Water Pollution

Water is the source of life. However, the waters we live on have been polluted seriously which deeply affects our life quality. Generally speaking, there are chemical pollution, acid-base pollution and inorganic pollution of water pollution.

Chemical pollution is caused by industrial effluent, agricultural drain and domestic sewage. Industries like metallurgy, electromechanics, galvanoplastics, papermaking, the leather making, petroleum, pesticides, fertilizer, food, printing and dyeing, mineral processing contain most toxic pollutants. Pesticides, fertilizer, and the fallen leaves and branches of crops in agricultural drain and aerobiotic organic substances in domestic sewage are also the reasons for water pollution.

There are many damages of chemical pollution. First, aerobiotic organic substances cause the dramatic decrease of water oxygen. Second, toxic substances (like cyanide, arsenide and pesticide) cause chronic poisoning of aquatic life. Third, mercury, copper, lead and other heavy metals not only cause acute poisoning of aquatic life, but also accumulate in living beings. Fourth, arsenic, chromium, nickel, reaming, aniline, polycyclic aromatic hydrocarbons and halogenated hydrocarbon cause mutation, teratogenesis and cancers. Fifth, organochlorine compounds like OCPs, PCB poison baby fishes and shrimps or accumulate in their bodies, decreasing their reproductive capacity. Such compounds threat life of the creature at the top of the food chain.

Then how can we control the chemical water pollution? First, industries try to reform production process to reduce the toxic substances. Second, people should save water and reduce the volume of wastewater. Third, people need to purify as much wastewater as possible and make use of it. Fourth, discharging of toxic and harmful chemicals is forbidden.

Acid-base pollution means PH of water is abnormal. Generally speaking, PH of normal water is between 6.5 and 8.5. When PH is less than 6.5 or greater than 8.5, it means the water has been polluted by acids or alkalis.

The acid substances mainly come from wastewater of acid plants, chemical plants, viscose fiber plants, acid pickling shops and mine drainage and acid rain.

The alkali substances mainly come from wastewater of pulp mills, paper mills, alkali works, printing and dyeing mills, leather making plants and refinery. Both acid substances and alkali substances increase the corrosivity of water. Therefore, water pipes, hydraulic buildings and ships can be damaged. Abnormal PH causes death of aquatic life, especially microorganism, thus the self cleaning capacity of water decreased, biotic population altered. Fishes and shrimps can even die out.

Then, how can we prevent acid-base water pollution? First, the leak of acids or alkalis is strictly forbidden. Second, control emissions of sulfur dioxide to alleviate the damages caused by acid rain. Third, wastewater that contains acids or alkalis must be discharged after the neutralization treatment.

Inorganic pollution means the concentration of metal or non-metal minerals in water is abnormal.

Inorganic pollutants mainly come from first, mine drainage and mineral stones dropped in halfway of transportation; second, wastewater of metallurgy, electromechanics, galvanoplastics, paint& coatings industries; third, surface runoff, especially runoff containing some minerals; fourth, agricultural drainage; fifth, inorganic dust falling to the water from the air; fifth, inorganic substances from natural processes like rock decay and volcanic eruption.