This is a time of mounting urbanization and industrialization and resulting stress on water and wastewater systems. Clean and ample sources of water for municipal uses are becoming harder to find and more expensive to develop. Effective design and efficient operation of engineering works ask, above all, for a fuller understanding and application of scientific principles. The results of scientific research are being incorporated with remarkable success in new designs using both U.S. and SI systems equations, examples and problems as well as new operating procedures. This classic text, now updated, grounds readers in both the science and art of water and wastewater engineering that global engineers need to service their customers and communities.