Waste water treatment is Primary, secondary and in some cases, tertiary treatment. steps vary from facility to facilityhmmm wrote:What's the order of the wastewater treatment process?
Different sites have different answers
Primary treatment removes suspended and floating particles, such as sand and silt, by mechanical processes such as screening and gravitational settling. The solid material that settles out at this stage is primary sludge. Primary treatment does little to eliminate the inorganic and organic compounds that remain suspended in the wastewater.
Secondary treatment uses microorganisms (aerobic bacteria) to decompose the suspended organic material in wastewater, One of the several types of secondary treatment is trickling filters, in which wastewater trickles through aerated rock beds that contain bacteria and other microorganisms, which degrade the organic material in the water. In another type of secondary treatment, the activated sludge process, wastewater is aerated and circulated through bacteria-rich particles; the bacteria degrade suspended organic material. After several hours, the particles and microorganisms are allowed to settle out, forming secondary sludge, a slimy mixture of bacteria-laden solids. Water that has undergone primary and secondary treatment is clear and free of organic wastes such as sewage. The wastewater treatment facilities for about 62% of the U.S. population have both primary and secondary treatments.
Advanced wastewater treatment methods, or tertiary treatment, include a variety of biological, chemical, and physical processes. Tertiary treatment reduces phosphorus and nitrogen, the nutrients most commonly associated with enrichment. Tertiary treatment purifies wastewater for reuse in communities where water is scarce. The wastewater treatment facilities for about 27% of the U.S. population have primary, secondary, and tertiary treatments.
Solar system, Water Quality, Anatomy and Physiology- 1st State & Regional 
Heredity 4th state, 2nd regional 
