Utilization of sewage sludge in EU application of old and new methods—A review
TL;DR: In this article, the authors review past and future trends in sludge handling, focusing mainly at thermal processes (e.g. pyrolysis, wet oxidation, gasification) and the utilization of sewage sludge in cement manufacture as a co-fuel.
Abstract: The European Union has made progress in dealing with municipal wastewater in individual countries and as a corporate entity. However, it intends to make still further and substantial progress over the next 15 years. Currently, the most widely available options in the EU are the agriculture utilization, the waste disposal sites, the land reclamation and restoration, the incineration and other novel uses. The selection of an option on a local basis reflects local or national, cultural, historical, geographical, legal, political and economic circumstances. The degree of flexibility varies from country to country. In any case sludge treatment and disposal should always be considered as an integral part of treatment of wastewater. There is a wide range of other uses for sludge, which exploit its energy or chemical content, namely the thermal processes. The present paper sought to review past and future trends in sludge handling, focusing mainly at thermal processes (e.g. pyrolysis, wet oxidation, gasification) and the utilization of sewage sludge in cement manufacture as a co-fuel.
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01 Jan 2011
TL;DR: The wet pyrolysis process, also known as hydrothermal carbonization, opens up the field of potential feedstocks for char production to a range of nontraditional renewable and plentiful wet agricultural residues and municipal wastes as discussed by the authors.
Abstract: The carbonization of biomass residuals to char has strong potential to become an environmentally sound conversion process for the production of a wide variety of products. In addition to its traditional use for the production of charcoal and other energy vectors, pyrolysis can produce products for environmental, catalytic, electronic and agricultural applications. As an alternative to dry pyrolysis, the wet pyrolysis process, also known as hydrothermal carbonization, opens up the field of potential feedstocks for char production to a range of nontraditional renewable and plentiful wet agricultural residues and municipal wastes. Its chemistry offers huge potential to influence product characteristics on demand, and produce designer carbon materials. Future uses of these hydrochars may range from innovative materials to soil amelioration, nutrient conservation via intelligent waste stream management and the increase of carbon stock in degraded soils.
1,360 citations
TL;DR: In this paper, three strategies of CO2 reduction including energy saving, carbon separation and storage as well as utilizing alternative materials in detail have been reviewed and the barriers against worldwide deployment of such strategies are identified and comprehensively described.
Abstract: Cement industry has been always among the largest CO2 emission sources. Almost 5–7% of global CO2 emissions are caused by cement plants, while 900 kg CO2 is emitted to the atmosphere for producing one ton of cement. In this work, global strategies and potentials toward mitigation of CO2 emissions in cement plant have been discussed and the most promising approaches have been introduced. Moreover the barriers against worldwide deployment of such strategies are identified and comprehensively described. Three strategies of CO2 reduction including energy saving, carbon separation and storage as well as utilizing alternative materials in detail have been reviewed. In case of energy saving approaches, shifting to more efficient process for example from wet to dry process with calciner, shows the best results since potentially reduces up to 50% of required energy and mitigates almost 20% of CO2 emissions in the process. Carbon capture and storage (CCS) is also considered as an effective way to avoid release of CO2. However economical and technical challenges still play a remarkable obstacle against implementing such processes in the cement plant. As far as alternative materials are the case, utilizing waste-derived fuel (WDF) and industrial by-products instead of conventional fuels and materials result in the significant emission mitigation. Industrial wastes which can be used as both fuel and raw material simultaneously mitigate emissions in cement plants and landfills.
903 citations
TL;DR: The main objective of the current study was to outline the current situation and discuss future perspectives for sludge treatment and disposal in EU countries, where sludge reuse in land and sludge incineration seem to be the main practices further adopted in EU-27 (all Member States up to 2020.
Abstract: Municipal wastewater treatment results to the production of large quantities of sewage sludge, which requires proper and environmentally accepted management before final disposal. In European Union, sludge management remains an open and challenging issue for the Member States as the relative European legislation is fragmentary and quite old, while the published data concerning sludge treatment and disposal in different European countries are often incomplete and inhomogeneous. The main objective of the current study was to outline the current situation and discuss future perspectives for sludge treatment and disposal in EU countries. According to the results, specific sludge production is differentiated significantly between European countries, ranging from 0.1 kg per population equivalent (p.e.) and year (Malta) to 30.8 kg per p.e. and year (Austria). More stringent legislations comparing to European Directive 86/278/EC have been adopted for sludge disposal in soil by several European countries, setting lower limit values for heavy metals as well as limit values for pathogens and organic micropollutants. A great variety of sludge treatment technologies are used in EU countries, while differences are observed between Member States. Anaerobic and aerobic digestion seems to be the most popular stabilization methods, applying in 24 and 20 countries, respectively. Mechanical sludge dewatering is preferred comparing to the use of drying beds, while thermal drying is mainly applied in EU-15 countries (old Member States) and especially in Germany, Italy, France and UK. Regarding sludge final disposal, sludge reuse (including direct agricultural application and composting) seems to be the predominant choice for sludge management in EU-15 (53% of produced sludge), following by incineration (21% of produced sludge). On the other hand, the most common disposal method in EU-12 countries (new Member States that joined EU after 2004) is still landfilling. Due to the obligations set by Directive 91/271/EC, a temporary increase of sludge amounts that are disposed in landfills is expected during the following years in EU-12 countries. Beside the above, sludge reuse in land and sludge incineration seem to be the main practices further adopted in EU-27 (all Member States) up to 2020. The reinforcement of these disposal practices will probably result to adoption of advanced sludge treatment technologies in order to achieve higher pathogens removal, odors control and removal of toxic compounds and ensure human health and environmental protection.
853 citations
TL;DR: The high microplastic enrichment in marine sediments compared to most literature data for seawater at the surface supports the hypothesis of a seabed sink for these materials.
Abstract: Environmental contamination by plastic particles, also known as 'microplastics', brings synthetic materials that are non-degradable and biologically incompatible into contact with ecosystems. In this paper we present concentration data for this emerging contaminant in wastewater treatment plants (WWTPs) and freshwater and marine systems, reflecting the routes via which these particles can travel and the ecosystems they potentially impact along their path. Raw sewage influents, effluents and sewage sludge from seven municipal WWTPs in the Netherlands contained mean particle concentrations of 68-910L-1, 51-81L-1 and 510-760kg-1 wet weight (ww), respectively (particle sizes between 10 and 5000μm). Even after treatment, wastewater constitutes a source of microplastic pollution of surface waters, and via biosolids applications in farming and forestry, plastic retained in sewage sludge can be transferred to terrestrial environments. The WWTPs investigated here had a mean microplastics retention efficiency of 72% (s.d. 61%) in the sewage sludge. In the receiving waters of treated and untreated wastewaters, we detected high microplastic levels in riverine suspended particulate matter (1400-4900kg-1 dry weight (dw)) from the Rhine and Meuse rivers. Amsterdam canal water sampled at different urban locations contained microplastic concentrations (48-187L-1), similar to those observed in wastewater that is emitted from sewage treatment facilities in the area. At least partial settling of the particles occurs in freshwater as well, as indicated by microplastics in urban canal sediments (<68 to 10,500particleskg-1dw). Microplastics in suspension in the water column have the potential to be discharged into the sea with other riverine suspended particulates. We report microplastic concentrations from 100 up to 3600particleskg-1 dry sediment collected at 15 locations along the Dutch North Sea coast. The high microplastic enrichment in marine sediments compared to most literature data for seawater at the surface supports the hypothesis of a seabed sink for these materials. Marine species are heavily exposed to plastic particles. Body residues between 10 and 100particlesg-1dw were measured in benthic macroinvertebrate species inhabiting the Dutch North Sea coast: filter-feeding mussels and oysters (species for human consumption) as well as other consumers in the marine food chain.
710 citations
TL;DR: An updated review on two subjects: the available alternatives to produce biochar from a biomass feedstock and the effect of biochar addition to agricultural soils on soil properties and fertility is provided.
Abstract: According to the International Biochar Initiative (IBI), biochar is a charcoal which can be applied to soil for both agricultural and environmental gains. Biochar technology seems to have a very promising future. Nevertheless, the further development of this technology requires continuing research. The present paper provides an updated review on two subjects: the available alternatives to produce biochar from a biomass feedstock and the effect of biochar addition to agricultural soils on soil properties and fertility. A high number of previous studies have highlighted the benefit of using biochar in terms of mitigating global warning (through carbon sequestration) and as a strategy to manage soil processes and functions. Nevertheless, the relationship between biochar properties (mainly physical properties and chemical functionalities on surface) and its applicability as a soil amendment is still unclear and does not allow the establishment of the appropriate process conditions to produce a biochar with de...
631 citations
References
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TL;DR: In this paper, an analytical procedure involving sequential chemicai extractions was developed for the partitioning of particulate trace metals (Cd, Co, Cu, Ni, Pb, Zn, Fe, and Mn) into five fractions: exchangeable, bound to carbonates, binding to Fe-Mn oxides and bound to organic matter.
Abstract: An analytical procedure involving sequential chemicai extractions has been developed for the partitioning of particulate trace metals (Cd, Co, Cu, Ni, Pb, Zn, Fe, and Mn) into five fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and residual. Experimental results obtained on replicate samples of fluvial bottom sediments demonstrate that the relative standard deviation of the sequential extraction procedure Is generally better than =10%. The accuracy, evaluated by comparing total trace metal concentrations with the sum of the five Individual fractions, proved to be satisfactory. Complementary measurements were performed on the Individual leachates, and on the residual sediments following each extraction, to evaluate the selectivity of the various reagents toward specific geochemical phases. An application of the proposed method to river sediments is described, and the resulting trace metal speciation is discussed.
10,518 citations
"Utilization of sewage sludge in EU ..." refers background in this paper
...Over the last decades, a great variety of extraction schemes, both simple and sequential have been developed and, although some methods have been widely used [12,13] none has been unreservedly accepted by the scientific community....
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Book•
01 Jan 1972
TL;DR: Wastewater Engineering: An Overview of Wastewater Engineering, Methods and Implementation Considerations as mentioned in this paper is a good starting point for a discussion of the issues of wastewater engineering. But, it is not a complete survey of the entire literature.
Abstract: Wastewater Engineering: An Overview. Wastewater Flowrates. Wastewater Characteristics. Wastewater Treatment Objective, Methods, and Implementation Considerations. Introduction to Wastewater Treatment Plant Design. Physical Unit Operations. Chemical Unit Processes. Biological Unit Processes. Design of Facilities for Physical and Chemical Treatment of Wastewater. Design of Facilities for the Biological Treatment of Wastewater. Advanced Wastewater Treatment. Design of Facilities for the Treatment and Disposal of Sludge. Natural-Treatment Systems. Small Wastewater Treatment Systems. Management of Wastewater from Combined Sewers. Wastewater Reclamation and Reuse.
3,826 citations
TL;DR: In this article, a review of the current and future issues related to the combustion of sewage sludge is presented, and a number of technologies for thermal processing of sludge are discussed in three groups, i.e., mono-combustion, cocombustions and alternative processes.
Abstract: In the current review paper, various issues related to the combustion of sewage sludge are discussed. After briefly explaining the formation and treatment of sewage sludge, current and future sludge production are discussed. Thereafter, the four sludge disposal methods which are currently used, i.e. recycling in agriculture, landfilling, dumping into sea and incineration, are examined, and the future trend presented showing the increasing role of sludge incineration. Thereafter, technologies for thermal processing of sewage sludge are presented. They are discussed in three groups, i.e. mono-combustion, co-combustion and alternative processes. Various mono-combustion incinerators, including multiple hearth, fluidized bed and smelting furnaces are briefly discussed, whereas for co-combustion, attention has been given to co-combustion with coals in pulverized and fluidized bed coal combustors, as well as co-incineration with municipal solid wastes in various furnaces. Where possible, data from large scale plants are presented. Currently being discussed in the sludge disposal cycles are the alternative thermal processes to sludge combustion. These include wet oxidation, pyrolysis, oil from sludge processes, and combinations of pyrolysis, combustion and gasification processes. Some of these alternative technologies are also briefly discussed. An important aspect during thermal processing of sewage sludge is its combustion mechanisms. Compared to coals, sewage sludge has very high contents of moisture and volatile matter which can affect the combustion process. The importance of the drying and devolatilization processes for sewage sludge combustion is thus examined. In a special case, the release and combustion of the volatiles during sludge combustion in fluidized bed combustors is analysed, and some information concerning the combustion of sludge char is presented. Another important issue of sludge combustion is the emissions of pollutants gases as well as the handling of solid by-products. Of concern include the heavy metals, mercury, dioxins and furans, acid gases, as well as NOx and N2O. These are also briefly discussed. A peculiar characteristic of sewage sludge is its high content of nitrogen, and attention has been given to see how this affects the N2O and NOx emissions. In a special case, emission performance of large scale combustors of sewage sludge is presented.
1,026 citations
"Utilization of sewage sludge in EU ..." refers background in this paper
...Multiple hearth and fluidized bed furnaces are the most popular and the latter is becoming widely applied [24]....
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...Analysis has shown that about 78–98% of Cd, Cr, Cu, Ni, Pb and Zn present in the sewage sludge are retained in the ash, whereas up to 98% of the Hg may be released into the atmosphere with the flue gas [24]....
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...The whole process is occurring in two distinctive regimes [24]:...
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TL;DR: In this article, the authors proposed a standardization with respect to grain size effects, commonly achieved by analyzing the sieve fraction <63μm, which is used to pin point major sources of metal pollution and to estimate the toxicity potential of dredged materials.
Abstract: Sediment analyses are used to pin‐point major sources of metal pollution and to estimate the toxicity potential of dredged materials on agricultural land. For source assessments (Part I of the present review) standardization is needed with respect to grain size effects, commonly achieved by analyzing the sieve fraction <63μm. Further aspects include sampling methods, evaluation of background data and extent of anthropogenic metal enrichment.
530 citations