Safe water: A closer look

In the introductory article of this series, we’ve learnt that one out of every nine people lack access to a safe water source; unsafe water is the silent killer of this world.  But what does the term “safe water” mean?  Where or how is safe water secured?  This article will consider what safe water sources represent and what treatment options are available to ensure safe water.

 

Water safe for consumption - a basic human need, yet absent for many

Water safe for consumption – a basic human need, yet absent for many

 

For many African, Asian and Latin American countries, water of low and unsafe quality is often the status quo.  For water to be considered as safe, it needs to be microbiologically safe and free of chemical contaminants, only then is water suitable for human consumption without health consequences.  Consuming water that is not microbiologically safe poses severe threats to human health and is the  leading cause of many pandemic waterborne disease outbreaks with high mortalities.  But what are the reasons for the significant portion of the world population without access to safe water supply?  The answer lies in poor infrastructure development, the lack of financial capital for such developments, lack of human resources, harsh environmental conditions as well as environmental disasters causing immediate water safety crisis situations.  For many of the developing countries suffering from this dilemma, a combination of water treatment options can be designed for implementation – bringing immediate and lasting relief from unsafe water and all its cumulative health, environmental and economic impacts. 

The core function of water treatment is to  suspend and dissolve contaminant, which can include particulate matter, microbes and chemicals. Three basic water treatment options that can be implemented to secure safe water supply include sedimentation, filtration and disinfection.  These are simplistic treatment options – but that’s why these treatment options are successful throughout the developing world.  The treatment options are robust, low-cost, and environmentally acceptable while being easy to maintain and operate.

Sedimentation

Sedimentation treatment is based on the physics principle of particles in fluids settling due to gravity.  In nature, the sedimentation process is observed in calm lakes, ponds or oceans where particles settle to the bottom of the lake, pond or ocean.  In treating water, this physical separation of particles and water enables for the suspended solids to be removed from or taken out the water.  But free settling of particles is not always the quickest and most effective sedimentation process.  For this reason, water treatment through sedimentation often involves the adding of chemicals – and specifically chemicals with positive electrical charges.  These chemicals are described as coagulant chemicals.  A typical example of a coagulant chemical is Aluminum sulfate, although a number of salts can be used as coagulant chemicals.  By adding coagulation chemicals to the water, the opposing charges of the chemical and particles attract one another, resulting in heavier clumps or floc being formed.  With the particles now trapped in heavier clumps, the sedimentation process is guaranteed to be more effective.  Following the sedimentation process, the improvement in water quality can be seen with the naked eye.  The turbidity or cloudiness of the water is now accumulated in the floc.  This leaves the water with improved clarity and suspended articles collecting at the bottom of the water.

Filtration

Once the heavier clumps of particles have settled to the bottom of the water, it is necessary to filter the water.  Filtering separates the purified water from the floc and particle clumps.  Rural communities often rely on mechanical filters such as sand or other granular materials.  The filter medium retains the solid particles as the fluid passes through the filter medium.  Filtration can be applied at either community or household level.  For community filtration, a larger filtration system making use of storage tanks and a collection of filters can be used whereas individual households can benefit from smaller filtration units using locally available material.  It is however very important to realize that although sediments are removed from unsafe water through the filtration process, the water may still be subject to chemical contaminants and pathogens such as E.coli and therefore, continued disinfection is necessary.

Water disinfection

Physical separation (or filtration) is not always effective at removing disease-causing pathogens such as protozoa, bacteria and viruses from water. However, appropriately-designed disinfection processes can inactivate these microorganisms and  render water safe for human consumption.  Two disinfectants commonly used to purify water are chlorine and monochloramine.  The process of disinfecting water serves a further purpose namely the elimination of organic contaminants.

Being the pathogens’ food sources, organic contaminants play a key role in the pathogen’s lifecycle.  For this reason, the effective removal of organic contaminants through disinfection means that pathogens can no longer survive in the water.  Although disinfection effectively sterilizes the water, pathogenic activity can quickly return if the disinfectant used does not remain in the water source in some residual amounts.  But with the use of chlorine, this hindrance is defeated as chlorine remains in residual amounts in the water source allowing for safe water for a longer period of time.  Chlorine is also widely available through the developing world which makes it an even more suitable option for water treatment.  Water disinfection should be carefully pared with the type of water source and community conditions.  But at its baseline, water disinfection remains a cost-effective treatment option.

Living WaterTM Treatment System

The Living WaterTM Treatment System (LWTSTM) is a safe water solution developed by Water Missions International and is specifically aimed at securing safe water through water purification.  WMI has been implementing this system in both developing and disaster areas suffering from unsafe water for more than ten years, continuing to incorporate new and innovative technology along the way past.    This purification system operates on a similar basis as a small municipal treatment system and uses a combination of filtration and chemical disinfection to secure safe water.  The system’s success is evident in WMI’s decades of serving communities plagued by poor water quality.

The LWTSTM incorporates a number of innovative features which makes it well-suited for the often harsh environments where safe water sources are desperately needed.  A single LWTSTM can treat up to 10 gallons (approximately 37.8 liters) of water per minute.  Recall from the previous article that between five and 13 US gallons of water are necessary to meet daily basic human needs.  When one considers the amount of water the LWTSTM can purify per day, and the amount of water needed per person for basic needs, the feasibility of the LWTSTM becomes clear.  One of these water treatment systems can continuously support a community of up to 3,000 individuals – a major improvement from unsafe water to a community now provided with access to safe water. In disaster situations, a single LWTS™ can serve up to 5,000 people.  Multiple LWTS™ systems can also be used to adequately serve larger populations.     

Active LWTS in Sri Lanka

Active LWTS in Sri Lanka

 

Management & operation

The best-suited water treatment option depends on the community’s local circumstances, infrastructure available and the available water sources and the water quality.  But regardless of which treatment option or combination of treatment options is implemented, management and operation always remain central in securing safe water supply.  The design of Water Mission International’s LWTSTM has taken this into account.  The LWTSTM design allows for simple operation and easy management.  The LWTSTM is usually implemented in rural areas where technical expertise and specialized training are often lacking.  The system is so uncomplicated that it can be set up in less than an hour, delivering safe and treated water within three hours.  For this reason, the LWTSTM treatment option with its features for easy operation and management, serves a great purpose.  Operational energy requirements are another critical factor that needs to be considered when recommending water treatment options for developing countries.  Often in rural areas, a constant and reliable source of electricity may be lacking.  Similarly, a reliable source of affordable fuel may are also lacking in many instances.  As an alternative for this situation, water treatment options that rely on renewable energy (solar, wind, biomass) are highly recommended.  Recognizing this potential operational pitfall, the LWTSTM operates with solar energy as sole energy source.  By making use of renewable energy, the cost of operation is also significantly reduced, from $3.00 per 1,000 gallons to $0.75 per 1,000 gallons!

With this background on safe water sources and how water can be treated to secure adequate quality, the next article in this series will focus on the process of implementing safe water solutions.

Safe water: a reason to smile

Safe water: a reason to smile

 

Photo credits: all rights reserved by Water Missions International (2013) and some rights reserved by Water, Sanitation, and Hygiene Photos via flickr [Creative Commons].

Sources:

Centers for Disease Control and Prevention (2013).

Engineering for Change 

Reiff F., Roses M., Venczel L., Quick R., Will V. (1996) Low cost safe water for the world: a practical interim solution. Health Policy; 17: 389-408.

Safe Drinking Water is Essential (2008). Global Health & Education Foundation.  National Academy of Sciences.

Water Missions International 

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