Study On Optimal Design Of Water Allocation Network

Effective utilization of water is the key factor of sustainable development in process industries. Driven by water scarcity and increasing severe environmental pollution, the research in water network design has achieved significant progress. On the basis of analyzing the actual status and development trend of water network design thoroughly, the paper discusses the optimal methods and integration techniques in detail to direct the water saving and pollution reducing of process industries in theory. The content of this paper is listed as follows:1. The removal ratio of treatment process is an important parameter in wastewater treatment network. In the past, the optimal water networks are determined by given removal ratio with fixed values, but it is difficult to fulfill in practice. This paper presents a method for designing water network with variable removal ratio of treatment process based on biochemical treatment model. The removal ratio is calculated by Lawrence-McCarty model applied in plug-flow reactor. Comparing with traditional methods, the approach can assure that the calculated values of the concentration at the outlet of treatment process consists with the practical values;hence the more feasible water network can be obtained. The proposed approach is demonstrated with an example and the result is more close to practical values compared with literatures.2. The factors contributing to the cost of wastewater treatment are the wastewater quantity and quality. Water pinch analysis focuses on decreasing the quantity of wastewater, but can't improve the wastewater quality. Oxygen pinch analysis is an effective method for this problem. This paper proposes water-oxygen pinch analysis for water network design to obtain optimal network. But when multi-contaminants are presented, pinch analysis is difficult to realize. Mathematical programming methods are effective in optimizing large-scale systems, but it is difficult to interpret, giving designers less insights compared with pinch analysis. The paper presents a new method that combines water-oxygen pinch analysis with mathematic programming, which is effective to solve above problems.3. Simultaneous designing water utilization network and wastewater treatment network can not only reduce further the fresh water consumption, but also decrease the cost of treatment units. The paper presents the step-by-step pinch analysis method for water network design, considering water reuse, regeneration reuse as well as regeneration recycle. It also presents priority regulations and design approaches to optimize waternetwork.4. Mathematical programming is the main tool to perform simultaneous design. The paper proposes the method that combines mathematical programming and pinch analysis to design water utilization network and wastewater treatment network simultaneously. Firstly, set up the superstructure and mathematic model of water network considering water reuse, regeneration reuse as well as regeneration recycle. Then delete impossible streams by pinch analysis to simplify the superstructure. Finally, solve the network by adaptive simulated annealing genetic algorithm.