In order to protect groundwater quality, Orange County Water District and Orange County Sanitation District (OCSD) jointly sponsored a groundwater replenishment system to minimize seawater intrusion. Seawater intrusion compromises water quality of the existing groundwater supply. In areas like Orange County, California, groundwater basins have been depleted and seawater is drawn into vulnerable coastal aquifer zones. While direct potable reuse still faces challenges of public acceptance, indirect potable reuse applications are increasing. The future of US conventional water supplies such as rivers and aquifers will be sustained through advanced treatment of other water sources such as impaired rivers, post-consumer wastewater reuse and groundwater affected by seawater intrusion ( Blomquist et al., 2003). increased salinity, micropollutants, turbidity and nutrients) and the cost for such treatment to protect public health increases. The field of drinking water treatment is dynamic and still evolving as the quality of drinking water resources decreases (e.g. Numerous technologies for the detection and treatment of naturally occurring and manmade pollutants have been achieved through significant advances in the past 30 years ( Trussell, 2006). Spatari, in Metropolitan Sustainability, 2012 16.3.2 Water treatment If the chloride content of a water has to be reduced then some form of desalination has to be applied ( Section 10.43). However, in arid or semi-arid areas, people may have to drink water containing much higher levels of chloride if no alternative supply is available.Ĭonventional water treatment processes do not remove chlorides. A sensitive palate can detect chloride in drinking water at as low a level as 150 mg/l and concentrations above 250 mg/l may impart a distinctly salty taste ( Section 7.49). High concentrations of chloride tend to enhance the corrosion rates of iron, steel and plumbing metals, especially when coupled with low alkalinity ( Section 10.41). Brackish or estuarine waters can contain several hundred mg/l of chloride, with seawater typically containing around 20 000 mg/l.Įxcessive chlorides can give rise to corrosion and also to taste problems. The chloride content of a sewage effluent under dry weather flow could increase the chloride content of the receiving water by as much as 70 mg/l. Most rivers and lakes have chloride concentrations of less than 50 mg/l Cl and any marked increase may be indicative of sewage pollution or, if the increase is seasonal, urban run-off linked to the application of rock salt (‘grit’) to roads. It is usually combined with sodium and to a lesser extent with potassium, calcium and magnesium, which makes chloride one of the most stable components in water. Ratnayaka BSc, DIC, MSc, FIChemE, FCIWEM, in Twort's Water Supply (Seventh Edition), 2017 7.15 ChlorideĬhloride is found in nearly all waters and is derived from a number of sources, including natural mineral deposits seawater intrusion or airborne sea spray agricultural or irrigation discharges urban run-off due to the use of de-icing salts or from sewage and industrial effluents. With rising sea levels along the Bangladesh coast the following components of the coastal zones are at risks of salinity intrusion: (1) coastal rivers draining fresh-water from upstream areas, (2) tidal inlets and creeks penetrating saltwater inland, (3) coastal wetlands (both freshwater and saltwater marshes), (4) coastal soils, and (5) coastal aquifers. Increased salinity in coastal Bangladesh may also be considered as a secondary impact of climate change, since it is consequent upon SLR as its primary impact. Salinity intrusion in coastal Bangladesh due to global warming–induced sea level rise (SLR) is an example of secondary salinization. The latter can occur on a time scale as short as decades or even more rapidly. In contrast, increase in salt concentrations caused by anthropogenic forces, such as climate change, is known as secondary salinization ( Herbert et al., 2015). Accumulation of salts in the coastal environment by such natural processes is called primary salinization because they occur naturally in response to glacial and interglacial cycles that occur over a time scale of approximately 100,000 years or longer in some cases ( Herbert et al., 2015). Seawater intrusion into coastal water bodies and accumulation of salts in coastal soils, aquifers, and wetlands are natural processes as waves, storm surges, tides, and currents interact with different components of the coastal environment. Bimal Kanti Paul, Harun Rashid, in Climatic Hazards in Coastal Bangladesh, 2017 Primary Versus Secondary Salinization
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