Common Methods of Water Purification

With all the different methods of water purification available, how do you decide? Hopefully we can help.

• Chlorine
• NaDCC Sodium Dichloroisocyanurate
• Iodine
• Boiling
• Filtration / RO / Equipment
• Chlorine Dioxide

Chlorine:

Chlorine is universally accepted as a safe and effective water disinfectant. Free chlorine or hypochlorous acid is the most commonly used method of water purification in the world and has saved millions of lives since it became popular in the 1920’s. Chlorine has virtually eliminated widespread epidemics of waterborne disease where implemented. Chlorine comes in a variety of different formats including liquid, granules and tablets as well different base agents including calcium hypochlorite and sodium hypochlorite. Other forms of chlorination include what are called halazone tablets. Chlorine is very effective against almost all bacteria, viruses and cysts.

There a few things to be aware of regarding water purification using Chlorine. Many Chlorine tablets are considered as dangerous good and need to be handled very carefully. Direct contact with chlorine tablets or resulting dust can cause severe skin and respiratory irritation. Chlorine tablets are also highly flammable and potentially explosive when mixed with acids or other common chemicals. The biggest complaint that is reported by those using Chlorine tablets for water purification is the taste. Halazone Tablets, Household Bleach or Calcium / Sodium Hypochlorite create a very strong “Chlorine” taste and odour in the water. Many indigenous populations around the world refuse to use water purification tablets made from Chlorine because the resulting water is very unpalatable. The concern of course is that users from any population will not use the water purification tablet because of the resulting taste and odour, and will risk drinking unsafe water.

NaDCC Sodium Dichloroisocyanurate:

When added to water Sodium Dichloroisocyanurate (NaDCC) Water Purification Tablets dissolve to release a measured dose of hypochlorous acid or free available chlorine which is universally recognized as a safe and effective water disinfectant. NaDCC is not chlorine. Rather it reacts within water to create free chlorine. The difference is substantial. Chlorine itself, Calcium or Sodium Hypochlorite (household bleach) is hazardous to handle in either tablet or liquid form and produces very strong tastes and odours when used for water purification. NaDCC is not dangerous to handle, is completely stable and inert as a tablet and when used to purify water produces free chlorine without the traditional chlorine taste and odour.

In laymans terms, it's like getting the best of both worlds – the benefits and effectiveness of free Chlorine without the negative tastes and odours. It is for these reasons that NaDCC has become so widely accepted as the most popular form of water purification tablet. NaDCC is comparable to Iodine for effectiveness and efficacy against waterborne bacteria, viruses, cysts and disease but has no unpleasant taste or colour and more importantly, has no negative health effects. NaDCC is certified to NSF/ANSI Standard 60 and has been approved for drinking water treatment by the U.S. EPA (Environmental Protection Agency) and the WHO (World Health Organization)/JECFA.

NaDCC is effective against the cyst Giardia when used in sufficient strength and for a sufficient contact time.

• Popular brands of NaDCC Water Purification Tablets include: Aquapura Water Purification Tablets and Akrosept.

Iodine:

Iodine is one of the oldest forms of water purification. Iodine comes either as a water purification tablet or a disinfectant solution continually charged by Iodine crystals. Iodine itself does a pretty good job in making water safe from bacteria, viruses and some cysts. Water to be purified should be clear before treatment. Iodine is however sensitive to light and must be kept in a dark bottle. For deactivation of Giardia, the source water must be at least 21 C (68 F). If the water is colder (as it usually is), you will need to let it sit longer - possibly overnight for cold stream water.

The biggest challenge when using Iodine for water purification is the resulting taste, odour and colour. Iodine often causes a yellowing of the water upon treatment and produces a taste and odour that many find unpalatable. Most suppliers of Iodine tablets often provide a “taste neutralizer” tablet to help counteract the harsh taste. The concern of course is that users will not purify suspect water because of the resulting taste and odour, and will risk drinking unsafe water.

CAUTION! Some people are allergic to Iodine and cannot therefore use it to purify water that they will drink. Many studies have also linked serious health risks and side affects to Iodine exposure resulting from water purification. People with thyroid problems or on lithium, women over fifty and pregnant women should consult their physician prior to using Iodine for water purification. There are also reports that some people who are allergic to shell fish are also allergic to Iodine. 

Boiling:

The most effective means of water purification is boiling. Keeping water at a vigorous and rolling boil for 1 to 3 minutes depending on elevation will eliminate all bacteriological contaminants. The challenges in using boiling as a means of water purification include finding a heat source, finding electricity or fuel, waiting for the water to cool down before it can be consumed and protecting it from recontamination. It is for exactly this reason that municipalities use chlorine in their drinking water systems. Chlorine provides the treated water with ongoing protection from recontamination. Any bacteria or virus that comes into contact with the treated water is inactivated by the chlorine that exists in the water. If you are purifying water by boiling, it is strongly recommended that you use a water purification tablet such as Aquapura to provide your water with protection from recontamination.

Filtration / RO / Equipment

Purifying water by filtration/reverse osmosis equipment or water purification equipment is not as simple as it sounds. There are hundreds of different types and sizes of filters to choose from. Some filters only remove sand, grit and sediment while others remove more. Very few are capable of removing common waterborne viruses. Some require electricity, some require manual pumping. Even the most compact filters are not something to be carried around in ones shirt pocket or purse. Are you prepared to find a source of electricity or huddle over a pump during lunch? Filters of course also need to be cleaned or replaced when fouled. When using a water filter, be sure that you know how to clean it, when to clean it, or when to change it. Improper maintenance of a water filter can in fact lead to dangerous levels of bacteria building and growing within the actual filter, similar to a dirty kitchen sponge. Charcoal filters are especially at risk for bacteria buildup.

Purifying water by filtration also leaves water prone to recontamination. As soon as the water leaves the filter it is immediately susceptible to any sort of bacteria or virus that may be in the air, in the receptacle or bottle receiving the water, etc. It is for exactly this reason that municipalities use chlorine in their drinking water systems. Chlorine provides the treated water with ongoing protection from recontamination. Any bacteria or virus that comes into contact with the treated water is inactivated by the chlorine that exists in the water. If you are using a filter to purify water, it is strongly recommended that you use a water purification tablet such as Aquapura to provide your water with protection from recontamination.

Chlorine Dioxide

Chlorine Dioxide is an entirely different water purification agent than Chlorine. Chlorine Dioxide has traditionally been used to purify water as a gas but recent developments in technologies has seen the creation of tablets and two part liquids that when introduced to water creates Chlorine Dioxide. While very effective as a water purification chemical, Chlorine Dioxide generation via tablets or liquids is quite a new technology and consumers should read all directions, claims, etc. very carefully. The origins of Chlorine Dioxide for water purification come from its use in releasing odour causing bacteria in various applications.

The downfall of Chlorine Dioxide when used to purify water includes both cost and taste. Chlorine Dioxide water purification liquids or tablets are quite expensive generally listing between INR 1000-1200 (US$20–25) on the shelf for 30 tablets. Chlorine Dioxide liquid products generally require two liquids to be mixed together and then allowed to sit for a set time before introduction into the raw water. This of course requires both time and concentration and may not be suitable in many settings.