Waste Management & Research current issue

Editorial

Aage Hansen, J., Agamuthu, P. — 2008-10-15

Immobilization of copper flotation waste using red mud and clinoptilolite

Coruh, S. — 2008-10-15

The flash smelting process has been used in the copper industry for a number of years and has replaced most of the reverberatory applications, known as conventional copper smelting processes. Copper smelters produce large amounts of copper slag or copper flotation waste and the dumping of these quantities of copper slag causes economic, environmental and space problems. The aim of this study was to perform a laboratory investigation to assess the feasibility of immobilizing the heavy metals contained in copper flotation waste. For this purpose, samples of copper flotation waste were immobilized with relatively small proportions of red mud and large proportions of clinoptilolite. The results of laboratory leaching demonstrate that addition of red mud and clinoptilolite to the copper flotation waste drastically reduced the heavy metal content in the effluent and the red mud performed better than clinoptilolite. This study also compared the leaching behaviour of metals in copper flotation waste by short-time extraction tests such as the toxicity characteristic leaching procedure (TCLP), deionized water (DI) and field leach test (FLT). The results of leach tests showed that the results of the FLT and DI methods were close and generally lower than those of the TCLP methods.

Sources and levels of potentially toxic elements in the biodegradable fraction of autoclaved non-segregated household waste and its compost/digestate

Papadimitriou, E.K., Barton, J.R., Stentiford, E.I. — 2008-10-15

Waste that reflected the average UK composition of household waste was treated by autoclaving at the three set pressure/temperature levels of 2.7 bar/130 °C, 6.2 bar/160 °C and 15.5 bar/200 °C. The biodegradable fraction of the autoclaved household waste (`floc') was manually separated by screening and underwent characterization for its Cd, Cr, Cu, Pb, Hg, Ni, and Zn content. Autoclaving did not guarantee the production of compost/digestate that met the UK specification for compost, BSi PAS100, without restrictions being made on the composition of the waste feedstock. Results indicate that the levels of Zn and Cd associated with floc materials alone could lead to compost limit values being exceeded. For all other potentially toxic elements (PTEs), the estimated excessive (i.e. above levels of compliance) PTEs levels for compost/digestate were mainly due to external (i.e. non-floc) materials, primarily electronic/electrical waste. Batteries may have also contributed to the high levels of Zn and Hg. In this study, for all PTEs examined, with the exception of Cd and Zn, autoclaving had a performance comparable to that of the most effective mechanical biological treatment systems.

Application of magnetic separation technology for the recovery of colemanite from plant tailings

Alp, I. — 2008-10-15

In this study, colemanite was recovered from tailings produced by the Kestelek (Turkey) Processing Plant by magnetic separation. Magnetic susceptibility measurements revealed that colemanite is diamagnetic in character whereas gangue minerals are weakly paramagnetic, apparently due to the presence of the iron-bearing silicates such as smectite and, to a less extent, illite. Three-stage magnetic separation tests were performed on the size fractions coarser than 75 µm produced from the tailings (31.52% B₂O₃) using a high-intensity permanent magnetic separator. Under the test conditions a colemanite concentrate with a B₂O₃ content of 43.74% at 95.06% recovery was shown to be produced from the tailings. The mineralogical composition of the tailings appears to allow the removal of gangue minerals by magnetic separation and hence the production of a concentrate of commercial grade.

Site selection of sanitary landfills on the small island of Mauritius using the analytical hierarchy process multi-criteria method

Ramjeawon, T., Beerachee, B. — 2008-10-15

This paper focuses on the application of a multi-criteria analysis methodology — the analytical hierarchy process — for the locating of a sanitary landfill on the small island of Mauritius. Four candidate sites were assessed using three main criteria (environmental, technical and socio-economic) and twenty-one sub-criteria. Scores were assigned to each criterion and sub-criterion by stakeholders in the solid waste sector, based on the impact assessment of each site so as to obtain their relative importance. The analytical hierarchy process was then applied, which involved the combination of the weights obtained at the different stages of pair-wise comparisons. The candidate sites were finally ranked to obtain the optimum site. Because of political factors, the second best ranked site was chosen by the authorities for the location of a new landfill on the island. This technique provides a realistic approach for use by small island developing states such as Mauritius for choosing and justifying to all stakeholders the best location for a sanitary landfill site or any other waste management site.

Slope failures in municipal solid waste dumps and landfills: a review

Blight, G. — 2008-10-15

Between 1977 and 2005 six large-scale failures of municipal solid waste dumps and landfills have been recorded in the technical literature. The volumes of waste mobilized in the failures varied from 10—12 000 m³ in a failure that killed nearly 300 people to 1.5 million m³ in a failure that caused no deaths or injuries. Of the six failures, four occurred in dumps that, as far as is known, had not been subjected to any prior technical investigation of their shear stability. The remaining two failures occurred in engineer-designed landfills, one of which practised leachate recirculation, and the other co-disposed of liquid waste along with solid waste. The paper reviews, describes and analyses the failures and summarizes their causes.

Hydraulic conductivity of compacted clay liners permeated with inorganic salt solutions

Yilmaz, G., Yetimoglu, T., Arasan, S. — 2008-10-15

Due to their low permeability, geosynthetic clay liners (GCLs) and compacted clay liners (CCLs) are the main materials used in waste disposal landfills. The hydraulic conductivity of GCLs and CCLs is closely related to the chemistry of the permeant fluid. In this study, the effect on the hydraulic conductivity of clays of five different inorganic salt solutions as permeant fluid was experimentally investigated. For this purpose, NaCl, NH₄Cl, KCl, CaCl₂, and FeCl₃ inorganic salt solutions were used at concentrations of 0.01, 0.10, 0.25, 0.50, 0.75 and 1 M. Laboratory hydraulic conductivity tests were conducted on low plasticity (CL) and high plasticity (CH) compacted raw clays. The change in electrical conductivity and pH values of the clay samples with inorganic salt solutions were also determined. The experimental test results indicated that the effect of inorganic salt solutions on CL clay was different from that on CH clay. The hydraulic conductivity was found to increase for CH clay when the salt concentrations increased whereas when the salt concentrations were increased, the hydraulic conductivity decreased for the CL clay.

Formulation of a landfill pollution potential index to compare pollution potential of uncontrolled landfills

Sharma, A., Meesa, S., Pant, S., Alappat, B. J., Kumar, D. — 2008-10-15

Generally speaking, landfilling is one of the prominent methods of waste disposal around the globe, but some under-developed and developing countries still continue to practice uncontrolled open dumping of waste. These uncontrolled landfills pose a relatively high threat to the various elements of the environment in comparison with the conventional engineered landfills that are used in many developed countries. However, some closed, un-engineered landfills do exist in developing countries. This paper presents a novel approach to compare the pollution potential of uncontrolled landfills using an index. The landfill pollution potential index (LPPI) has been developed using the Delphi technique and is an aggregation of six pollution indices that have already been developed for the quantification of different environmental elements. The LPPI is an increasing scale index, in which a higher index value indicates a higher pollution threat. The LPPI of a landfill in Delhi was calculated and the high LPPI value indicates that the respective landfill poses a significant threat to the environment. The LPPI can be used as an aid to diagnose a landfill's pollution potential relative to other landfills and therefore also to rank remediation investments.

Report: New guidelines for characterization of municipal solid waste: the Portuguese case

da Graca Madeira Martinho, M., Silveira, A. I., Fernandes Duarte Branco, E. M. — 2008-10-15

This report proposes a new set of guidelines for the characterization of municipal solid waste. It is based on an analysis of reference methodologies, used internationally, and a case study of Valorsul (a company that handles recovery and treatment of solid waste in the North Lisbon Metropolitan Area). In particular, the suggested guidelines present a new definition of the waste to be analysed, change the sampling unit and establish statistical standards for the results obtained. In these new guidelines, the sampling level is the waste collection vehicle and contamination and moisture are taken into consideration. Finally, focus is on the quality of the resulting data, which is essential for comparability of data between countries. These new guidelines may also be applicable outside Portugal because the methodology includes, besides municipal mixed waste, separately collected fractions of municipal waste. They are a response to the need for information concerning Portugal (e.g. Eurostat or OECD inquiries) and follow European Union municipal solid waste management policies (e.g. packaging waste recovery and recycling targets and the reduction of biodegradable waste going to landfill).