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In this presentation I discuss two challenges facing environmental engineers and scientists - the emission of greenhouse gases and the widespread presence of organic micropollutants in the environment. Nitrous oxide is a potent greenhouse gas and its emission is projected to have an increasingly greater impact on the environment in future. Microbial activity during nitrogen cycling (e.g., in agricultural soils) plays a central role in nitrous oxide emissions, but our understanding of the responsible bacterial pathways is at present incomplete. Organic micropollutants include hormones, pharmaceuticals, and antibiotics chemicals that have been shown to affect organism development and behavior under controlled laboratory and field conditions at ng/l concentrations. Much effort is currently being placed on developing treatment systems to efficiently degrade these chemicals.
Reconstructed metabolic network modeling is a technique made popular in systems biology. This technique can be used to gain insight into processes occurring within bacteria that lead to emission of nitrous oxide from biological wastewater treatment systems. In this presentation we use a reconstructed metabolic network model in combination with flux balance analysis to assess the effect of oxic-anoxic transitions on nitrous oxide production by Nitrosomonas europaea. The oxic to anoxic as well as anoxic to oxic transitions are shown to cause an imbalance in the electron pool and trigger different pathways for nitrous oxide formation.
The degradation of organic micropollutants by the green catalyst iron Tetra-amido macrocyclic ligand (Fe-TAML) is discussed. As opposed to ozone based advanced oxidation technologies this biomimetic catalyst uses a non-Fenton mechanism to efficiently degrade a wide range of chemicals. Using the synthetic estrogen Ethinylestradiol as a model micropollutant we show that chemical degradation does not necessarily lead to toxicity reduction and advocate the need to complement chemical degradation with the monitoring of byproducts and toxicity. Additionally, the potential for using density functional theory to explain the sequence of micropollutant transformation is shown by applying it to model the pathways of Bisphenol A, Triclosan, and Nonylphenol degradation by Fe-TAML.
Jan Heijs has managed planning teams and planning projects most of his 30+ years working life. Jan will present a number of his observations related to modelling support to planning processes. Are there quicker and better ways to get the outcomes we are looking for. Where is the business case to do accurate and detailed catchment modelling. Are we building in a safety factor in our calculations and what is the price for getting it wrong? How does the modelling community presents itself to the ignorant clients? How does the modelling community respond to the call for quick and dirty and where are the risks?