By now the Flint water crisis — when the city’s drinking water was contaminated with lead — is a well-known case globally. And history might repeat itself in Karachi. To understand why Pakistan’s largest metropolis might soon have poisonous contaminants in its water supply, one has to study what happened in Flint.

The seventh largest city in Michigan, with a population of 102,434, is located along the Flint River; 106km northwest of Detroit. The water contamination stems from the decision by authorities, in April 2014, to stop purchasing treated water from the city of Detroit and to instead use water from the Flint River. The quality of water in the river, however, wasn’t properly assessed.

Typically, surface water sources such as rivers, canals, and streams are more turbid than ground water — the Flint River was no exception. The authorities used relatively large amounts of chlorine to clean the water which raised the levels of carcinogenic chloromethane in the river. Ferric chloride, a coagulant, was then added to remove the contaminants; this raised the already elevated levels of chloride.

With unchecked levels of lead, the new K-IV water supply project could mean the metropolis is heading for a public health disaster

The water coming from the Flint River had a high level of chloride content, around 92mg/l; in contrast the Detroit water had 11.4 mg/l of chloride. The high chloride level meant the water coming from the river was corrosive to iron and lead.

The Chloride-to-Sulfate Mass Ratio (CSMR) is a measure of corrosivity to lead. Anything above 0.5 is considered a red flag. The Flint water had a CSMR of 1.6 (indicating very high corrosivity).The water from the Flint River was made more unsafe to drink by the authorities’ decision not to use a corrosion inhibitor chemical, orthophosphate. Interestingly, even though the Detroit water was not corrosive, as a precaution, authorities chose to add orthophosphate.

Flint River’s corrosive water leached lead from the pipes of the city. The residents found that the water coming through the taps looked murky and rusty, and had a distinct, bad odour. The children of the city lost hair and developed skin rashes.

Upon examination, the lead content in water was found to be 400μg/L; multiple times higher than the recommended dose: according to the World Health Organisation’s drinking water quality guidelines, the lead content should not exceed 10μg/L in drinking water.

In short, the switch in water source had freed lead from the city’s aging pipes, exposing many of its 100,000 citizens to hazardous levels of the potent neurotoxin. Exposure to lead can result in retarded mental development and physical growth in children; in adults, it can cause blood pressure and kidney problems.

While the US Centres for Disease Control and Prevention has set the safe upper threshold of lead in the blood as 10μg/dL, recently published research has documented measurable childhood IQ deficits at blood lead levels as low as 2.5μg/dL — a level previously believed to be well below the threshold for observable neurological damage.

Closer to home

Lead in drinking water can come not just from lead pipes but from a variety of sources, including raw water sources, which receive industrial wastewater discharges from industries such as textiles, oil reformulating units, light engineering, chemical units, metal industries, and from many other industries. And this is where Karachi comes into the picture.

In order to meet the drinking water shortages in Karachi, the K-IV project pledges to provide 650 million gallons per day of water to fulfill the city’s drinking water requirement for the next 50 years.

And just as in the case of Flint, all the future water supply for Karachi will be sourced from surface water originating from the Indus River. In addition to the industrial constituents (eg lead), the city’s raw water is also subjected to agrochemicals, due to the indiscriminate use of pesticides in the catchment.

The metropolis receives raw water from various sources which includes the Kalri-Baghar (KB) Feeder. The KB feeder acts as a recipient water body, receiving raw and untreated wastewaters from industries in the Kotri industrial area, including those that have lead in their wastewaters.

In addition, water treatment plants in Karachi are not equipped to filter out these contaminants: they are of the conventional types (typically, rapid sand filters). Conventional water treatment plants do not remove toxic metals such as lead, ie whatever lead comes in the influent, will pass on to the final treated effluent.

Lead can be removed through advanced or tertiary water treatment processes, like ion exchange, activated carbon treatment, and the coagulation-precipitation process. All these processes are, beyond doubt, costly. In case of individual homes, heating or boiling water will not remove lead; instead the lead concentration can actually increase slightly as the water is boiled.

The water service provider in Karachi should take control of the catchment areas that feed raw water sources. In the long run, it makes sense (and is cost effective, as well) to prevent the discharge of pollutants than to provide costly tertiary water treatment. It is also essential that a third party should monitor the quality of the treated water that is provided to the people of Karachi.

In addition, Karachiites need to learn to use water more efficiently. Currently, water is wasted through such practices as washing cars and driveways with hose pipes directly connected to water pump; water theft (people vandalising water mains); commercial use of water through tanker service; non-metering of drinking water; and significant use of water in flushing toilets (the volume of domestic flush tanks is about 11 litres; usually five litres of water should suffice). As much as 40pc of the water used, for instance, can be saved if efficient water devices are installed in toilets.

As the city’s population booms and resources become scarce, the people of Karachi need to rethink the way they live and utilise essential utilities — before it’s too late.

The writer has a master’s degree in water and wastewater engineering from the Asian Institute of Technology, Bangkok

Published in Dawn, Sunday Magazine, June 19th, 2016