Bismuth oxyhalide, usually employed as a photocatalyst, has not been tested as an activator of peroxide for water purification. This work explores the potential application of bismuth oxyhalide (BiOX, X = Cl, Br, I)-activated peroxide (H 2 O 2 ; peroxymonosulfate (PMS) and peroxydisulfate) systems for the degradation of carbamazepine (CBZ) in water destined for drinking water. BiOBr showed the highest activity toward the peroxides investigated, especially toward PMS. The most efficient combination, BiOBr/PMS, was selected to further research predominant species responsible for CBZ degradation and toxicity of transformation products. With repeated use of BiOBr, low bismuth-leaching and subtle changes in crystallinity and activity were observed. CBZ degradation was primarily (67.3%) attributable to attack by sulfate radical. Toxicity test and identification of the oxidation products indicated some toxic intermediates may be produced. A possible degradation pathway is proposed. Besides substitution of the hydroxyl groups on the surface of the catalyst particles, PMS's complexation with the lattice Bi(III) through ion exchange with interlayer bromide ion was involved in the decomposition of PMS. The Bi(III)-Bi(V)-Bi(III) redox cycle contributed to the efficient generation of sulfate radicals from the PMS. Our findings provide a simple and efficient process to produce powerful radicals from PMS for refractory pollutant removal.

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The paradigm of “divide and conquer” has been well used in Water Distribution Systems (WDSs) zoning planning in recent years. Indeed, Water Network Partitioning (WNP) has played an irreplaceable role in leakage control and pressure management; meanwhile it also has certain drawbacks, such as reduction of the supply reliability of the pipe network system and increased terminal dead water, as a result of the closure of the pipe section. In this paper, an improvement is made to the method proposed by Di Nardo et al. (2013) for optimal location of flow meters and valves. Three improvements to the genetic algorithm are proposed in this work for better and faster optimization in the dividing phase of WNP: preliminary hydraulic analysis which reduces the number of decision variables; modifications to the crossover mechanism to protect the superior individuals in the later stage; and boundary pipe grouping and mutation based on the pipe importance. The objective function considers the master–subordinate relationship when minimizing the number of flow meters and the difference of hydraulic state compared to original WDS. Another objective function of minimizing the deterioration of water quality compared to original WDS is also evaluated. The proposed method is applied for the WNP in a real WDS. Results show that it plays an effective role in the optimization of layout of the flow meters and valves in WNP.

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Apart from water quality, leakage control and energy consumption management are the most concerning challenges for water treatment plants (WTPs). The joint scheduling of pumps and pressure reducing valves (PRVs) in the water distribution network can reduce excessive pressure and distribute pressure more evenly, which achieves comprehensive reduction of leakages and energy consumption. Taking into account the main shortcomings of the commonly used methods, such as scheduling pumps or PRVs separately, or optimizing PRV settings when their position is given, etc., this paper has taken the PRV (position and setting) and the working status of variable speed pumps (VSPs) as decision variables and the cost savings contributed by leakage reduction and energy consumption savings as the objective function, which maximized the economic benefits brought by PRV and/or VSP scheduling. A genetic algorithm (GA) was used to optimize the solution under multiple working conditions. The performance of three control strategies (PRV-only scheduling, VSP-only scheduling, and joint scheduling of PRVs and VSPs) are compared to each other based on a small network. Joint scheduling has achieved the best economic benefits in reducing the gross cost (contributed by leakage and energy consumption) of the three control strategies, which results in a leakage reduction of 33.4%, an energy consumption reduction of 25.4%, and a total cost reduction of 33.1%, when compared to the original network, and saving about 1148 m 3 water (7% of the original consumption) and 722 kWh electric energy (25.4% of the original consumption) per day.