Water Filtration Systems for Developing Countries


Source: healingwaters.org - By: deborah.bense

What is Ultrafiltration and Reverse Osmosis?

Ultrafiltration and reverse osmosis are two ways to treat water. These processes remove dangerous contaminants, making the water safe to drink.

Water treatment technologies like ultrafiltration and reverse osmosis provide solutions to the problem of water scarcity. The need for solutions is overwhelming. By 2025, more than half of the world's population is expected to be living in areas where there is not enough clean water.

How Does Ultrafiltration Work?

Ultrafiltration uses filters that contain long membranes. Holes run lengthwise through the membranes. 

The water flows into the membranes through the holes and then gets squeezed out through tiny pores, which have a diameter of about 20 nanometers. To give you a sense of how small these pores are, a human hair or a piece of paper is about 100,000 nanometers thick. The diameter of a strand of DNA is about 2.5 nanometers. A virus is about 20 to 250 nanometers, and a bacterium (one bacteria) is about 1,000 nanometers long.

Because the pores are so small, they are able to trap viruses, bacteria, and other harmful debris that is in the water. Substances, like salt, however, that are dissolved in the water, will flow through the pores.

How Does Reverse Osmosis Work?

Reverse osmosis pushes water through a semipermeable membrane. This creates two streams of water, one that is treated and one that is rejected.

The reverse osmosis process is capable of filtering out even dissolved substances. Major commercial producers of bottled water use reverse osmosis. The process produces a product that is uniform in taste and chemical composition.

Difference Between Ultrafiltration and Reverse Osmosis

The two water treatment technologies have several differences. Most of the time, ultrafiltration will be the right choice for water filtration systems for developing countries. However, the decision on which technology to use will depend on what harmful substances are in the local water and on the needs of the community.

Differences Between Ultrafiltration and Reverse Osmosis

The two main differences between ultrafiltration and reverse osmosis are:

  1. Reverse osmosis removes dissolved substances from the water.
  2. Ultrafiltration systems are far more economical to install and maintain.

Advantages and Disadvantages of Ultrafiltration

Ultrafiltration has several advantages over reverse osmosis:

  1. Ultrafiltration is ideal for many situations. It removes viruses and bacteria from water, which are what cause most water-borne diseases. Using ultrafiltration water filtration systems for developing countries makes a huge difference in people's lives.
  2. The low cost of ultrafiltration makes it possible to set up systems in a greater number of sites.
  3. A single ultrafiltration filter can purify drinking water for 500 people per day.
  4. It only takes about 10 to 20 minutes a day to clean the filters, and it's easy to train people to do it. Even if the filters are not properly maintained, the result will be that the system runs slower. It won't affect the cleanliness of the water. Reserve osmosis, by contrast, requires hours of maintenance a day, usually by professionals. If it's not done correctly, the risk is that the water will be contaminated. 

A disadvantage of ultrafiltration is that it does not remove toxic chemicals from the water. However, toxic chemicals are a problem in only about five to 10 percent of sites. When Healing Waters International prepares to install a water treatment system, our technicians conduct tests to see if these chemical contaminants are present. If they are, then HWI will provide additional treatment steps, including reverse osmosis technology when necessary.

Advantages and Disadvantages of Reverse Osmosis

The main advantage of reverse osmosis over ultrafiltration is its ability to filter out dissolved substances. Large high-end commercial water bottling companies, which want to produce a product that always tastes the same, like to use reverse osmosis for this reason.

However, many people in water-stressed areas prefer the taste of water from an ultrafiltration system. This may be because the water retains enough of the naturally occurring salts and minerals from the area to taste familiar to those who drink it.

In addition to filtering out salts and minerals, reverse osmosis can also filter out toxic chemicals such as arsenic, mercury, or lead. In the rare cases where such chemicals are present in the local water, then systems designed for water-stressed areas would need to incorporate reverse osmosis or another process that is able to filter the chemicals out of the water.

The main disadvantages of reverse osmosis are the costs, the amount of maintenance that's required, and how much water is wasted.

  1. Installing a reverse osmosis system for a community experiencing water scarcity might cost $15,000, with operating costs as high as $9,000 per year. An equivalent ultrafiltration system would cost about $9,000 with annual costs of around $1,800. The lower the cost, the greater the number of communities that can benefit from having these systems installed.
  2. Reverse osmosis systems require about two to four hours of maintenance every day, usually done by a professional. If the maintenance is not done correctly, the result could be contaminated water.
  3. A significant amount of water is wasted with reverse osmosis systems. For every gallon of good, treated water, the systems may produce four gallons or more of water that is not usable.

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