Currently, generation of solid waste per capita in Malaysia is about 1.1 kg/day. Over 26,500 t of solid waste is disposed almost solely through 166 operating landfills in the country every day. Despite the availability of other disposal methods, landfill is the most widely accepted and prevalent method for municipal solid waste (MSW) disposal in developing countries, including Malaysia. This is mainly ascribed to its inherent forte in terms cost saving and simpler operational mechanism. However, there is a downside. Environmental pollution caused by the landfill leachate has been one of the typical dilemmas of landfilling method. Leachate is the liquid produced when water percolates through solid waste and contains dissolved or suspended materials from various disposed materials and biodecomposition processes. It is often a high-strength wastewater with extreme pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), inorganic salts and toxicity. Its composition differs over the time and space within a particular landfill, influenced by a broad spectrum of factors, namely waste composition, landfilling practice (solid waste contouring and compacting), local climatic conditions, landfill’s physico-chemical conditions, biogeochemistry and landfill age. This paper summarises an overview of landfill operation and leachate treatment availability reported in literature: a broad spectrum of landfill management opportunity, leachate parameter discussions and the way forward of landfill leachate treatment applicability.

An overview of municipal solid waste management and landfill leachate treatment: Malaysia and Asian perspectives

This paper presents the results of laboratory investigations into the deformation of coal fouled ballast stabilized with geogrid at various degrees of fouling. A novel track process simulation apparatus was used to simulate realistic rail track conditions subjected to cyclic loading, and the void contamination index (VCI) was used to evaluate the level of ballast fouling. The experimental results show that coal fines act as a lubricant, causing grains of ballast to displace and rotate, and as a result, accelerate its deformation. However, coal fines also reduce ballast breakage because of a cushioning effect, that is, by reducing interparticle attrition. The inclusion of geogrid at the interface between the layer of ballast and subballast provides additional internal confinement and particle interlocking via geogrid apertures, which reduces deformation. A threshold value of VCI=40% is proposed to assist practitioners for conducting track maintenance. If the level of fouling exceeds this threshold,...

Deformation of coal fouled ballast stabilized with geogrid under cyclic load

Polyaniline-based adsorbents for aqueous pollutants removal: A review

Preparation of a nano bio-composite based on cellulosic biomass and conducting polymeric nanoparticles for ibuprofen removal: Kinetics, isotherms, and energy site distribution.

Comparative analysis of dynamic constitutive response of hybrid fibre-reinforced concrete with different matrix strengths

Prediction of air quality in Tehran by developing the nonlinear ensemble model

The main aim of the present work was to characterize the mesophilic anaerobic co-digestion of food waste (FW) and sewage sludge (SS) by considering different mixing ratios of primary sludge (Pr), secondary sludge (Sc) and food waste. The experiments were carried out using batch reactors (R1-R7). The applied ratios included VSPr:VSSc (1:1 and 2:1) and VSFW:VSSS (0:4, 1:3, 2:2 and 4:0) with VSx (g) as the volatile solids content of the substance x within the total feed of each reactor and VSSS as the sum of VSPr and VSSc. According to the obtained results, ratio of carbon to nitrogen (C:N) was much more effective than VSPr:VSSc ratio considering VS reduction and biogas production efficiencies. A second-order polynomial curve fitted well the data of VS reduction vs. C:N, representing an optimum C:N around 16 to achieve the highest VS removal. A high R-squared linear correlation was found between data of gas production and C:N ratio according to which, with increasing the C:N within the test range (8–19.7), the biogas production increased steadily. Doubling VSPr:VSSc under lower ratios of VSFW:VSSS (0:4 and 1:3) positively affected both VS reduction and biogas production, while under higher VSFW:VSSS ratio (2:2) it influenced adversely. Doubling VSPr:VSSc also improved the digestate dewaterability under all applied ratios of VSFW:VSSS. A synergistic gas production was observed for the reactors with 50% share of VSFW (VSFW:VSSS of 2:2) between which, R5 with VSPr:VSSc of 1:1 showed the highest synergistic gas production. The highest methane content (70.3%) also belonged to R5.

Characterization of food waste and sewage sludge mesophilic anaerobic co-digestion under different mixing ratios of primary sludge, secondary sludge and food waste

Effectiveness of geogrid reinforcement in improvement of mechanical behavior of sand-contaminated ballast

Abstract In the present research, magnetic rhamnolipid-Co/Al layered double hydroxide (MR-LDH) was synthesized to uptake methylene blue (MB) and reactive orange 16 (RO16) from aqueous solution. The main parameters, including pH, adsorbent dosage, contact time, and initial analyte concentration, were optimized to achieve the best adsorption efficiency. Accordingly, the elimination of MB on MR-LDH is improved in the basic medium due to the electrostatic interactions between the negative charge of MR-LDH and the positive charge of MB dye. In contrast, the acidic medium (pH = 3) was favored for RO16 adsorption because of hydrogen bonding between the protonated form of azo dye and protonated hydroxyl groups at the surface of MR-LDH. The calculated maximum adsorption capacities for MB and RO16 were 54.01 and 53.04 mg/g at 313 K, respectively. The Langmuir model, which assumes monolayer adsorption on the adsorbent surface, provides the best explanation for the adsorption of both dyes (R 2 = 0.9991 for MB and R 2 = 0.9969 for RO16). Moreover, the pseudo-second-order kinetic model best described the adsorption process for MB (R 2 = 0.9970) and RO16 (R 2 = 0.9941). The proposed adsorbent maintains stable adsorption performance for four consecutive cycles. After each adsorption process, MR-LDH is easily separated by an external magnet. The findings show that MR-LDH was found to be an excellent adsorbent for the removal of both cationic and anionic organic dyes from aqueous solutions. 

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Adsorption behavior of rhamnolipid modified magnetic Co/Al layered double hydroxide for the removal of cationic and anionic dyes

Sisal is a natural fibrous low-cost biomaterial that is frequently found in the surrounding environment and has no toxic effects. To upgrade its performance and applicability, sisal was modified with polypyrrole/polyaniline via in-situ chemical oxidative polymerization technique for reactive orange 5 elimination from aqueous media. Nowadays, dye pollution and its subsequent adverse effects have been of great concern for all around the world. The prepared composite was characterized by SEM, FTIR, and XRD analysis; they indicated that the polypyrrole and polyaniline were successfully coated on sisal. Optimum contact time was found at 120 min, and at the adsorbent dosage of 200 mg, almost 97 % of dye was removed. At low dye concentration (5−10 ppm), the efficiency of the sorption system was significantly acceptable (99 %). pH 2 had the maximum adsorption capacity due to attraction between negatively charged dye and positive nature of sisal composite. In view of thermodynamics, the process was endothermic and so better removal was observed at 45 °C. Langmuir/Freundlich and Pseudo-second order could satisfactorily expound the sorption system with R2 values of greater than 0.99, exhibiting that physisorption/chemisorption occurred. Sisal/polypyrrole/polyaniline was more than 5.69 times effective than raw sisal for dye adsorption. In the case of synthetic wastewater, the removal efficiency reached 81 %. Hence, the low-cost sisal/polypyrrole/polyaniline composite was a promising alternative for reactive orange 5 removal.

H. Ghiasinejad

Papers

Prediction of air quality in Tehran by developing the nonlinear ensemble model

Characterization of food waste and sewage sludge mesophilic anaerobic co-digestion under different mixing ratios of primary sludge, secondary sludge and food waste

Effectiveness of geogrid reinforcement in improvement of mechanical behavior of sand-contaminated ballast

Adsorption behavior of rhamnolipid modified magnetic Co/Al layered double hydroxide for the removal of cationic and anionic dyes

Low-cost sisal fibers/polypyrrole/polyaniline biosorbent for sequestration of reactive orange 5 from aqueous solutions