•Municipal solid waste characterization study was conducted in Johannesburg.•Effect of seasonal variation was evaluated.•A forecast was conducted on the trend of the wastes generated.
The huge ...increase generation of municipal solid waste (MSW) has recently become an issue of global concern. This is because waste generation increases as the population increases and the management of this waste has equally become a bit difficult. This study aims at determining the characterization and the pattern of municipal solid waste (MSW) in the City of Johannesburg (CoJ), South Africa. The results revealed that plastics and organic wastes constitute the highest waste content in both the daily refuse (DR) and round collected refuse (RCR). The results further showed that DRs are 28% and 26% for plastic wastes, while 28% and 29% organic wastes accounted for the RCRs during the summer and winter seasons respectively. The carbon to nitrogen ratio (C:N) content of the food wastes employed in this study was evaluated to be 22.66 and the empirical equation generated was C27H44NO16. STATA 12 software and ANOVA statistical technique were used to evaluate the seasonal variation between the winter and summer seasons (spanning a space of six months). The p-values obtained for the DR was (p-value = 0.9775) and for the RCR, it was (p-value = 0.9760) at 95% confidence level using STATA 12 tests. Similarly, the p-value obtained for the DR was (p-value = 0.999) and for the RCR, it was (p-value = 0.991) in turn using ANOVA tests at 95% confidence level. Furthermore, Minitab software was used to forecast the trend of waste generation between 2016 and 2025. Based on the overall results, it was concluded that the differences between the wastes generated in both seasons were not statistically significant (p > 0.05). Furthermore, a total of 102,406 tonnes of wastes would be generated during the period under consideration (a period of ten years). This indicates a negative trend for CoJ in terms of waste generation. However, this trend can be mitigated through Zero waste (ZW) implementation.
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•Cost benefit analysis of a municipal solid waste recycling facility.•Internal Rate of Return and Net Present Value of a project.•MATLAB, Python and R-Studio for comparation and ...validation.
Rapid population and economic growth, changes in consumption pattern etc. have become major contributing factors to severe municipal solid waste generation globally. Thus, various methods are being employed to manage the incessant municipal solid waste generation for a sustainable solid waste management and one of the viable approaches is the recycling option. The main objective of this paper is to determine the cost benefit analysis of setting up a recycling facility for the processing of various wastes for use as raw materials by industries. The cost benefit analysis was carried out based on historic data obtained from the municipality and some recent waste composition data. The overall analysis was done using Excel software. From the Excel software analysis, Internal Rate of Return on investment was 42%, Internal Rate of Return on equity was 98% and Net Present Value was R 63, 420,000 (USD$ 4646225.33). In ascertaining the result obtained from the Microsoft Excel, three data analysis and technical computing software (MATLAB, Python, and R-Studio) were employed. This was necessary to compare and validate the cost-benefit indicators (Net Present Value and Internal Rate of Return). Besides, evaluating the performance of each software with regards to the cost-benefit evaluation is ideal for a recycling plant like this to establish the feasibility of the project. Moreover, sensitivity analysis was conducted, and a breakeven point of 211 tons of waste was obtained. In addition, the total benefit of recycling was valued and was given as R 486,008,582.85 (USD$ 35605572.16). From the overall analysis, it was observed that the IRR and Net Present Value were alike, about 677 potential jobs could be created on the project and the Net Present Value > 0. Based on the overall analysis, it was concluded that the project is viable.
•Family size and level of education are weak drivers of separation intention.•The quality of council services is a moderator of separation intention.•Perceived behavioural control have no impact on ...attitude towards source separation.•Long distances to buyback centre is a deterrent.
Waste recycling, in particular source separation contribute significantly to the extension of landfill life and the evolution of green communities. Factors that affect participation in source waste separation amongst Metropolitans Johannesburg residents was investigated by social survey using field questionnaire data to assess socio-demographic factors and was analysed by statistical tools and behavioural constructs i.e. attitudes, subjective norms, perceived behavioural control, intentions, and situational factors. The results revealed that for graduates, source separation was driven by social responsibilities and family size while council awareness campaign, financial incentives and provision of recycling facilities are the driving force for source separation amongst respondents with matric and lower formal education. Family size and level of education are correlated to attitude with low correlations. The weak correlation was due to the perception of quality of services provided by the council. Incentives are moderators of intention of source separation but distances to buyback centre have to be carefully selected in order not to be a deterrent. Waste management agencies should accommodate the level of formal education and different family size in the formulation of source separation program.
Sustained train traffic loading result in rounding of sub angular ballasts and consequently reduce the interparticle friction. Reduced particle interlocking can result in instability, non-alignment ...of rail line and derailment and thus screening of insitu rail foundation ballasts is required during the service life to track changes in textural and mechanical properties. Two different particle grading categories (A and F) of quartzite ballasts from a Johannesburg quarry were degraded by sulphate solution and cycles of temperature. The ballasts were progressively abraded to failure in a Los Angeles abrasion device and the textural properties; average particle size (d50), flakiness index (FA), roundness (RND) and Los Angeles abrasion index (LAAI) were analyzed after each cycle of abrasion. The fouling potential of the particles generated by abrasion was classified according to the Fouling Index (FI) and Relative ballast fouling ratio (RBFR). Decrease in d50 and increase in FA with increase in number of abrasion cycles (N) were observed in the two grades of ballasts. Particle gradation and shape affected the degree of abrasion differently and with decreasing abrasion ratio, mean roundness becomes increasingly dependent on both the effect of degradation and grading. RBFR estimated the void volume occupied by fouling material and was found to be a better indicator of ballast fouling than FI. Regression equation of the ballast abrasion process based on abrasion ratio, relative ballast fouling ratio was formulated but required more data for potential application in track inspection and maintenance schedule.
•LAA test causes fragmentation due to impact and rounding of aggregates.•Flakiness index of both Grade A and Grade F quartzites increased abrasion cycles.•Mean roundness was dependent on grading and degree of degradation.•Regardless of the grading, change in roundness is more pronounced for degraded ballast.•Relative ballast fouling ratio is a better indicator of ballast fouling than Fouling index.
Sub-angular-shaped aggregates are used as rail foundation ballasts and must remain sub-angular during their service life time to maintain particle–particle interlocking, in order to ensure the ...stability of the rail line and prevent accidents by derailment. Here, the screening of dolerite quarry aggregates for use as railway foundation ballasts was investigated by employing simple digital image and chart methods. The average particle size (
d
50
), flakiness index (FI), Los Angeles abrasion index (LAAI), sphericity (SPH) and roundness (RND) were determined for two batches of dolerite ballasts from the Rooikraal quarry in Johannesburg and Ngagane quarry in Newcastle. Thirty samples from each of the two batches of ballast were analysed. The ballasts were progressively abraded using a Los Angeles abrasion device and were analysed after each cycle of abrasion. A decrease in
d
50
and an increase in FI with increased number of abrasion cycles were observed for both batches of dolerite ballast. The difference in the chart and digital image values of RND and SPH were marginal before abrasion; however, these differences increased with each abrasion cycle. The LAAI,
d
50
, mean RND and mean SPH correlated significantly and were found to have high regression coefficients. Thus, statistical models are proposed for the non-destructive routine screening of in-place ballasts in order to track marginal changes in aggregate shapes, facilitate ballast replacement programmes and avoid rail line instability.
Open dumping of industrial wastes and tailings can lead to infiltration and contamination of subgrade soils leading to a reduction in good quality pavement subgrades. It is therefore important to ...evaluate the properties of contaminated soils as well as the effectiveness of different methods of stabilization in order to secure the volume of potential pavement subgrade. The present work is focused on the laboratory investigation of the chemical properties, shear strength, and erosion-induced particle detachment of a compacted residual semi-arid soil which was treated with up to 10% salts of mixture of sodium phosphates and sodium carbonates. The effect of lime stabilization and inclusion of discrete polypropylene fibre on salt-treated soils before and after flume erosion was also investigated. The tests results indicated that soil treated with low concentration of salts exhibited brittle direct shear response, while higher concentration of salts (> 3%), induced a more ductile strain softening behaviour. Increase in salt dosage resulted in decreased mobilized friction angle of lime stabilized soil as well as increase in cohesion from 4 to 20 kPa. The change in shear strength parameters is due to high concentration of monovalent cation, 1:2 clay minerals, and anothite. The observed mass loss due to flume erosion was strongly correlated to pozzolanic index. Optimum soil performance in relation to mobilized shear strength, ductility, and resistance to soil particle detachment was observed for 8% lime stabilized soil with 1% fibre.
This study presents the use of marginal material as a stabiliser for expansive soil and therefore provides opportunity for high volume use of waste material for low cost, low volume road ...construction. Desilicated fly ash (DFA) was stabilised with lime up to 40 %. The effect of composite moisture content, lime content and curing temperature was studied. A 70:30 DFA:lime composite cured at 80 °C for 96 h had the highest unconfined compressive strength (UCS) of 8.57 MPa, a 19.5 % water absorption after a 24 h soak with a corresponding 23.5 % reduction in UCS. The green composite (70:30) was then used to stabilise expansive soil. Expansive soil stabilised with 30 % 70:30 DFA: lime composite was found to have a UCS of 4.1 MPa and resulted in a 50.1 % reduction in the liquid limit and a 15.1 meq/100 g reduction in cation exchange capacity of the soil. The formation of calcium silicate hydrate and tricalcium aluminate in the expansive soil was responsible for the strength gain in the stabilised soil. The stabilised soil met the minimum requirements for the American Concrete institute’s requirements for rigid pavement layers.
This work highlights the incorporation of two locally available materials, cassava peels ash (CPA) and laterite, in concrete production for construction purposes. The abundance of these materials in ...West Africa paved the way for this study. The effect of partial substitution of cement with an agricultural waste (CPA) on the compressive strength of laterised concrete (LATCON) was investigated. Physical and chemical tests on CPA and laterite revealed them to have satisfactory characteristics for concrete production. A total of 192 cubic specimens of 100 mm dimensions were cast and cured by complete submergence in water for 7, 14, 21 or 28-day hydration periods, adopting a 28-day targeted strength of 25 N mm
−2
as the control. The ordinary portland cement/CPA and sand/laterite replacement ratios ranged from zero to 30% with a view to determining the best compositions matrix. The density and compressive strength performance decreased with increase in the CPA and laterite content. However, gradual strength development in the CPA-LATCON was observed as the hydration period increased. The 28-day density and compressive strength of standard concrete was 2 385 kg m
−3
and 27.05 N mm
−2
, whereas those of the 10% CPA+10% laterite sample (i.e. the best replacement matrix) were 2 322 kg m
−3
and 25.57 N mm
−2
, respectively. The strength of the CPA-LATCON (25.57 N mm
−2
) was higher than the targeted strength of 25 N mm
−2
after hydration for 28 days, which makes it suitable as a building material. As such, it can be adopted in the construction of simple foundations and masonry units as a reliable alternative to the scarce and expensive conventional materials for prime cost reduction in rural housing and development without compromising standards.
•BOFS based geopolymers can be used as attenuators to remove contaminants from AMD.•Over 99% of metals and sulphates removal efficiency was achieved.•BOFS based geopolymers can neutralize AMD over a ...period of 60 days.•BOFS based geopolymers prepared with 1.5% H2O2 had the highest reusability.•Precipitation was identified as the dominant mechanism to remove metals and sulphates.
This paper presents column studies conducted to evaluate and assess the potential use of Fly Ash (FA). Basic Oxygen Furnace Slag (BOFS) based geopolymers to remove metals, sulphates and acidity from Acid Mine Drainage (AMD). Geopolymers were prepared using NaOH, Fly ash (FA) was used as source of silica additive to supplement BOFS. The blending ratio was fixed to 10% FA and the S/L ratio was kept 20%. The H2O2 was used as a blowing agent to increase the porosity of the FA/BOFS based geopolymer at four different percentages (1.5%, 1%, 0.5% and 0%). The four different geopolymers with distinct porosities were employed in different columns respectively. It was found that over 99% removal efficiency of metals and sulphates was achieved in the first 60 days of column studies. The dissolution of Ca(OH)2 was the main constituent responsible for the removal of acidity in AMD. Characterization revealed that precipitation was the main mechanism for removal of metals. Gypsum was the main byproduct formed with precipitated metals presented by goethite, spertite and manganite.
The generation and disposal of phosphogypsum (PG) is a worldwide challenge, due to the environmental pollution posed by the material. The contaminants laden in the material are the major limitations ...for the utilisation of PG. Other materials considered as wastes such as fly ash (FA) and basic oxygen furnace slag (BOF slag) are generated by numerous industrial activities and disposed into environment. This study investigated the use of three wastes materials for the development of a composite applicable for road construction. Two types of PG were investigated, namely citric acid treated PG (TPG), for the removal of the contaminants and raw PG (RPG). Lower content PG containing 20% and 30% were investigated and modified with FA, Lime (L) and BOF slag. The effect of particle size distribution (PSD) on unconfined compressive strength development, durability of the composites and hydration products contributing to strength development were studied. Modification of PG with FA-L-BOF slag significantly improved the unconfined compressive strength of PG. The PG content of 20%o for the RPG and TPG yielded the highest strengths of 7.4 MPa and 5.4 MPa, respectively when cure at elevated temperatures. Normal curing of the composites over 7 days and 28 also showed an increase in strength development. Particle size played a significant role in the unconfined compressive strength development. Kieserite, calcium aluminium sulphate and calcite were the predominant hydration products formed during the curing process.
