Design Of Total Water Networks Of Multiple Contaminants With Regeneration Units By Using Iterative Approaches

Water is an irreplaceable and important resource.The study on water conservation and reducing wastewater discharging is a very important research field.The integration of water networks is an efficient technique for both water conservation and reducing wastewater discharging.This thesis investigated one of the important research topics in integration of water networks: design of total water networks with multiple contaminants.The main contents of the thesis are as follows:1.For a total water network with only one regeneration unit,the design procedure is divided into the following steps:(1)Estimating the initial concentrations of the regenerated stream,adding the regenerated stream into the original network to obtain the data for design of the network with regeneration unit,(2)Determining the performing order of the demands,and designing the water network with regeneration unit,(3)Checking if the discharging wastewater meeting the environmental limits,if the limits were not met,adjust the amount of wastewater treatment flowrate,(4)Checking the convergence conditions,if the conditions were not met,return to step(2)till all the conditions were met.2.For design of total water networks with a few regeneration units,we proposed a new iterative procedure.Compared to the networks with only one regeneration unit,one of the features of the networks with a few regeneration units is that there might be several possible regenerated streams.Therefore,the key steps in the design of a network with a few regeneration units are to estimate the initial concentrations of the regenerated streams and identify the applicability of the streams in the network.The design procedure is divided into the following steps: Step 1,estimation of the initial concentrations of all the possible regenerated streams;Step 2,adding the regenerated streams into the original network to obtain the sufficient data for design of the network with a few regeneration units;Step 3,determining the performing order of the demands,and identifying the applicability of the regenerated streams in the network,and obtaining the design of the network with a few regeneration units;Step 4,checking if the wastewater meeting the emission limits,if the limits were not met,adjust wastewater treatment network;Step 5,checking the convergence conditions,if the conditions were not met,calculate the concentrations of the regenerated streams for the next iteration based on the current iteration results,and return to step 2 till all the convergence conditions were met.3.In the above design procedure proposed for the total water networks with multiple regeneration units in this thesis,estimating the initial concentrations of the regenerated streams and identifying the applicability of the regenerated streams in the network are tedious steps.To avoid the above tedious calculations,a new procedure,subnetwork-dividing and iterative technique,was proposed.The design procedure includes the following steps:(1)Dividing the whole network into subnetwork before regeneration and subnetwork after regeneration;(2)Designing the subnetwork before regeneration,the regenerated streams could be obtained by regenerating the outlet streams of the above network;(3)Designing the subnetwork after regeneration;(4)If the concentrations of the wastewater not meeting the emission limits,adjust the wastewater treatment system to meet the limits;(5)If the regenerated streams meeting the convergence conditions,the iteration will stop,otherwise,returning to step(2)till all the convergence conditions were met.The above procedures were illustrated with a few literature Cases.It is shown that the results obtained in this work are comparable with those obtained in the literature.In addition,the design procedures proposed in this work have clear engineering meanings.