Response surface methodology analysis of the photocatalytic removal of Methylene Blue using bismuth vanadate prepared via polyol route

Visible-light driven photocatalyst bismuth vanadate (BiVO₄) photocatalyst was synthesized by the polyol route using ethylene glycol. The precipitate was washed, dried and calcined at 450℃ for 3 hr. The sample was characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), zeta potential, surface area (BET method) and band gap energy via diffuse reflectance spectroscopy (DRS). The synthesized BiVO₄ has a monoclinic phase with a surface area of 4.3 m²/g and a band gap energy of 2.46 eV. A majority of the particles were in the range of 90-130 nm as obtained from the particle size distribution histrogram. The efficiency of the sample as a visible-light driven photocatalyst was examined by photodegrading Methylene Blue (MB). The effects of some operational photodegradation parameters such as mass loading, initial dye concentration and pH were also examined. Experimental design methodology was applied by response surface modeling and optimization of the removal of MB. The multivariate experimental design was employed to develop a quadratic model as a functional relationship between the percentage removal of MB and three experimental factors (BiVO₄ loading, MB initial concentration and pH). The percentage removal of MB approached 67.21% under optimized conditions. In addition, a satisfactory goodness-of-fit was achieved between the predictive and the experimental results.     

Histopathological studies and oxidative stress of synthesized silver nanoparticles in Mozambique tilapia (Oreochromis mossambicus)

To evaluate the potential environmental effects of engineered nano metals, it is important to determine the adverse effects of various nanomaterials on aquatic species. Adult tilapia (Oreochromis mossambicus) were maintained in 10 L glass aquaria, and exposed to a graded series of synthesized silver nanoparticles (Ag-NPs) at 25, 50 and 75 mg/L for eight days. The LC₅₀ value was 12.6 mg/L. Reduced activities of antioxidant enzymes and the contents of antioxidants were lowered in the gills and liver of fishes treated with Ag-NPs, which resulted in heavy accumulation of free radicals. Histopathological results imply that the balance between the oxidative and antioxidant system in the fish was broken down during Ag-NPs exposure. The principal concern related with the release of nanomaterials and their smaller particle may change the materials transport and potential toxicity to aquatic organisms compared to larger particles.     

Economic valuation of Shadegan International Wetland,Iran: notes for conservation

Wetlands are among the most productive ecosystems on the earth. They produce various market and non-market goods and services, which have a significant role in human welfare. Despite the great opportunities from sustainable development, wetlands all over the world are under serious threat from a diverse range of non-sustainable activities. One of the major reasons for excessive depletion and the conversion of wetland resources is due to underestimating the non-market values of wetlands during development decisions. Shadegan International Wetland (SIW) in southern Iran is one of these wetland areas that is threatened by undervaluation and overexploitation from commercial activities. This study utilizes the contingent valuation method to estimate the economic benefits of SIW from the view point of peoples’ willingness to pay (WTP). The logit model was defined based on dichotomous choice to measure individuals’ WTP. The estimated mean WTP was US$ 1.74 per household as a onetime donation. This study concludes that the benefits of SIW to society could encourage managers to set priorities to ensure that the health of the ecosystem, its integrity, and its uniqueness would be conserved in a proper manner.     

Non-users’ trade-off between natural scenery, water quality, ecological functions and biodiversity conservation: a way to preserve wetlands

The inclusion of both non-use values and values placed by non-users provide more reliable results about the real values of wetlands. A choice experiment method was conducted to estimate the willingness to pay for environmental conservation in non-users’ communities adjacent to the Shadegan International Wetland (SIW) in Iran. A random parameter logit (RPL) model was developed to derive the marginal value and compensating surplus of the respondents for five attributes of the non-market values of SIW. The trade-off between five different wetland attributes showed that water quality improvement and biodiversity conservation were the most highly valued attributes. The results demonstrated that about 66 % of non-users were willing to donate money for the contribution in SIW conservation, suggesting that non-users have the potential to contribute to SIW conservation programs.     

The performance of Electro-Fenton oxidation in the removal of coliform bacteria from landfill leachate

Leachate pollution is one of the main problems in landfilling. Researchers have yet to find an effective solution to this problem. The technology that can be used may differ based on the type of leachate produced. Coliform bacteria were recently reported as one of the most problematic pollutants in semi-aerobic (stabilized) leachate. In the present study, the performance of the Electro-Fenton process in removing coliform from leachate was investigated. The study focused on two types of leachate: Palau Borung landfill leachate with low Coliform content (200 MPN/100 m/L) and Ampang Jajar landfill leachate with high coliform content (>24 × 10⁴ MPN/100 m/L). Optimal conditions for the Electro-Fenton treatment process were applied on both types of leachate. Then, the coliform was examined before and after treatment using the Most Probable Number (MPN) technique. Accordingly, 100% removal of coliform was obtained at low initial coliform content, whereas 99.9% removal was obtained at high initial coliform content. The study revealed that Electro-Fenton is an efficient process in removing high concentrations of pathogenic microorganisms from stabilized leachate.     

Challenges of soil erosion and sludge management for sustainable development in Indonesia

Most developing countries, particularly Indonesia, will be facing problems of sludge pressure in the next decades due to the increase in practices of legal and illegal logging as well as land and water demands. Consequently, they will also be facing the challenges of soil erosion and sludge management due to increased quantities of sludge coming from several potential sources, such as activated sludge, chemical sludge, fecal sludge and solid wastes as well as erosion and sedimentation. Although the government of Indonesia has enacted laws and policies to speed up the implementation of the programs and activities related to sludge management, the detailed practice concepts in implementing the programs need to be identified. Discussion of role-sharing amongst the related government agencies, private institutions and other stakeholders is urgent for clarifying the participation of each party in the next years to come. This paper proposes a management approach and level of responsibilities in sludge management. Implementation of zero ΔQ, zero ΔS and zero ΔP policies needs to be adopted by local and central governments. Application of sludge on the agricultural lands and other uses will promote sustainable development.     

城市能源管理：马来西亚的举措

无论遵循哪种发展模式,城市的增长都会给能源的使用和管理施加巨大的压力 .基于可持续性的城市发展需要使这些模式具有有效性,包括考虑它们已经产生的影响 .有一点是可以说服人的,城市能源问题的解决办法（比如能源效率和减少使用化石燃料）需要基于适合可持续发展的经济和商业原则 .     

Indoor air pollution evaluation with emphasize on HDI and biological assessment of HDA in the polyurethane factories

Today, many raw materials used in factories may have a dangerous effect on the physiological system of workers. One of them which is widely used in the polyurethane factories is diisocyanates. These compounds are widely used in surface coatings, polyurethane foams, adhesives, resins, elastomers, binders, and sealants. Exposure to diisocyanates causes irritation to the skin, mucous membranes, eyes, and respiratory tract. Hexamethylene diamine (HDA) is metabolite of hexamethylene diisocyanate (HDI). It is an excretory material by worker’s urine who is exposed to HDI. Around 100 air samples were collected from five defined factories by midget impinger which contained dimethyl sulfoxide absorbent as a solvent and tryptamine as reagent. Samples were analyzed by high-performance liquid chromatography with EC\UV detector using NIOSH 5522 method of sampling. Also, 50 urine samples collected from workers were also analyzed using William’s biological analysis method. The concentration of HDI into all air samples were more than 88 xxxμg/m³, and they have shown high concentration of pollutant in the workplaces in comparison with NIOSH standard, and all of the workers’ urine were contaminated by HDA. The correlation and regression test were used to obtain statistical model for HDI and HDA, which is useful for the prediction of diisocyanates pollution situation in the polyurethane factories.     

Removal of phenols and other pollutants from different landfill leachates using powdered activated carbon supplemented SBR technology

In this research, two types of sequencing batch reactors (SBRs) with 8 h of cycle times, namely non-powdered activated carbon (NPAC-SBR) and powdered activated carbon (PAC-SBR), were used for the treatment of raw leachates at Kulim and Pulau Burung landfill sites. To test the performance of SBRs, phenols, total iron, zinc, ammonia, nitrite, nitrate, color, suspended solids, chemical oxygen demand, biochemical oxygen demand, and total dissolved salts removal efficiencies and sludge volume index (SVI) were studied at both sites. The rates of phenols removal, for instance in NPAC-SBRs and PAC-SBRs at Kulim, were 25% and 55%, respectively, whereas those at Pulau Buring were 94.81% and 97.75%, respectively. PAC as adsorbent in PAC-SBRs enhanced the removal efficiencies of the aforementioned pollutants from leachates at both sites. In addition, PAC as adsorbent decreased the SVI values at Kulim (59.7 mL/g) and Pulau Burung (91.4 mL/g) leachates and improved the nitrification and denitrification processes.