended amount of desiccant added was insufficient to reduce moisture to the suggested 25% for pathogen destruction and C/N ratios remained in the range of raw human faeces. Importantly, pathogens, mainly helminths, were still present in compost stored for the 6-month contact time. The latrines have conflicting goals of pathogen destruction and aerobic decomposition. Recommendations are made regarding operation of composting latrines and disposal of composted material.     

The risk of enteric infections associated with wastewater reuse: the effect of season and degree of storage of wastewater

The effect of season and wastewater storage on the risk of Ascaris lumbricoides infection and diarrhoeal disease associated with wastewater reuse was studied in Mexico in 1991. Data were collected from 10,489 individuals during a dry-season survey. Exposure was to untreated wastewater, or effluent from 1 reservoir (< or = 1 nematode egg/L), or no wastewater irrigation (control group). The results were compared with a previous rainy-season survey which included effluent from 2 reservoirs in series. Direct exposure to untreated wastewater was associated with an excess risk of A. lumbricoides infection in children aged < 5 years (OR = 18.0) and persons aged > 5 years (OR = 13.5) and an increased risk of diarrhoea, particularly to children aged < 5 years (OR = 1.75); effects were stronger in the dry than in the rainy season. There was also an excess risk associated with the 1-reservoir group for A. lumbricoides infection (OR = 21.2 and 9.4) and for diarrhoeal disease (OR = 1.1 and 1.5) but little excess associated with the 2-reservoirs group. Therefore, wastewater retention in 1 reservoir (quality 10(5) faecal coliforms/100 mL, < or = 1 egg/L) does not significantly reduce risks of Ascaris infection and diarrhoeal disease whereas retention in 2 reservoirs in series (quality 10(3) faecal coliforms/100 mL, no detectable eggs/L) does.     

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.     

强制通风堆肥技术处理农村生活垃圾的可行性研究

对北京市海淀区北部新区农村生活垃圾中的有机成分进行3组不同物料配比的堆肥试验,在堆肥周期内对堆体的理化性质、腐熟度指标与控制参数进行了研究.结果表明:农村生活垃圾中的有机成分含水率偏高,不利于直接堆肥.采用强制通风静态好氧堆肥,堆肥过程中温度、含水率、体积、pH、电导率、碳氮比的变化与一般堆肥过程各参数的变化规律相似,...     

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.     

Human viruses in sediments, sludges, and soils

Recent studies have provided a greater understanding of the movement of viruses in the environment by their attachment to solids. These studies have focused on solids-associated viruses present in wastewater discharged into the ocean and on viruses in sludge and wastewater that may be retained in soil following their land disposal. Such ocean or land disposal of wastewater and sludge may result in a discharge of one or more of 120 human enteric virus pathogens including those causing poliomyelitis, viral hepatitis A and acute gastroenteritis.