Complete mix activated sludge system (CMAS)
typical CSTR
pro: adapt to many types of wastewater, can tolerate shock loads
con: filamentous sludge building
Conventional plug flow
typical PFR
pro: adaptable to other processes (i.e. step feed, selector design, anoxic/aerobic)
con: hard to match O2 supply to O2 demand
Step feed
influent goes into aeration tank through four separate entrances
gets rid of shock loading because only a fourth of the flow goes into each entrance
pro: flexible operation, adaptable to other processes
con: flow split not usually measured accurately, com
contact stabilization
stabilization and contact divided into two separate tanks. flow goes into contact tank (short time) and is recycled into stabilization tank (microbes).
used when you have a higher flow than expected
pro: smaller aeration volume
con: little to no nitrifica
two-sludge AB process
two separate loops: normal aeration loop followed by nitrification loop. first loops degrades org. C, second loop degrades NH4+.
most efficient process, but takes up a lot of space
pro: smaller aeration tank volume than PFR, less aeration energy,
con: req
high purity oxygen
complete mix reactors in series. use surface aerators because surface is pure oxygen.
used in big cities (i.e where there is not a lot of space)
pro: small aeration tank volume, uses more energy than air aeration, produces good settling sludge
con: low ca
sequencing batch reactor
when there is small flow, and NOT a continuous flow into the system. one tank with four different processes (fill, aeration, settle, decant). equalization basin at the end of the four processes. you'll get high headless unless you pump.
for chlorine and U
counter current aeration system (CCAS)
pro: high quality effluent is possible
oxygen transfer efficiencies are higher than conventional aeration systems
well stabilized sludge
process design can be modified to accommodate nutrient removal
con:fine screening is required to prevent diffuser foul
oxidation ditch
pro: simple system. highly reliable
organic C removal, has paddles that mix
can handle shock and toxic loads without affecting effluent quality
economical for small plants
use less energy than extended aeration
adaptable to nutrient removal
high quality e