CIV342H1 Lecture Notes - Lecture 2: Activated Sludge, Flocculation, Anaerobic Digestion
Document Summary
Physical unit operations: screening, mixing, gas transfer, sedimentation, filtration. Chemical unit operations could involve precipitation, adsorption, disinfection. Biological unit operations: biological filtration, activated sludge, anaerobic digestion. Primary concern in wastewater treatment: reduction of solids and bod. Pretreatment - removal of constituents that may cause operational issues. Primary (sedimentation) - removal of suspended matter by reducing water velocity. Secondary (biological stabilization) - activated sludge, etc. Tertiary (chemical treatment) - p & n removal, disinfection. 1) discrete/ free settling: low concentration, no interaction between particles. 2) flocculent settling: particles coalesce while settling - increase in mass = faster. 3) hindered/ zone settling: particles settle with distinct interface. 4) compression settling: settling can only occur by compressing or compacting mass. Charges are usually negative - positively charged coagulant neutralizes this negative charge and allows particles to stick together. Multivalent ions work well as coagulants - single ion can neutralize more charge.
