URBAN WASTEWATER URBAN WASTEWATER URBAN WASTEWATER URBAN WASTEWATER TREATMENT TREATMENT TREATMENT TREATMENT TECHNOLOGIES TECHNOLOGIES Statistical, Economic and Social Research and Training Centre for Islamic Countries Higher Council for Environment and Natural Resources “Water Resources Management” Water Resources Management 23rd-24th November, 2011 Khartoum,Sudan
CONTENT CONTENT � Source of Wastewater Source of Wastewater � Wastewater Treatment Technologies Wastewater Treatment Technologies � Activated sludge � Activated sludge Activated sludge Activated sludge � Nutrient Removal Nutrient Removal � Aerated Lagoons Aerated Lagoons � Trickling filters Trickling filters g � Rotating Biological Contactors Rotating Biological Contactors � Stabilization Ponds � Stabilization Ponds Stabilization Ponds Stabilization Ponds � Constructed Wetlands Constructed Wetlands � Completely Mixed Anaerobic Digestion Completely Mixed Anaerobic Digestion
Source of Wastewater Source of Wastewater Waste-water originates predominantly from water usage by residences and commercial and industrial establishments, together with groundwater, surface water and storm water.
Major contaminants in Major contaminants in Major contaminants in Major contaminants in municipal sewage municipal sewage • Suspended solids (TSS) Suspended solids (TSS) • Biodegradable organics (BOD) • Biodegradable organics (BOD) • Nutrients (N, P) • Nutrients (N, P) • Toxic compounds/heavy metals • Toxic compounds/heavy metals p p y y • Endocrine disruptors • Endocrine disruptors • Pathogens (bacteria, viruses, worm eggs, • Pathogens (bacteria, viruses, worm eggs, g g ( ( , , , , gg , gg , protozoa,parasites) protozoa,parasites)
Wastewater Treatment Technologies Ph Physical, chemical i l h i l and biological methods are used to remove contaminants from waste-water. In order to achieve different levels of contaminant removal, individual waste- water treatment procedures are combined into a variety of systems, classified as primary, secondary, and tertiary waste-water treatment.
Biological Unit Processes Biological Unit Processes Biological processes are usually used in conjunction with physical and chemical processes with the main objective of reducing the organic chemical processes, with the main objective of reducing the organic content and nutrient content of waste-water. Biological processes used for waste-water treatment may be classified Bi l i l d f t t t t t b l ifi d under five major headings: (a) Aerobic processes; (b) Anoxic processes; (c) Anaerobic processes; ( ) (d) Combined processes; (e) Pond processes. These processes are further subdivided, depending on whether the treatment takes place in a suspended-growth system an attached-growth system or a combination of both
Activated-Sludge Process g So far it is the most widely used biological process for the treatment of municipal and industrial wastewaters the treatment of municipal and industrial wastewaters in developed countries. Mi Microbial community (activated sludge) is highly bi l it ( ti t d l d ) i hi hl diverse and competitive
Activated-Sludge Process Liquid-solids separation occurs in sedimentation tank • A recycle system for returning solids removed from the liquid-solids separation unit back to the reactor to maintaining a high concentration of cells • Formation of flocculent settleable solids that can be removed by gravity settling Basic activated sludge process flow sheet Basic activated sludge process flow sheet
Activated-Sludge Process g Advantages • Adapted to any size of community (except very small ones) • Good elimination of all the pollution p parameters (SS,COD, N, P); • Partially-stabilized sludge • Small area required Small area required Disadvantages • Relatively high capital costs y g p • High energy consumption • Requires skilled personnel and regular monitoring regular monitoring • Sensitivity to hydraulic overloads • Settling property of sludge is not always easy to control (bulking sludge) always easy to control (bulking sludge) • High production of sludge
Nutrient Removal Nutrient Removal Nitrogen Nitrogen and and phosphorus phosphorus are are the the principal principal nutrients nutrients of of concern concern in in waste waste- - water water discharges discharges. . Discharges Discharges containing containing nitrogen nitrogen and and phosphorus phosphorus may may accelerate the accelerate the eutrophication eutrophication of of lakes lakes and and reservoirs reservoirs and and stimulate stimulate the the g growth growth of of algae algae and g and rooted rooted aquatic aquatic plants q plants in p in shallow shallow streams streams. .
Removal of Phosphorus by Removal of Phosphorus by Biological Methods Biological Methods A/O Process (Mainstream Phosphorus Removal) A/O Process (Mainstream Phosphorus Removal) ( ( p p ) ) The proprietary A/O process is The proprietary A/O process is used combined carbon oxidation and phosphorus removal from wastewater The A/O process is a wastewater. The A/O process is a single-sludge suspended-growth system that combines anaerobic and d aerobic bi sections ti i in sequence. “In A/O Processes there is no nitrification, and the anaerobic detention time is 30 min to 1h for biological phosphorus removal. SRT (solid retention time) of the aerobic zone mixed liquor is 2 to ( ) q 4 d, depending on temperature.”
Removal of Phosphorus by Removal of Phosphorus by Biological Methods Biological Methods Biological Methods Biological Methods PhoStrip Process (Sidestream Phosphorus Removal) PhoStrip Process (Sidestream Phosphorus Removal) In In In fact In fact fact PhoStrip fact PhoStrip PhoStrip Process PhoStrip Process Process consists Process consists consists of consists of of of � � biological biological and and chemical chemical process process. . � A part part of of the the return return activated activated sludge sludge i i is is transported transported t t t d t d t to to an an anaerobic anaerobic bi bi stripper stripper tank tank. . The The retention retention time time in in this this tank tank ranges ranges from from 8 8 to to 12 12 hours hours. . � A A Acetic acid Acetic ti ti acid or id id or influent i fl influent is i fl t i t is added i added to dd d t dd d to stripper stripper tank tank to to supply supply phosphorus phosphorus release release. . The The phosphorus phosphorus released released in in in the in the the stripping the stripping stripping tank stripping tank tank passes tank passes passes out passes out out of out of of of the the tank tank in in the the supernatant, supernatant, and and the the phosphorus phosphorus- -poor poor activated activated sludge sludge is is returned is is returned returned to returned to to the to the the aeration the aeration aeration tank aeration tank tank tank. The The phosphorus phosphorus- -rich rich supernatant supernatant is is � treated treated with with lime lime or or another another coagulant coagulant in coagulant in coagulant in a separate in a separate separate tank separate tank tank tank. So So So So phosphorus phosphorus will will be be removed removed in in chemical chemical sludge sludge. .
Combined Removal of Nitrogen and Combined Removal of Nitrogen and Phosphorus Biological Methods Phosphorus Biological Methods Phosphorus Biological Methods Phosphorus Biological Methods A2 2/O /O Process Process A2 2/O /O process process is is a a modification modification of of the the A/O A/O process process and and provides provides an an anoxic anoxic zone zone for for denitrification denitrification. . The The detention detention time time in in the the anoxic anoxic zone zone is is approximately approximately one one hour hour.
Combined Removal of Nitrogen and Combined Removal of Nitrogen and Phosphorus Biological Methods Phosphorus Biological Methods Phosphorus Biological Methods Phosphorus Biological Methods Bardenpho Process (five Bardenpho Process (five- -stage) stage) Bardenpho process contains an initial anaerobic zone where PAOs Bardenpho process contains an initial anaerobic zone where PAOs take up and B B d d h h i i i i i l i i i l bi bi h h PAO PAO take up and k k d d store VFAs that are either present in the influent wastewater or store VFAs that are either present in the influent wastewater or produced produced by by fermentation in this zone. fermentation in this zone. Effluent from the anaerobic zone flows into an anoxic Effluent from the anaerobic zone flows into an anoxic zone where nitrate zone where nitrate- -rich rich mixed liquor from the downstream aerobic zone (mixed mixed liquor from the downstream aerobic zone (mixed liquor recycle, MLR) is liquor recycle, MLR) is added to provide nitrate added to provide nitrate- -nitrogen to allow denitrification to nitrogen to allow denitrification to occur. occur.
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