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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TL;DR: Modeling indicated that particulate metabolic products generated by sludge acclimated to high sludge age undergo slow biodegradation under prolonged stabilization, and showed that both microbial decay and hydrolysis of non viable cellular material proceeded at much slower rates as compared with biological systems sustained with substrate feeding.
8 citations
TL;DR: The agronomic application of SS in agriculture requires additional and more effective technologies in order to promote its complete decontamination and its safe disposal in the environment.
Abstract: A problem that has been dragging in recent decades is the final disposal of the waste produced in the wastewater treatment process. In addition to its high amount of organic matter and nutrients, this waste, known as sewage sludge (SS), may also contain toxic compounds that, when in the environment, can cause deleterious effects to organisms and lead to severe and irreversible consequences to human health. In order to understand the potential of inducing cellular and chromosomal instabilities, the species Allium cepa was employed to assess the presence of toxic agents in SS samples. Seeds of A. cepa were exposed to several dilutions of aqueous extract of SSs from 5 wastewater treatment plants (WWTPs), whose characteristics of treated sewage and the technologies employed differ among them. The results obtained showed that all the studied SSs induced significant genotoxic and mutagenic alterations, even in smaller dilutions tested. With these results, it was also possible to observe that SSs from WWTPs that present system of activated sludge and receive sewage of industrial origin induced a greater number of toxicogenetic alterations in the test organism. The high frequencies of chromosomal and nuclear aberrations observed, induced by contaminants present in the SS, represent worrying results because it proves a direct action of this agent on the genetic material of the exposed organism. Therefore, the agronomic application of SS in agriculture requires additional and more effective technologies in order to promote its complete decontamination and its safe disposal in the environment.
8 citations
TL;DR: In this article, the optimal size of the cogeneration unit cooperating with the gas boiler as heat sources for a given drying plant case with the maximum net present (NPV) value as the objective function was investigated.
Abstract: The treatment of growing production of municipal sewage sludge has become a significant global problem. Drying of digested sewage sludge is a promising alternative to sludge disposal at dumping sites. The research objective of this study was to find the optimal heat source for a sludge drying plant in a large municipal sewage treatment plant (people equivalent: 250,000). Two boundary heat supply cases were analyzed in the paper: cogeneration of heat and power (CHP) units, internal combustion (IC) engines fired with natural gas, and plant supplied with a gas boiler. The aim of the research was to find the optimal size of the cogeneration unit cooperating with the gas boiler as heat sources for a given drying plant case with the maximum net present (NPV) value as the objective function. The results of the conducted optimization show higher profitability of cases with larger cogeneration unit. For the basic assumptions, the maximum NPV is obtained for the largest analyzed CHP unit: 1300 kW of thermal power output. Sensitivity analyses show that the varying gas and electricity prices can relocate the NPV maximum towards smaller CHP sizes. A supplementary energy analysis shows that implementing larger CHP units yields a higher energy efficiency of the system, up to 0.52.
8 citations
31 Aug 2020
TL;DR: In this article, the authors examined the characteristics of the wet air oxidation (WAO) process and the factors influencing the process, together with the advantages and disadvantages of using WAO in sewage sludge treatment.
Abstract:
Wet air oxidation (WAO) is an attractive technique for sewage sludge treatment. The
WAO process and the factors influencing the process are examined in detail, together with the advantages
and disadvantages. Catalytic wet air oxidation (CWAO) is emphasized because it can lower
operational conditions, and the commonly-used and new homogeneous and heterogeneous catalysts
are introduced. Homogeneous catalysts tend to be more appropriate for the CWAO treatment
of sewage sludge, and Cu-based homogeneous catalysts such as CuSO4 are the most popular for industrial
applications. Heterogeneous catalysts include non-noble metal catalysts, noble metal catalysts,
metal-organic frameworks (MOFs) catalysts, and non-metal catalysts. Non-noble metal catalysts
typically contain hetero-elements as in Mo-based, Ce-based, Cu-based, Fe-based catalysts,
multi-metal supported catalysts, and polyoxometalates catalysts. In general, Mo-based catalysts
and Ce-based catalysts have higher activities than other metal-based catalysts. The commonly-used
noble metal elements are based on Ru, Pt, Pd, Rh, and Ir. The MOF catalysts tend to have high catalytic
activity, and the non-metallic carbon catalysts may be used in environments that would otherwise
be toxic to traditional metal catalysts. To conclude, a summary of the challenges and
prospects of WAO technology in sewage sludge treatment is given.
8 citations
01 Jan 2019
TL;DR: In this article, the influence of sewage sludge soil application on the phytobiome was assessed using specific indicators such as microbial functional diversity, community level, and physiological profiles.
Abstract: Safe soil application of sewage sludge is a challenging environmental issue. Scientists' views on the impact of sewage sludge on the phytobiome are very different and inconsistent. Also, practitioners have differing views, especially foresters and farmers who are strongly opposed to the use of sewage sludge while sewage sludge producers and environmental engineers are in favor of land application. The aim of the present work is to assess the influence of sewage sludge soil application on the phytobiome. Changes in microbial functional diversity, community level, and physiological profiles due to sewage sludge soil treatment are measured and assessed using specific indicators. Moreover, the indicators are also strictly correlated with the sewage sludge processing and treatment before soil application.
8 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.
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