Question:
What are physical and chemical processes involved during a water purification process?

those used in extraction of pur water fron sewage water in a large scale...

Answer: The physical steps include settling, filtering, flocculation using alum, aereation,Chemical processes include adding chlorine to kill germs. This is done to the liquid part.The solids are composted which is a chemical process, much heat is developed. These are used for some fertilizing where no food plants are grown. They also do not use them on fields where sports are played. They are concerned about heavy metals that got into the water from industrial sewage.Sometimes it is lagooned, some times sent to a landfill, some times injected into fields where animals will eat the hay. (If no heavy metal present)