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In Bhuj, Gujarat, tap water is not just tasted - it’s measured. And the number on a pocket-sized Total Dissolved Solids (TDS) meter can determine whether residents drink what’s piped in or turn to a reverse osmosis (RO) purifier. In his thought-provoking paper, ‘Tasting numbers: The numerical politics of Total Dissolved Solids and the privatisation of drinking water quality in Bhuj city, India,’ published in Water Alternatives, Amitangshu Acharya explores how water quality governance has shifted from the state to citizens and how TDS - once a technical indicator - has become a market enabler.
What are RO filters? Is it a ‘one-size-fits-all’ solution?
RO purifiers treat water based on the process of Reverse Osmosis (RO), where water is made to pass through a membrane (a polymer film) that has very small-sized pores. These weed out minerals and contaminants in the water. The impurities collected are then flushed out through an outlet pipe.
The growing RO market in Gujarat reflects a wider anxiety around drinking water quality in India where RO businesses are flourishing and RO filters are emerging as popular choice for ‘safe and clean drinking water’. However, their effectiveness continues to be questioned and the possible adverse impacts of RO filtered water on health debated.
Despite being costlier than other purification technologies, RO systems have become essential in Bhuj. Why? Because in the public imagination, RO filters are seen as the ultimate safeguard against “bad” water. These systems work by forcing water through a membrane that filters out both contaminants and essential minerals. The result is purified, low-TDS water—and, ironically, a lot of wasted water too.
This mirrors trends across the Global South, where private purification solutions often fill the vacuum left by weak or mistrusted public supply systems. This need has been filled in by Reverse Osmosis (RO) filters that hold the largest India Water Purifier Market share according to 2023 figures. Around 44 percent of households in India use RO purifiers at home to get safe drinking water.
What are total dissolved solids?
Total Dissolved Solids (TDS) include "inorganic salts, mainly calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulphates, and small amounts of organic matter that are dissolved in water." From a hydrochemical perspective, it is not the quantity of dissolved solids in water that is harmful to human health; it’s the type that matters. TDS is measured with a TDS meter—a small, pocket-sized device with a digital display that makes it possible to visually confirm the extent of dissolved solids in water.
Though municipalities monitor a range of water quality parameters in water treatment plants, TDS has become the easiest and "the one and only measurable parameter" for citizens to monitor the quality of their supplied water in Gujarat.
What has triggered the extensive use of RO filters in Gujarat
The TDS meter has gradually replaced traditional measures of water quality that depended on taste and smell and evolved into a market-enabling metric that has led to the proliferation of RO markets and privatisation of drinking water in the state. How has this happened? What has led to this extensive use of RO filters in Gujarat?
Gujarat, located in western India, depends mostly on rainfall and, with 70 percent of its area being drought-prone, has been extracting groundwater at rapid rates from deep tubewells and has been a testing ground for RO membrane-based water purification since the 1970s.
The study traces the reasons prompting people to opt for RO membrane-based water purifiers in the representative town of Bhuj in the Kutch district of Gujarat. It demonstrates how the traditional measures of water quality have changed with new technologies, and the numerical politics of the water quality parameter of Total Dissolved Solids (TDS) has shaped the privatisation of drinking water quality in Bhuj.
Shift from community wells to state managed drinking water schemes in Bhuj
Until the 1960s, drinking water in Bhuj was mostly obtained from community-managed drinking water wells that yielded meetha jal ('sweet water), according to people. Wealthy upper-caste families also had smaller wells located inside their homes, and the water was described as khaara jal ('salty water'). The taste of this water was described as tura—neither sweet nor bitter—by some and bhanvra—without swad, i.e., 'taste,' and hence unfit for drinking or cooking.
In 1969, the Bhuj Municipality developed the city’s first tubewell-based water supply system at a village called Bhujodi, seven kilometres away from the city and from a different and deeper aquifer, which was later formalised into the Kukma water supply scheme. Nine tubewells were drilled to meet the water supply of the city.
As the taste of the water changed, different ways of describing water quality emerged, such as peela ('yellow'), kadwa ('bitter'), feeka ('flat'), kayo ('reddish'), and saar ('dissolved salts'). Thus, descriptions of water quality changed with a new water-producing technology—the deep tubewell. The water procured from deep tubewells has high amounts of dissolved solids due to the geology and the type of aquifers in the region.
Water quality uncertainty and rise of RO markets
The proliferation of RO membrane-based water purification in Bhuj happened due to this change in water quality in the city and an earthquake in 2001 that completely altered the city’s geohydrological regime and temporarily impaired piped water supply, leading to a sharp rise in tanker water and the demand for bottled drinking water as a temporary solution. This uncertainty gave rise to the RO membrane-based water purification technology.
Tankers and bottled water often derived the water from fragile aquifers in the region, and the dependence on fragile aquifers thus saw a rise, and these produced water with higher concentrations of iron and other dissolved solids. As a result, the demand for RO-based water purifiers witnessed a steady rise in specific areas of the post-earthquake city.
Prices dropped with the arrival of cheaper Chinese imports of membranes and other components. An RO-based water purifier, which used to cost an average of INR 12,000-15,000 between 2005 and 2012, began to be available for INR 3,000-4,000. Thus, by 2018, almost all middle-class housing societies were accessing water purified by RO-based membrane technologies, and almost 90 percent of people in the city are now drinking RO water, in some form or the other.
When numbers replace experience
TDS meters, once confined to labs, found their way into households, shops, and even wedding trousseaus. A high TDS reading became shorthand for “unsafe.” Citizens, especially the urban middle class, began relying on numbers rather than taste or municipal reports to determine water safety.
This quantification of trust transformed TDS from a technical parameter into a market-enabling metric. As Acharya argues, the popularity of RO systems is not just about health—it’s about the numbers. The TDS meter, in effect, legitimised the RO market and undermined public confidence in piped supply.
He says in the study, “The stabilisation of TDS into everyday discussions on water has simultaneously legitimised and entrenched the inevitable use of RO membrane-based purification. The numerised translation of water quality has political consequences, as the counting of TDS through a digital meter produces a "market-enabling metric." The TDS meter also numerically compares and illustrates the success of private markets over municipal water supply, allowing for the creation of a market where it previously didn’t exist.”
Who gets left behind?
This shift has deepened existing inequalities. Middle-class households, equipped with RO filters and TDS meters, have gradually opted out of engaging with the public water system. Their withdrawal from collective water governance has diverted pressure away from municipal utilities and left the urban poor to bear the brunt of unreliable or unsafe supply.
Meanwhile, the cost of RO installation and maintenance remains out of reach for many, despite a drop in prices due to Chinese imports. The responsibility of securing safe water has been subtly transferred from the state to individuals, without the regulatory checks to ensure equity.
A market of metrics
The irony is stark. While municipalities continue to monitor multiple water quality parameters, citizens are fixated on a single number. This has allowed the narrative of “low TDS = good water” to thrive, even though health experts caution that extremely low TDS can strip water of beneficial minerals.
Acharya’s study highlights how this numerical logic creates a self-sustaining market where perception drives consumption and policy quietly retreats. The governance of water quality, once a collective public concern, is increasingly becoming a private burden.
Rethinking the politics of purity
The case of Bhuj isn’t just about RO filters or TDS meters—it’s about how we define, measure, and delegate the responsibility of clean water. In the rush to adopt technological fixes, we risk overlooking structural solutions, like improving public water systems or addressing the ecological impact of over-extraction.
As India continues to urbanise and commodify water, this study urges us to ask: who decides what’s “safe”? And who pays the price when purity becomes a private concern?