Sustainable Stormwater Management: A Holistic Planning Approach for Water Sensitive Cities

The planning of sustainable stormwater infrastructures for future water-sensitive cities requires new holistic methods. In the Indo-German research project SMART&WISE, a structured approach was de-veloped to improve the planning processes for water infrastructure systems. The developed approach attempts to map the entire decision-making process when planning suitable infrastructures. A basic distinction is made between retrofit and greenfield planning. Four analyses form the basis of the planning approach: (1) Flood Protection, (2) Water Balance, (3) Water Scarcity and (4) Heat Islands. An indexation of different analyses results enables to overlay and visualize the overall result. The approach was tested successfully in two pilot projects: An Indian pilot case in a semi-arid climate zone and a German pilot case in an arid climate zone. It could be shown that the approach is suitable to cope with heterogeneous population and settlement development, climate change and increasing resource scarcity. The approach can help to facilitate interdisciplinary collaborations (especially urban planners and engineers for urban drainage). Increase in evaporation and a decrease in heat is the decisive advantage of low impact development measures (LIDs) for a sustainable stormwater management. However, an increase in evapotranspiration is not recommended in semi-arid or arid regions, since it would further increase water stress. For regions at risk of water scarcity, a balance between water sources, storage, reuse, and demand must be achieved

Optimal estimation of roughness in open-channel flows

The inverse problem of estimating the open-channel flow roughness is solved using an embedded optimization model. Measurement data for flow depths and discharges at several locations and times are used as inputs to the optimization model. The nonlinear optimization model embeds the finite-difference approximations of the governing equations for unsteady flow in an open channel as equality constraints. The Sequential Quadratic Programming Algorithm is used to solve the optimization model. The performance of the proposed parameter estimation model is evaluated for different scenarios of data availability and noise in flow measurement data. Solution results for illustrative problems indicate the potential applicability of the proposed model

Simplification of water distribution networks using non-linear Thevenin theorem and its application for maximum power transfer

The boundaries of existing cities are expanding rapidly due to the exponential growth in urban population. Therefore, the existing water distribution networks (WDNs) need to be expanded up to the newly developed areas to meet the additional water demand. The optimal design of a sub-network planned for network expansion requires multiple simulations under various constraints. Simulating the additional sub-network along with the existing network takes a lot of CPU time. In this study, a methodology is proposed to replace an existing large pipe network with its equivalent network consisting of a single source and a single pipe by applying the non-linear Thevenin theorem being used for electrical circuits. The equivalent network model parameters are extracted by fitting the driving-node head-loss characteristics at the connecting node. Unlike all other available methods except the traditionally used reservoir–pump model, the equivalent network presented in this study reduces to only two elements. The theoretical aspect of the reservoir–pump model can be explained by the proposed Thevenin reduction method. The advantage of the proposed method is put forward by deriving an analytical expression for the condition of maximum power transfer from the equivalent main network to the sub-network. The economic diameter value of the connecting pipe is subsequently determined. The proposed network reduction method is demonstrated on different WDNs for various demand patterns. The reduced networks yield accurate results and simulate faster when compared with those of the original networks. The proposed methodology is beneficial for a focused analysis of a sub-network and to transfer maximum power to the sub-network connected to a large existing hydraulic network. HIGHLIGHTS Using the non-linear Thevenin theorem, a methodology is proposed for water distribution network simplification.; The equivalent network consists of only two elements.; The equivalent network is giving exact results as that of the original network.; This methodology gives computational advantage.; The relation between connecting pipe diameter and sub-network demand for maximum power transfer is derived using the equivalent network.

Analysis of Breakthrough Behaviors of Hydrophilic and Hydrophobic Pharmaceuticals in a Novel Clay Composite Adsorbent Column in the Presence and Absence of Biofilm

The present study investigated the use of a novel clay composite adsorbent in simultaneous removal of hydrophilic and hydrophobic pharmaceuticals in a fixed bed column. The potential of a biologically active clay composite adsorbent in removing the pharmaceuticals was examined in detail. The mechanism of adsorption was elucidated based on an equilibrium sorption and mass transfer approach. The effects of dispersion, mass transfer zone, empty bed contact time, and an interfering substance such as humic acid on column operation were investigated in detail. It was observed that adsorption was the dominating mechanism of removal in the biologically active adsorbent column, and the amount of biodegradation gradually increased with an increase in contact time. Breakthrough behaviors of pharmaceuticals were numerically simulated using an equilibrium sorption approach as well as a mass transfer approach. Although both the equilibrium sorption model (EQM) and linear driving force (LDF) model predicted breakthrough behaviors satisfactorily, tailing of the breakthrough curve was better predicted by the LDF model. On the basis of the LDF model, surface diffusion coefficients for atenolol, ciprofloxacin, and gemfibrozil were estimated to be 6.5 × 10^–4, 9.4 × 10^–4, and 1.2 × 10^–3 cm/h, respectively