Sb release characteristics of the solid waste produced in antimony mining smelting process

Sb release characteristics of blast furnace slag, mining waste rock and tailing sand were investigated in static immersion and dynamic leaching test. These three kinds of waste samples were collected from the antimony mine in Lengshuijiang, China, produced in mining smelting process. Effects of solid/liquid ratio, sample size and pH of leaching solution on Sb release characteristics were inspected based on the analysis of scanning electron microscope, pH and EC of leachate. The optimal parameters for Sb leaching of each sample were analyzed. For blast furnace slag and mining waste rock, Sb release contents increased along with the decline of solid/liquid ratio. The maximum accumulative release contents were 42.13, 34.26 mg/kg at the solid/liquid ratio of 1:20. While Sb release content for tailing sand decreased first and then increased with the reduction of solid/liquid ratio. When the solid/liquid ratio was 1:5, the accumulative Sb release content reached the most (24.30 mg/kg). Sb release content of mining waste rock increased with the drop of leaching solution pH, with the highest accumulative release content of 26.01 mg/kg at pH 2.0. Sb release contents of blast furnace slag and tailing sand showed positive correlation with the variation of leaching solution pH. The maximum accumulative release contents of these two samples were 215.91 and 147.83 mg/kg, respectively, when leaching solution pH was 7.0. In summary, Sb release capacity of the three samples in descending order was tailing sand, blast furnace slag and mining waste rock. pH and EC of the leachate in dynamic test varied independently with the initial pH of leaching solution while showing close relationship with mineral hydrolysis in the waste.     

Review of municipal solid waste management options in Malaysia,with an emphasis on sustainable waste-to-energy options

A beautiful and clean environment is the desire of every society. Malaysia is facing an uncontrolled increase in municipal solid waste (MSW) generation due to population growth, economic advancement, and industrialization, but the current, most common waste disposal practice of landfilling is not sustainable. The increasing standard of living also saps more energy from the power generation systems in which fossil fuels are the major source of fuel for the plants. Malaysia generates about 0.5–1.9 kg/capita/day of MSW; a total of about 25,000 tonnes/day of MSW is currently generated and is estimated to exceed 30,000 tonnes/day by 2020. Malaysian MSW is mainly composed of 45 % food waste, 24 % plastic, 7 % paper materials, 6 % metal, 4 % wood and 3 % glass, which are commingled, and is thus characterised by 52–66 % moisture content. Currently, 80–95 % of collected MSW is landfilled and 5 % is recycled, while composting and energy recovery are rarely practiced. This paper reviews the solid waste practice in Malaysia and looks into alternative management options for sustainability. Malaysia MSW represents recyclable power and energy potential if properly sorted. This study considered the practice of sorting at the source and the use of combustible MSW components as fuel to generate heat for a hybrid solar, flue gas, chimney power plant.     

The feasibility of converting solid waste into refuse-derived fuel 5 via mechanical biological treatment process

The aim of our study was to investigate the feasibility of utilizing solid waste after mechanical biological treatment (MBT) processing at a landfill site in Phitsanulok, Thailand, as refuse-derived fuel 5 (RDF-5). The waste composition, and physical and chemical characteristics of each waste fraction were determined to evaluate the suitability of the waste for recycling and reuse as RDF-5. Results showed that after MBT processing, the solid waste >40 mm in size was observed to have 33.8 MJ/kg of calorific value. The average concentrations of heavy metals were also found to be within the acceptable limit for plastic waste combustion, thus proving that MBT-processed solid waste >40 mm in size has high potential for use as RDF-5. The optimal weight ratio of MBT-processed solid waste and crude oil sludge for transformation into RDF-5 was found to be 80:20. With this optimum ratio, the average calorific values of the RDF-5 were determined to be 47 MJ/kg, with sulfur and chlorine contents of 0.16 and 0.74 %, respectively. The characteristics of the produced RDF-5 could meet the specified ASTM standards in terms of calorific value (>15 MJ/kg), and sulfur and chlorine contents. In addition, the compressive strength of the produced RDF-5 was also found to be suitable for compact storage and transportation without any damage. Finally, the energy production cost from this RDF-5 process was estimated as USD $0.05/kWh.     

Gasification applicability study of polyurethane solid refuse fuel fabricated from electric waste by measuring syngas and nitrogenous pollutant gases

To recycle polyurethane foam waste generated from electric appliance recycling centers for use as fuel in a gasification process, polyurethane solid refuse fuel fabricated as pellets was analyzed for the characteristics of elemental composition, proximate analysis, heating value, and thermo-gravimetric testing. It has a high heating value of 29.06 MJ/kg with a high content of combustibles, which could be feasibly used in any thermal process. However, the nitrogen content, of up to 7 %, was comparably higher than for other fuels such as coal, biomass, and refuse-derived fuel, and may result in the emission of nitrogenous pollutant gases of HCN and NH₃. By conducting gasification experiments on polyurethane solid refuse fuel in a fixed-bed reactor, a syngas with a heating value of 9.76 kJ/m³ and high content of both H₂ and CO were produced with good gasification efficiency; carbon conversion 54 %, and cold gas efficiency 60 %. The nitrogenous pollutant gases in syngas were measured at the concentrations of 160 ppm hydrogen cyanide and 40 ppm ammonia, which may have to be reduced using proper cleaning technologies prior to the commercialization of gasification technology for polyurethane waste.     

Physical containment of municipal solid waste incineration bottom ash by accelerated carbonation

Accelerated carbonation of municipal solid waste incineration residues is effective for immobilizing heavy metals. In this study, the contribution of the physical containment by carbonation to immobilization of some heavy metals was examined by some leaching tests and SEM–EDS analysis of untreated, carbonated, and milled bottom ash after carbonation that was crushed with a mortar to a mean particle size of approximately 1 μm. The surface of carbonated bottom ash particles on SEM images seemed mostly coated, while there were uneven micro-spaces on the surface of the untreated bottom ash. Results of Japan Leaching Test No. 18 (JLT18) for soil pollution showed that milling carbonated bottom ash increased the pH and EC. The leaching concentration of each element tended to be high for untreated samples, and was decreased by carbonation. However, after the milling of carbonated samples, the leaching concentration became high again. The immobilization effect of each element was weakened by milling. The ratio of physical containment effect to immobilization effects by accelerated carbonation was calculated using the results of JLT18. The ratio for each element was as follows: Pb: 13.9–69.0 %, Cu: 12.0–49.1 %, Cr: 24.1–99.7 %, Zn: 20.0–33.3 %, and Ca: 28.9–63.4 %.     

Leachate generation and biogas energy recovery in the Jebel Chakir municipal solid waste landfill,Tunisia

A survey was conducted between 2006 and 2008 in order to identify municipal solid waste (MSW) composition and its influence on leachate generation and to assess the amount of biogas yield from the Jebel Chakir landfill in Tunis City. The organic fraction was the predominant compound in the MSW, followed by paper, fine, plastic, leather, rubber, metal, textile, glass and ceramic. The average MSW moisture content varies from 60 % in the wet season to 80 % in the dry one. The recognised MSW composition is well representative if compared to that of cities in developing countries. A large leachate quantity is produced in the landfill of Jebel Chakir, despite the negative water balance of the site. Based on the annual MSW landfilled quantities and using the LandGEM model, the expected peak landfill gas (LFG) production is estimated to occur 1 year after the landfill closure with a rate of 3.53 × 10⁷ m³/year. The analysis of the potential conversion of LFG to electric energy shows it at a total LFG-to-electricity energy of around 257 GWh with a heating value of 4,475 kcal/m³ based on an LFG collection efficiency of 33 % and energy efficiency of 33 % giving an economic feasibility for a 10 MW power plant.     

Assessment of factors affecting household solid waste generation and its composition in Gulberg Town,Lahore, Pakistan

This paper analyzes and compares the findings of the characterization study of collected solid waste from households of three different socioeconomic groups in Lahore, Pakistan, over the four seasons, i.e. Spring (March–April, 2008), Summer (May–June, 2008), Monsoon (August–September, 2008) and Winter (December 2008 and January 2009). The generation rate of waste was 0.96 kg/cap/day for high-income, 0.73 kg/cap/day for middle and 0.67 kg/cap/day for low-income group. The average of total household solid waste (HSW) generation is 0.79 kg/cap/day (including 0.75 kg/cap/day for spring, 0.77 kg/cap/day for summer, 0.86 kg/cap/day for monsoon and 0.76 kg/cap/day. The breakdown for the major physical components of the waste shows that organic waste accounts for the largest proportion (67.46 %). The relations between waste generation rates by physical category and subcategory, in addition to factors such as socioeconomic groups (population density levels, household income and household size), seasonal variation, and daily variation (difference of HSW generation among days of a week) were also analyzed. Statistical analysis shows that there was no significant difference in overall waste generation among days of a week. A significant difference between the seasons for food waste, cardboard, PET, HDPE, other hazardous waste, battery cells, and dust and stone (p < 0.001) was found. The generation rates were found to be higher when compared to other developing countries.     

Sustainability analysis of organic fraction of municipal solid waste conversion techniques for efficient resource recovery in India through case studies

Worldwide solid waste generation is nearly 1.3 billion tonnes/year, whereas in India 62 million tonnes of solid waste is generated per year by 377 million urban people. The increasing amount of solid waste in India, nearly 50% of which is organic matter, is the major concern for treatment and waste management. Several technologies are already in practice for the treatment of organic fraction of municipal solid waste (OFMSW) in India. It is important to assess the sustainability of these processes. In this study, the existing OFMSW technologies in India were examined. Case-study approach was taken for this purpose along with some published secondary reports. It was found that the selection of technology quite depends on the composition of the OFMSW. Food waste rich fractions are recommended for biomethanation, whereas the fractions rich in market waste and household waste are suitable for composting. Fractions rich in lignin and lignocellulosic materials are suitable for pyrolysis and gasification, whereas the rejects are to be sent for RDF preparation. Based on the findings, a sustainable framework has also been proposed, implementation of which may result in better waste management.     

Greenhouse gases emissions from solid waste: an analysis of Expo 2010 Shanghai,China

The management of greenhouse gases (GHGs) emissions is currently a very important environmental issue. Mega-event organizers and host cities have attached great importance to GHGs emissions associated with event-related activities. However, GHGs emissions from event solid waste have never been thoroughly discussed. This study investigated GHGs emissions of major event’s solid waste using life cycle assessment, based on Shanghai Expo case. The results showed that GHGs from collecting and sorting, transportation and landfill treatment amount to 9790 t CO₂e. And the emission intensity is estimated to be 134 g CO₂e per event service. GHGs reduction from recycling amounts to 48 kt CO₂e, with 78 % of these the result of construction waste recycle. It illustrates that waste recycle plays a vital role in GHGs mitigation. Finally, the study suggests that the concept of waste avoidance, waste reuse and waste recycle is an effective waste management to mitigate climate change and should be implemented in major event to achieve the goal of green event.     

Study of hydrodynamic characteristics in a circulating fluidized bed gasifier for plastic waste by computational fluid dynamics modeling and simulation

For designing an efficient circulating fluidized bed reactor, understanding the complex hydrodynamic characteristics in the reactor is required. Hence, in the present study, the modeling and simulation of the circulating fluidized bed gasifier using plastic waste were carried out with Eulerian-Granular approach. Several cases were investigated as changing superficial gas velocities or sizes of plastic waste particle. Firstly, cases were examined with four different velocities when the particle diameter is 1 mm. At the gas velocity of 6 or 8 m/s, gas volume fraction is more than 95 % throughout the reactor and particle velocity has positive value overall. Therefore, a circulating fluidized bed seems to be formed in both cases. Comparing those two cases, better solid mixing can be expected considering the mass fraction and solid velocity at the superficial gas velocity of 6 m/s. Thus this case was further studied for the effect of particle size. As the diameters of plastic waste particle are 1 or 3 mm, it is considered that a circulating fluidized bed is formed. And plastic waste and sand particles are well mixed throughout the reactor. However, the particle diameter increases over 3 mm then, it is very hard to maintain circulating fluidization condition.     

A study of the effects of LCD glass sand on the properties of concrete

In order to study the recycling of discarded liquid crystal display (LCD) glass into concrete (LCDGC), a portion of the usual river sand was replaced by sand prepared from discarded LCD glass. Three different mix designs were regulated by the ACI method (fc(28)=21, 28, and 35MPa) with 0%, 20%, 40%, 60%, and 80% LCD glass sand replacements investigated; their engineering properties were determined. Test results revealed that, when compared to the design slump of 15cm, the 20% glass sand concrete for the three different mix designs kept good slump and slump flow. Furthermore, a slump loss ranging from 7 to 11cm was observed for specimens with 60% and 80% glass sand replacement for the design strengths of 28 and 35MPa. The compressive strengths of the concrete with glass sand replacement were higher than the design strengths. Moreover, the durability of the concrete with 20% glass sand replacement was better than that of the control group. Surface resistivity for specimens with different amounts of LCD glass sand replacement was also higher than that in the control group for mid to long curing ages. The sulfate attack in concrete with different amounts of glass sand replacement caused less weight loss than in the control group. Moderate chloride ion penetration was observed for glass sand concrete. Furthermore, the measured ultrasonic pulse velocities for LCD glass sand concrete specimens were higher than 4100m/s, which qualified these specimens as good concrete. OM and SEM indicate that the dense C-S-H gel hydrate was produced at the interface between the glass sand and cement paste. The test results indicate that the addition of 20% LCD glass sand to concrete satisfies the slump requirements and improves the strength and durability of concrete. This suggests that LCD glass sand can potentially be used as a recycled material in concrete applications.     

Networks of recyclable material waste-picker’s cooperatives: An alternative for the solid waste management in the city of Rio de Janeiro

The objective of this study is to discuss the role of networks formed of waste-picker cooperatives in ameliorating problems of final disposal of solid waste in the city of Rio de Janeiro, since the city’s main landfill will soon have to close because of exhausted capacity. However, it is estimated that in the city of Rio de Janeiro there are around five thousand waste-pickers working in poor conditions, with lack of physical infrastructure and training, but contributing significantly by diverting solid waste from landfills. According to the Sustainable Development Indicators (IBGE, 2010a, IBGE, 2010b) in Brazil, recycling rates hover between 45% and 55%. In the municipality of Rio de Janeiro, only 1% of the waste produced is collected selectively by the government (COMLURB, 2010), demonstrating that recycling is mainly performed by waste-pickers. Furthermore, since the recycling market is an oligopsony that requires economies of scale to negotiate directly with industries, the idea of working in networks of cooperatives meets the demands for joint marketing of recyclable materials. Thus, this work presents a method for creating and structuring a network of recycling cooperatives, with prior training for working in networks, so that the expected synergies and joint efforts can lead to concrete results. We intend to demonstrate that it is first essential to strengthen the waste-pickers’ cooperatives in terms of infrastructure, governance and training so that solid waste management can be environmentally, socially and economically sustainable in the city of Rio de Janeiro.     

Recycling of electrolytic manganese solid waste in autoclaved bricks preparation in China

China has played a dominant role in global electrolytic manganese metal (EMM) production, accounting for over 98 % of the total world capacity since 2008. However, with the rapid development of the EMM industry and depletion of mineral ores, electrolytic manganese solid waste (EMSW) is piling up, so more large-scale landfills are needed. The environmental problems generated by EMSW pose severe threats to soil and ground water, and have become the hot issues in society. The aim is to consume and recycle EMSW, and the primary route is to make autoclaved bricks. However, less attention has been given to the procedure and strength-forming mechanism of EMSW bricks, not to mention the production line of the brick. On the basis of physical and chemical property analysis, the pretreatment process of EMSW was indispensable to solidify/stabilize the heavy metals, such as Mn, Zn, Cd, Pb, etc.. This paper expatiated on the procedure of making EMSW autoclaved bricks, analyzed in detail the strength formed by different cementitious materials with cement properties, and introduced the practical engineering of EMSW autoclaved bricks. The results showed that the pretreatment process with quicklime was effective in solidifying/stabilizing the heavy metals. The compressive strength of EMSW bricks reached 10.05 MPa when quicklime 9 % (w/w) added. Cement may be an ideal cementitious material to create EMSW bricks of high strength in experiments and on the production line. Quicklime and cement used simultaneously produced a lower strength than that when adding cement alone because the gypsum from EMSW and an alkali could generate deleterious effects, e.g., expansion or burst. In the production line of EMSW bricks, an appropriate mix proportion to make high-quality autoclaved bricks was determined: EMSW 30–40 %, cement 10–20 %, and aggregates 40–60 %. The low content of heavy metals tested by toxicity leaching may deduce that the EMSW autoclaved bricks have low environmental risk. However, long-term environmental risk evaluation will be needed, requiring more tests and leaching modeling. Employing EMSW to make high-quality autoclaved bricks may be a promising waste-to-resource strategy.     

Anaerobic co-digestion of tannery waste water and tannery solid waste using two-stage anaerobic sequencing batch reactor: focus on performances of methanogenic step

In this study, anaerobic co-digestion of the tannery waste water (TWW) and tannery solid waste (TSW) with four TWW to TSW mixing ratios (100:0, 75:25, 50:50 and 25:75) was carried out using semi-continuous two-phase anaerobic sequencing batch reactor system under mesophilic temperature (38?±?2 °C). During the experimental study, effluents resulted from previously optimized acidogenic reactors were used to feed subsequent methanogenic reactors and then operated at hydraulic retention time (HRT) of 20, 15 and 10 days and equivalent organic loading rate. The findings revealed that methanogenic reactor of 50:50 (TWW:TSW) treating the effluent from previously optimized acidogenic step exhibits best process performances in terms of daily biogas (415 ml/day), methane production (251 ml/day), methane content (60.5%) and COD removal efficiency (75%) when operated at HRT of 20 days. Process stability of methanogenic step also evaluated and the obtained results showed suitable pH (6.8), no VFA accumulation, i.e., VFA/Alkalinity (0.305), alkalinity (3210 mgCaCO₃/l) and ammonia (246 mg/l with in optimum operating range). In general, improved process stability as well as performance was achieved during anaerobic co-digestion of TWW with TSW compared to mono-digestion of TWW.     

Effect of leachate recirculation on the migration of copper and zinc in municipal solid waste and municipal solid waste incineration bottom ash co-disposed landfill

Municipal solid waste incinerator (MSWI) bottom ash was allowed to be disposed of with municipal solid waste (MSW) in landfill sites in the recently enacted standard of China. In this study, three sets of simulated landfill reactors, namely, conventional MSW landfill (CL), conventional MSWI bottom ash and MSW co-disposed landfill (CCL), and leachate recirculated MSWI bottom ash and MSW co-disposed landfill (RCL), were operated to investigate the environmental impact of the co-disposal. The effect of leachate recirculation on the migration of Cu and Zn in the co-disposed landfill was also presented. The results showed that the co-disposal of MSWI bottom ash with MSW would not enhance the leaching of Cu and Zn from landfill. However, the co-disposal increased the Cu and Zn contents of the refuse in the bottom layer of the landfill from 56.7 to 65.3 mg/kg and from 210 to 236 mg/kg, respectively. The recirculation of the leachate could further increase the Cu and Zn contents of the refuse in the bottom layer of the landfill to 72.9 and 441 mg/kg, respectively. Besides these observations, the results also showed that the co-disposed landfill with leachate recirculation could facilitate the stabilization of the landfill.     

LCA to Evaluate the Environmental Impact for Chemical Pre-treatment in Plastics Metallization

The life cycle assessment methodology was used to calculate the environmental impacts of the current chemical pre-treatment with chromium(VI) for electroplating acrylonitrile butadiene styrene. The inventory comprised: the procurement of chemicals; the manufacturing process with successive baths and rinses that requires, in addition to chemicals, energy to heat baths, air agitation, filtration, and so forth, wastewater treatment and air emissions; and also the treatment of sludges from wastewater treatment and exhausted baths. Chromic acid was almost the unique responsible of eco-toxicity (97.5 %) and human toxicity-cancer (99.8 %) and it was one of the highest contributor to climate change, cumulative energy demand, fossil fuel depletion, human toxicity non-cancer, and in abiotic depletion.     

Use of vitrified MSWI bottom ashes for concrete production

Bottom ashes from a north Italian municipal solid waste incinerator (MSWI) were vitrified at 1450 degrees C without adding any vitrifying agent, then ground and sieved to different granulometry (ranging from 50 microm to 20mm), and used as filler, sand, or aggregate for concrete. Samples were characterized via slump tests (UNI 9418), alkali-silica reactivity (UNI 8520/22 and ASTM C 298), and compression strength tests (UNI 6132, 6132/72, 6686/72), and compared to reference samples obtained without vitrified bottom ashes (VBA). Our results show that vitrified bottom ashes are unsuitable as a sand substitute; however, concrete containing up to 20 wt.% of VBA filler used as a substitute for cement and up to 75 vol.% of VBA as a substitute for natural aggregate retains the same mechanical properties as reference samples. Alkali-silica or other detrimental reactions were not observed in VBA-containing concrete samples after a period of two years. The results of this work demonstrate that vitrified bottom ashes from MSWI can be used instead of natural aggregates in mortar and concrete production.     

Quality improvement of recycled fine aggregate using steel ball with the help of acid treatment

There is a need to promote high-value added utilization of recycled aggregates, considering the aspect of effective use. It should be noted, however, that recycled fine aggregates are generally low in quality due to the presence of cement paste attached to the aggregate surface. Based on this, there have been studies, which aimed to improve the quality of recycled aggregates using mechanical abrasion methods of removing the cement paste based on the principles of crushing, grinding and abrasion and beneficiation method using heat or acid. Accordingly, this study was performed as part of the research to improve the quality of recycled fine aggregates with the aim to effectively remove cement paste using steel ball as mechanical method and acid as chemical method. The results of the experiment showed that the oven-dry density and absorption ratio obtained after the abrasion process using sulfuric acid solution were 2.51 g/cm³ and 2.3%, respectively. This evidenced the quality improvement of the recycled aggregates as they satisfied the quality criteria of over 2.2 g/cm³ and under 5%, respectively, for Class I concrete proposed in the quality standards for recycled aggregates as well as natural sand proposed in Korea Standard criteria of over 2.5 g/cm³ and under 3%.     

Characterizations of temperature effects on sintered ceramics manufactured with waste foundry sand and clay

The objects of this study were to use waste foundry sand (WFS) to manufacture reclaimed resource tiles and to determine the effects of different kiln temperatures on the properties of the reclaimed WFS tiles. In this study, clay was replaced with 0 or 15 % WFS to manufacture tile specimens. Four different kiln temperatures (1000, 1050, 1100, and 1150 °C) were used in this study for the manufacture of tile specimens. The test results showed that using 15 % WFS in the tile specimens allowed the kiln temperature to be lowered by 50 °C. This temperature reduction is helpful for reducing costs and energy consumption and carbon reduction. Moreover, when the kiln temperature increased from 1000 to 1100 °C and the specimens were placed in acidic and alkaline solutions, the weight loss of the tile specimens containing 15 % WFS was half that of the specimens containing 0 % WFS. The acid-alkali resistance of the tile specimens containing 15 % WFS was also improved. This result suggested that the WFS replacement and kiln temperature affected the properties of the tile specimens.     

Valorization of post-consumer waste plastic in cementitious concrete composites

The sheer amount of disposable bottles being produced nowadays makes it imperative to identify alternative procedures for recycling them since they are non-biodegradable. This paper describes an innovative use of consumed plastic bottle waste as sand-substitution aggregate within composite materials for building application. Particularly, bottles made of polyethylene terephthalate (PET) have been used as partial and complete substitutes for sand in concrete composites. Various volume fractions of sand varying from 2% to 100% were substituted by the same volume of granulated plastic, and various sizes of PET aggregates were used. The bulk density and mechanical characteristics of the composites produced were evaluated. To study the relationship between mechanical properties and composite microstructure, scanning electron microscopy technique was employed. The results presented show that substituting sand at a level below 50% by volume with granulated PET, whose upper granular limit equals 5mm, affects neither the compressive strength nor the flexural strength of composites. This study demonstrates that plastic bottles shredded into small PET particles may be used successfully as sand-substitution aggregates in cementitious concrete composites. These new composites would appear to offer an attractive low-cost material with consistent properties; moreover, they would help in resolving some of the solid waste problems created by plastics production and in saving energy.