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SAI INTERNATIONAL SCHOOL
                                                      CLASS-VII

                                            SUBJECT - CHEMISTRY
                                TOPIC- MANAGEMENT OF WASTE WATER
                                SUB TOPIC- WASTE WATER TREATMENT


                                                                     Secondary Treatment:-

               Secondary treatment is used to decompose the biological content or the organic
               waste which are derived from human waste, food waste, toilet water containing
               soaps and detergents with the help of bacteria.


































               This process is done in an open tank called aeration tanks. Air is blown into the
               tank to speed up the action of aerobic bacteria. This process is called digestion.
               During this process, biogas is produced, which can be used as a fuel.

               Tertiary treatment:-

               The water undergoes chemical treatment that depends on the composition of water
               at this stage. The water is disinfected using chlorine it may also be exposed to
               ultraviolet rays to kill disease causing microorganisms. The cleaned water is then
               released into rivers or seas.

               Uses of treated water and sludge:-

               Water treated in this way can be used for a variety of purposes and is safe to be
               drained into water bodies. Sludge is rich in organic matter, nitrogen, phosphorus,
               inorganic salts and heavy metals. It is the residue of chemical, biological and




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