Integrated modeling in urban hydrology: reviewing the role of monitoring technology in overcoming the issue of ‘big data’ requirements

Increasingly, the application of models in urban hydrology has undergone a shift toward integrated structures that recognize the interconnected nature of the urban landscape and both the natural and engineered water cycles. Improvements in computational processing during the past few decades have enabled the application of multiple, connected model structures that link previously disparate systems together, incorporating feedbacks and connections. Many applications of integrated models look to assess the impacts of environmental change on physical dynamics and quality of landscapes. Whilst these integrated structures provide a more robust representation of natural dynamics, they often place considerable data requirements on the user, whereby data are required at contrasting spatial and temporal scales which can often transcend multiple disciplines. Concomitantly, our ability to observe complex, natural phenomena at contrasting scales has improved considerably with the advent of increasingly novel monitoring technologies. This has provided a pathway for reducing model uncertainty and improving our confidence in modeled outputs by implementing suitable monitoring regimes. This commentary assesses how component models of an exemplar integrated model have advanced over the past few decades, with a critical focus on the role of monitoring technologies that have enabled better identification of the key physical process. This reduces the uncertainty of processes at contrasting spatial and temporal scales, through a better characterization of feedbacks which then enhances the utility of integrated model applications

Biomethanation potential of biological and other wastes

Anaerobic technology has been traditionally applied for the treatment of carbon rich wastewater and organic residues. Anaerobic processes can be fully integrated in the biobased economy concept for resource recovery. After a brief introduction about applications of anaerobic processes to industrial wastewater treatment, agriculture feedstock and organic fraction of municipal solid waste, the position of anaerobic processes in biorefinery concepts is presented. Integration of anaerobic digestion with these processes can help in the maximisation of the economic value of the biomass used, while reducing the waste streams produced and mitigating greenhouse gases emissions. Besides the integration of biogas in the existing full-scale bioethanol and biodiesel production processes, the potential applications of biogas in the second generation lignocellulosic, algae and syngas-based biorefinery platforms are discussed.(undefined

Sorption and high dynamics of micropollutants in sewers

Down-the-drain household chemicals are mostly discharged intermittently (i.e. with water pulses, e.g. pharmaceuticals from toilet flushing) and well soluble micropollutants can, therefore, be subject to significantly high short-term fluctuations. It is not known how these fluctuations are attenuated by sorption to sewer sediments or biofilm. First, we investigated in this paper the effect of sorption for substances with high, medium and low affinity to particulate matter based on computational experiments. For substances with high Koc we found that the additional attenuation of a load pattern due to sorption is in the same order of magnitude as caused by dispersion in a typical main sewer. The mass flux between wastewater and the first biofilm layer was identified as the most sensitive parameter. Furthermore, the interplay of systematic, slow diurnal variations does not affect short-term fluctuations. Second, during rain events partial erosion of the biofilm can lead to increased micropollutant loads for substances with high Koc. This increase is in the same order of magnitude as diurnal variations of the loads in the liquid phase and the TSS

Sampling for representative micropollutant loads in sewer systems

Most commercially available auto-sampling devices do not support a continuous flow-proportional sampling mode, which would conceptually be the best for collecting representative composite samples. Instead different discrete sampling modes are available. Household chemicals can show considerable random short-term variations. With the anticorrosive benzotriazole, relating to a middle-frequent household activity, we show that, besides an accurate flow meter, mainly three factors are decisive for the representativeness of a substance's average load: the substance's load pattern, the sampling frequency and the length of the composite sample. When the sampling intervals are 10 minutes or longer, errors in the order of ±40% (standard deviation) or more have to be accepted, if the substance of interest is contained in a low number of wastewater pulses (i.e. the level of household activity). This particularly holds true for specific pharmaceuticals e.g. carbamazepine. Ammonium would be less critical, because it relates to a larger number of sources in the same catchment

Modeling Stochastic Load Variations in Sewer Systems

n wastewater treatment and environmental risk assessments increasing attention is paid to the fate of micropollutants. These are time-consuming, expensive and difficult to detect and quantify. If a substance's load or concentration is subject to high dynamic fluctuations, it is demanding to take representative samples, especially when the "variation" is unknown. Therefore, we developed a concept to model stochastic load variations in sewer systems. We gathered readily available information from existing databases (population and consumption data) and combined it with the characteristics of household activities and appliances. We succeeded in predicting realistic short-term variations of benzotriazole (contained in dishwasher detergents) and validated them with a high-frequency measuring campaign. Benzotriazole stands as an example for other household chemicals, which cannot be measured so easily. All required information used within this case study is also available for other substances and catchments. This allows the forecast of stochastic load variations for many chemical compounds of interest. It helps to plan measuring campaigns, to estimate discharged loads from combined sewer overflows and to have a characteristic input for modeling purposes