KARACHI: A recent study highlights how continued flow of untreated domestic and industrial effluents from the city has destroyed the biodiversity of a major creek supporting livelihood of a large number of fishermen.

Titled Impact of indiscriminate disposal of untreated effluents in Korangi creek, the study is conducted at Karachi University’s Institute of Environmental Studies (IES) by Prof Moazzam Ali Khan and Dr Aamir Alamgir.

Once carrying freshwater from the Indus river, Korangi creek is a tidal channel receiving highly polluted water from multiple sources, including Korangi and Landhi industrial areas and the Malir river. Constant discharge of solid and liquid waste from Cattle Colony into the creek, the study points out, has increased the load of organic pollutants.

The creek connected with Kadiro, Jhari and Ganglaro creeks is navigable through small vessels and runs parallel to a hilly range starting from Ibrahim Hyderi.

‘Concentration of oil and grease found exceptionally high in water and sediment samples’

Like rest of the city, towns and settlements along the creek lack a proper system for waste collection and disposal, which is dumped along and into the creek. Fishing villages along the creek include Rehri village, Ayub village, Chashma village and Jamote village.

All these factors, the study says, have seriously affected the creek’s ecology, causing loss of fishes’ spawning grounds. These effects are noticeable in terms of fisheries’ quality that has commercial importance, it says.

“The creek provides livelihood to more than 100,000 people who are directly or indirectly engaged in fisheries. Twenty-seven bird species, many threatened or vulnerable, were recorded from this area in 1999,” the study says.

Findings

Under the study, 38 samples of water and sediments were collected from various spots of and along Korangi creek. It found that its water was primarily polluted by organic load originating from nearby human settlements. The concentration of oil and grease was found to be “exceptionally high in water and sediment samples, which is detrimental for marine life”. The mean biological oxygen demand (a measurement of the amount of dissolved oxygen used by microorganisms for decomposing organic matter in water) of seawater tested and sediments was 288mg/l and 1645mg/l while chemical oxygen demand was 1231.9mg/l and 1645mg/kg, respectively.

The national environmental quality standard for BOD in seawater is 80mg/l and COD in seawater is 400mg/l.

The concentration of phenol and cyanide was much higher in the sediment samples as compared to the seawater whereas the load of phosphate, organic nitrogen and ammonia was higher in the samples collected from mangrove areas.

Out of six heavy metals tested, the concentration of lead was very high (5.49 mg/l), which might be an indication of fuel leaking from defective motor boats.

The national environmental quality standard for lead in wastewater is 0.5 mg/l. “The creek ecology once supporting livelihood of a large number of fishermen and contributing to economy has been destroyed by the continued discharge of untreated domestic and industrial waste. “This high level of pollution is also contaminating the quality of groundwater as well in the area,” said Dr Aamir Alamgir, a researcher and teacher at the IES, while sharing his observations during the study.

Dr Alamgir has also done a study on the quality of area’s groundwater and found it to be contaminated especially with high fluoride content. People living along the polluted creek, he said, were found to suffer from numerous ailments, especially those related to body growth and skin.

“People are also exposed to toxic fumes emanating from the industrial waste. We also saw very vulnerable water lines passing along gutter lines,” he said, adding that pollution had also badly damaged mangroves. Fishermen now had to travel long distances to catch fish and the team hardly observed any important bird species in the area, he said.

Published in Dawn, July 30th, 2018