Water treatment and water use (p.55)

1. The treatment of water may be divided into three major categories: 1) purification for domestic use, 2) treatment for specialized industrial applications, 3) treatment of wastewater for release and reuse.Water for domestic consumption must be disinfected to eliminate disease-causing microorganisms.The function of a modern water treatment plant is to produce clear, safe and tasteful drinking water from raw water.The raw water taken from wells first goes to an aerator.After aeration lime is added to raise the pH causing the formation of precipitates.These precipitates settle from the water in a primary basin.The settling of the coagulated solids occurs in a secondary basin.Sludge from both the primary and secondary basins is pumped to a sludge lagoon.The water is finally chlorinated, filtered and pumped to the city water mains.

Radiation and its origin (p.65)

1. Man has always lived in naturally radioactive world.Some radiation today is man - made, but the greatest exposure comes from natural sources.Only few elements which occur in nature emit radiation.Uranium is one of the best known elements.The structure of atom decides the type of radiation which is produced. Naturally radioactive materials are distributed in soils, rocks, water and plants. -i. The radiation emitted from the surroundings is called terrestrial radiation.Radiation emitted from naturally radioactive materials is known as internal radiation.Radiation from outer space and from the sun is called cosmic radiation.The X" ray equipment is probably the best known source of man-made radiation.

Effects of radiation (p.70)

1. Radiation can destroy, damage, or disturb the function of the living cells in the body tissue.The effect of radiation depends on the type of radiation, its intensity, the period of exposure, and the irradiated organs of the body.Radiation cannot be detectedby the human senses.But it can easily be detected and measured by simple instruments.Standards of radiation protection are consistent throughout the world.Many countries, including Ukraine, have strict limits to the amount of radiation a person may receive.Radiation occurs in nature and can be produced artificially.On average, radiation of natural origin gives the highest exposure to man.Exposure to artificial radiation is easily controlled.

What ionizing radiations are (p.78)

1. Ionizing radiations arise when radioactive atoms disintegrate and turn into new atoms.At the same time ionizing radiations emit one or more of the positive, negative or uncharged particles.There are the following sources of ionizing radiations: natural and artificial radionuclides, nuclear reactors and cosmic rays.All forms of ionizing radiations may be classified into heavy-charged particles - alpha, proton radiation; light-charged particles - electrons; photon radiation - gamma rays, х- rays and neutron radiation - neutrons of different energies.While passing through matter particles or photons interact with orbital electrons knocking out the electrons from their orbits.Neutral medium atoms receive positive charge and become positive ions.The released electrons together with positive ions form ion pairs.So, ionizing radiations are particles or photons producing large numbers of ion pairs.By the way of interaction with matter ionizing radiations are divided into directly and indirectly ionizing.