Implementation of the semi-aerobic landfill system (Fukuoka method) in developing countries: a Malaysia cost analysis

Most of the existing solid waste landfill sites in developing countries are practicing either open dumping or controlled dumping. Proper sanitary landfill concepts are not fully implemented due to technological and financial constraints. Implementation of a fully engineered sanitary landfill is necessary and a more economically feasible landfill design is crucial, particularly for developing countries. This study was carried out by focusing on the economics from the development of a new landfill site within a natural clay area with no cost of synthetic liner up to 10 years after its closure by using the Fukuoka method semi-aerobic landfill system. The findings of the study show that for the development of a 15-ha landfill site in Malaysia with an estimated volume of 2,000,000 m(3), the capital investment required was about US 1,312,895 dollars, or about US 0.84 dollars/tonne of waste. Assuming that the lifespan of the landfill is 20 years, the total cost of operation was about US 11,132,536 dollars or US 7.15 dollars/tonne of waste. The closure cost of the landfill was estimated to be US 1,385,526 dollars or US 0.89 dollars/tonne of waste. Therefore, the total cost required to dispose of a tonne of waste at the semi-aerobic landfill was estimated to be US 8.89 dollars. By considering an average tipping fee of about US 7.89 dollars/tonne of waste in Malaysia in the first year, and an annual increase of 3% to about US 13.84 dollars in year-20, the overall system recorded a positive revenue of US 1,734,749 dollars. This is important information for the effort of privatisation of landfill sites in Malaysia, as well as in other developing countries, in order to secure efficient and effective landfill development and management.     

Spatiotemporal variations in rocky intertidal malacofauna throughout Japan in the 1970s and 1980s

Spatial and temporal variations of benthic fauna over a wide region (>1,000 km) that includes complex ocean currents have seldom been quantitatively studied. The present study revealed malacofaunal variations on Japanese rocky shores affected by the Soya, Tsushima, Oyashio, and Kuroshio currents, and in the Inland Sea. On 29 shores in seven regions in these sea areas, previous researchers have recorded the number of molluscs in quadrats in spring and summer of 1978 and 1984–1986. Reanalyses of these records revealed the following patterns. (1) Shore-to-shore variation in malacofauna was correlated with shore-to-shore geographical distance less clearly for more southern regions. This might show that in southern regions many taxa with low relative abundance are haphazardly recorded on some shores and blur the effect of shore-to-shore distance on malacofaunal dissimilarity. (2) Region-to-region variation in malacofauna was significantly correlated with region-to-region geographical distance. This suggests the influences of environments and paleontological events specific to each current surrounding each region. (3) The pattern of dissimilarity between the Inland Sea and the other sea areas greatly changed from the 1970s to 1980s. This was due in part to the following density fluctuations on some shores in the Inland Sea: increases in the non-indigenous mussel Mytilus galloprovincialis, cultured oyster Crassostrea gigas, and littorinid Littorina brevicula reportedly abundant in sheltered areas; and decreases in the littorinid Nodilittorina radiata reportedly abundant in exposed areas and muricid gastropods Thais spp. showing imposex. This suggests an increase of anthropogenic perturbations during the study period in the Inland Sea which is surrounded by large cities and ports. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Enantioselective recognition of mono-demethylated methoxychlor metabolites by the estrogen receptor

Metabolites of methoxychlor such as 2-(p-hydroxyphenyl)-2-(p-methoxyphenyl)-1,1,1-trichloroethane (mono-OH-MXC) and 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (bis-OH-MXC), have estrogenic activity. Mono-OH-MXC is a chiral compound in which the carbon atom bridging two benzene rings is the chiral centre. In previous studies the estrogenic activity of racemic mono-OH-MXC has been measured, and the activity of each enantiomer of this compound has not yet been elucidated. In this study, we evaluated the estrogen receptor-binding activity of each enantiomer of mono-OH-MXC to clarify the enantioselective recognition by the estrogen receptor. (S)-mono-OH-MXC showed 3-fold higher binding activity than that of the (R) enantiomer. The activity of bis-OH-MXC was only 1.7-fold higher than that of (S)-mono-OH-MXC. This result suggests that the one hydroxy group and the orientation of the CCl3 group of mono- and bis-OH-MXCs are important for the interaction with the estrogen receptor. The result also points out the estrogenic activity of methoxychlor after metabolic activation in vivo, which predominantly produces the (S)-mono-OH-MXC, may be higher than estimated from the in vitro activity of racemic mixtures.     

Finding upper-level sets in cellular surface data using echelons and saTScan

Across a spectrum of contemporary contexts from public health to landscape ecology and natural resources, there is need for objective determination of elevated occurrence in phenomena such as disease incidence and biodiversity. Occurrences of such phenomena constitute response surfaces, but data regarding the surface is typically acquired in a cellular framework. The cells may comprise a regular grid, or may be of irregular shapes such as counties in which statistics are collected. Echelons are a topologically based approach to systematic determination of spatial structure in a step surface. Spatial scan statistics are a probability-based approach to the same issue when interest lies in a rate variable. Here we examine the use of echelons both separately and in conjunction with the SaTScan implementation of spatial scan statistics for purposes of determination and visualization of upper-level sets. Consideration is given to both conventional geographic space and to the cellular pseudo-space of contingency tables for ordered categorical variables. Received: August 2002 / Revised: July 2005     

Amperometric hydrogen peroxide biosensor based on immobilization of DNA-Cu(II) in DNA/chitosan polyion complex membrane

DNA/chitosan polyion complex membrane was used as a support for immobilization of electrocatalytic species-copper ions, which specifically bound to dsDNA and catalyzed the hydrogen peroxide reduction. The polyion complex membrane consisted with DNA-Cu(II) complex and chitosan was prepared on a glassy carbon electrode (GCE). Electrochemical measurements of the DNA-Cu(II)/chitosan membrane-modified GCE revealed that the copper ion embedded in the DNA/chitosan layer exhibited good electrochemical behaviors. The DNA-Cu(II)/chitosan/GC electrode showed an excellent electrocatalytic activity for the H₂O₂ reduction. Even in the presence of dissolved oxygen, the sensor exhibited highly sensitive and rapid (response time, about 6 s) response to H₂O₂. The steady-state cathodic current responses of the sensor obtained at ?0.2 V versus Ag/AgCl in air-saturated 100 mmol/L phosphate buffer (pH 5.0) increased linearly up to 10 mmol/L with the detection limit of 3 μmol/L. Effects of applied potential and buffer pH upon the response currents of the sensor were investigated for an optimum analytical performance. Ascorbic acid and glucose almost have no interference to measurement of H₂O₂. In addition, the sensor exhibited good reproducibility.     

Assays of dioxins and dioxin-like compounds in actually contaminated soils using transgenic tobacco plants carrying a recombinant mouse aryl hydrocarbon receptor-mediated β-glucuronidase reporter gene expression system

The transgenic tobacco plant XD4V-26 carrying the recombinant mouse aryl hydrocarbon receptor XD4V-mediated β-glucuronidase (GUS) reporter gene expression system was used for assay of dioxins and dioxin-like compounds consisting of polychlorinated dibenzeno-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls (Co-PCBs) in actually contaminated soils. The transgenic tobacco plant XD4V-26 showed a significant dose-dependent induced GUS activity when cultured on MS medium containing PCB126 [toxic equivalency factor (TEF) = 0.1]. In contrast, PCB169 and PCB180, which have 0.03 of TEF and unassigned TEF values, respectively, did not significantly induce GUS activity under the same conditions as with PCB126. When the tobacco plants were cultivated for up to 5 weeks on actually contaminated soils with dioxins and dioxin-like compounds collected from the periphery of an incinerator used for disposal of residential and industrial wastes, GUS activity in the leaves was dose-dependently increased. The plants clearly detected 360 pg-TEQ g(-1) of dioxins and dioxin-like compounds in this assay. There was a positive correlation between GUS activity and TEQ value of dioxins and dioxin-like compounds in the plants. This assay does not require any extraction and purification processes for the actually contaminated soil samples.     

Using remote sensing and GIS to detect and monitor land use and land cover change in Dhaka Metropolitan of Bangladesh during 1960–2005

This paper illustrates the result of land use/cover change in Dhaka Metropolitan of Bangladesh using topographic maps and multi-temporal remotely sensed data from 1960 to 2005. The Maximum likelihood supervised classification technique was used to extract information from satellite data, and post-classification change detection method was employed to detect and monitor land use/cover change. Derived land use/cover maps were further validated by using high resolution images such as SPOT, IRS, IKONOS and field data. The overall accuracy of land cover change maps, generated from Landsat and IRS-1D data, ranged from 85% to 90%. The analysis indicated that the urban expansion of Dhaka Metropolitan resulted in the considerable reduction of wetlands, cultivated land, vegetation and water bodies. The maps showed that between 1960 and 2005 built-up areas increased approximately 15,924 ha, while agricultural land decreased 7,614 ha, vegetation decreased 2,336 ha, wetland/lowland decreased 6,385 ha, and water bodies decreased about 864 ha. The amount of urban land increased from 11% (in 1960) to 344% in 2005. Similarly, the growth of landfill/bare soils category was about 256% in the same period. Much of the city's rapid growth in population has been accommodated in informal settlements with little attempt being made to limit the risk of environmental impairments. The study quantified the patterns of land use/cover change for the last 45 years for Dhaka Metropolitan that forms valuable resources for urban planners and decision makers to devise sustainable land use and environmental planning.     

Determining storm sampling requirements for improving precision of annual load estimates of nutrients from a small forested watershed

This study sought to determine the lowest number of storm events required for adequate estimation of annual nutrient loads from a forested watershed using the regression equation between cumulative load (∑L) and cumulative stream discharge (∑Q). Hydrological surveys were conducted for 4 years, and stream water was sampled sequentially at 15-60-min intervals during 24 h in 20 events, as well as weekly in a small forested watershed. The bootstrap sampling technique was used to determine the regression (∑L-∑Q) equations of dissolved nitrogen (DN) and phosphorus (DP), particulate nitrogen (PN) and phosphorus (PP), dissolved inorganic nitrogen (DIN), and suspended solid (SS) for each dataset of ∑L and ∑Q. For dissolved nutrients (DN, DP, DIN), the coefficient of variance (CV) in 100 replicates of 4-year average annual load estimates was below 20% with datasets composed of five storm events. For particulate nutrients (PN, PP, SS), the CV exceeded 20%, even with datasets composed of more than ten storm events. The differences in the number of storm events required for precise load estimates between dissolved and particulate nutrients were attributed to the goodness of fit of the ∑L-∑Q equations. Bootstrap simulation based on flow-stratified sampling resulted in fewer storm events than the simulation based on random sampling and showed that only three storm events were required to give a CV below 20% for dissolved nutrients. These results indicate that a sampling design considering discharge levels reduces the frequency of laborious chemical analyses of water samples required throughout the year.     

Recovery of Nd and Dy from rare earth magnetic waste sludge by hydrometallurgical process

This paper describes a hydrometallurgical process for recovering neodymium (Nd) and dysprosium (Dy) from a magnetic waste sludge generated from the Nd–Fe–B(–Dy) manufacturing process. Phase analysis by XRD study revealed Nd(OH)₃ and Fe₂O₃ as main mineral phases, and chemical analysis by ICP showed the contents of 35.1 wt% Nd, 29.5 wt% Fe, 1.1 wt% Dy and 0.5 wt% B. A solution of 1 M HNO₃ + 0.3 M H₂O₂ was used to dissolve up to 98 % Nd and 81 % Dy, while keeping Fe dissolution below 15 % within 10 min. Fe dissolved in solution was completely removed as Fe(OH)₃ at pH 3 followed by precipitation of Nd and Dy with oxalic acid (H₂C₂O₄) and recovered 91.5 % of Nd and 81.8 % of Dy from solution. The precipitate containing Nd and Dy was calcined at 800 °C to obtain Nd₂O₃ as final product with 68 % purity, and final recovery of 69.7 % Nd and 51 % of Dy was reported in this process.