How many of the following are not incorrect with respect to wastewater treatment? (1) A major component of waste water is human excreta (2) The municipal waste-water is called sewage which contains large amounts of inorganic matter and microbes. Many of which are pathogenic (3) Sewage is treated in sewage treatment plants to make it non-polluting (4) Treatment of waste water is done by the aerobic microbes naturally present in the sewage