activated sludge method is primary or secondary

Activated sludge: British researchers Edward Ardern and W.T. Lockett coined the phrase “activated sludge” in 1914, and they patented the process for utilizing activated culture or flocs from the aeration tank and hence called as activated sludge treatment process. This brownish culture, grown under controlled conditions, can aerobically stabilize the organic content of wastewater. Bacteria,…