WWT&SYSENG. Getting systems engineering into regional wastewater treatment strategies.

Within the WWT & SYSENG project, we will investigate the fate of xenobiotic compounds (e.g. pesticides, pharmaceuticals) in the urban water system by means of mathematical modelling and model development. To achieve detailed knowledge about the different pathways of xenobiotics, we will first focus on their fate in biological treatment systems, which in a large extent mimic natural environments. We will then broaden the boundaries to include the influence of rainfall-runoff relationships on the distribution of xenobiotics and then the final destinations, i.e. the recipients. One project goal is to establish how detailed the various compartments should be described in order to formulate an integrated fate model that can be used for decision making and risk assessment.

In wastewater treatment plants (WWTPs), xenobiotic compounds are affected by on the one hand physico-chemical processes such as sorption/desorption, volatilisation and stripping and on the other hand by biological degradation. Several attempts have been made to summarise these processes into predictive fate models but according to literature, the description of the biological degradation of the xenobiotics form a bottleneck while trying to improve them. We will aim at developing correct descriptions, which then can be incorporated into some of the well-established biological WWTP models of today.

Dynamic experiments will be carried out at the Lynetten WWTP (Copenhagen, Denmark), a facility treating municipal and industrial wastewater corresponding to some 1.1 million citizens. In connection with the full scale plant, a pilot plant has recently been erected at the site. The experimental procedure will involve addition of selected xenobiotic compounds to the influent wastewater of this pilot plant. The screening of xenobiotics is characterised by rather time consuming and expensive analyses of compounds present in the environment at low concentrations (ng/l-µg/l) and as a consequence, we will try to minimise the number of necessary samples and analyses. A reliable model of the treatment plant helps to design the experiments as it can be used to isolate relevant investigations from the less important ones. With this in mind, a plausible first step of the work will be to get hold of a reliable WWTP model over the pilot plant that describes standard wastewater parameters. For this, the Activated Sludge Model No. 1 (ASM1), will be used. The results will then motivate model extensions and/or reductions. Although the model will be helpful during the experimental procedure, a reliable model necessarily depends on the experimental results. Consequently, modelling and experimental work will be carried out simultaneously.