Efficiencies of the Wastewater Treatment Units...

Typical Constituents that may be Found in Treated Wastewater and Their Effects...

Constituent Effect Critical concentration
( mg / L )
Suspended solids May cause sludge deposits or interfere with receiving water clarity Variable
Biodegradable organics May deplete oxygen resources Variable
Priority pollutants - Toxic to humans and carcinogenic
- Toxic to aquatic environment		 - Varies by individual constituent
- Varies based on presence in water column, biota, or sediment
Volatile organic compounds Toxic to humans, carcinogenic, form photochemical oxidants ( smog ) Varies by individual constituent
Ammonia - Increases chlorine demand, can be converted to nitrates and, in the process, can deplete oxygen resources, with phosphorus, can lead to the development of undesirable aquatic growths
- Toxic to fish 		- Any amount
- Variable
Nitrate - Stimulates algal and aquatic growth
- Can cause methemoglobinemia in infants ( blue babies )		 - 0.3
- 45
Phosphorus - Stimulates algal and aquatic growth
- Interferes with coagulation
- Interferes with lime - soda softening		 - 0.015
- 0.2 - 0.4
- 0.3
Calcium and magnesium Increase hardness and total dissolved solids Variable
Chloride - Imparts salty taste
- Interferes with agricultural and industrial processes		 - 250
- 75 - 200
Sulfate Cathartic action 600 - 1,000
Surfactants Cause foaming and may interfere with coagulation 1.0 - 3.0

Constituent Removal by Advanced Wastewater Treatment Operations and Processes...

Principal removal function Description of operation or process Type of wastewater treated
Suspended solids removal - Filtration
- Microstrainers		 - EPT, EST
- EST
Ammonia oxidation Biological nitrification EPT, EBT, EST
Nitrogen removal Biological nitrification / denitrification EPT, EST
Nitrate removal Separate stage biological denitrification EST + nitrification
Biological phosphorus removal - Mainstream phosphorus removal
- Sidestream phosphorus removal		 - RW, EPT
- RAS
Combined nitrogen and phosphorus removal by biological methods Biological nitrification / denitrification and phosphorus removal RW, EPT
Nitrogen removal by physical or chemical methods - Air stripping
- Breakpoint chlorination
- Ion exchange		 - EST
- EST + filtration
- EST + filtration
Phosphorus removal by chemical addition - Chemical precipitation with metal salts
- Chemical precipitation with lime		 - RW, EPT, EBT, EST
- RW, EPT, EBT, EST
Toxic compounds and refractory organics removal - Carbon adsorption
- Activated sludge + powdered activated carbon
- Chemical oxidation		 - EST + filtration
- EPT
- EST + filtration
Dissolved inorganic solids removal - Chemical precipitation
- Ion exchange
- Ultrafiltration
- Reverse osmosis
- Electrodialysis		 - RW, EPT, EBT, EST
- EST + filtration
- EST + filtration
- EST + filtration
- EST + filtration + carbon adsorption
Volatile organic compounds Volatilization and gas stripping RW, EPT
EPT : Effluent from primary treatment
EBT : Effluent from biological treatment ( before clarification )
EST : Effluent from secondary treatment ( after clarification )
RW : Raw ( untreated ) wastewater
RAS : Return activated sludge

Examples of Advanced Wastewater Treatment Flow Diagrams...


A : Air
Ae : Aerobic tank
Al : Alum
An : Anaerobic tank
Ao : Anoxic tank
AS : Activated sludge
ASN : Activated sludge nitrification
C : Chlorine
CA : Carbon absorver
CT : Contact tank
DT : Denitrification tank
F : Filter
FE : Final effluent
IC : Intermediate clarifier
M : Methanol
MS : Metal salt
P : Polymer
PC : Primary clarifier
RAS : Return activated sludge
RW : Raw wastewater
S : Sludge
SC : Secondary clarifier
WAS : Waste activated sludge
WW : Washwater

Effect of Various Treatment Operations and Processes on Nitrogen Compounds...

Treatment operation or process Organic nitrogen NH3/NH4+ NO3- Removal of total nitrogen entering process ( % )
Conventional treatment
Primary 10 - 20 % removed No effect No effect 5 - 10
Secondary 15 - 50 % removed
urea====>NH3/NH4+		 < 10 % removed Slight effect 10 - 30
Biological processes
Bacterial assimilation No effect 40 - 70 % removed Slight effect 30 - 70
Denitrification No effect No effect 80 - 90 % removed 70 - 95
Harvesting algae Partial transformation to NH3/NH4+ ====>Cells ====>Cells 50 - 80
Nitrification Limited effect ====>NO3- No effect 5 - 20
Oxidation ponds Partial transformation to NH3/NH4+ Partial removal by stripping Partial removal by nitrification - denitrification 20 - 90
Chemical processes
Breakpoint chlorination Uncertain 90 - 100 % removed No effect 80 - 95
Chemical coagulation 50 - 70 % removed Slight effect Slight effect 20 - 30
Carbon adsorption 30 - 50 % removed Slight effect Slight effect 10 - 20
Selective ion exchange for ammonium Slight, uncertain 80 - 97 % removed No effect 70 - 95
Selective ion exchange for nitrate Slight effect Slight effect 75 - 90 % removed 70 - 90
Physical operations
Filtration 30-95 % of suspended organic N removed Slight effect Slight effect 20 - 40
Air stripping No effect 60 - 95 % removed No effect 50 - 90
Electrodialysis 100 % of suspended organic N removed 30 - 50 % removed 30 - 50 % removed 40 - 50
Reverse osmosis 60 - 90 % removed 60 - 90 % removed 60 - 90 % removed 80 - 90

Treatment Levels achievable with Various Combinations of
Unit Operations and Processes Used for Advanced Wastewater Treatment...

Treatment process Typical effluent quality
SS (mg/L) BOD5 (mg/L) COD (mg/L) Total N (mg/L) NH3-N (mg/L) PO4-P (mg/L) Turbidity (NTU)
Activated sludge + granular medium filtration 4-6 <5-10 30-70 15-35 15-25 4-10 0.3-5
Activated sludge + granular medium filtration + carbon adsorption <3 <1 5-15 15-30 15-25 4-10 0.3-3
Activated sludge / nitrification, single stage 10-25 5-15 20-45 20-30 1-5 6-10 5-15
Activated sludge / nitrification - denitrification, separate stages 10-25 5-15 20-35 5-10 1-2 6-10 5-15
Metal salt addition to activated sludge 10-20 10-20 30-70 15-30 15-25 <2 5-10
Metal salt addition to activated sludge + nitrification - denitrification + filtration 5-10 5-10 20-30 3-5 1-2 <1 0.3-3
Mainstream biological phosphorus removal 10-20 5-15 20-35 15-25 5-10 <2 5-10
Mainstream biological nitrogen and phosphorus removal + filtration <10 <5 20-30 <5 <2 <1 0.3-3

Effect of Various Treatment Operations and Processes on Phosphorus Removal...

Treatment operation or process Removal of phosphorus entering system ( % )
Conventional treatment
Primary 10 - 20
Activated sludge 10 - 25
Trickling filter 8 - 12
Rotating biological contactors 8 - 12
Biological phosphorus only
Mainstream treatment 70 - 90
Sidestream treatment 70 - 90
Combined biological nitrogen and phosphorus removal 70 - 90
Chemical removal
Precipitation with metal salt 70 - 90
Precipitation with lime 70 - 90
Physical removal
Filtration 20 - 50
Reverse osmosis 90 - 100
Carbon adsorption 10 - 30