An algorithm for waste and pollutants reduction in reactor design is presented in this paper. This algorithm use potential environmentalimpact balance (PEI) and PEI rate-law expression to track the generated PEI throughout reaction process within a reactor; and study howreaction conditions (temperature, pressure, concentration, etc.) and various engineering factors (heat and mass transfer, and back-mixing andso on) affect process environmental performance. The form of PEI rate-law expression should be consistent with the method for calculatingthe overall PEI of mixtures of chemicals inside reactors. The algorithm can be used as a tool to aid in designing chemical reactors withenvironmentally friendliness processes. The use of the methodology is illustrated with the reaction system of allyl chloride production.

In this paper, the application of the water networks with internal mains is introduced. A design methodology for multiple-contaminant water networks with single internal water main is presented. A new concept of "water-saving factor" is proposed. Emphasis is placed on the location of the first internal water main, which is related to the maximum water-saving potential. The paper is accompanied by several case studies to illustrate the methodology. According to these case studies, water networks with just one internal water main determined by the presented method can obviously reduce water consumption, approaching the minimum water consumption target.

Reuse of industrial wastewater is an important strategy for reducing freshwaterconsumption and wastewater generation. This paper outlines a methodology forassessing the economic performance of industrial wastewater reuse systems thatinvolve water upgrading. From an economic perspective, wastewater reuse reduces the costsof freshwater supply and wastewater disposal. Reusing signicant quantities of wastewatertypically involves regeneration=treatment of the available wastewater to meet the higher waterquality requirements of water-using activities. However, the cost of wastewater regeneration=treatment rises exponentially with increasing contaminant removal effciency. This paperdemonstrates the importance of balancing these competing cost factors (freshwater andwastewater disposal costs vs wastewater regeneration=treatment cost), which are functions ofthe post-regeneration=post-treatment contaminant concentration. The proposed cost optimizationprocedure can be used to minimize the total cost of a wastewater reuse system with eitherwastewater regeneration reuse or wastewater treatment reuse.

Water networks incorporating a regeneration recycle can minimize freshwaterconsumption and wastewater discharge, to the extent of approaching the inherentminimum value. Based on the water network structure provided with internal watermains, this paper addresses the design methodology for water recycling with regeneration, andextends prior work to cases involving multi-contaminant systems. In such a structure water issupplied to each water-using process from freshwater main, regenerated water main, or regenerationwater main according to water quality. How to determine the contaminant concentrationsin the regeneration water main is the key in such a water network design. Theregeneration concentrations should be the lowest compatible with the freshwaterconsumption of the system equal to its inherent minimum value. The corresponding designmethodology focuses on how to determine which main to use as the water source and howmuch the water flow rate is to be for each water-using process, on the basis of mass balanceand the inlet contaminant concentration condition of that process. Finally, an example is givento illustrate the design method.