Groundwater contaminated with the high explosive Demolition eXplosive, or hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) may also contain the nitroso-RDX metabolites hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX). Although adsorption to activated carbon effectively removes RDX from contaminated water, the treatability of the nitroso-RDX compounds by adsorption has not been previously reported. Single-component isotherms were completed and the Freundlich parameters ( $K$ and $1/n$ ) were calculated for adsorption of these compounds to Calgon F400 from unbuffered high purity water under aerobic and anoxic ( $<1\text{mg}/\text{L}$ dissolved oxygen) conditions. Under both conditions, MNX was the most adsorbable, followed by RDX, DNX, and TNX. The presence of dissolved oxygen slightly increased the Freundlich parameters for all compounds except TNX. Under aerobic conditions, Freundlich capacity parameters $\left(K\right)$ ranged from $46.4\left(\text{mg}/\text{g}\right){\left(\text{L}/\text{mg}\right)}^{1/n}$ for TNX to $164.2\left(\text{mg}/\text{g}\right){\left(\text{L}/\text{mg}\right)}^{1/n}$ for MNX, while under anoxic conditions, $K$ ranged from $47.1\left(\text{mg}/\text{g}\right){\left(\text{L}/\text{mg}\right)}^{1/n}$ for TNX to $133.6\left(\text{mg}/\text{g}\right){\left(\text{L}/\text{mg}\right)}^{1/n}$ for MNX. Additional testing showed that 7 days were sufficient for adsorption equilibration in most cases. Simplified granular activated carbon (GAC) column modeling demonstrated that the presence of these compounds in groundwater can reduce GAC service life.

In this paper some of the practical issues involved in the development and application of an extraction-photodegradation remediation technology for polychlorinated biphenyl (PCB) impacted weathered soils are addressed. The extraction of PCBs from weathered soils was investigated using the conventional Soxhlet extraction and by shake extraction using different solvents. The shake extraction has the potential for up-scaling to a field technology. The photodegradation of the extracted PCBs was investigated under direct ultraviolet light at 254 nm wavelength as well as under photosensitized light at 350 nm. The production of biphenyl, a by-product of the dechlorination of PCBs was investigated and it was found to degrade in the same ultraviolet system.

This study is performed to develop a comprehensive software package entitled “simulation of chemical industrial accident (SCIA).” The SCIA can be integrated with geographical information system (GIS) to predict and display the risk and consequence of chemical hazards from two categories of hazardous materials, namely toxic and flammable materials. This paper describes how the existing models are used for predicting accident scenarios and their impact to humans and the environment. The technique for assessing the consequences from chemical accidents is developed by integrating the models in the system with the help of the GIS tools. The software is coded in Visual Basic, and is compatible with Windows working environments. The validity of the software has been confirmed by comparing the results of several applications with other commercial software. The software is a user-friendly and effective tool for evaluating the consequences of major chemical accidents, process decision making for land-use planning namely locating suitable hazardous installations, hazardous waste disposal areas and emergency response plan.

The WASP/EUTRO model was used to model a low dissolved oxygen (DO) stream in Taiwan as part of the water quality management effort to restore the stream. The low DO is the result of industrial wastewater discharges causing significant oxygen consumption due to carbonaceous and nitrogenous biochemical oxygen demand in the receiving water. The modeling effort was supported by a field monitoring program including two water quality surveys of the stream. The model calibrated with these two data sets, and also used unit response analysis to calculate the DO deficit contributed by individual loads. The calibrated model was used to evaluate wastewater management alternatives to restore the stream.

Coprecipitation of arsenic by alum or iron salts produces a large quantity of arsenic-laden sludge (an average of $6.10\text{g}{\text{As/dm}}^3$ of sludge on dry basis) in conventional arsenic removal plant (ARP). This toxic sludge, along with acclimated composite organic waste slurry containing a mixture of partially digested liquefied market waste, primary sludge of sewage treatment plant, and liquefied water hyacinth at 1–10% by volume of the total, was anaerobically digested for a period of 30–50 days. The maximum removal of arsenic was obtained as 99.69% at a digestion period of 50 days. The minimum biogas generation at 30 days digestion period was found to be $0.560{\text{m}}^3$ (at standard temperature and pressure) per cubic meter of composite feed slurry at 10% of ARP sludge. The results show that presence of arsenic in adequately acclimated composite feed sludge does not significantly inhibit the anaerobic digestion process. It may thus be stated that anaerobic digestion of arsenic-laden composite organic waste sludge could be a viable option for the safe and cost-effective disposal of arsenic-laden sludge available from existing arsenic removal water plants in arsenic affected areas.

A modified method was used to increase the adsorption of heavy metals from aqueous solutions by using sawdust. Sawdust was collected from waste timber industry and modified with different tartaric acid concentrations (0.1 to 1.5 M) at $90°\text{C}$ for 90 min. The performance of the modified sawdust and unmodified sawdust have also been studied. The batch removal of the selected heavy metals, Cu(II), Zn(II), and Cd(II), from aqueous solutions under different experimental conditions was carried out in this study. The adsorption capacities of tartaric acid modified sawdust (TMSD) and nonmodified sawdust (NESD) were compared. The effect of initial metal concentration, temperature, pH, time, and adsorbent dosage on the removal of the metallic species have been reported. Two different of kinetic models viz. Lagergren-first-order and pseudosecond-order equations, were used to investigate the adsorption mechanism. The batch sorption kinetics and the applicability of the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms for the present system have been tested at $25\pm 2°\text{C}$ . NESD and TMSD were found to remove heavy metals from aqueous solutions efficiently.

This paper proposes a generalized constitutive model for municipal solid waste, based on the framework derived from critical state concepts and incorporating the effects of mechanical creep and time-dependent biodegradation, to predict total landfill compression under incremental loading and with time. The model parameters are calculated based on laboratory one-dimensional compression and triaxial compression tests, and data available from published literature. To illustrate the applicability of the proposed model, settlements due to incremental loading of waste with time are predicted for typical landfill conditions. The predicted settlement results using the proposed model are compared with the predicted settlement results using 14 different reported models. It is shown that the predicted settlements can vary significantly depending on the model used and the parameter values selected. The proposed model predicts the total settlement in a range similar to the reported models that consider all three components (mechanical, creep, and biodegradation) of the settlement. Further validation of the model is required based on field measured settlement at different landfill sites.

The Kaoping River Basin, located in southern Taiwan, flows through approximately 171 km and drains toward the South Taiwan Strait. It is the largest and the most intensively used river basin in Taiwan. However, due to the concentrated rainfall in the wet season, short rivers and rapid flows, poor flow conditions, uneven time distribution of flows, and rapid rise of flow peak cause the unevenly distributed water resource in this region. Based on the results from the water resource analysis and water demand evaluation, a shortage of water supply in the basin would occur in 5 years. Sustainable water resource management strategies have been proposed to effectively utilize the limited water resource in the basin. The proposed strategies include construction of water collection gallery system, installation of riverbank infiltration system, installation of groundwater recharge and extraction systems, recycling the effluent from the secondary wastewater-treatment plant, and replacement of old water supply pipes. These measures are more sustainable and more environmentally acceptable compared with other traditional construction measures (e.g., reservoir and long-distance water transportation conduit). Results and experience obtained from this study will be helpful in developing water resource management strategies for other similar river basins.