How does the sewage treatment process ensure that water is safe to be reused? Chlorine is added to the water to reduce the number of dangerous microorganisms. Oil dispersants are used to remove microorganisms. . -0) Oxygen is added to destroy dangerous microorganisms in the water. Solid materials are filtered out from the sewage.​

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1) a giant star is a star with a radius much larger than that of our sun (even hundreds of times bigger). they can be either blue giants or red giants: in the first case, the surface temperature is very high, higher than that of the sun, while in the second case the surface temperature can be lower than that of the sun. the same applies to the mass: blue giants are very massive stars, burning quickly their nuclear fuel, while red giants can have small masses (a little bit bigger than that of our sun).

2) we can find giant stars in the upper part of the hr diagram, blue giants will be on the upper left corner since they have high luminosity and high temperature, while red giants will be on the upper right corner, having high luminosity but low temperature.