Thursday, May 12, 2016

Water Treatment Plants - Uses, Operation and Maintenance

Water treatment plants

Water treatment plants are used to make water suitable for a specific end use. The end use can be drinking, water supply for industrial usage, irrigation, water recreation etc. These plants either remove contaminants or reduce their concentration in water so that it becomes suitable for it's desired use.Water treatment plants vary widely with respect to their working mechanism, capacity etc. The plants can range from consisting of a single machine that provides purified water to a small congregation of families to large and varied combination of machines that provide water to entire cities.

Components of water treatment plants

Water treatment plants are used across many countries the world over, with the biggest beneficiaries being the gulf countries such as Saudi Arabia, Kuwait etc, who suffer from a perennial water shortage problem. In the aforementioned countries, these are generally used to make sea water fit for drinking, while in some other countries these are used to treat waste or used water to make it fit for reuse. Although a bit expensive to set up initially, the treatment plants are gradually finding usage in almost all major countries owing to the long term benefits that these provide.

Components of water treatment plants:

A water treatment plant consists of various components that aid in specific stages of water purification. These components are,
  •     Backwash recovery tank
  •     Sand filters
  •     Sludge drying beds
  •     Flocculation tanks
  •     Sedimentation tanks
  •     Treated water reservoir
  •     Aeration enablers
Water treatment plants:General principles and treatment stages

Treatment of water includes removal of unwanted substances that may have adverse short term or long term health effects. The substances that are generally removed by water treatment plants are excess salt, bacteria, algae, virus, suspended solids, fungi etc. Some of these substances can be removed by only a simple process, while some may need multiple procedures for removal. For a better elaboration, below is a list of all major removal stages( Please note that all of these stages aren't required every time)

  • Removal of suspended matter – Suspended matters such as leaves, water plants, soil etc. that are present in water are retained at the raw water reservoir of the treatment plant
  • Prechlorination – We all know that chlorine has oxidizing and disinfecting properties. By adding chlorine to the water, all forms of organic and inorganic materials like iron, hydrogen sulphide etc. are oxidized, killing all the pathogenic or other micro organisms
  • Aeration of water – In this stage, air is added to water in order to kill all anaerobic micro organisms
  • Flocculation – Flocculation means the addition of aluminum sulphate, it is necessary for removing the organic particles that are present in the raw water and also for changing the color of water from green to clear.
  • Sedimentation – Sedimentation is the process of clarifying the water of sludge's that form as a result of the addition of aluminum sulphate
  • Filtering – In this stage the water passes through special rapid sand filters where it is filtered for removing all the remaining particles that are present in water.
  • Addition of lime – In this stage, lime is added to water for correcting it's pH value (acidity). The noteworthy thing here is that the addition of lime is only done when it is considered absolutely essential
  •  Post chlorination – After the treatment process is complete, chlorine is added once again to water to ensure that there is no growth of any pathogenic microorganisms in the water supplied for end use

Desalination plants are also water treatment plants, with the difference being that these take a slightly different approach towards making water suitable for end usage, i.e- removing excess salt. The processes used by desalination plants generally are,
  • Pre treatment – This process consists of prechlorination, fine filtration and pH correction of sea water
  • Reverse osmosis – At this stage, high pressure pumps supply the needed pressure to enable the water to pass through the membranes and reject the excess salt
  • Post treatment – In this stage, water is stabilized and then prepared for wide distribution

Disinfectants used in water treatment plants

Of all the disinfectants used by treatment plants, four are the most favored. They are,
  •  Chlorine
  •  Aluminum sulphate
  •  Ozone
  •  Ultraviolet radiation
Operation and maintenance of water treatment plants:

The plants must be operated as designed for their optimal performance. Keeping in mind that water affects human health in both positive and negative way, it is thus pertinent to ensure that the plants always perform at their optimal functionality. Only trained operators should be allowed to operate these plants.

Since water treatment plants are functional every day and in every weather be it rain, hailstorm, snow, heat wave, so it is imperative that preventive maintenance of these machines is done accordingly. Preventive maintenance means doing fixed periodic inspections of all it's parts and keeping records of key performance parameters. Most breakdown can be easily avoided if preventive maintenance is undertaken as soon as the plant is put into operation.

The need for water treatment plants

The below mentioned points aptly sum up why waste water treatment plants are essential

  • Waste water treatment is essential for keeping our rivers, drains and other flowing water bodies clean, so as to ensure optimal hygiene all around us and also in the things that we use daily
  • Waste water containing human waste is a carrier of various pathogens and microorganisms that may have many adverse health effects. Thus it is essential that water is treated before releasing it in the environment so that it doesn't pollute the surface soil and by extension plants
  • Various industrial waste flows daily in various water bodies such as rivers, lakes etc. This is one of the biggest sources of water pollution and also an incubator of harmful pathogens. The industrial waste needs to be first treated by water treatment plants
  • The application of commercial fertilizers and pesticides combined with sediments from growing construction activities continues to be a major source of water pollution as the runoff flows into the water. This makes the use of water treatment plants all too imperative.
Key challenges faced by water treatment plants today

Water treatment plants have been largely successful in attaining their objective of delivering purified water for end use. Still due to changing usage patterns, developmental activities, their efficiency has somewhat reduced in the last few years. The challenges include
  • Many of the waste water treatment plants are old and inefficient, since they have not been repaired or improved for some decades now. This has resulted in the quantity of waste water being purified getting reduced leading to a cyclical effect on human health and also environment.
  • The character and quantity of the contaminants present today are far more complex than in the past
  • Population growth is taxing many existing water treatment plants and creating the need for newer plants
  • Farm runoff and rapid urbanization provide additional sources of pollutants that are difficult to control by present waste water treatment methods
  • A major part of new development is served by decentralized systems such as septic tanks. This creates additional hurdles in the proper functioning of these plants.

Issues relating to the use of water provided by water treatment plants:

We all have to accept that there is a general lack of awareness amongst people when it comes to using treated water. Treated water is still in some societies thought of as unfit for drinking or for other general uses. A large part of the blame for this should go to people's attitude that still regards anything from human waste as anathema . Government's across the world have made efforts to make people aware about the fact that plant treated water is as good for drinking as normal purified water but still a lack of enthusiasm is there among people.

To put it simply, the lack of enthusiasm flies in the face of basic scientific facts that have proven time and again that treated water is perfectly fit for drinking and all other uses. To be fair, a little change in attitude has been seen lately in some people, hopefully it becomes a lot more widespread soon.

Water treatment plants: The future

As everyone knows, large parts of the world are going through major water shortages that is almost bordering on a crisis. As is common knowledge, this situation will only worsen with time. Recent research suggests that there are more drought prone areas in the world today than they ever were. This coupled with rapidly increasing population is an ideal situation for a widespread drought like situation leading to massive public unrest.

To get around this problem, more water treatment plants need to be built. Also, as mentioned above, presently there already is a wide list of contaminants that are difficult to filter out, thus more advanced plants are also needed that optimally filter out all contaminants. There is an effort being put into this by researchers across the world. Hopefully, we will soon see some fruitful results.

Another point to mention here is that apart from getting drinking water, more treatment plants need to be built to keep our water bodies such as lakes, rivers and even seas and oceans clean. We never focus on keeping oceans clean, with the thought process being that oceans are too large to be contaminated. Well this thought seems to be incorrect as we all know about a large stretch of pacific ocean that is cluttered with waste. By some accounts the area affected is larger than the total area of a lot of countries. All these reasons make a strong case for more water treatment plants