Reverse Osmosis Use Analysis

As part of my research on developing household desalination products, I spent the month of January 2016, with my colleague Catherine O'Connor, visiting households in different Indian cities. We were trying to understand how families interact with their household water purification systems, with a particular interest in Reverse Osmosis systems. This human-use analysis is based on my interactions with their machines and the insight that was developed through the interviews.

This work was completed with support from the Tata Center for Technology and Design at MIT.

Contributions

  • User Research
  • Concept Generation

Collaborators

  • Catherine O'Connor

What is a Reverse Osmosis System?

A large fraction of the drinking water in India relies on groundwater supplies; however, much of this water naturally occurs at salinities that exceed the 500 ppm threshold recommended for drinking with the WHO or the Bureau of Indian Standards. In order to address the high salinity of this supply, many Indian households use in-home Reverse Osmosis (RO) water purification systems. They are typically designed to desalinate feeds of up to 2000 ppm total dissolved salt (TDS) content, to levels that are both safe for consumption (below 500 ppm) and improve taste (below 100 ppm). They are either mounted on the wall, or stand on the kitchen counter.

From my interviews with users of these devices, I was interested in identifying features that they appreciated in their products, and those that they sought to improve. I specifically focus on the following four aspects here, and suggest improvements at the end.

  • Water Storage Tank
  • Spigot
  • Waste Line
  • Maintenance

Tata Swach Ultima RO System

Bad! How much water remains? The tank is inaccessible.

Bad! A light indicates when the tank is full. This is not intuitive, and only a binary (full/not-full) measure. The tank remains inaccessible.

Good! Clear and removable tank allows the user to intuitively judge the amoung of water that remains.

Water Storage Tank

Treated water is stored in a storage tank so that it is available on-demand. When electricity is not available, users may want to know how much water is stored. For assurance, users also may way to manually clean the tanks.

Spigot

It allows the user to access the purified water. It should be robust, because its failure renders the whole product useless. Some level of control over the flow-rate is desirable to prevent overfilling and spillage.

Bad! A common complaint was that these spigots broke often. Pushing down too hard on the handle can cause it to fracture near its attachment. They tend to lock in the fully-open or fully-closed position.

Okay! Rotation of the switch activates the release of water. The surrounding structure limits the range of motion to prevent fracture. They also tend to lock in the fully-open or fully-closed positions.

Great! The user presses their glass or bottle against the lever to fill, without needing to use their other hand. It is spring-loaded and allows control over the flow-rate.

Bad! This is often what was seen. The flexible piping is not cut to an appropriate length. It dangles everywhere or is wrapped around the faucet above the sink. No waste water is being collected.

Bad! Some users collect water manually. One user, Vijay, tried to collect the water in a pot placed within the sink. Once, he returned home to find that the water had overflown and formed a puddle on the floor because the sink drain was covered.

Okay! The KENT Supreme has a separate 9L tank within the same system for waste-water collection. To maintain the same drinking water storage capacity, the additional tank increases the size and weight of the system.

Waste-Line

Of the total water fed to the system, only approximately 25% is recovered for drinking purposes, while the remainder is often drained down the sink.

"The [waste] water is not used because it is a pain to collect." - Benjamin

"You can hear the constant dripping." - Annu

Maintenance

Filters in the RO systems are replaced every few months. They are not cheap. Therefore, it is preferable to use the filters for the full duration of their life, but not for any longer. Filter life varies for the different filters in system; therefore, it unlikely that they all have to be replaced at the same time. Lastly, the input water quality affects the filter life and may vary from one home to another.

Bad! No indicators! The user uses the system until the filter is clogged or the taste of the water changes. Alternatively, the filter is replaced periodically whether or not it has been fully utilized. Note that this system also had a clear tank, therefore the "Tank Full" indicator is unnecessary.

Bad! The Change GKK1 and Change GKK2 (3rd and 4th) indicators start flashing 15 days before they need replacement. The term GKK (Germ Kill Kit) is incomprehensible, and is only used by this manufacturer. The indicators for these filters are indistinguishable from the power (1st) and full tank (2nd) indicators.

Okay! Some systems are non-intuitive. This is a picture from the Tata Swach RO system manual. Note that the display has six different indicators.

Suggested Improvements!

The concept below address some of the concerns that were identified in this human-use analysis. An opaque tank, with a transparent water-level indicator was implemented. Redundant lights that perform the same function were avoided. The visual indication is expected to be more familiar for users.

Most RO systems that are currently available in the Indian market were found to have poor maintenance feedback mechanisms. Here, the filters are arranged behind a transparent section as shown. Filter-life indicators are placed directly in-line with the appropriate marked filter so that the user is visually prompted to make the association. Each indicator can turn red (end of filter life), yellow (near end of filter life), or green (normal operation). A complex set of symbols and colour schemes is avoided in favour of a more intuitive system.

The user should not have to adopt their own solution for collecting the waste water. If possible, the additional storage should not affect the size of the purification device because kitchens in Indian homes are generally small and have limited wall-space. Lastly, the separate collection device should have overflow protection and be capable of draining directly into the sink.

To avoid enlarging the sytem, a waste-water tank was not implemented in the RO device. Instead, the user is provided with a dish rack that can either sit within the sink or beside it. Waste water is collected for cleaning dishes or other domestic use. A pressure valve is implemented on the underside to drain the water and avoid overflow.