Two million tonnes of urban excrement are produced every year and 50 percent of this ends up in the clean water. Moreover, where sewers exist, and that too often open, they are laid parallel to the drinking water pipes lines, and leakage from sewerage pipe lines contaminate the drinking water," environment experts said here on Wednesday.
According to them, National Conservation Strategy (NCS) states that almost 40 percent of deaths are the result of water borne diseases. In Pakistan, drinking water supply lines and open sewage drains in the streets are laid side by side. Consequently, water is frequently get contaminated when pipes erode. Most main sewers are between 30-50 feet below ground level and are made of 10 feet cement sections linked without proper safety seals. Poor connections combined with deteriorating low quality sewer pipes cause a lot of leakage. This outflow from sewer mixes with the water and the contamination is carried to deeper levels.
Hence, the ground water, which is considered safe, becomes adulterated with lead, cyanides, mercury, solvents, hydrocarbon compounds, hospital and pharmaceutical industry waste. "The situation is further aggravated by the addition of untreated wastes from industries."
Industrial wastewater contains toxic chemicals. They just dispose of untreated toxic waste into nearby drains, canals or rivers. Lahore, Faisalabad, Karachi, Sialkot contribute major pollution loads into their water bodies. According to an estimate, 9000 million gallons of wastewater are daily discharged into water bodies from the industrial sector.
Automobile service stations are another major contributor to surface water pollution. Untreated oil, grease and dirt find its way into nearby canals and rivers where it damages the ecosystem," they added. According to them, most of the industries in the country are located in or around major cities and a recognised as key sources of increasing pollution in natural streams, rivers, as well as the Arabian Sea through discharging toxic water.
The contamination of shallow groundwater near industrial plants has been an area of concern, as groundwater pollution is often permanent and it may take 100s or even 1000s of years for pollutants (such as toxic metals from the tanneries) to be flushed out of a contaminated aquifer.
In Pakistan, only one percent of wastewater is treated before being discharged directly into rivers and drains. They said the Pakistan Council of Research in Water Resources carried out a water survey of 21 cities and it reported that bacterial contamination in water was very frequent. "In 17 cities, bacterial contamination was greater than 50 percent and in four of these cities, 100 percent of the samples were considered as unsuitable for human consumption," they added.