Research On Controlling Optimal Model Of Pumps And Sluices Based On Water Purification Capacity

Water environment deterioration has been becoming a common problem in plain rivernet region both at home and abroad. The river water quality can be locally and effectively improved by the water diversion project in a short term, because it can increase the flow rate in a river and shorten the period of the replacement of water body by regulating its hydraulic structures such as pumps and sluices in a plain river network. However, the researches on the controlling optimal model of pumps and sluices are mostly focused on the establishment of the model or the direct application of the project. The factors, which may affect the improvement of receiving water quality, such as sediment, temperature of upper water, water velocity, the water quality of diverted water, and diversion ratio, have not been considered thoroughly in the previous works. Therefore, this paper aims to improving the hydrodynamic controlling optimal model based on water purification capacity and maximizing the improvement of water quality with minimum operating costs of pumps and slice gates. The main contents are as follows:Firstly, the water environment model of plain river network of a demonstration area in Jiaxing city was established based on MIKE11, while the fundamental data for the model was obtained via field works.Secondly, bench-scale experiments using the nitrogen and phosphorus nutrients as water quality index were conducted and four influencing factors (sediment, reaeration, flow velocities and temperature) were evaluated. The experimental results show that reoxygenation is the most important factor to affect the ability of water purification, diversion time can be reduced in summer due to the ability of water purification, and the optimal velocity of recieving water during the water diversion period is about0.1m·s-1.Thirdly, experiments on the improvement of receiving water quality contributed by the different water quality of diverted water and the ratio of diversion water were conducted. The results show that the external water that has the ratio of ammonia and nitrate of1:3～1:5, and the ratio of phosphate and organic phosphorus to be1:4can improve receiving water quality mostly; while the ratio of water volume diverted by pumps and slice gates to the water volume of the original receiving water body be1:5can also improve quality mostly.Fourthly, the hydrodynamic controlling optimal model that considering diversion factors, taking the optimal velocity in the river, the water quality of diverted water and the diversion ratio be the restrict conditions and completing the objective function by considering all the costs, has been established.Finally, the water environment model of the river network demonstration area in Jiaxing was established with the application of MIKE11. The MATLAB was used to couple the water environment model of plain river network with the revised hydrodynamic control optimization model, and hybrid genetic algorithm was employed to filter the best scheme for water diversion, in contrast with the previous optimization scheme. The results of the case in Jiaxing reveal that the revised hydrodynamic control optimization model improved in this study can provide an timely, effective and low-loss diversion scheme even with a variable water quality of diverted water.