Does the water supplied to your home smell strange or taste metallic? With growing concerns over drinking water contamination in Chennai, it is a wake-up call for residents to question what is coming out of their taps.
A survey conducted by IIT-Madras revealed that water in 75% of city homes is contaminated with E. coli, a bacteria responsible for causing diarrhoea and vomiting. Moreover, another IIT-Madras study discovered the presence of harmful chemicals known as forever chemicals or pre- and polyfluoroalkyl substances (PFAS) in major water bodies such as the Buckingham Canal, Adyar River, and Chembarambakkam Lake.
Samples from a nearby water treatment plant (WTP) were also found to be contaminated. These PFAS are a group of synthetic chemicals that can cause serious health issues, including liver damage, hormonal imbalances, fertility problems, and even cancer.
Despite the findings, the government has rejected these claims, stating that Chennai’s drinking water sources, including lakes, are free from contaminants and safe to consume. However, many residents wonder, “Is the water I drink at home safe?” In this first part of our series, we offer a detailed guide for those interested in testing their water to ensure its safety.
What contributes to water contamination in Chennai?
But first, what makes the water unsafe? The primary sources of water contamination in Chennai are garbage dumping and untreated sewage being released into water bodies. However, these are not the only contributors. A government order (GO) from the Water Resources Department, dated March 7, 2024, highlights that only two out of 51 revenue subdivisions (or firkas) in Chennai, namely Puzhal and Sholinganallur, are considered safe for groundwater extraction. The remaining areas are either over-exploited or at risk of becoming critically contaminated.
This indicates that we are not recharging the groundwater as much as we are extracting. While the GO notes Sholinganallur as one of the safe groundwater extraction firkas in Chennai, Prabhakaran Veeraarasu, an environmental engineer and activist from Poovulagin Nanbargal, points out in an earlier report that areas like Sholinganallur in OMR might have a better groundwater level, but the water may not be potable.
Chennai’s coastal location also contributes to water contamination. For instance, TD Babu, a civic activist and resident of Besant Nagar, notes that groundwater salinity in coastal areas is notably high. The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) supplies drinking water in Adyar, Neelankarai, Kottivakkam, Besant Nagar, and Thiruvanmiyur from the Nemmeli Seawater Desalination Plant. “However, the Total Dissolved Solids (TDS) in this water is often too high, making it unfit for consumption,” he notes.
Read more: Pollution and indiscriminate development threaten Madambakkam Lake’s survival
How do you identify if your water is contaminated?
It is not always easy to identify water contamination just by looking at it. For instance, in Chitlapakkam, residents were unaware that the water supplied to them from Madambakkam Lake was contaminated. Despite the absence of visual indicators such as changes in colour or smell, private lab tests revealed the presence of fecal coliform bacteria, a sign of sewage contamination.
One of the early warnings came when locals observed that the wells from which water was extracted were surrounded by water hyacinths. These plants typically grow when the water is contaminated by sewage. Additionally, a frequent accumulation of silt in underground water tanks prompted residents to test the water quality.
In another case, residents of Valmiki Nagar in Thiruvanmiyur noticed that the desalinated water supplied to their homes had a noticeably salty taste. They also observed frequent malfunctions in electrical appliances that used the same water.
Such incidents highlight the importance of testing water to confirm its safety.
Read more: Why residents in northern parts of Chennai throw away pots of water every week
Key parameters for testing water quality
To ensure water is safe for consumption, it must meet specific physical, chemical, and biological standards. The permissible limits for each category can be found on the CMWSSB website. Generally, water quality is tested for the following parameters:
- Physical: Colour, odour, turbidity
- Chemical: pH, Total Dissolved Solids (TDS), Total Hardness
- Biological: Presence of harmful bacteria, such as E. coli and Total Coliforms
| Substance or Characteristic | Requirement (Acceptable Limit) | Permissible Limit |
|---|---|---|
| Colour | Colourless & Clear | |
| Odour | Agreeable | Agreeable |
| Turbidity (N.T.U) | 1 | 5 |
| Total Dissolved Solids at 105 0 C (mg/l) | 500 | 2000 |
| Calcium (As Ca) (mg/l) | 75 | 200 |
| Magnesium (As Mg) (mg/l) | 30 | 100 |
| Total Hardness (As CaCO3) (mg/l) | 200 | 600 |
| Chlorides (As Caco3) (mg/l) | 250 | 1000 |
| Ammoniacal Nitrogen (as N)(mg/l) | – | – |
| Albuminoid Nitrogen (as N)(mg/l) | – | – |
| Nitrous Nitrogen (As N)(mg/l) | – | – |
| Oxygen absorbed (Tidy’s 4 hours test)(mg/l) | – | – |
| Hydrogen Ion Concentration (pH) | 6.5 to 8.5 | No Relaxation |
| Alkalinity to Phenolphthalein (AS CaCO3) (mg/l) | Nil | – |
| Alkalinity to methyl orange (As CaCO3) (mg/l) | 200 | 600 |
| Sulphates (As SO4)(mg/l) | 200 | 400 |
| Phosphates (as PO4)(mg/l) | – | – |
| Iron (As Fe) (mg/l) | 0.30 | No Relaxation |
| Florides (as F)(mg/l) | 1.0 | 1.5 |
| Specific Conductance(micro Siemens /cm at 25o C) | – | – |
| Residual Chlorine (mg/l) | 0.2 | 1.0 |
| Nitrate (mg/l) | 45 | No Relaxation |
| Bacterlological Quality MPN(Total Coliforms in 100 ml) | – | – |
How often does CMWSSB test its water?
As per BIS 10500:2012, CMWSSB tests around 300 water samples daily from public fountains and household connections. During the monsoon season, this number increases to 500-600 samples. The water is tested for colour, odour, turbidity, pH levels, and Total Dissolved Solids, among other parameters.
On request, CMWSSB also provides more specific tests, including analysis of Calcium, Magnesium, Total Chloride, Total Alkalinity, Residual Chlorine, Ammonia, Nitrite, Fluoride, Sulphate, Iron, Albuminoid Nitrogen, Oxygen Absorbed, Phosphate and Bacteriology tests.
“When the CMWSSB finds that the water quality is not satisfactory, the field officials are alerted and informed for taking up rectification works. Once the rectification works are completed, the water sample is tested for potability,” says Dr TG Vinay, the Managing Director of CMWSSB.
However, there is a call for greater transparency in this process. Dayanand Krishnan from Chitlapakkam Rising urges CMWSSB to upload the results of these tests on their public website to reassure the public about the safety of their drinking water.
How can you test your water for contaminations?
Residents within the limits of the Greater Chennai Corporation (GCC) can have their water tested through the Quality Assurance wing of CMWSSB. To do so, individuals must collect two litres of drinking water in a clean white container and submit it to the CMWSSB laboratory in Kilpauk.
The testing fees are as follows:
| Individual Houses/Flats – Drinking Purpose | Rs.1450/-(Excluding GST) |
| Commercial – Drinking Purpose | Rs.2000/-(Excluding GST)/Per sample |
| Water Sample(a) Bacteriological Analysis(Total Coliforms)(b) E.coli | Rs.400/-Rs.800/-(Excluding GST)/Per sample |
| Waste Water Testing (effluents only) | Rs.2000/-(Excluding GST)/Per sample |
| Waste Water Effluent (a) BOD (Biochemical Oxygen Demand) (b) COD (Chemical Oxygen Demand) | Rs.800/-(Excluding GST)/Per sample Rs.800/-(Excluding GST)/Per sample |
In addition to CMWSSB, there are also private laboratories in Chennai that offer water testing services. The cost and procedures vary depending on the type of tests being carried out.
What happens if you find contamination in your water?
When the residents of Chitlapakkam tested their water and publicised the results, the National Green Tribunal took suo motu cognisance of the matter, and the contaminated water supply was promptly halted. While individual test results may not always lead to immediate large-scale actions, knowing that your water is unsafe enables you to take necessary precautions, such as switching to bottled or filtered water or even raising awareness within your community.