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This article investigates trihalomethanes (THMs) production and simulates water age in Assiut drinking water system using WaterCAD software. Prechlorinated water samples were collected from Nazlet Abdellah water treatment plant and post-disinfected with chlorine/chloramines with different chlorine-to-nitrogen ratios (Cl2/N). Experiments have examined varying residence times, ratios of Cl2/N, pH conditions, and storage containers’ type on THMs formation. The results showed that as the residence time increased, THMs concentrations increased. Water age in Assiut drinking water distribution network reaches more than 10 h. Using chloramines instead of free chlorine for post-disinfection resulted in lowering THMs concentrations to 58.9 % after 48 h of disinfection. Ratios of Cl2/N (2:1–6:1) were comparable and effective on lowering THMs concentrations, and the most effective ratio was 4:1. Also, as the pH increased, the THMs increased. The measured THMs concentrations in chloraminated water stored in glass and plastic bottles were approximately the same.

This study investigated the possibilities of improving methane yield production from, the anaerobic co-digestion of wheat straw (WS) and primary sludge (PS). The batch experiment was conducted under mesophilic conditions. Different mixtures of WS and PS depending on its C/N ratio were carried out to investigate the optimum C/N ratio for effective methane production. The cumulative methane yields (CMYs) for co-digestion of PS with WS at C/N ratios of 35, 25, 20, 15 and 10 were 1.29, 1.62, 1.33, 2.44 and 2.16 time than digesting PS alone, respectively. The maximum CMYS was observed at C/N ratio of 15 with an increase of 89 %, 50.93 %, 83.61 % and 13.12 % compared with the other C/N ratio of 35, 25, 20 and 10 respectively. This result showed the positive synergy of co-digesting of PS and WS for methane production caused by improving the C/N ratio of the feed stock.

Simplification is an important design step of water supply and irrigation pipes networks. It is recognized by making the original network easier to be understood and analyzed. Water hammer in water-supply networks may give rise to high and low pressures, due to the superposition of reflected pressure waves. The effect of pipes networks’ simplification on water hammer phenomenon is investigated. This study uses a simple two loops pipes network composed of 12 high density polyethylenes (HDPE) pipes with different diameters, thicknesses, and roughness coefficients representing of a general parallel/series system. The network is fed from a boundary head reservoir and loaded by either distributed or concentrated boundary water demands. According to both hydraulic and hydraulic plus water quality equivalence, three levels of simplifications on the original network are performed. Also, the effect of water demands’ concentration on the transient flow is checked. The transient flow in the network is initialized by either concentrated or distributed boundary water demands which are suddenly shut-off or released. Water hammer and mass oscillation (WHAMO) software which uses the implicit finite difference scheme for solving the momentum and continuity equations at unsteady-state case is used in the simulation. All scenarios produced results showed that both hydraulic equivalence and demands’ concentration simplifications increase the transient pressure and flow rate in the simplified network compared with the original one. However, hydraulic plus water quality equivalence simplification results in an adverse effect. It was found that, as the degree of simplification increases the transient pressure head and flow rate of the simplified network deviate more from those of the original network. Therefore, simplifications of the distribution networks should be done with very careful caution.