Wastewater Treatment, Secondary : Wastewater treatment unit processes usually consisting of primary treatment and biological oxidation using activated sludge or trickling filtration followed by clarification
NFPA 820 Standard for Fire Protection in Wastewater Treatment and Collection Facilities, 2008 ed. http://www.nfpa.org/codes-and-standards/document-i nformation-pages?mode=code&code=820, (Std: Fr Prac in Wastewater Treatment and Collection Fcilty - Amer) {351 NFC}