3 Important Pollutants found in Ground Water

The following points highlight the three important pollutants found in ground water. The pollutants are: 1. Nitrate 2. Arsenic 3. Fluoride.

Pollutant # 1. Nitrate:

Nitrate in ground water is derived mainly from mineralization of soil organic matter or from use of excessive nitro­gen fertilisers. The content of nitrate in drink­ing water is safe in the range of 1-50 mg NO₃ per litre. Above the range of 50 mg NO₃ per litre leads to methanoglobinoanemia where 10 percent of the haemoglobin in the blood is converted into the methanoglobin form.

Death may result if 40 percent of the haemoglobin in the blood is converted to methanoglobin as it has induced oxygen car­rying capability. High nitrate concentration can also reduce the assimilation of iodine resulting in goitre. Increased nitrate intake through drinking water in pregnant women carries increased risk for bearing a malformed child.

Pollutant # 2. Arsenic:

Arsenic contamination of ground water is very common throughout the world. Major incidence occurring in India is reported in West Bengal, where a vast area is under the arsenic calamity. As a result about 8,00,000 people suffer from arsenicosis.

The water of the intermediate aquifer is generally polluted with arsenic. The shallow first and the deeper third aquifer are not arsenic polluted. The minimum arsenic content occurring in ground water is in the 20-60 m range, ranging from < 0.01 mg/litre to a maximum of 2.0 mg/litre. Ground water in arseniferous areas is characterised by high iron, arsenic, Ca, Mg and bicarbonate with low chloride, sulphate and fluoride.

The effects of arsenic on man are:

1. Bronchitis, azma and other pulmo­nary problems.

2. Liver damage.

3. Skin disease with affected nail and hair.

4. Rashes on limbs.

5. Blue patches on face and skin.

6. Renal diseases.

7. “Black foot” disease.

As the ground water of many areas of West Bengal are contaminated with arsenic, it is essential to identify those sources and prevent the inhabitants from using and con­suming such water. As deep tube-well or dug-well does not contain appreciable amount of arsenic it is wise to provide these people with such alternative source of treat­ed surface water for drinking.

As the dissolved arsenical substance can form complex with various alums, it can eas­ily be precipitated and then filtered to remove the contaminated arsenic. The toxic arsenite (III) can be oxidised to the nontoxic arsenate by a number of micro­organisms like Achromobacter, Pseudomonas arthrobacter etc. Contrary to it, Candida (a yeast), chlorella (algae) and some marine bacteria are capable of reducing arsenate to the toxic arsenite.

Pollutant # 3. Fluoride:

Fluoride contamination was also reported in some districts of West Bengal and Assam. Previously, in Andhra Pradesh, contamination of fluoride was reported in surface waters. Contamination of ground water with fluoride results in both short-term and long-term crisis.

Bony deformity and associated problems of locomotory organs has been reported. Children are more suscep­tible than adults. Such areas of contamina­tion should be identified and proper steps should be taken to supply non-contaminated water for cooking and drinking.