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.
Citations
More filters
13 Sep 2018
TL;DR: Biosolids, the residual solids from wastewater treatment operations and once considered a waste product by the industry, are now becoming increasingly recognized as a multifunctional resource with growing opportunities for marketable use as discussed by the authors.
Abstract: Biosolids, the residual solids from wastewater treatment operations and once considered a waste product by the industry, are now becoming increasingly recognised as a multifunctional resource with growing opportunities for marketable use This shift in attitude towards biosolids management is spurred on by increasing volatility in energy, fertilizer and commodity markets as well as moves by the global community towards mitigating global warming and the effects of climate change This chapter will provide an overview of current global biosolids practices (paired with a number of Australian examples) as well as discuss potential future uses of biosolids Additionally, present and future risks and opportunities of biosolids use are highlighted, including potential policy implications
2 citations
Dissertation•
17 Jun 2015
TL;DR: In this article, the effect of ultrasound, low-temperature thermal and alkali with NaOH treatment on WAS rheology, dewatering, hygienisation and anaerobic digestion was analyzed.
Abstract: The development of treatment processes to reduce or reuse sewage sludge is crucial for a proper environmental management. Segregating primary from secondary sludge allows for better reuse of secondary sludge, since digested secondary sludge is better suited for agricultural application, containing about double concentration in nutrients but significantly less contaminants. However, secondary sludge (also called waste activated sludge (WAS)) is difficult to dewater compared with primary sludge due to the existence of colloidal materials and extracellular polymeric substances (EPSs), which strongly retain water. WAS is also more difficult to digest under anaerobic conditions due to the presence of glycan strands in microbial cell walls. The low dewaterability and digestibility of WAS can be improved by applying treatments, which can partially disintegrate the WAS by disrupting flocs and cells and solubilising the EPSs. The treatments studied in this thesis were ultrasound, low-temperature thermal and alkali with NaOH. Specifically, it has been analysed the effect of the aforementioned treatment on WAS rheology, dewatering, hygienisation and anaerobic digestion. Rheology is the study of stress-strain relationships of viscoelastic materials. All the sludges analysed (untreated and treated) behaved as non-Newtonian pseudoplastic fluids, which indicates that the viscosity decreases with the applied shear rate. The sludges were also thixotropic (showing a hysteresis area in the plot of stress versus shear rate), which means that the viscosity is time dependent. The three aforementioned treatments resulted in the reduction of the steady state viscosity and the hysteresis area. Complementarily, a rheological structural model was proposed to examine the variations in the thixotropic behaviour of WAS after the application of the treatments. Sludge dewatering is essential to obtain a product dry enough to allow a reduction in storage volume. The three conditions of the thermal treatment (60, 80 and 90 oC; 1 h, including the heating time to reach the temperature) and the higher intensities of ultrasound (27,000 kJ/kg TS) and alkali (157 g NaOH/kg TS) treatments improved sludge dewatering by centrifugation. To further evaluate the effect of treatments on the sludge dewatering, the EPSs contained in sludge were extracted and characterised. The EPSs were fractionated to generate two different EPS fractions: loosely bound EPSs (LB-EPSs) and tightly bound EPSs (TB-EPSs), where the latter is the innermost fraction and harder to release. An analysis of the untreated sludge revealed that the proteins, followed by the humic acids and polysaccharides, were the major constituents of the EPSs. Each of these components was primarily observed in the TB-EPS fraction. The treatments, particularly the alkali treatment, thoroughly solubilised the EPS, as indicated by the increase in the TOC, protein, humic acid and polysaccharide contents in the LB-EPS fraction. As a result, the dewaterability of WAS was improved. Hygienisation of the sludge is of uttermost importance if the sludge is intended for agriculture. The level of hygienisation was evaluated using three indicator organisms: Escherichia coli, somatic coliphages (SOMCPH) and spores of sulfite-reducing clostridia (SSRC). The thermal treatment at 80 oC and the alkali treatment at 157 g NaOH kg TS allowed the hygienisation of the sludge, thus satisfying normal levels accepted by the EPA and the 3rd official draft from the EU. Conversely, the conditions tested for the ultrasound treatment barely reduced the levels of microbial indicators. Mesophilic anaerobic digestion is a widely used method to stabilise the sludge. The alkali pre-treatment (157 g NaOH/kg TS) exhibited the greatest methane production increase (34%) followed by the ultrasonication (27,000 kJ/kg TS; 13%), whereas the thermal pre-treatment (80 oC, 15 min) presented a methane potential similar to the untreated sludge. However, the use of NaOH as a pre-treatment is rather limited because of the rising sodium concentration in the digester.
2 citations
Cites background from "Utilization of sewage sludge in EU ..."
...However, sludge is being produced all year round, whereas its application on land takes place once or twice a year; consequently the sludge should be stored (Fytili and Zabaniotou, 2008)....
[...]
...Sludge disposal routes There is no universal solution to the issue of sludge management, but the solution must be appropriate to local or national, cultural, historical, geographical, legal, political and economic circumstances (Lundin et al., 2004; Fytili and Zabaniotou, 2008)....
[...]
...There is no universal solution to the issue of sludge management, but the solution must be appropriate to local or national, cultural, historical, geographical, legal, political and economic circumstances (Lundin et al., 2004; Fytili and Zabaniotou, 2008)....
[...]
...The modifications that should be made, concern mainly the necessity for treatment in sludge before being used, the establishment of lower limits in metal content as well as the introduction of some new criteria (Fytili and Zabaniotou, 2008)....
[...]
TL;DR: Biosolids contain high amounts of human pathogenic bacteria that are excreted in feces and urine and the enteric pathogenicacteria Salmonella sp.
Abstract: Biosolids contain high amounts of human pathogenic bacteria that are excreted in feces and urine. The enteric pathogenic bacteria Salmonella sp., Escherichia coli (enteropathogenic and ent...
2 citations
01 Jul 2019
2 citations
References
More filters
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....
[...]
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]....
[...]
...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]....
[...]
...The whole process is occurring in two distinctive regimes [24]:...
[...]
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