Choosing an emergency response water treatment system (ERWTS) for your ERP is a difficult decision. There is a wide selection of water treatment companies, technologies and products to choose from and it can be a challenge to find the one that is right for your organization.

  • Hospital
  • First Nations Community
  • Fire Department
  • Private Business
  • Health Department
  • Municipality
  • Community

Emergency water purification systems can go by many names and acronyms such as:

  • Emergency Response Water Treatment System (ERWTS)
  • Lightweight Water Purification System ( LWPS)
  • Tactical Water Purification System (TWPS)
  • Small Unit Water Purifier (SUWP)
  • Water Purification System (WPS)
  • Expeditionary Unit Water Purifier (EUWP)

1. How Much Water Will You Need?

How much water will you need to purify each day? Before reaching out to a supplier, manufacturer or even your favourite search engine, try and get a handle on how much water you will need. Most emergency water purification systems are rated on a daily basis. Get out your pen, paper and calculator and sketch out how much water you will need.

Example A)

Providing emergency water rations to a community might be a simple exercise of calculating the total number of people x the quantity of water required per person per day. When determining how much water each person will require, the World Health Organization (WHO) recommends 7.5 – 15 L of water per person per day for basic survival, hygiene and cooking needs.

Calculation: 6,700 people x 7.5 L per person per day = 50,250 L potable water per day

Example B)

A hospital might require more work to calculate water requirements for drinking, hygiene, cooking, ice, laundry, toilets, etc. As a starting point, The WHO recommends 40-60 litres per in-patient per day.

Additional quantities may be needed for ice making and/or laundry equipment, flushing toilets, etc.

TIP Don’t forget that daily outputs are based on a 24 hour day. Adjust accordingly if you cannot operate 24/7.

2. Will You Be Treating Fresh, Brackish or Salt Water Sources?

Water purification equipment is often separated or classified by the type of raw water that it can treat. You can save yourself a lot of work (and money) by determining if you need the ability to desalinate brackish or seawater sources. Currently, the only effective way of desalinating water is by using a technology called reverse osmosis, commonly referred to as RO. If your worst case scenario is a boil water advisory caused by bacteria or cysts involving municipally supplied water, you probably do not require a water purification system built around reverse osmosis technology. The following technologies (or a combination thereof) will easily eliminate bacteria, viruses, protozoan cysts, turbidity and most colour/odour issues:

  • Microfiltration
  • Ultraviolet light (UV)
  • Chlorination
  • Ultrafiltration (UF)

If however your ERP assumes that you must treat sea water or brackish water than you really have no choice but to seek out reverse osmosis technology.

3. What Level of Portability Do You Require?

  • Does your ERP require the water purification system (WPS) to be deployed throughout a geographical area? If so, how will you respond if roads are flooded, washed out or otherwise compromised?
  • Does your ERP require the WPS to deployed through a building? If so, how will you respond if elevators fail, forklifts run out of fuel or power, etc.? Will the water purification system fit through doorways, into elevators, etc.?
  • Does your ERP require the WPS to be moved from storage to site? If so, how will you respond if forklifts, trailers or pallet jacks are not available? Will the water purification system fit into available transportation? Is hand portable important?
  • Does your ERP require or include transportation by helicopter, all-terrain vehicle (ATV),  small aircraft or boat? If so, will the WPS physically fit into worst case methods of transportation (door dimensions, weight limits, etc.)?

When it comes to how portable your water purification system needs to be, perform a table top exercise to really understand where it will be stored, how it will be moved, how it will be transported, where it will be used and what resources will be available post disaster. We are all guilty of overlooking the small details. We attended the World Conference on Disaster Management one year and had to move a mobile water purification system through a man door after the loading doors were closed to the floor. It was too wide by about 2.

If you need larger volumes of water than a single water purification system can provide, consider purchasing multiple units and running side by side. Small, portable units can always be run side by side while offering maximum flexibility for portability and logistics. One large, trailer or truck mounted water purification system will always be limited.

  • Can the water purification system be dismounted from its primary method of transportation in order to move it across a washout, flooded road, etc.?
  • Can the water purification system be dismounted in the event of a broken axle, flat tire, engine failure, etc.?
  • How easy is it to dismount and mount the water purification system?

4. How Will the Treated Water Be Distributed?

Treating or purifying the water is only half the job. What do you do with it as it leaves the water purification system?

  • Do you need to distribute the water immediately via multiple taps or faucets?
  • Do you need to store the treated water in a tank or bladder? Tip Storing the water will allow you to purchase a smaller system as water can be produced during the night or day and then given out rapidly during peak distribution periods.
  • Do you need to move or transport the treated water? Tip Purify the water as close as you can to the intended users. Water is extremely heavy and difficult to move. For instance, it is far easier to deploy 4 small water purification systems throughout a region or large community and purify on site vs. securing the heavy logistics required to move water into 4 different areas day after day. One of the difficulties in New Orleans after Hurricane Katrina was not a lack of potable water but rather a lack of helicopters and other logistics to move water to where it was needed.
  • How the treated water will be distributed and what level of portability you may need are directly connected. There are benefits to smaller, more portable, easier to handle water purification systems but only you will know what’s right for your application and emergency response plan.

5. Certifications

Don’t overlook the most important part of any portable, emergency water purification system. It has to work. It has to create safe, potable drinking water that you, your team, your family and your community can rely on. And it has to work under what will probably be some very challenging conditions. When considering different products, technologies and systems, make sure that you look for available certifications and/or independent test data.

If considering a water purification system that includes ultraviolet (UV) light disinfection, make sure that it meets NSF 55, Class A certification. Class A systems (40,000 uwsec/cm2) are designed to disinfect and/or remove microorganisms from contaminated water, including bacteria and viruses, to a safe level. This certification ensures sufficient UV dosage levels, proper real-time monitoring of said dosage as well as alarms and safety devices in the event of a low dosage condition. Anything less than NSF 55, Class A certification is in my mind a significant health and safety risk. For more information please read our post, Why You Should Insist on NSF 55 Class A Certification in Your Water Purification System.

For more information on NSF 55, Class A certification for ultraviolet light disinfection systems, please refer to .

Often, there is no one size fits all certification available for emergency water purification systems. Some certifications are for specific technologies and most are not for complete systems, just specific components. When reviewing water purification systems, be sure to:

  1. Understand the certifications being presented. Some certifications are for efficacy while others simply address aesthetic values or the safety of components within the system (I.E. lead free piping and fittings, etc. which while important do not indicate protection for immediate and life threatening contaminants such as E. coli, Cholera, etc.
  2. Ask for documentation (test data, certificates, etc.) and retain on file in order to fulfill health and safety requirements.
  3. Review local state, provincial or federal regulations to ensure the equipment you are considering will be accepted. There is nothing worse than having your water purification system shut down by a health official because it fails to meet required regulations.


  1. Make sure that the water purification system you are considering has sufficient output for your needs and applications.
  2. Find out if you truly require desalination capability or not which can significantly affect the technology required.
  3. Think through the level of portability that you require, taking into account all aspects of storage, training, deployment and logistics.
  4. Give consideration as to how the water being treated will be distributed and make sure that the that the systems being considered can handle your needs.
  5. When evaluating a water system for your Emergency Response Plan, ensure that you understand and ask for as much certification as is available and applicable.
  6. Most importantly, understand the treatment chain being offered and always strive for a multi-barrier system (I.E. ultrafiltration and ultraviolet light instead of just one or the other).

Emergency Response Plan.