Inactivation of viable Ascaris eggs during faecal sludge co-composting with chicken feathers and market waste

Faecal Sludge (FS) contains high concentrations of pathogenic microorganisms that are 10–100 times higher than those in domestic wastewater. Proper and sustainable treatment is required to inactivate these pathogens if FS is to be recycled in agriculture, so as to minimise public health and environmental risks. Composting is one of the common low-cost technologies of sanitising FS in Urban Africa; however, it is associated with longer pathogen inactivation periods that make it commercially uneconomical. This study investigated the effect of different organic wastes types and their mixing ratios with FS on the inactivation efficiency of viable Ascaris eggs (suum and lumbricoides) during composting. Dewatered FS was mixed with market waste (MW), chicken feathers (CF) and sawdust (SD) in different ratios. Compost piles of FS:MW:SD and FS:CF:SD both in volumetric ratios of 1:2:1 and 1:3:1 were set-up in duplicate (3m3 each), composted and monitored weekly for viable Ascaris eggs presence for a period of 15 weeks. The results suggest that the organic waste types have a significant effect on the temperature evolution and pathogen inactivation efficiency while their mixing ratios do not. Piles containing CF achieved the shortest pathogen survival period of 4 weeks compared with 6–8 weeks for those with MW. The temperature–time factor was found to be the most important variable responsible for viable Ascaris eggs inactivation. However, other mechanisms such as microbial antagonism or antibiotic action induced by indigenous microorganisms and toxic by-products such as free ammonia were found to have also played an important role in Ascaris eggs inactivation. All piles attained 100% Ascaris eggs inactivation from FS, and therefore, the compost was safe for use in agriculture. The study findings suggest that composting of FS with CF can reduce Ascaris eggs inactivation periods by 42%, which may thus reduce the operational costs of FS treatment facilities

MANAGEMENT PRACTICES OFWASTEWATER SLUDGE

Large amounts of wastewater sludge, a secondary pollutant of wastewater treatment plants, commonly containing over 90% water and pathogens, organic pollutants and heavy metals, are produced daily worldwide.  Main treatment routes of wastewater sludge are: landfill, anaerobic digestion, land application and incineration. Anaerobic sludge digestion is a technology employed worldwide to reduce solids, stabilize organic matter, and destroy pathogens and to produce biogas as a source of energy.Compositing is applied for sludge treatment and conversion of complex biowaste into a stabilized product that can be used as organic fertilizer in agriculture. In this paper we present the main practices employed in the management of wastewater sludge, in order to reduce its volume, to capitalize it and to protect the environment

A Neural Network Model for Decision-Making with Application in Sewage Sludge Management

Wastewater treatment (WWT) is a foremost challenge for maintaining the health of ecosystems and human beings; the waste products of the water-treatment process can be a problem or an opportunity. The sewage sludge (SS) produced during sewage treatment can be considered a waste to be disposed of in a landfill or as a source for obtaining raw material to be used as a fertilizer, building material, or alternative fuel source suitable for co-incineration in a high-temperature furnace. To this concern, this study's purpose consisted of developing a decision model, supported by an Artificial Neural Network (ANN model), allowing us to identify the most effective sludge management strategy in economic terms. Consistent with the aim of the work, the suitable SS treatment was identified, selecting for each phase of the SS treatment, an alternative available on the market ensuring energy and/or matter recovery, in line with the circular water value chain. Results show that the ANN model identifies the suitable SS treatments on multiple factors, thus supporting the decision-making and identifying the solution as per user requirements

Wastewater treatment sludge composting

In recent years, the amount of sewage sludge generated by wastewater treatment plants (WWTPs) has increased due to worldwide population growth and to efficiency of biological treatment processes [1,2]. Sludge is an important source of secondary pollution to aquatic environments and a potential risk to human health; moreover, it represents one of the most important cost items in the functioning of water treatment plants [3–5]. About 60% of the operating costs of secondary wastewater treatment plants in Europe can be associated with the treatment and disposal of products [6]. For this reason, proper sludge management becomes increasingly important, at both national and international level, and it becomes necessary to find effective measures to limit the environmental impacts and to reuse sludge as a resource, within a circular economy vision [2,7]. Current methods of utilization of sewage sludge include agricultural application, landfilling, incineration, drying, and composting and/or vermicomposting. Composting is a widely used cost-effective and socially acceptable method for treating solid or semisolid biodegradable waste [8]. In agriculture sewage sludge is used for rehabilitation of degraded soils, reclamation, or adaptation of land to specific needs [9]. The above consideration comes from several studies showing that the application of sludges to agricultural land can improve soil fertility and, therefore, crop productivity [10–12]. This field of use is also possible due to its composition; in fact, it is rich in organic matter, nitrogen, phosphorus, calcium, magnesium, sulfur, and other microelements needed by plants and living native organisms in the soil. However, sewage sludge may contain a wide range of harmful toxic substances such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzo-p-furans, polychlorinated biphenyls, di(2-ethylhexyl) phthalate, polybrominated diphenyl ethers, detergent and drug residues, pharmaceutical and personal care products (PPCPs), endogenous hormones, synthetic steroids and pathogenic organisms [13,14], which can cause harm to the environment and humans. Due to the presence of those toxic elements, stabilization of sewage sludge is necessary to avoid any environmental risk [15]. Stabilization of sewage sludge is defined as “biological, chemical or thermal treatment, long-term storage or any other appropriate process aimed at reducing its fermentability and the health hazards arising from its use” [16]. This definition is found in Council Directive 86/278/EEC, which was issued to regulate the use of sludge in agriculture, the primary objective of which is the environment, in particular the soil, and the protection of human health. European Directive 86/278/EEC was implemented in Italy by Legislative Decree 99/1992 [17]. Both the European Directive and the Italian legislative decree can be considered obsolete, this is why the European Union is moving towards amending them to reflect the new needs of the sector and to keep up with technological innovations. Currently, there are several processes for sludge stabilization, including composting, which is one of the most widely used methods for stabilizing organic matter in general, reducing the number of pathogenic microorganisms and the amount of toxic elements [18]. This is possible because during the composting process the organic compounds present in the biomass to be composted are converted into chemically recalcitrant, that is, stabilized, humic substances, while pathogens are eliminated due to the heat generated during the process thermophilic phase [19,20]. During the composting of sludges, the addition of bulking agents is needed, as they ameliorate the composting performance by providing structural support that improves aeration and regulates moisture content and C/N ratio of composting mass [21,22]. Sludge composting, however, has to be focused on limiting some secondary causes of pollution related to the process itself, such as greenhouse gas (GHG) emissions and heavy metal contamination [23]. Indeed, in the last decades, the handling of sewage sludge with traditional methods has led to the release of an enormous amount of greenhouse gases. The choice of an appropriate bulking agent is, therefore, fundamental to limit the emission of climate-altering gases, and, at the same time, to increase the microbial activity thus improving the quality of the compost [24,25]. This chapter aims (1) to give an overview of the national and international legislation on sludge management and reuse, (2) to analyze the composting process and the state of the art regarding sludge composting to understand the limitations at large-scale application, and (3) to discuss the technological innovations in the field and highlight future perspectives

Co-Management of Sewage Sludge and Other Organic Wastes: A Scandinavian Case Study

Wastewater and sewage sludge contain organic matter that can be valorized through conversion into energy and/or green chemicals. Moreover, resource recovery from these wastes has become the new focus of wastewater management, to develop more sustainable processes in a circular economy approach. The aim of this review was to analyze current sewage sludge management systems in Scandinavia with respect to resource recovery, in combination with other organic wastes. As anaerobic digestion (AD) was found to be the common sludge treatment approach in Scandinavia, different available organic municipal and industrial wastes were identified and compared, to evaluate the potential for expanding the resource recovery by anaerobic co-digestion. Additionally, a full-scale case study of co-digestion, as strategy for optimization of the anaerobic digestion treatment, was presented for each country, together with advanced biorefinery approaches to wastewater treatment and resource recovery

Influence of organic matter transformations on the bioavailability of heavy metals

6 páginas, 3 tablas.The agricultural use of anaerobically digested sewage sludge (ADSS) as stable, mature compost implies knowing its total content in heavy metals and their bioavailability. This depends not only on the initial characteristics of the composted substrates but also on the organic matter transformations during composting which may influence the chemical form of the metals and their bioavailability. The objective of this work was to examine the relationships between the changes in the organic matter content and humus fractions, and the bioavailability of heavy metals. A detailed sampling at 0, 14, 84, and 140 days of the composting process was performed to measure C contents in humic acids (HAs), fulvic acids, (FAs) and humin, the total content of Zn, Pb, Cu, Ni, and Cd, and also their distribution into mobile and mobilisable (MB), and low bioavailability (LB) forms. Significant changes of C contents in HA, FA, and Humin, and in the FA/HA, HA/Humin and Chumus/TOC ratios were observed during composting. The MB and LB fractions of each metal also varied significantly during composting. The MB fraction increased for Zn, Cu, Ni, and Cd, and the LB fraction increased for Pb. Stepwise linear regressions and quadratic curve estimation conducted on the MB and LB fractions of each metal as dependent on the measured organic variables suggested that Zn bioavailability was mainly associated to percentage of C in FAs. Bioavailability of Cu, Ni and Cd during composting was associated to humin and HAs. Pb concentration increased in the LB form, and its variations followed a quadratic function with the Chumus/TOC ratio. Our results suggest that the composting process renders the metals in more available forms. The main forms of metal binding in the sludge and their availability in the final compost may be better described when metal fractionation obtained in sequential extraction and humus fractionation during composting are considered together.This work was part of the Generalitat Valenciana projects IIARCO2004-A-196, IIARCO2004-A-212, and IIARCO/2004/213, and the national project 135/2004/3 (Ministerio de Medio Ambiente). We thank FACSA Sewage Treatment Plant (Castellón, Spain), and University Jaume I of Castellón (Spain) for providing materials and technical assistance. We thank the two anonymous reviewers for their useful comments on the manuscript.Peer reviewe

Influence of organic matter transformations on the bioavailability of heavy metals in a sludge based compost

[EN] The agricultural use of anaerobically digested sewage sludge (ADSS) as stable, mature compost implies knowing its total content in heavy metals and their bioavailability. This depends not only on the initial characteristics of the composted substrates but also on the organic matter transformations during composting which may influence the chemical form of the metals and their bioavailability. The objective of this work was to examine the relationships between the changes in the organic matter content and humus fractions, and the bioavailability of heavy metals. A detailed sampling at 0, 14, 84, and 140 days of the composting process was performed to measure C contents in humic acids (HAs), fulvic acids, (FAs) and humin, the total content of Zn, Pb, Cu, Ni, and Cd, and also their distribution into mobile and mobilisable (MB), and low bioavailability (LB) forms. Significant changes of C contents in HA. FA, and Humin, and in the FA/HA, HA/Humin and C-humus/TOC ratios were observed during composting. The MB and LB fractions of each metal also varied significantly during composting. The MB fraction increased for Zn, Cu, Ni, and Cd, and the LB fraction increased for Pb. Stepwise linear regressions and quadratic curve estimation conducted on the MB and LB fractions of each metal as dependent on the measured organic variables suggested that Zn bioavailability was mainly associated to percentage of C in FAs. Bioavailability of Cu, Ni and Cd during composting was associated to humin and HAs. Pb concentration increased in the LB form, and its variations followed a quadratic function with the C-humus/TOC ratio. Our results suggest that the composting process renders the metals in more available forms. The main forms of metal binding in the sludge and their availability in the final compost may be better described when metal fractionation obtained in sequential extraction and humus fractionation during composting are considered together. (C) 2011 Elsevier Ltd. All rights reserved.This work was part of the Generalitat Valenciana projects IIARCO2004-A-196, IIARCO2004-A-212, and IIARCO/2004/213, and the national project 135/2004/3 (Ministerio de Medio Ambiente). We thank FACSA Sewage Treatment Plant (Castellon, Spain), and University Jaume I of Castellon (Spain) for providing materials and technical assistance. We thank the two anonymous reviewers for their useful comments on the manuscript.Ingelmo Sánchez, F.; Molina, MJ.; Soriano Soto, MD.; Gallardo, A.; Lapeña, L. (2012). Influence of organic matter transformations on the bioavailability of heavy metals in a sludge based compost. Journal of Environmental Management. 95(Suplemento):104-109. https://doi.org/10.1016/j.jenvman.2011.04.015S10410995Suplement

Obtaining new-generation biomass fuels and bio-based fertilisers from sludges through biodrying and advanced composting technologies to enhance the overall resource recovery of the water sector

En el context de l'actual pla d'acció europeu d'economia circular, els fangs de depuradora presenten un potencial com a font de nutrients i d'energia. A causa d'algunes limitacions tècniques, ambientals i/o econòmiques de les tecnologies convencionals de valorització de fangs, s'estan desenvolupant alternatives innovadores de valorització de fangs. Es poden obtenir combustibles de biomassa i fertilitzants de base biològica d'alta qualitat i sostenibles aplicant tecnologies de bioassecatge i compostatge avançat a fangs amb un contingut elevat de nutrients i energia, respectivament. En el marc d'aquesta tesi, es va construir una planta pilot completament operativa de bioassecatge i compostatge avançat. La viabilitat tècnica de les tecnologies de bioassecatge i compostatge avançat es va avaluar a través de l'eficiència dels seus processos desenvolupant amb aquesta finalitat nous indicadors de procés innovadors. El bioassecatge de fangs aconsegueix obtenir combustibles de biomassa amb uns potencials calorífics considerables, mentre que la producció de fertilitzants de base biològica segura i d'alta qualitat a partir de fangs rics en fòsfor va ser possible mitjançant l'aplicació de compostatge avançat. Les dimensions ambientals i econòmiques de les tecnologies avançades de bioassecatge i compostatge aplicades als fangs es van avaluar mitjançant el seguiment de les emissions de gasos contaminants rellevants i l'anàlisi tecno-econòmica basada en la metodologia LCC. Les solucions afavoreixen al fi de l'estat de residus de dels fangs, fent passos ferms cap a la independència de les energies no renovables i les fonts de nutrients.In the context of the current European circular economy action plan, sewage sludge presents potential as nutrient and energy source. Due to some technical, environmental and/or economic limitations of conventional technologies for sludge valorisation, innovative sludge valorisation alternatives are being developed. High quality and sustainable biomass fuels and bio-based fertilisers can be obtained by applying biodrying and advanced composting technologies to sludges with high nutrient and energy content, respectively. In the framework of this thesis, a completely operative pilot plant was built for biodrying and advanced composting. The technical feasibility of biodrying and advanced composting technologies was assessed through their process efficiencies developing for that purpose new innovative process indicators. Biodrying of sludges succeed in obtaining biomass fuels with considerable calorific values while the production of safe and high-quality bio-based fertilisers from phosphorus rich sludge was possible by using advanced composting. The environmental and economic dimensions of biodrying and advanced composting technologies applied to sludges were assessed through the monitoring of relevant polluting gaseous emissions and the techno-economic analysis based on LCC methodology. The solutions boost the end of waste status of sludge making in turn, firm steps towards the independency of non-renewable energy and nutrient sources.Ciències Experimentals i Tecnologie

Sustainability assessment of faecal sludge treatment technologies for resource recovery in Phnom Penh, Cambodia

Selection of appropriate sustainable treatment technologies involves satisfying user requirements, quality standards on treatment and products, and specific socio-technical constraints in the intended context. Using locally adapted multi-criteria assessment (MCA), this study investigated faecal sludge treatment technologies that enable resource recovery in Phnom Penh. A four-step structured approach was applied, involving i) identification of available options, ii) prerequisite screening, iii) MCA and iv) stakeholder discussions and ranking. Data were collected in a literature review, stakeholder interviews and an online survey. Lists of suitable primary (n = 7) and secondary (n = 13) treatment technologies were compiled based on the literature. Four secondary treatment technologies (solar drying, co-composting, vermicomposting, black soldier fly larvae (BSFL) composting) were retained after prerequisite screening and subjected to MCA. Co-composting was ranked highest in MCA, since it performed well in multiple aspects, especially for health criteria. However, when economic return on investment was prioritised and a lower treatment class was accepted, e.g. USEPA Class B biosolids, the highest ranking was achieved by vermicomposting or BSFL composting. If institutional criteria were included in the assessment, solar drying would likely be the highest-ranked option, since this simple technology requires less logistically complex stakeholder arrangements than co-composting. These results show that the ranking obtained for different sludge treatment options depends on criteria weighting and tradeoffs. Considering secondary treatment options is crucial during early planning for faecal sludge management in a city of low-and-middle income countries, as the primary treatment must yield appropriate feedstock quality for the secondary treatment step