Indus water pollution
By F.H. Mughal
TWO MERCY appeals by the Sindh Chamber of Agriculture (Jan. 25 & March 1, 1997) two news items in the DAWN (March 3 & 4, 1997) and, a write-up by Ms Mumtaz Rashdi (March 14, 1997), highlight the problems of disposing of the saline water into the Indus, through WAPDA’s RBOD (Right Bank Outfall Drain) project. Nearly two years ago, on March 15, 1995, the writer, in an article titled, “Water Quality Modelling for Indus River”, in the DAWN, had written, “Despite being the lifeline of Sindh, it seems, the Indus river’s water quality has been taken for granted, with no control over it”.
According to Ms Elizabeth Dowdeswell, Executive Director, United Nations Environment Programme, “with finite fresh water resources on the one hand, and increasing demand, both in quantity and variety of uses, on the other, the need for water resources protection and management has never been greater. Major clashes over dwindling supplies of water may well constitute the source of future conflicts between nations”. (Our Planet, Vol. 6, No. 3, 1996, pp. 3). Worldwide serious efforts have been made to prevent pollution of water bodies. Some examples are: Thames river in the UK, Chao Phya river in Thailand, rivers in the Ruhr in Germany, French river basins and, host of rivers in the US. In UK, one cannot throw a handful of ashes in Thames river, without the permission of the National Rivers Authority. In USA, the EPA regulates effluent disposal into a river through “permit” system.
Water pollution in the Indus occurs through three sources: municipal wastewater discharges, industrial wastewater discharges and, return-agriculture flows through drainage structures. Most of the cities and towns of Sindh discharge their municipal waste water into the Indus river. Treatment plants (oxidations ponds), provided in cases, are not maintained properly, as a result of which, the wastewater does not receive the desired degree of treatment. The parameter of major concerns is the discharge of organic matter. This causes depletion of dissolved oxygen of river water. In extreme cases, when the assimilative capacity of the river is exceeded, anaerobic (septic) conditions result. This could be a problem in the river, during the months of low dilution (December and January), or, when there is water shortages in the Indus. At present, water shortages are feared during the incoming crop season. Under anaerobic conditions, iron and manganese become more soluble and, becomes a potential source of ground water pollution. In addition, due to high coliform content, use of water for drinking purposes, without appropriate treatment, would result in water-borne diseases like malaria, typhoid, cholera & dysentery. Industrial waste water discharges, depending upon the nature of industry, comprise of wide-ranging variables. This includes organic matter; ions like sodium, potassium, calcium, magnesium, carbonates and bicarbonates, chloride; other inorganic variables like fluoride, silica, cyanide; metals like cadmium, chromium, copper, mercury, lead, zinc, nickel, etc. The return-agriculture flow characteristics include salinity, total dissolved solids, sodium adsorption ratio (SAR), nitrates, phosphates and pesticides.
In case of industries, like thermal power plants, the variable of major concern is temperature. Sudden increase in surface water temperature by 3 degrees Celsius is harmful for marine organisms. As water temperature increases, growth rates (especially for bacteria and phytophlankton) and, respiration rates of aquatic organisms increase, leading to increased oxygen consumption. Required levels of oxygen are usually not available, as the increased water temperature also decrease the solubility of oxygen in water.
Salinity, in case of return-agriculture flows, is an important unitless property and, in the present case, of major concern to the Sindh Chamber of Agriculture. Disposal of saline effluent in the Indus river spoils its water quality. The ground water quality in the Indus basin is impacted by the water quality of the river. According to a case study, conducted by the United Nations Economic and Social Commission for Asia and the Pacific, Bangkok, titled “Desertification in Indus Basin due to salinity and waterlogging, 1989″, …ground water is becoming increasingly saline making it less useful for agriculture. A large population in the area is also affected because they are using the saline underground water for drinking purposes”.
Salinity refers to the type and quantity of salts, dissolved in water. It is determined by measuring the electrical conductivity of water. The saltier the water, the greater its conductivity of water. The saltier the water, the greater its conductivity. Values of salinity are also reported as total dissolved solids (TDS). Electrical conductivity is commonly expressed in millimhos per centimetre (mmho/cm), or deciSiemens per metre (dS/m). Typically, the electrical conductivity in water, when used for crop production, should not exceed 3.0 mmho/cm at 25 degrees Celsius. The maximum guideline value of TDS is 900 mg/1 (milligrams per litre).
The SAR is an indicator of probable influence the sodium ion has, on the solid properties. The SAR value in water, meant for agriculture, should be less than 15. For a more correct estimate, the SAR needs to be adjusted to include a more correct estimate of calcium, that can be expected to remain in the soil water, after an irrigation. This is called adjusted SAR.
In addition to agriculture use, the Indus river water is also used for drinking purposes. Small rural areas in Sindh do not receive adequately-treated water, for drinking purposes and of course, major cities, like Karachi, get contaminated water. Natural organic matter reacts with chlorine, used in water treatment plants for disinfection, to form trihalomethanes (THMs). Epidemiological studies have conclusively shown increased risks of cancers of the colon, rectum and bladder, associated with drinking-water, containing high levels for THMs (greater than 30 micrograms/litre).
Nitrate-nitrogen level of greater than 10mg/1 in drinking-water cause, what is referred to as infant methemoglobinemia, or, “blue baby” syndrome. Relatively low acidity of an infant’s stomach allows the bacteria to convert nitrate into potentiality dangerous nitrite. Nitrite is then absorbed from the infant’s intestine and, enters into a chemical reaction with haemoglobin in the infant’s blood, changing it to methemoglobin. Methemoglobin cannot carry oxygen, unlike haemoglobin which carries oxygen. As more blood haemoglobin is converted to methemoglobin, the oxygen-carrying capacity of the blood is reduced, causing symptoms of bluish discolouration of skin, lips and nailbeds. Hence the name “blue baby”.
Boiling water that is contaminated with nitrate, will not be helpful. On the contrary, it will be a health risk, as it will increase the concentration of nitrate. Flouride level in drinking water of more than 2 mg/1 produce dental fluorosis (mottling of teeth). Fecal contamination of water cause gastro-enteric infections, dysentery, hepatitis, typhoid fever, cholera and giardiasis.
Pestidices residues cause dermal and nervous systems toxiciety. Wastes from cement, paper and paint industries cause cancer. Wastes from mining and smelting industries damage kidneys. Wastes from industries, producing batteries and making lead-soldered pipe joints, cause brain and nerve damage and, is highly dangerous for infants and pregnant women. Industrial solvents like benzene and trichloroethylene are strongly carcinogenic.
Most of the industrial wastewater contains heavy metals. Some of the heavy metals (zinc, copper, boron and nickel) are toxic to plants, when they enter the edible part of a plant. Cadmium, cobalt and zinc accumulate through the food chain, with accumulation increasing at every trophic level (plants, grazing herbivores, primary carnivores and secondary carnivores). Since polluted waters lead to breading of insects, majority of people in rural Sindh are affected by malaria. Poor water quality of the Indus would affect its wetland and birds’ ecology, as the Indus basin and its wetlands are home to a large number of migratory birds. Indus delta falls in the Siberia-Kazakhstan- Indus delta migratory route, known as Flyway 4.
Due to water pollution in Indus river, the species diversity of fish has been reduced. Breeding of “palla” (Hilsa ilisha), a famous staple diet for people in Sindh, is reported to be on the decline. Mangroves productivity has also been adversely effected due to deteriorating water quality of Indus river, e.g. “Avicennia marina” in the lower Indus delta. The Indus river “Blind Dolphin” (Platanista minor), mainly concentrated on a length of 180 km, alongthe river, between Guddu and Sukkur barrages, is facing extinction (Dawn, March 1, 1997). No estimate has yet been made, to assess the economic impacts and ecological consequences, of the loss of fish-life in Indus river, due to water pollution.
All water and waste water discharges into the Indus river, need to be strictly controlled. Objectionable discharges (e.g. saline effluents in high quantity) should not allowed. Municipal and industrial wastewater discharges should be allowed only, after they meet the prescribed site-specific water quality standards. Controlling water pollution in Indus river is not an easy job. It requires sincere efforts, adequate laboratory facilities and, above all, a high-level of technical expertise in the field of environmental engineering.