A critical review of resource recovery from municipal wastewater treatment plants : market supply potentials, technologies and bottlenecks

In recent decades, academia has elaborated a wide range of technological solutions to recover water, energy, fertiliser and other products from municipal wastewater treatment plants. Drivers for this work range from low resource recovery potential and cost effectiveness, to the high energy demands and large environmental footprints of current treatment-plant designs. However, only a few technologies have been implemented and a shift from wastewater treatment plants towards water resource facilities still seems far away. This critical review aims to inform decision-makers in water management utilities about the vast technical possibilities and market supply potentials, as well as the bottlenecks, related to the design or redesign of a municipal wastewater treatment process from a resource recovery perspective. Information and data have been extracted from literature to provide a holistic overview of this growing research field. First, reviewed data is used to calculate the potential of 11 resources recoverable from municipal wastewater treatment plants to supply national resource consumption. Depending on the resource, the supply potential may vary greatly. Second, resource recovery technologies investigated in academia are reviewed comprehensively and critically. The third section of the review identifies nine non-technical bottlenecks mentioned in literature that have to be overcome to successfully implement these technologies into wastewater treatment process designs. The bottlenecks are related to economics and value chain development, environment and health, and society and policy issues. Considering market potentials, technological innovations, and addressing potential bottlenecks early in the planning and process design phase, may facilitate the design and integration of water resource facilities and contribute to more circular urban water management practices

Municipal wastewater treatment with pond technology : historical review and future outlook

Facing an unprecedented population growth, it is difficult to overstress the assets for wastewater treatment of waste stabilization ponds (WSPs), i.e. high removal efficiency, simplicity, and low cost, which have been recognized by numerous scientists and operators. However, stricter discharge standards, changes in wastewater compounds, high emissions of greenhouse gases, and elevated land prices have led to their replacements in many places. This review aims at delivering a comprehensive overview of the historical development and current state of WSPs, and providing further insights to deal with their limitations in the future. The 21st century is witnessing changes in the way of approaching conventional problems in pond technology, in which WSPs should no longer be considered as a low treatment technology. Advanced models and technologies have been integrated for better design, control, and management. The roles of algae, which have been crucial as solar-powered aeration, will continue being a key solution. Yet, the separation of suspended algae to avoid deterioration of the effluent remains a major challenge in WSPs while in the case of high algal rate pond, further research is needed to maximize algal growth yield, select proper strains, and optimize harvesting methods to put algal biomass production in practice. Significant gaps need to be filled in understanding mechanisms of greenhouse gas emission, climate change mitigation, pond ecosystem services, and the fate and toxicity of emerging contaminants. From these insights, adaptation strategies are developed to deal with new opportunities and future challenges

Analysis of the revenue-sharing contract under different power structures with application in the biodiesel niche market

Master'sMASTER OF ENGINEERIN

Rural biomass energy 2020: People's Republic of China

The developing world is looking for effective, creative ideas for upscaling clean, renewable energy. No place will gain more socially, economically, and environmentally from increased access to clean, reliable energy than poor, rural areas. Biomass energy, produced from animal and crop wastes, is a sensible renewable energy option for rural areas and it can be cost-effective at community and industry scales if guided effectively by governments. This publication explores the potential of biomass energy to close the urban–rural energy gap, raise farmer incomes, and mend the environment in the People’s Republic of China (PRC). Its findings are instructive for other developing and medium-income countries exploring energy-for-all strategies. The report examines the promises and limitations of leading biomass energy technologies and resources for various distribution scales, including but not limited to household biogas digesters. The information is based on lessons learned and experiences from the Asian Development Bank–financed Efficient Utilization of Agricultural Wastes Project in the PRC, as well as findings and conclusions from a technical assistance grant to assist the government draft a national strategy for developing rural biomass energy.rural biomass energy; rural development; biomass resources; biomass technologies; China

Production of short-chain fatty acids (SCFAs) as chemicals or substrates for microbes to obtain biochemicals

Carboxylic acids have become interesting platform molecules in the last years due to their versatility to act as carbon sources for different microorganisms or as precursors for the chemical industry. Among carboxylic acids, short-chain fatty acids (SCFAs) such as acetic, propionic, butyric, valeric, and caproic acids can be biotechnologically produced in an anaerobic fermentation process from lignocellulose or other organic wastes of agricultural, industrial, or municipal origin. The biosynthesis of SCFAs is advantageous compared to chemical synthesis, since the latter relies on fossil-derived raw materials, expensive and toxic catalysts and harsh process conditions. This review article gives an overview on biosynthesis of SCFAs from complex waste products. Different applications of SCFAs are explored and how these acids can be considered as a source of bioproducts, aiming at the development of a circular economy. The use of SCFAs as platform molecules requires adequate concentration and separation processes that are also addressed in this review. Various microorganisms such as bacteria or oleaginous yeasts can efficiently use SCFA mixtures derived from anaerobic fermentation, an attribute that can be exploited in microbial electrolytic cells or to produce biopolymers such as microbial oils or polyhydroxyalkanoates. Promising technologies for the microbial conversion of SCFAs into bioproducts are outlined with recent examples, highlighting SCFAs as interesting platform molecules for the development of future bioeconomy

Production of Short-Chain Fatty Acids (Scfas) As Chemicals or Substrates for Microbes to Obtain Biochemicals

[Abstract] Carboxylic acids have become interesting platform molecules in the last years due to their versatility to act as carbon sources for different microorganisms or as precursors for the chemical industry. Among carboxylic acids, short-chain fatty acids (SCFAs) such as acetic, propionic, butyric, valeric, and caproic acids can be biotechnologically produced in an anaerobic fermentation process from lignocellulose or other organic wastes of agricultural, industrial, or municipal origin. The biosynthesis of SCFAs is advantageous compared to chemical synthesis, since the latter relies on fossil-derived raw materials, expensive and toxic catalysts and harsh process conditions. This review article gives an overview on biosynthesis of SCFAs from complex waste products. Different applications of SCFAs are explored and how these acids can be considered as a source of bioproducts, aiming at the development of a circular economy. The use of SCFAs as platform molecules requires adequate concentration and separation processes that are also addressed in this review. Various microorganisms such as bacteria or oleaginous yeasts can efficiently use SCFA mixtures derived from anaerobic fermentation, an attribute that can be exploited in microbial electrolytic cells or to produce biopolymers such as microbial oils or polyhydroxyalkanoates. Promising technologies for the microbial conversion of SCFAs into bioproducts are outlined with recent examples, highlighting SCFAs as interesting platform molecules for the development of future bioeconomy.This article is based upon work from COST Action Yeast4Bio (CA18229), supported by COST (European Cooperation in Science and Technology). Open access funding provided by Swedish University of Agricultural Sciences. CK, NOL, MCV from the BIOENGIN group, are grateful to Xunta de Galicia for its financial support to Competitive Reference Research Groups (ED431C 2021/55). They also thank the Spanish Ministry of Science and Innovation and European FEDER funding (PID2020-117805RB-I00) for financing ongoing research, at the BIOENGIN group, on the topic of this paper. ETP, CGF and SG acknowledge the projects BIOMIO + H2 (PID2020-119403RBC21) funded by MCIN/AEI/http://dx.doi.org/10.13039/501100011033 and OLEOFERM (EraBoBiotech; PCI2021-121936) funded by MCIN/AEI/http://dx.doi.org/10.13039/501100011033 and “European Union NextGenerationEU/PRTR”. ETP also acknowledges the grant RYC2019-027773-I funded by MCIN/AEI/http://dx.doi.org/10.13039/501100011033 and by “ESF Investing in your future”. VP and BM were supported by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas) [grant number 2018–01877]Xunta de Galicia; ED431C 2021/55Suecia. Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas); 2018–0187

Optimization of the production of biodiesel from recycled grease trap waste

This thesis investigated the technical and economic feasibilities of biodiesel produced from recycled grease trap waste (GTW) which accumulates in the wastewater system coming from food outlets and food processing sectors. The study was carried out by performing four principal tasks, these being: (1) extraction of fats, oils and grease (FOG) from GTW and investigation of its characterisation as a potential feedstock for biodiesel production; (2) development of an analytical methodology for the quantitative analysis of free fatty acid ethyl ester profiles; (3) optimisation of the process parameters for the synthesis of biodiesel from the extracted FOG via esterification and transesterification reactions; (4) scaling-up the laboratory-based process using a process simulator, and evaluating the economic feasibility of producing biodiesel from GTW. The GTW investigated in this study was provided by Peats Soil and Garden Supplies Ltd. Pty., (Adelaide, South Australia). The provided GTW was collected from the floating grease layer in a storage tank in which the lipid content was concentrated due to its lower density (approximately 51 wt%). Lipid extraction was then performed at ambient temperature (25ºC), employing hexane (HEX) and diethyl ether (DEE) as the solvents. A 97% lipid yield was obtained under the optimum operating conditions, these being: 1:1 DEE to GTW ratio (v/w); 300 rpm stirring speed, and 5 hr reaction time. Due to the high level of free fatty acids (>80 wt%) in the extracted oil, the esterification reaction was then conducted to reduce the FFA level in the feedstock. Two approaches, an esterification reaction with the use of the co-solvent acetone, and an esterification reaction without acetone were investigated and optimized. The optimal conditions for both reactions were determined using response surface methodology (RSM) based on central composite design (CCD). Optimum conditions for the esterification reaction without acetone were found to be 6:1 ethanol to oil molar ratio, 3 hr reaction time, 75ºC reaction temperature, and 3 wt% H₂SO₄ loading per FOG weight. In the presence of acetone, the optimal conditions were 35% v/v acetone to FOG, 6:1 ethanol to oil molar ratio, 3 hr reaction time, and 3 wt% H₂SO₄ loading. The ester yields obtained were 81 wt% and 80 wt%, respectively. The crude oil obtained from the previous pre-treatment was then subjected to a transesterification reaction to convert the remaining glycerides to ethyl esters. Two approaches, which were specified by the priority of the added components, were investigated to determine the optimal operating parameters. The results showed that a 96.7 wt% ester yield could be obtained under the optimum conditions, which were; 4:1 ethanol to oil molar ratio, 1 hr reaction time, 65ºC reaction temperature, and 1 wt% KOH loading. Importantly, approximately 30% of the excess ethanol could be reduced when ethanol and the base catalyst were heated first, while the extracted oil was added later at a specific rate. It was also found that the characterization of the GTW-derived biodiesel obtained satisfied most of the performance and compositional parameters required by the Australian Biodiesel Standard. After obtaining the optimal process parameters, two simulation models were constructed using Aspen Plus® V8.8 to generate the equipment and utility data required for the economic evaluation. Those simulation models were classified by the use of the co-solvent acetone in the esterification reaction. The result showed that the minimum production price of GTW-derived biodiesel was US$1,337.5/t, obtained through the process without using acetone. It can be concluded that the production of biodiesel from recycled greases is technically feasible and the economic aspect is also promising, although further studies need to be conducted to produce a biodiesel fuel which all satisfies the current mandatory standards.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Chemical Engineering, 201

Best Environmental Management Practice in the Tourism Sector

The tourism sector has a large potential to reduce its environmental impacts and many measures are already effectively implemented by companies of this sector. This document describes what are the best practices employed by frontrunners in all aspects under their direct control or on which they have a considerable influence. They cover cross-cutting issues, destination management, tour operators and travel agents, water and energy consumption and waste production in accommodation, restaurant and hotel kitchens, and campsites management. The document also contains sector-specific environmental performance indicators and benchmarks of excellence. These can be used by all the actors involved in the tourism sector to monitor their environmental performance and to benchmark it against the performance of frontrunners in each given specific area. Overall, this document aims at supporting all actors in the tourism sector who intend to improve their environmental performance and seek for reliable and proven information on how best to do it.JRC.J.5-Sustainable Production and Consumptio