International evaluation of current and future requirements for environmental engineering education

The field of environmental engineering is developing as a result of changing environmental requirements. In response, environmental engineering education (E3) needs to ensure that it provides students with the necessary tools to address these challenges. In this paper the current status and future development of E3 is evaluated based on a questionnaire sent to universities and potential employers of E3 graduates. With increasing demands on environmental quality, the complexity of environmental engineering problems to be solved can be expected to increase. To find solutions environmental engineers will need to work in interdisciplinary teams. Based on the questionnaire there was a broad agreement that the best way to prepare students for these future challenges is to provide them with a fundamental education in basic sciences and related engineering fields. Many exciting developments in the environmental engineering profession will be located at the interface between engineering, science, and society. Aspects of all three areas need to be included in E3 and the student needs to be exposed to the tensions associated with linking the three.

Modelling of two-stage anaerobic digestion using the IWA Anaerobic Digestion Model No. 1 (ADM1)

The aim of the study presented was to implement a process model to simulate the dynamic behaviour of a pilot-scale process for anaerobic two-stage digestion of sewage sludge. The model implemented was initiated to support experimental investigations of the anaerobic two-stage digestion process. The model concept implemented in the simulation software package MATLAB(TM)/Simulink(R) is a derivative of the IWA Anaerobic Digestion Model No.1 (ADM1) that has been developed by the IWA task group for mathematical modelling of anaerobic processes. In the present study the original model concept has been adapted and applied to replicate a two-stage digestion process. Testing procedures, including balance checks and 'benchmarking' tests were carried out to verify the accuracy of the implementation. These combined measures ensured a faultless model implementation without numerical inconsistencies. Parameters for both, the thermophilic and the mesophilic process stage, have been estimated successfully using data from lab-scale experiments described in literature. Due to the high number of parameters in the structured model, it was necessary to develop a customised procedure that limited the range of parameters to be estimated. The accuracy of the optimised parameter sets has been assessed against experimental data from pilot-scale experiments. Under these conditions, the model predicted reasonably well the dynamic behaviour of a two-stage digestion process in pilot scale. (C) 2004 Elsevier Ltd. All rights reserved.

Similarity solution of axisymmetric flow in porous media

Applications of the axisymmetric Boussinesq equation to groundwater hydrology and reservoir engineering have long been recognised. An archetypal example is invasion by drilling fluid into a permeable bed where there is initially no such fluid present, a circumstance of some importance in the oil industry. It is well known that the governing Boussinesq model can be reduced to a nonlinear ordinary differential equation using a similarity variable, a transformation that is valid for a certain time-dependent flux at the origin. Here, a new analytical approximation is obtained for this case. The new solution,, which has a simple form, is demonstrated to be highly accurate. (c) 2005 Elsevier Ltd. All rights reserved.

Steepness expansion for free surface flows in coastal aquifers

Free surface flow of groundwater in aquifers has been studied since the early 1960s. Previous investigations have been based on the Boussinesq equation, derived from the non-linear kinematic boundary condition. In fact, the Boussinesq equation is the zeroth-order equation in the shallow-water expansion. A key assumption in this expansion is that the mean thickness of the aquifer is small compared with a reference length, normally taken to be the linear decay length. In this study, we re-examine the expansion scheme for free surface groundwater flows, and propose a new expansion wherein the shallow-water assumption is replaced by a steepness assumption. A comparison with experimental data shows that the new model provides a better prediction of water table levels than the conventional shallow-water expansion. The applicable ranges of the two expansions are exhibited. (c) 2004 Elsevier B.V. All rights reserved.

Aeration for plant root respiration in a tidal marsh

This paper investigates the tidal effects on aeration conditions for plant root respiration in a tidal marsh. We extend the work of Ursino et al. ( 2004) by using a two-phase model for air and water flows in the marsh. Simulations have been conducted to examine directly the link between the airflow dynamics and the aeration condition in the marsh soil. The results show that the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances. Single-phase models based on Richards' equation, which neglect such effects, may not be adequate for quantifying the aeration condition in tidal marsh. The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass ( TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated. This may explain the observation that some salt marsh plant species grow better near tidal creeks than in the inner marsh areas. Our analyses, based on the two-phase model and predicted TAAM flux magnitude, provide further insight into the positive feedback'' mechanism proposed by Ursino et al. ( 2004). That is, pioneer plants may grow successfully near the creek where the root aeration condition is optimal. The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects. These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions.

Sources of hydrogen sulfide in groundwater on reclaimed land

Fisherman Islands is an area of reclaimed land at the mouth of the Brisbane River in Queensland, Australia. Ongoing groundwater monitoring has found elevated concentrations of hydrogen sulfide (H2S) in the groundwater on the island. The presence of H2S on Fisherman Islands is of concern because of its toxic nature, the potential for acid sulfate soil formation, and its noxious odor. The aim of this study was,to, identify the sources of H2S within the groundwater on Fisherman Islands. It was hypothesized that the H2S is being formed by sulfate reducing bacteria acting on sulfate from seawater, rather than the introduction of sulfide with the dredge sediments. Groundwater and soil samples were collected and analyzed for sulfide, sulfate, and organic carbon contents. Elevated concentrations of sulfides coincide with,elevated concentrations of sulfate in the groundwater and elevated concentrations of organic carbon in the sediments, supporting the hypothesis that sulfide formation is the result of heterotrophic, sulfate reducing organisms.

Sustainability metrics for coal power generation in Australia

The basis of this work was to investigate the relative environmental impacts of various power generators knowing that all plants are located in totally different environments and that different receptors will experience different impacts. Based on IChemE sustainability metrics paradigm, we calculated potential environmental indicators (P-EI) that represent the environmental burden of masses of potential pollutants discharged into different receiving media. However, a P-EI may not be of significance, as it may not be expressed at all in different conditions, so to try and include some receiver significance we developed a methodology to take into account some specific environmental indicators (S-EI) that refer to the environmental attributes of a specific site. In this context, we acquired site specific environmental data related to the airsheds and water catchment areas in different locations for a limited number of environmental indicators such as human health (carcinogenic) effects, atmospheric acidification, photochemical (ozone) smog and eutrophication. The S-EI results from this particular analysis show that atmospheric acidification has highest impact value while health risks due to fly ash emissions are considered not to be as significant. This is due to the fact that many coal power plants in Australia are located in low population density air sheds. The contribution of coal power plants to photochemical (ozone) smog and eutrophication were not significant. In this study, we have considered emission related data trends to reflect technology performance (e.g., P-EI indicators) while a real sustainability metric can be associated only with the specific environmental conditions of the relevant sites (e.g., S-EI indicators).