Chapter 11 - Case Histories

Abstract

This chapter deals with the largest nanofiltration plant in the world producing potable water from river water. The rivers mentioned in the chapter have a relatively high level of pollution from organic matter. The use of water from the river imposes an unusually high level of constraints on the design of the plant, due to possible extremes in temperature and the variable level of solids in suspension and other pollutants. Although conventional materials and filtration processes abound within a new unit, the heart of the new plant, the actual nanofiltration plant relies heavily on plastic materials for both the filtration membranes and the pressure vessels containing the membranes. Before actually entering the nanofiltration vessels, the water is pumped through a final prefilter, which will remove any remaining large particles that may result from any dysfunction in the previous stages of filtration. The pressure is then increased from 8 to 15 bar depending on the temperature of the water and enters the filtration vessels. The nanofiltration technology permits the production of a very high quality of potable water by filtering water under pressure through membranes, which have openings 10,000 times smaller than a human hair. The nanofiltration membranes ensure the elimination of organic materials and dissolved organic compounds, and in particular, their biodegradable constituents that are the nutritive source for bacteria.