Waste Management & Research最新文献

Biomethane production by anaerobic digestion (AD) of sludge from municipal wastewater treatment is a viable practice to valorise the residues of these plants. However, although the relevant literature is abundant, no comprehensive reviews have been recently published on this topic. Detailed information concerning the factors influencing the AD process and values of biomethane production from the sludge from municipal wastewater treatment plants (MWWTPs) on the global scale may support technicians and researchers in both the planning and the design steps of an AD process. This study proposes a systematic review and a meta-analysis of the factors that noticeably influence biomethane yield deriving from AD of sludge from MWWTP. The reported values were systematically analysed compared to the main factors driving AD, including publication year, geographical area of each study, type of digested sludge, treatment in the water line of the MWWTP, possible sludge pre-treatments, type of digestion process, hydraulic retention time (HRT) and temperature regime of the AD process. A higher biomethane production was registered in North American plants compared to countries in other continents. Older studies published between 2001 and 2005 reported lower mean values compared to the more recent experiments. A gradient of 'primary sludge' > 'mixed sludge' > 'wastewater activated sludge' was found for the mean biomethane yield in relation to the digested sludge type. The mean biomethane yields for different types of sludge on a global scale are 0.425, 0.296 and 0.176 Nm³ kg _VS^-1 for primary sludge, mixed sludge and waste activated sludge, respectively. Overall, the study demonstrates: (i) the very large variability of biomethane yields from AD of the residues from MWWTPs (mainly due to the different characteristics of sludge) and (ii) the non-significance of some factors (i.e. treatment in the water line, pre-treatments, type of process, HRT and temperature regime) on energy yields from the AD process.

An efficient municipal solid waste (MSW) system is critical to modern cities in order to enhance sustainability and liveability of urban life. With this aim, the planning phase of the MSW system should be carefully addressed by decision makers. However, planning success is dependent on many sources of uncertainty that can affect key parameters of the system, for example, the waste generation rate in an urban area. With this in mind, this article contributes with a robust optimization model to design the network of collection points (i.e. location and storage capacity), which are the first points of contact with the MSW system. A central feature of the model is a bi-objective function that aims at simultaneously minimizing the network costs of collection points and the required collection frequency to gather the accumulated waste (as a proxy of the collection cost). The value of the model is demonstrated by comparing its solutions with those obtained from its deterministic counterpart over a set of realistic instances considering different scenarios defined by different waste generation rates. The results show that the robust model finds competitive solutions in almost all cases investigated. An additional benefit of the model is that it allows the user to explore trade-offs between the two objectives.

Printed circuit boards (PCBs) are the most complex and valuable component of electronic devices, but only 34% of them are recycled in an environmentally sound manner. Improving the recycling rate and efficiency requires a fast, reliable and uncostly analytical method. Although the X-ray fluorescence (XRF) shows high potential, it is often unreliable. In this study, we propose a novel XRF methodology for the elemental analysis of PCBs, using the certified reference material (CRM) to decrease uncertainty and enhance accuracy. The results show significant improvement in robustness and accuracy of portable XRF(pXRF) analyses for elements Cu, Pb, Ni, As and Au, with a relative average inaccuracy of approximately 5% compared to referenced values. The methodology validation carried out by comparing pXRF and inductively coupled plasma mass spectroscopy analyses of personal computer motherboard samples shows no statistically significant difference for elements Cu, Cr and Ag. The study shows that the calibration of pXRF by CRMs enables the necessary analysis of PCBs in an efficient and reliable manner and could be also be applied to different types of PCBs and other electronic components, batteries or contaminated soil samples.

In the area of Solid Waste Management, transportation of the collected waste is a critical aspect considering the substantial time spent by garbage trucks on public roads. Studies have reported that transporting garbage has challenges related to public exposure and aesthetics. This study presents a generalised bi-objective formulation for the optimal routing of garbage trucks from transfer stations to recycling sites/landfills considering the trade-off between public exposure and aesthetic loss and constraining the operating cost. The formulation uses the novel link capacity function to account for the delay at traffic signals and the mix of trucks and cars on link performance. The proposed formulation is solved using the weighted sum and ε-constraint methods and applied to a realistic case study of the City of Chicago, USA. The Pareto Front obtained for the bi-objective formulation offers diverse trade-off solutions catering to distinct performance metrics. The results highlight the disparity across the solutions; the solution (P0.95 on Pareto Front) for minimum operating cost (or travel time or distance travelled) is very different from the solution (P0.4 on Pareto Front) for aesthetic cost and public exposure. The parametric study indicated that a modest operating budget may suffice for achieving aesthetic benefits, but minimising public exposure requires a higher operating budget. Finally, the proposed framework is adaptable to address various challenges pertaining to waste transportation, thereby serving as a valuable tool for evaluating policies and practices geared towards sustainability objectives.

The aim of this research is to analyse the performance of the extended producer responsibility model for the management of end-of-life tires (ELTs) in Ecuador that has been implemented since 2013. For this research, we conducted case studies of, and subsequently, a comparative analysis between, the ELT management system in Ecuador with respect to the ELT management models in Colombia and Brazil. Our findings show that although the programme implementation represented a significant advance in Ecuador's waste management system there are important challenges that should be considered in future adaptations of the programme. Among the measures that can be adopted to improve the ELT management system are the consolidation and stimulation of the market for products made from ELT waste; promotion of other productive sectors linked to the creation of new products and sectors that generate complementary products; enhancement of the generation, socialization and access to knowledge of the waste by-products for micro-, small- and medium-sized enterprises; increase the tire consumer fee, known as 'Ecovalor' and improvement of the quality and availability of information and indicators regarding ELT management. In this sense, the experiences of Colombia and Brazil show important lessons for the Ecuadorian case.

Thermal phase separation technology is a new comprehensive treatment technology, which heats oil-based cuttings to a certain temperature to vaporize oil and water components. Based on a large oil-based drilling cuttings comprehensive utilization project, the engineering design and application effect of thermal phase separation technology were analysed. The practice shows that thermal phase separation technology can reduce the oil content of purified residue to 0.1-0.2%, the average recovery rate of base oil is 94.12% and the annual recovery of base oil is about 4800 t; the purified residue does not have corrosive, leaching toxicity and other dangerous characteristics, and can be used for making bricks or building materials. Thermal phase separation technology is a comprehensive utilization and treatment technology with excellent engineering and environmental benefits, which has a high promotion value.

Removing water-soluble chlorides (WSCs) through water extraction is a common pretreatment technology for recycling municipal solid waste incineration (MSWI) fly ash (FA). However, the extracted solution often contains heavy metals, the concentrations of which exceed standards for effluent. This study aims to investigate the adsorption of heavy metals by palygorskite in water-extracted solution and explore the feasibility of stabilizing heavy metals through comilling palygorskite-adsorbed heavy metals (PAHMs) with water-extracted fly ash (WFA). The experimental parameters include: two-stage water extraction with a liquid-to-solid ratio of 5, adding 0, 0.125, 0.25, 0.5, 1, 2 or 3 g of palygorskite to 100 mL of water-extracted solution, and comilling the mixture of PAHMs and WFA for 0, 0.5, 1, 2, 4, 8, 12, 24 or 96 hours. The experimental results revealed that 3 g of palygorskite in 100 mL of extracted solution could absorb Pb, Cd, Cr, Cu and Zn, meeting the effluent standards. The total amount of Pb, Cd, Cr, Cu and Zn removal rate reached 99.7%. Moreover, 98.44% of the WSCs were not adsorbed, the water extraction process for removing WSCs was not compromised. After the comilling of PAHMs and WFA, the distribution of the heavy metals in the milled blended powder was greater than 99.44%; moreover, toxicity characteristic leaching procedure concentrations were determined to conform to regulatory standards, and the sequential extraction procedure revealed that the heavy metals tended to be in stable fractions. This achieves the goal of preventing secondary pollution from heavy metals during the MSWI FA recycling process.

The article presents the possibility of increasing the water resistance of gypsum binders (GBs) obtained based on synthetic gypsum by introducing additives derived from industrial wastes. Regularities were obtained for the influence of the type and amount of additives on the water/gypsum ratio (W/G), strength indicators and water resistance of high-strength GB. The introduction of a single-component additive to improve water resistance does not have a significant effect. Complex additives based on Portland cement, granulated blast-furnace slag, electric steel-smelting slag, expanded clay dust and granite screenings of various fractions have been developed that make the maximum contribution to improving the water resistance of a high-strength GB based on synthetic calcium sulphate dihydrate, which made it possible to increase the water-resistance coefficient from 0.39 to 0.82.

The growing tendency towards 'urbanization' is promoting an increase in resource consumption and waste generation, which requires proper waste separation management with active participation of the population. To this end, it is essential to know the personal modifiable factors that predict recycling. The primary aim of the present study is to develop and evaluate the psychometric properties of a Spanish language questionnaire designed to measure determinants of household waste separation for recycling purposes (ReDom Questionnaire). A cross-cultural adaptation, translation and psychometric evaluation was undertaken of an extant questionnaire originally developed in Swedish, and the resultant Spanish questionnaire was then subjected to reliability and validity testing. The questionnaire was developed using survey data from 759 respondents and 33 participants performed the retest to assess reliability. The resultant 'ReDom Questionnaire' is composed of three factors that draw on relevant elements of the COM-B framework: motivation (seven items), physical opportunity (three items) and social opportunity (three items). The accuracy of the scores is adequate both in terms of internal consistency (factorial weights >0.60; comparative fit index = 0.994; root mean square error of approximation = 0.049; root mean square residual (RMSR) = 0.053) and reliability (Pearson correlation >0.65; Cronbach's alpha >0.75). In conclusion, the Spanish ReDom Questionnaire showed adequate psychometric properties and appears useful for assessing the determinants of household waste separation.