Module 21: Chemical Addition

This paper aims at analyzing the drinking water issue in the Mediterranean region, highlighting the principal problems and the appropriate technologies applicable in the different countries. The countries of this area are characterized by a huge variety from social, cultural, economic and environmental point of view. In particular, water distribution is inhomogeneous between the North, East, and South; even the type of water sources and the related quantity and quality problems differ country by country. Potable water comes from brackish and seawater, surface water, groundwater and water reservoirs with each source face different issues. The main problem of brackish and seawater for example is the high salinity and the contamination by disinfection byproducts, in addition to the microbiological and chemical contamination due to human activities that characterize also other surface water sources. Groundwater is also affected by human activity and it is not exempted from salinity because of the water intrusion. Moreover, water reservoirs are often contaminated by seasonal algal blooms. Technologies applied for drinking water treatment vary country by country. The paper presents the main treatment processes associated with the main water pollutants, according to the Mediterranean region. Case studies of drinking water treatment plants are also analyzed, presenting alternative technologies appropriate for specific contexts, among others. The characteristics of each specific context should be carefully analyzed in order to develop the most appropriate technologies; high-end technologies for drinking water treatment may not be applied equally to all countries or communities of the Mediterranean region.

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.

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.