Water Treatment Lecture 5: Filtration

. Knowledge about the processes of the removal of nitrogen and phosphorus from wastewater by biological processes . Knowledge about systems with enhanced biological treatment processes

Surging population, energy demands, and climate change will push us, ever more urgently, to find new approaches to meet growing water demands. Most often, this will involve harvesting lower quality or impaired water supplies (e.g., seawater or brackish groundwater) as a source for drinking water. Recently desalination using membrane-based processes (e.g., reverse osmosis [RO], electrodialysis [ED], and nanofiltration [NF]) has shown promise for providing additional sources of fresh water across the United States. However, the current membrane separation processes are commonly energy intensive and produce large volumes of concentrated brine which poses unique challenges. Particularly in land-locked urban center brine disposal often relyes on surface water discharge or deep-well injection which pose economic and practical difficulties for wide-spread adoption of such technologies. Thus, there is an urgent need for energy-efficient desalination technologies that reduce the amount of concentrate produced, or identify cost-effective solutions for concentrate management.

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.

Aluminium in drinking water comes from natural sources and the alum used as coagulant in the water treatment process. Exposure to aluminium has been implicated in dialysis dementia, Parkinson and Alzheimer’s disease. Drinking water containing aluminium was considered to be one of the main sources of Al intake into human body. For this reason, the removal of aluminium from drinking water is vital to our health. In this study, removal of aluminium was carried out by using a chelating resin.

The goal of this project is to validate proof-of-concept testing for iron enriched granular activated carbon (GAC) composites (aerogel-GAC or iron-oxide impregnated) as a viable adsorbent for removing arsenic from groundwater and conduct technical and economic feasibility assessments for these innovative processes. Specific project objectives include: • Conduct batch experiments for aerogel-GAC and Fe-oxide impregnated GAC composites to evaluate their performance removing arsenic. • Evaluate Fe-GAC media performance in rapid small scale column tests (RSSCTs) to assess arsenic removal in a more dynamic treatment system. • Evaluate Fe-GAC potential for removal of other contaminants (e.g., methyl tertiary butyl ether, dissolved organic carbon). • Characterize Fe-GAC media. • Correlate performance and media characterization for possible selection of two media for a future second phase of this project.