Current Scenario of Drinking Water
According to research articles and news, most tap and well water in the India. now are not safe for drinking due to heavy industrial and environmental pollution. We have reached to a point that, all sources of our drinking water, including municipal water systems, wells, lakes, rivers, and even glaciers, contain some level of contamination.
Contaminants range from naturally-occurring minerals to man-made chemicals and by-products. While many contaminants are found at levels not enough not to cause immediate discomforts or sicknesses , it is proven that even low-level exposure to many common contaminants will, over time, cause severe illness including liver damage, cancer, and other serious ailments.
Even the chemicals commonly used to treat municipal water supplies such as chlorine and fluoride are toxic and are known to have significant adverse effects on the human body.
Is environmental water quality really a major concern?
Environmental water contamination is the leading worldwide cause of death and disease and it adversely affects over 1 billion people every day in developing countries. Even here in the India we often struggle with water pollution caused by natural disasters and human activities. A recent national report on our water quality revealed that 45% of assessed stream miles, 47% of assessed lake acres, and 32% of assessed bays square miles were classified as polluted. Ground and well water sources may also become contaminated due to the problems associated with industrial dumping, hydraulic fracking, and agricultural byproducts.
It is easy to see why water pollution is a major problem for the animals and plants which live in those ecosystems, but the truth is it also negatively affects people. These same contaminated water sources are also where we get our seafood, where we swim and play, and even where our tap water is drawn from. While tap water is treated thoroughly to reduce pollution, some contaminants may still remain including heavy metals, chemicals, microbes, and pharmaceuticals drugs. Everyone who uses tap or well water will be exposed to some level of these contaminants every day.
Water purification system
Because each purification technology removes a specific type of contaminant, none can be relied upon to remove all contaminants to the levels required for critical applications. A well-designed water purification system uses a combination of purification technologies to achieve final water quality.
Each of the purification technologies must be used in an appropriate sequence to optimize their particular removal capabilities. The schematic below shows a central laboratory water purification system designed to produce water for critical applications.
The first step is pretreatment equipment specifically designed to remove contaminants in the feed water. Pretreatment removes contaminants that may affect purification equipment located downstream, especially reverse osmosis (RO) systems. Examples of pretreatment are: carbon filters (or tanks) for chlorine removal, particulate filters for sediment/silt/particulate removal, and softening agents to remove minerals that cause "hard" water.
The next purification step is Reverse Osmosis (RO). RO removes 90 to 99% of all the contaminants found in water. It is the heart of any well designed water purification system because it effectively removes a broad range of contaminants.
However, the tight porosity of the RO membrane limits its flow rate. Therefore, a storage container is used to collect water from the system and distribute it to other points-of-use such as polishing systems.
Polishing systems purify pretreated water, such as RO water, by removing trace levels of any residual contaminants. Polishing elevates the quality of pretreated water to "Type I" or "ultrapure" water.
A polishing system is designed to remove residual traces of impurities from water already pretreated by some other means (such as reverse osmosis or deionization). Treating raw tap water using such a system would quickly exhaust its capacity and affect final quality.
A typical polishing system may consist of activated carbon, mixed-bed deionization, organic scavenging mixtures and 0.22 µm final filtration. Systems can also be enhanced with ultra filtration, ultraviolet oxidation or other features for use in specific applications.
This combination of purification technologies, combined with proper pretreatment, will produce water that is virtually free of ionic, organic and microbial contamination.