Everything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air. These four subsystems are called “spheres.” Specifically, they are the lithosphere (land), hydrosphere (water), biosphere (living things), and atmosphere (air)...
I hope this helps you with biology...
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sludge
<span>Sewage treatment is also known as wastewater treatment. It is
a process whereby contaminant is removed from wastewater. Thus, chemical,
biological and physical process are commonly used to remove contaminants from
wastewater and the by-products of wastewater treatment is usually inform of
solid waste known as sewage sludge.</span>
That the pace of everyday life is such that is prevents individuals from perceiving that which the society deemed as unimportant.
