Waste Management & Research: The Journal for a Sustainable Circular Economy

Sewage sludge and industrial steel slag (SS) pose threats of serious pollution to the environment. The experiments aimed to improve the stabilizing effects of heavy metal Ni and Cd morphology in composting sludge. The total Ni and Cd species distribution and chemical forms in the compost sewage sludge were investigated with the use of compost and co-compost with SS, including degradation. The carbon/nitrogen ratio of piles was regulated with the use of sawdust prior to batch aerobic composting experiments. Results indicated that the co-composting with SS and organic matter humification can contribute to the formation of Fe and Mn hydroxides and that the humus colloid significantly changed Ni and Cd species distribution. The decreased content of Ni and Cd in an unstable state inhibited their biological activity. Conclusions were drawn that an SS amount equal to 7% of the dry sludge mass was optimal value to guarantee the lowest amount of Cd in an unstable state, whereas the amount was 14% for Ni.

In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

This study aimed to evaluate the impact of landfill leachate concentration on the degradation behaviour of solidified clay liners and to propose a viable mechanism for the observed degradation. The results indicated that the unconfined compressive strength of the solidified clay decreased significantly, while the hydraulic conductivity increased with the leachate concentration. The large pore proportion in the solidified clay increased and the sum of medium and micro pore proportions decreased, demonstrating that the effect on the solidified clay was evident after the degradation caused by exposure to landfill leachate. The unconfined compressive strength of the solidified clay decreased with increasing leachate concentration as the leachate changed the compact structure of the solidified clay, which are prone to deformation and fracture. The hydraulic conductivity and the large pore proportion of the solidified clay increased with the increase in leachate concentration. In contrast, the sum of medium and micro pore proportions showed an opposite trend in relation to leachate concentration, because the leachate gradually caused the medium and micro pores to form larger pores. Notably, higher leachate concentrations resulted in a much more distinctive variation in pore proportions. The hydraulic conductivity of the solidified clay was closely related to the size, distribution, and connection of pores. The proportion of the large pores showed a positive correlation with the increase of hydraulic conductivity, while the sum of the proportions of medium and micro pores showed a negative correlation.

The aim of this work was to investigate anaerobic digestibility of artichoke waste resulting from industrial transformation. A series of batch anaerobic digestion tests was performed in order to evaluate the biochemical methane potential of the matrix in respect of the process. A comparison of the different performances of the laboratory-scale reactors operating in mesophilic conditions and utilizing three different values of the inoculum/substrate ratio was carried out. The best performance was achieved with an inoculum/substrate ratio of 2. Artichoke-processing byproducts showed a classical organic waste decomposition behaviour: a fast start-up phase, an acclimation stage, and a final stabilization phase. Following this approach, artichoke waste reached chemical oxygen demand removal of about 90% in 40 days. The high methane yield (average 408.62 mL CH₄ g_vs⁻¹ voltatile solids), makes artichoke waste a good product to be utilized in anaerobic digestion plants for biogas production.

In many developing countries, the inadequacy of data regarding the quantity and composition of healthcare waste is one of the major reasons for improper healthcare waste management. We investigated the generation rate and composition of healthcare wastes in six public and three private hospitals. We conducted healthcare waste composition and characterization measurements for seven consecutive days in the selected hospitals following the protocol described by the World Health Organization (WHO). The results revealed that the total generation rate of healthcare wastes of hospitals ranged from 0.25 to 2.77 kg/bed/day with a median value of 1.67 kg/bed/day for inpatients to 0.21–0.65 in kg/patient/day with a median value of 0.31 kg/patient/day for outpatients. The waste generation rate in private hospitals (median 3.9 kg/bed/day) was significantly greater (Kruskal–Wallis test, P < 0.05) than in government hospitals (median 1.5 kg/bed/day). The median values of percent hazardous waste estimated for private and government hospitals were 63.4% and 52.2%, respectively. These figures are about three times greater than the threshold values recommended by the WHO. This situation might be attributed to the improper practice of healthcare waste segregation by health professionals and auxiliary health workers due to inadequate risk perception and lack of enforced public health regulations. The study revealed that the generation rate and proportion of hazardous waste significantly varies between public and private hospitals and number of patients treated per day.

Thermal treatment of sewage sludge produces fly ash, also known as the air pollution control residue (APCR), which may be recycled as a component of artificial lightweight aggregates (ALWA). Properties of APCR are typical: high content of Ca, Mg, P₂O₅, as well as potential to induce alkaline reactions. These properties indicate that ALWA prepared with a high content of APCR may remove heavy metals, phosphorus, and ammonium nitrogen from wastewater with high efficiency. The aim of this preliminary study was to determine the optimal composition of ALWA for potential use as a filter media in wastewater treatment systems. Five kinds of ALWA were produced, with different proportions of ash (shown as percentages in subscripts) in mixture with bentonite: ALWA₀ (reference), ALWA_12.5, ALWA₂₅, ALWA₅₀, and ALWA₁₀₀. The following parameters of ALWA were determined: density, bulk density, compressive strength, hydraulic conductivity, and removal efficiency of ions Zn²⁺, NH₄⁺, and PO₄³⁻. Tests showed that ALWA had good mechanical and hydraulic properties, and might be used in wastewater filtering systems. Phosphates and zinc ions were removed with high efficiency (80-96%) by ALWA_25-100 in static (batch) conditions. The efficiency of ammonium nitrogen removal was low, <18%. Artificial wastewater treatment performance in dynamic conditions (through-flow), showed increasing removal efficiency of Zn²⁺, PO₄³⁻ with a decrease in flow rate.

Because of many limitations, the siting, construction and operation of a new solid waste management (SWM) facility is a significant challenge in Palestine. A SWM facility should operate in a sustainable in all aspects, including social acceptance, environmental protection, financial equity, and, in this particular case study, the political acceptance of all regional parts is extremely important. This article presents the outcomes of an extended study that aimed to investigate the concerns and attitudes of the residents of Hebron governorate related to the entire lifecycle of SWM facilities. A structured questionnaire was developed based on literature reviews and was distributed to residents in three different communities in the same governorate with various lifestyle backgrounds. The overall investigation focused on the collection of raw data regarding citizens’ levels of concern regarding the environmental impacts of SWM facilities, the general waste management aspects, the benefits gained by the operation of various types of SWM facilities and the attitudes during the construction period of each facility. The results show that concerns about water pollution are significant; the benefits gained as a result of the operation of SWM facilities, particularly the heat supply from incinerators, are welcomed; and ‘not in my backyard’ syndrome is highlighted. The outcomes of this research are input data for the development of a roadmap that may include educational programs, incentive schemes and active public involvement during all phases of the implementation of SWM facilities (planning, siting, operation), in order to also ensure public acceptance, participation and regional sustainable development.

Food waste is a waste stream with serious economic, environmental and social implications. The emphasis of the reported research is on the food waste generated by households in Greece. A structured questionnaire was utilised in order to identify the attitudes of the respondents and investigate the prevalence of certain behavioural good practices that can prevent the generation of food waste. The research, to our knowledge the first of its kind in Greece, took place in February and March 2012. Face-to-face interviews were employed, resulting to a total of 231 consumers fully completing the questionnaire. Results indicate that, based on self-reported behaviour, people in Greece have positive attitudes towards food waste prevention and that their habits are close to the good practices suggested in the literature for reducing food waste. For instance, most respondents do plan their food shopping in a multitude of ways and are very careful in their purchases of fresh food supplies. However, about 40% misunderstand the meaning of food date labels. The positive findings are strongly influenced by the severe recession experienced in the country, which makes consumers more conscious of their spending. Results may serve as a yardstick to further promote and establish food waste prevention behaviour at the household level on an environmental and social awareness basis that may outlast the economic crisis.

The development of modern cities favours the formation of metropolitan zones with urban and industrial areas. The central metropolitan area (CMA) of the Principality of Asturias (northwest Spain), takes up 9.6% of the territory and represents 78% of its population. The first and second wood transformation industries of the CMA generate rather large amounts of biomass residues suitable for both reclaim and energy valuation considering technical, economic, and environmental restrictions. The results obtained from the evaluation of the biomass and the bioenergy of these residues are 7.9 kt/year and 114.7 TJ/year, respectively. The location for the development of a densified solid biofuels plant to produce pellets from these available residues is proposed for the Siero municipality, which is in the CMA. The plant would have an annual potential production capacity for the conventional pelletization process equivalent to 10 MW of fuel output.

With respect to waste sorting, Shanghai sets an example for other Chinese cities on the standardized treatment of kitchen waste (KW) in China. According to the results of investigation, about 560 kilo tons of KW from different sources in Shanghai were produced in 2011. Of this, 45.6% (255.6 kilo tons) was collected and transported properly by a comprehensive and formal collection and transportation system. Landfilling and incineration, which are the traditional treatment technologies used, show downward trends because of increasing environmental awareness and land restrictions. Feed production, composting and biodiesel refining play increasingly important roles in the recycling of KW. Safe disposal, reduced KW quantity, public education, and technological innovation are still problematic issues and need to be considered in future waste management in Shanghai.

Dynamic waste management (DWM): Towards an evolutionary decision-making Approach by Gabriel Rojo, Mathias Glaus, Robert Hausler, Valérie Laforest and Jacques Bourgeois, Waste Manag Res December 2013 31: 1285–1292, doi :10.1177/0734242X13507306