what are the steps involved in the purification of water of natural resources for drinking purpose
Answers
In regard with the water shortage crisis due to contamination of water bodies and resources, engineers have been searching for methods to purify water. As per research done by AIChE (American Institute of Chemical engineers) Nitrkl chapter, Water purification process has specifically 10 basic steps where each step are supervised by chemical engineers. The other variants of this water purification process such as reverse osmosis, carbon filtration, etc are also done and supervised by chemical engineers.
According to the international charity Water Aid, one in eight human beings, mostly in the developing world, goes without clean, safe water. Every 20 seconds, one child dies from diarrhea caused by contaminated water and poor sanitation. In wealthier countries, illness and death from water contamination are far rarer because of wide-scale, mostly government-operated water purification systems. Although these water treatment systems vary, many safeguard public health through an eight-step purification process.
Pre-Treatment
Pumps bring “raw" or untreated water, often from lakes or rivers, into the purification plant through screens that exclude fish, weeds, branches and large pieces of debris. Screening may not be necessary for groundwater. The plant may aerate the water at this point to increase the oxygen content and thus help remove problematic odors and tastes.
Coagulation & Flocculation
The purpose of these two steps is to clear water of the small particles that cause it to be turbid or cloudy. Turbidity renders the water hard to disinfect. The water is rapidly agitated to disperse coagulant chemicals throughout it. The small particles, including many bacteria, begin to form large clumps called flocs or floccules. In flocculation, the water is mixed gently so that these clumps combine and precipitate out further.
Sedimentation
The water and flocs are pumped into sedimentation basins. Here, the flocs settle beneath the water so that they can be removed. About 85 to 90 percent of the suspended particles responsible for turbidity are removed at this point, including large amounts, but not all, of the bacteria.
Filtration
In filtration, the water flows through a multilayer medium such as quartz sand, activated carbon or anthracite coal in order to remove up to 99.5 percent of the solid materials remaining in it, whether flocs, microbes or minerals. This step usually is the last one in the process of removing solids from the water.
Disinfection
Disinfection kills off disease-bearing organisms in the water. Most water treatment plants use chemicals, generally chlorine compounds, as disinfectants. Although chlorine is still one of the most common disinfectants, ultraviolet radiation and ozone gas are becoming more widespread. Chlorine is increasing in cost and has some known toxic effects on humans and fish. In addition, some disease-carrying microbes like Giardia and Cryptosporidium resist chlorine.
Corrosion & Scale Control
The pH of the water is adjusted so that it neither corrodes nor deposits too much scale in pipes. Excessive amounts of scale can disrupt plumbing systems, but small quantities help pipes to function at their best. However, no amount of corrosion in the water distribution system is desirable. As well as causing leaks and other damage, corrosion releases pipe metals like lead and copper that jeopardize human health.
5 Steps of Water Purification
Water purification plays a key role in ensuring access to safe drinking water. Safe drinking water positively impacts the health of the entire community. Systems are in place to ensure ongoing water quality, including water quality testing. The testing helps ensure the water treatment process results in a product that meets federal water quality guidelines. Water analysis involves looking for several kinds of contaminants, including unsafe levels of organic, inorganic, microbial and/or radioactive contaminants.
Screening
Water from lakes, rivers or the ground passes through a screen as it enters the water treatment plant. When the water source is a lake or river, the screen serves an important function, keeping out large natural contaminants such as plants and wood, or fish. If ground water is used, screening may not be necessary since the water has passed through layers of the earth in what is essentially a natural screening function.
Coagulation
Treatment plant workers add alum and other chemicals to the water, which cause tiny sticky particles, or floc, to form. These floc attract dirt particles, making them eventually heavy enough to sink to the bottom of the water storage tank.
Sedimentation
The water and floc flow into a sedimentation basin. As the water sits there, the heavy floc settle to the bottom, where they remain until removal.
Filtration
Water passes through layers of gravel, sand and perhaps charcoal, which serve to filter out any remaining particles. The gravel layer is often about 1 foot deep and the sand layer about 2½ feet deep.
Disinfection
Water goes into a closed tank or reservoir. Chlorine or other disinfecting chemicals kill any remaining microorganisms or bacteria in the water and help keep the water clean until distribution. If a water treatment facility uses ground water as its only water source, disinfection may be the only step required to sufficiently treat the water. After it is disinfected, the purified water sits in the closed tank or reservoir until it flows through pipes to homes and businesses.