Water Treatment Lecture 2: Aeration

In efforts to make package plants more compact, affordable and easier to operate and maintain, it has been noted that the design and performance of some of these plants containing conventional treatment processes is sometimes compromised if technical expertise in this regard is lacking. Generally, there are several risks associated with poorly designed treatment systems, including loss of production, poor safety and compromised equipment and process unit efficiency with associated higher operating and maintenance costs. These risks have more severe consequences in the case of desalination (including water reclamation and water re-use) package plants. The objective of this project is to develop a set of guidelines to assist municipalities, water treatment practitioners, designers and package plant manufacturers in the specification and design of appropriate unit processes and operating parameters to fit the influent water quality, operating environment and other special treatment requirements.

Introduction: Desalination using seawater reverse osmosis (SWRO) technology is an important option available to water-scarce coastal regions. Worldwide sea water desalination is a very effective and economical way of producing potable water for drinking and industries. Reverse osmosis plants to convert sea water to potable drinking water and for other usages have been prevalent throughout the world for more than 4 decades. Design and operation of seawater reverse osmosis plants strongly depend on the raw seawater quality to be treated. The performance of desalination reverse osmosis (RO) systems relies upon the production of high quality pre treated water, and the selection of the best pre treatment technology depends on the raw seawater quality and its variations. Number of full-scale experiences has shown that pre treatment is the key for this application of reverse osmosis technology. It is why during these last years, an import effort has been done to identify and to characterise the diverse organic and mineral components present in the seawater in a view to optimise the seawater pre-treatment and to develop advanced analytical methods for feed water characterization, appropriate fouling indicators and prediction tools. This Chapter describes firstly a comprehensive approach to characterize raw seawater samples through analytical tools which allow the knowledge of the characterization of seawater from many aspects: (a) inorganic content, (b) natural organic matter, (c) enumeration of micro-organisms and phytoplankton. Secondly, this Chapter describes the effect of each of these parameters on the fouling of the reverse osmosis membrane. Finally, this chapter describes the different possible pre treatments available to reduce or remove the elements or substances up-stream reverse osmosis stage.