1. Wastewater Processes

2. Activated Sludge System
Complete mix
Plug flow
Oxidation ditch

3. Plug Flow

4. Extended Aeration
Extended aeration, is more common with oxidation ditch systems.
Extended aeration in complete mix reactors is only used for small plants due to the increased size of aeration basin.
Primary clarification is omitted as the key objective is to minimize the amount of sludge generated.
Ideally, all substrate removal is converted to energy and then oxidized so that no excess biomass is generated

5. Extended Aeration

6. Oxidation Ditches

7. Attached Growth Trickling Filters

8. Attached Growth Trickling Filters

9. Attached Growth Trickling Filters

10. Attached Growth Trickling Filters Example

12. Nitrification
Nitrification or ammonia oxidation depends on the population of nitrifying bacteria, which depend on:
temperature,
ammonia concentration,
organic substrate,
pH,
DO concentration,
residence time
From AWWA(1992), for each kg of ammonia oxidized to nitrate the following OOOJ[S:
4.18kg of O2 are consumed
14.1kg of alkalinity as CaC03 are destroyed .
0.15kg of new cells are produced (extra sludge) .
0.09 kg of inorganic carbon are consumed

13. Denitrification
Denitrification follows on completion of nitrification.
It is achieved biologically under anoxic conditions, i.e. in the absence of oxygen.
The energy required for denitrification comes from the organic content of the wastewater.
The overall d..enNitOrif)ic-a-tiNon--p+roNces2s is from AWWA (1992) as:
NO N2
Oxygen recovery is 2.86 kg O2 / kg NO3-N reduced
Alkalinity recovery is 3.0 kg CaCO3 / kg NO3-N
Biomass production is 0.4 kg VSS / kg COD removed