|
|
|
Poisoned water
THE POPULATION of Pakistan currently stands at 150 million, which is projected to grow to about 250 million by the year 2025. This tremendous increase would have a direct adverse impact on the quality of water.
The per capita availability of water, which was 5,600 cubic metres in 1956, has already dropped to 1,000 cubic metres. The quality of ground- and surface-water is fast deteriorating because of the indiscriminate disposal of untreated municipal and industrial wastes and excessive use of fertilizers and pesticides.
Our rivers and other bodies of water have become polluted particularly due to the dumping in them of effluents generated by various industrial units. According to the International Water Management Institute (IWMI), more than 40 million Pakistanis are currently dependent on irrigation water for their domestic needs. In many areas, irrigation water remains the only source of water for domestic needs.
Arsenic contamination has been observed in some areas that draw drinking water from polluted streams and rivers. In these areas, arsenic concentration is spreading at an alarming rate.
Different surveys carried out by various organizations have confirmed the large-scale contamination of ground- and surface-water in almost all parts of the country. According to a study conducted by the Pakistan Council of Research in Water Resources (PCRWR), high arsenic and fluoride concentrations have been detected in 11 cities in Punjab.
In another study, carried out by the Environment Protection Agency, 239 samples of water, of the 280 taken from 14 districts of Punjab, were found unsuitable for human consumption. About two million people in the areas surveyed used contaminated water, having much higher concentration of arsenic when compared to the limits prescribed by the World Health Organization.
These studies serve to show that deterioration in the quality of groundwater is due to the disposal of untreated industrial and domestic wastes in rivers and canals, especially in Lahore, Faisalabad, Multan, Kasur, Rawalpindi and Islamabad. The permissible limit for arsenic in drinking water for Pakistan has been standardized at 0.05 mg/litre or 50 parts per billion.
According to the survey, people residing in cities like Multan, Bahawalpur, Sheikhupura, Lahore, Kasur and Gujranwala suffer from chronic arsenic toxicity. A study conducted by Unicef depicts a similar picture — a significant portion of Punjab’s population is currently exposed to high arsenic concentrations, setting off severe health problems.
A study conducted jointly by the PCRWR and Unicef on the quality of water revealed that groundwater in districts of Jhelum, Gujrat, Multan, Bahawalpur, Rahim Yar Khan, Dera Ghazi Khan, Jhang, Layyah, Sargodha, Muzaffargarh, Dadu and Khairpur was largely unfit for human consumption. In addition to the mentioned organizations, many national and international bodies, such as the PCSIR, IWMI and FAO, have also expressed concerns over the worsening situation.
Impact on health
Excessive exposure to arsenic manifests itself in the shape of skin and lung cancers, diarrhoea, skin rashes, vomiting and nervous system problems, besides bone marrow, liver and kidney disorders. Drinking water having arsenic in amounts greater than the permissible doses may lead to neurological and cardiovascular complications.
The magnitude of toxicity relates to exposure intervals, doses and interaction of arsenic with other essential dietary nutrients, besides the sex and age of consumers. Its accumulation in the human body takes place in the hair, nail, skin and urine of people residing in the affected areas.
Urine samples of the affected individuals may contain arsenic up to 240 times, their nail samples up to 30 times and hair samples up to 80 times the normal figures. Overuse of water contaminated with arsenic gives rise to many acute and chronic diseases.
A study carried out in 1998 in northern Chile attributed five to 10 per cent of causalities among people of more than 30 years to arsenic-induced cancers. In 1999, the US National Research Council determined that complications arising out of the consumption of more than 50 micrograms per litre may easily lead to one person in 100 dying of cancer.
In Pakistan assessment of water quality and regular monitoring vis-à-vis health problems has been rather poor due to the lack of knowledge over the subject. And, lack of laboratories having the right equipment does not help either.
Over the years, lack of awareness about the ills of arsenic contamination has allowed many problems to go unchecked. In Multan, smallpox marks filled with blood have been detected on the bodies of many students. Various studies by different organizations like the Punjab Rural Support Programme and Unicef have found arsenic concentration far above the permissible limits in the case of students belonging to 23 of the 54 girls' schools surveyed in Multan District.
Remedial measures
Numerous arsenic removal techniques have been devised and introduced by universities, government organizations and private-sector groups. These technologies largely rely on the adsorption of arsenic to iron and aluminum oxides. If iron and aluminum oxides are added in sufficient quantities to water, the concentration of arsenic in it can be brought down to acceptable levels.
During the decontamination process, the principles that are given special weightage are: coagulation/co-precipitation, sedimentation, filtration, adsorption, ion exchange and membrane or reverse osmosis. At large scales it is difficult, even impossible, to purify water owing to huge expenditures involved. A question arises here as to what should be done to save the health of millions who are otherwise exposed to the ills of arsenic.
A perfect procedure is simply not possible. However, a three-pitcher water remediation technique is very simple and has gained much currency in recent years. It comprises three pitchers lying on top of each other, which are connected, allowing the water to move downwards from one pitcher to the other, as shown in the sketch.
At the bottom of the top pitcher, there’s a piece of cloth having a thick layer of iron chips, which is covered by coarse sand. The iron chips are meant to adsorb arsenic. The central pitcher is similar to the top one, the only difference being the use of fine sand instead of coarse sand and wood charcoal replacing the chips.
Contaminated water is poured into the upper pitcher and as it flows downwards, arsenic is adsorbed to the various barriers placed in its path. The decontaminated water is stored in the bottom pitcher. This is a very cheap and easy-to-implement solution to the problems posed by water contaminated with arsenic.
As opposed to this household-based technique, there’s a newly developed process, which can be employed to decontaminate water meant for small communities. In this technique a treatment unit is designed having a capacity of 600 litres. The bottom of the unit is conical in shape that enables the periodic removal of the settled sludge.
The tank has a manually operated mixer having impellers. Contaminated water and required quantities of oxidants and coagulants are put in the tank to initiate the remediation process. Then, impellers moving at 60 to 70 revolutions per minute mix water with the said chemicals thoroughly. The water is then allowed to stand overnight.
When the water is motionless, flocculation occurs. Flock formation is demonstrated by the hydraulic gradient of the rotating water. Purified water is drawn through a pipe attached at a few inches above the bottom of the tank, passing through a sand bed filter and finally collected through a tap for consumption purposes.
Policy needed
Although the PCRWR is ready to establish water-testing laboratories in 107 districts of country with an aid of about Rs1.8 billion, it might not provide a consistent and permanent solution to the problem. This is due to the lack of awareness among the masses about the harmful impacts of arsenic contamination.
For this purpose, an integrated approach should be adopted to deal with the issue. The non-governmental organizations and environment groups should try to create awareness on as large a scale as possible. Extraction of water from shallow water tables should be discouraged. The people should be told that they should draw from water from tables having a minimum depth of 200 metres.
At present the problem is in its infancy. If we fail to take worthwhile steps against the menace soon we may suffer badly later, much like India and Bangladesh. Timely steps, thus, are the need of the hour.
The writer is an intern at the Ayub Agricultural Research Institute, Faisalabad
|
|
|
|
