A series of five experiments was performed in a two-stage compound channel including various roughness conditions and different types of bridge models, namely, single-opening semi-circular arch bridge model (ASOSC), multiple-opening semi-circular arch bridge model (AMOSC), single-opening elliptic arch bridge model (ASOE), and single-opening straight-deck bridge model with and without piers (DECK) including different span widths. The performances of six different methods for computing backwater around bridge waterways were compared using the experimental data carefully taken on many combinations of cases. The results of the energy method, momentum method, WSPRO method, Yarnell's method, USBPR method, and arch bridge method were compared with experimental results. The results showed that energy method was able to simulate more accurately the measured backwater values than the other methods. The backwater differences between the experimental values and computed values by the energy method are generally within –3.2% and 0.8% in terms of flow depth. A simple generalized function for estimating bridge backwater is also proposed.Key words: bridge backwater, hydraulic model testing, flood control, compound channel flow, one-dimensional methods.

As the population continues to rise, the demand for resources and environmentally friendly management of produced wastes has shown a significant increase in concern. To decrease the impact of these wastes on the environment, it is important to utilize the wastes in producing and/or recovering usable products to provide for the sustainable management of resources. One non-renewable and rapidly diminishing resource is phosphorus, which is used in several products, the most important being its use in manufacturing chemical fertilizer. With the increase in demand but reduction in availability of naturally occurring mineral phosphorus, it is important to investigate other sources of phosphorus. Phosphorus is most commonly recovered through struvite (magnesium ammonium phosphate) precipitation. The recovery of phosphorus from various wastewater has been well established and documented with recovery rates mostly above 90%. However, one of the major drawbacks of the recovery is the high cost of chemicals needed to precipitate the phosphorus. Since the external magnesium needed to achieve struvite precipitation accounts for around 75% of the total chemical cost, applicability of low-cost magnesium sources, such as bittern or seawater, can help reduce the operational cost significantly. This paper investigates the different magnesium sources that have been used for the recovery of phosphorus, highlighting the different approaches and operating conditions investigated, and their corresponding phosphorus recovery rates. An investigation of the economic aspects of the magnesium sources used for removal/recovery show that costs are dependent on the raw waste treated, the source of magnesium and the location of treatment. A review of published articles on the economics of phosphorus removal/recovery also indicates that there is a lack of studies on the economics of the treatment processes, and there is a need for a comprehensive study on life cycle assessment of such processes that go beyond the technical and economical aspects of treatment processes.

The detection of leakages in Water Distribution Networks (WDNs) is usually challenging and identifying their locations may take a long time. Current water leak detection methods such as model-based and measurement-based approaches face significant limitations that impact response times, resource requirements, accuracy, and location identification. This paper presents a method for determining locations in the WDNs that are vulnerable to leakage by combining six leakage-conditioning factors using logistic regression and vulnerability analysis. The proposed model considered three fixed physical factors (pipe length per junction, number of fittings per length, and pipe friction factor) and three varying operational aspects (drop in pressure, decrease in flow, and variations in chlorine levels). The model performance was validated using 13 district metered areas (DMAs) of the Sharjah Electricity and Water Authority (SEWA) WDN using ArcGIS. Each of the six conditioning factors was assigned a weight that reflects its contribution to leakage in the WDNs based on the Analytic Hierarchy Process (AHP) method. The highest weight was set to 0.25 for both pressure and flow, while 0.2 and 0.14 were set for the chlorine and number of fittings per length, respectively. The minimum weight was set to 0.08 for both length per junction and friction factor. When the model runs, it produces vulnerability to leakage maps, which indicate the DMAs’ vulnerability classes ranging from very high to very low. Real-world data and different scenarios were used to validate the method, and the areas vulnerable to leakage were successfully identified based on fixed physical and varying operational factors. This vulnerability map will provide a comprehensive understanding of the risks facing a system and help stakeholders develop and implement strategies to mitigate the leakage. Therefore, water utility companies can employ this method for corrective maintenance activities and daily operations. The proposed approach can offer a valuable tool for reducing water production costs and increasing the efficiency of WDN.

This study investigates the performance of commercially available three-Dimensional (3D) numerical software, FLOW-3D, on the prediction of the water surface profiles using a series of experimental data obtained in a two stage channel with skewed bridge crossing. The experiments were carried out for four different types of bridge models with two different skew angles of ø = 30° and ø = 45°. FLOW-3D, which solves the Reynolds-averaged Navier - Stokes equations, was applied to experimental data for the prediction of water surface profiles along the compound channel from upstream to downstream. The comparison of free surface profiles of 3D model showed good agreement with the experimental data. Notably, the measured and computed afflux values are found to be almost identical.