Review and prospect of emerging contaminants in waste – Key issues and challenges linked to their presence in waste treatment schemes: General aspects and focus on nanoparticles

The presence in waste of emerging pollutants (EPs), whose behaviours and effects are not well understood, may present unexpected health and environmental risks and risks for the treatment processes themselves. EP may include substances that are newly detected in the environment, substances already identified as risky and whose use in items is prohibited (but which may be present in old or imported product waste) or substances already known but whose recent use in products can cause problems during their future treatment as waste. Several scientific studies have been conducted to assess the presence of EP in waste, but they are mostly dedicated to a single category of substance or one particular waste treatment. In the absence of a comprehensive review focused on the impact of the presence of EP on waste treatment schemes, the authors present a review of the key issues associated with the treatment of waste containing emerging pollutants. This review presents the typologies of emerging pollutants that are potentially present in waste along with the major challenges for each treatment scheme (recycling, composting, digestion, incineration, landfilling and wastewater treatment). All conventional treatment processes are affected by these new pollutants, and they were almost never originally designed to consider these substances. In addition to these general aspects, a comprehensive review of available data, projects and future R&D needs related to the impact of nanoparticles on waste treatment is presented as a case study.     

Energy implications of mechanical and mechanical–biological treatment compared to direct waste-to-energy

Primary energy savings potential is used to compare five residual municipal solid waste treatment systems, including configurations with mechanical (MT) and mechanical–biological (MBT) pre-treatment, which produce waste-derived fuels (RDF and SRF), biogas and/or recover additional materials for recycling, alongside a system based on conventional mass burn waste-to-energy and ash treatment. To examine the magnitude of potential savings we consider two energy efficiency levels (state-of-the-art and best available technology), the inclusion/exclusion of heat recovery (CHP vs. PP) and three different background end-use energy production systems (coal condensing electricity and natural gas heat, Nordic electricity mix and natural gas heat, and coal CHP energy quality allocation).The systems achieved net primary energy savings in a range between 34 and 140 MJ_primary/100 MJ_{input waste}, in the different scenario settings. The energy footprint of transportation needs, pre-treatment and reprocessing of recyclable materials was 3–9.5%, 1–18% and 1–8% respectively, relative to total energy savings. Mass combustion WtE achieved the highest savings in scenarios with CHP production, nonetheless, MBT-based systems had similarly high performance if SRF streams were co-combusted with coal. When RDF and SRF was only used in dedicated WtE plants, MBT-based systems totalled lower savings due to inherent system losses and additional energy costs. In scenarios without heat recovery, the biodrying MBS-based system achieved the highest savings, on the condition of SRF co-combustion. As a sensitivity scenario, alternative utilisation of SRF in cement kilns was modelled. It supported similar or higher net savings for all pre-treatment systems compared to mass combustion WtE, except when WtE CHP was possible in the first two background energy scenarios. Recovery of plastics for recycling before energy recovery increased net energy savings in most scenario variations, over those of full stream combustion. Sensitivity to assumptions regarding virgin plastic substitution was tested and was found to mostly favour plastic recovery.     

Quantifying capital goods for waste incineration

Materials and energy used for the construction of modern waste incineration plants were quantified. The data was collected from five incineration plants (72,000–240,000 tonnes per year) built in Scandinavia (Norway, Finland and Denmark) between 2006 and 2012. Concrete for the buildings was the main material used amounting to 19,000–26,000 tonnes per plant. The quantification further included six main materials, electronic systems, cables and all transportation. The energy used for the actual on-site construction of the incinerators was in the range 4000–5000 MW h. In terms of the environmental burden of producing the materials used in the construction, steel for the building and the machinery contributed the most. The material and energy used for the construction corresponded to the emission of 7–14 kg CO₂ per tonne of waste combusted throughout the lifetime of the incineration plant. The assessment showed that, compared to data reported in the literature on direct emissions from the operation of incinerators, the environmental impacts caused by the construction of buildings and machinery (capital goods) could amount to 2–3% with respect to kg CO₂ per tonne of waste combusted.     

Gasification of waste plastics by steam reforming in a fluidized bed

The process of producing synthetic gas from waste plastics by steam reforming was investigated. To evaluate this process, the steam reforming of the oils derived from low-density polyethylene and polystyrene were carried out using a laboratory-scale fluidized bed of Ni-Al₂O₃ catalysts. The performance of gasification in terms of carbon conversion, gas yield, and gas compositions was examined. Although oils derived from plastics contain many kinds of heavy hydrocarbons and aromatics, they were well gasified at temperatures above 1023 K with a steam/carbon ratio of 3.5 and a weight hourly space velocity of 1 h⁻¹. The hydrogen content of the product gas was very high at approximately 72 vol% for polyethylene-derived oil and 68 vol% for polystyrene-derived oil. These compositions agreed well with the values calculated from chemical equilibrium.     

Studies of the effects of environmental factors on the seasonal change of phytoplankton population in municipal waste water stabilization ponds

Studies were carried out on waste water stabilization ponds in the southern region of Tehran (Iran). Concrete waste stabilization ponds made up of 4 lagoons with 32,047?m³ volume handled 180?lit/ day sewage per capita. Samples were collected monthly from 3 regions of influent and effluent from January to December. Some of the samples were used for identification, culture and purification without any fixation of phytoplankton, but some of them were fixed. Algae were identified using bright field and dark field microscopes. The relationship between the environmental factors and the population density of the species at different times was also measured based on the data analysis factors. Results showed existing 53 taxa in 4 phylum and 38 genera of algae. Taxa were: Cyanophyta (17 taxa), Chlorophyta (22 taxa), Chrysophyta (11 taxa) and Euglenophyta (4 taxa) that fluctuated based on the environmental conditions.     

Goshute Native American Tribe and Nuclear Waste: Complexities and Contradictions of a Bounded-Constitutive Relationship

This essay examines discourse from members of the Skull Valley Goshute Native American tribe about the nuclear-waste proposal and tribal controversy. Building from Kinsella's “bounded-constitutive” theoretical model of communication, I argue the environment (material) is more than a context where Goshute culture and policy development (symbolic) plays out. Rather, environment, culture, and policy mutually define each other, and the material environment constrains Goshute culture. Instead of the symbolic unilaterally influencing the material, the material responds and acts to influence the symbolic. The symbolic becomes responsible to the material and vice versa as the relationship is multi-influential and interactive creating political, cultural, and environmental complexities and contradictions while fueling intra-tribal conflict.     

Impact of source segregation intensity of solid waste on fuel consumption and collection costs

Fuel consumption and collection costs of solid waste were evaluated by the aid of a simulation model for a given collection area of a medium-sized Italian city. Using the model it is possible to calculate time, collected waste and fuel consumption for a given waste collection route. Starting from the data for the current waste collection scenario with a Source Segregated (SS) intensity of 25%, all the main model error evaluated was ?1.2. SS intensity scenarios of 25%, 30%, 35% and 52% were simulated. Results showed an increase in the average fuel consumed by the collection vehicles that went from about 3.3 L/tonne for 25% SS intensity to about 3.8 L/tonne for a SS intensity of 52%. Direct collection costs, including crews and vehicle purchase, ranged from about 40 €/tonne to about 70 €/tonne, respectively, for 25% and 52% SS intensity. The increase in fuel consumption and collection costs depends on the density of the waste collected, on the collection vehicle compaction ratio and on the waste collection vehicle utilization factor (WCVUF). In particular a reduction of about 50% of the WCVUF can lead to an average increase of about 80% in fuel consumption and 100% in collection costs.     

Process development for recovery of copper and precious metals from waste printed circuit boards with emphasize on palladium and gold leaching and precipitation

A novel hydrometallurgical process was proposed for selective recovery of Cu, Ag, Au and Pd from waste printed circuit boards (PCBs). More than 99% of copper content was dissolved by using two consecutive sulfuric acid leaching steps in the presence of H₂O₂ as oxidizing agents. The solid residue of 2nd leaching step was treated by acidic thiourea in the presence of ferric iron as oxidizing agent and 85.76% Au and 71.36% Ag dissolution was achieved. The precipitation of Au and Ag from acidic thiourea leachate was investigated by using different amounts of sodium borohydride (SBH) as a reducing agent. The leaching of Pd and remained gold from the solid reside of 3rd leaching step was performed in NaClO-HCl-H₂O₂ leaching system and the effect of different parameters was investigated. The leaching of Pd and specially Au increased by increasing the NaClO concentration up to 10 V% and any further increasing the NaClO concentration has a negligible effect. The leaching of Pd and Au increased by increasing the HCl concentration from 2.5 to 5 M. The leaching of Pd and Au were endothermic and raising the temperature had a positive effect on leaching efficiency. The kinetics of Pd leaching was quite fast and after 30 min complete leaching of Pd was achieved, while the leaching of Au need a longer contact time. The best conditions for leaching of Pd and Au in NaClO-HCl-H₂O₂ leaching system were determined to be 5 M HCl, 1 V% H₂O₂, 10 V% NaClO at 336 K for 3 h with a solid/liquid ratio of 1/10. 100% of Pd and Au of what was in the chloride leachate were precipitated by using 2 g/L SBH. Finally, a process flow sheet for the recovery of Cu, Ag, Au and Pd from PCB was proposed.     

Siting landfills and incinerators in areas of historic unpopularity: Surveying the views of the next generation

The Campania Region in Southern Italy has suffered many problems with municipal solid waste management since the mid-1990s, leading to significant public disturbances and subsequent media coverage. This paper reports on the current views and knowledge of young people (university students) in this region about waste management operations and facilities, specifically the siting of landfills and incinerators. By means of a structured questionnaire, opinion and knowledge were systematically examined by degree type and course year. The study took place in 2011 at the University of Salerno campus. A sample of 900 students, comprising 100 students for each of the nine considered faculties, and 20 students for every academic course year, was randomly selected. Only about a quarter of respondents were not opposed to the siting of a landfill or an incinerator in their city. This clearly highlights that historic opposition to the construction of waste facilities is difficult to overcome and that distrust for previous poor management or indiscretions is long-lived and transcends generations. Students from technical faculties expressed the most reasonable opinion; opinion and knowledge were statistically related (Chi-square test, p < 0.05) to the attended faculty, and the knowledge grew linearly with progression through the university. This suggests that awareness of waste management practices develops with experience and understanding of environmental issues. There is general acceptance that many stakeholders – technicians, politicians and citizens – all have to be part of the decision process when siting a new waste management facility. The opinions of the young respondents were significantly influenced by their level of environmental knowledge.     

Cleaner production opportunity assessment for a milk processing facility

Possible cleaner production (CP) opportunities for a milk processing facility were examined in this study. The CP concept and its key tools of implementation were used to assess the potential CP opportunities in the facility studied. The general production process and its resulting environmental loads were investigated by taking possible CP opportunities as the basis of study. The methodology developed for CP opportunity assessment in the milk processing facility covered two major steps: preparation of checklists to assist auditing and CP opportunity assessment, and implementation of the mass-balance analysis. For mass-balance analysis, measurements and experimental analysis of the mass flows were utilized to determine the inputs and outputs. Prepared checklists were utilized to determine waste reduction options that could be implemented. Selected opportunities were evaluated considering their environmental benefits and economic feasibility. The results of the study indicated that 50% of the service water used, 9.3% of the current wastewater (WW) discharge, 65.36% of the chemical use and the discharge of 181.9 kg/day of chemical oxygen demand (COD) and 20.7 kg/day of total suspended solids (TSS) could be eliminated and 19.6% of the service water used could be recycled/reused.