WASTEWATER TREATMENT TECHNOLOGIES MEDAWARE Prof. George Ayoub Faculty of Engineering and Architecture American University of Beirut

OUTLINE Overview of the Conventional Wastewater Treatment Process Discussion of Existing Biological Treatment Technologies Examples from the Mediterranean Region Examples from the Lebanese Context

Conventional Wastewater Treatment Process Pretreatment involves: Screening Grit Removal Oil separation Flow equalization Chemical Treatment is used in conjunction with the physical and chemical processes: Chemical precipitation Adsorption Sludge Treatment and Disposal involves: grinding, degritting, blending, thickening, stabilization, conditioning, disinfection, dewatering, heat drying, thermal reduction, ultimate disposal Disinfection can use: Chlorine compounds Bromine Chloride Ozone UV Radiation

Biological Treatment In the case of domestic wastewater treatment, the objective of biological treatment is: To stabilize the organic content To remove nutrients such as nitrogen and phosphorus Types: Aerobic Processes Anoxic Processes Anaerobic Processes Combined Aerobic-Anoxic-Anaerobic Processes Pond Processes Attached Growth Suspended Growth Combined Systems Aerobic Maturation Facultative Anaerobic

Major Aerobic Biological Processes Type of Growth Common Name Use Suspended Growth Activated Sludge (AS) Carbonaceous BOD removal (nitrification) Aerated Lagoons Attached Growth Trickling Filters Carbonaceous BOD removal. nitrification Roughing Filters (trickling filters with high hydraulic loading rates) Carbonaceous BOD removal Rotating Biological Contactors Packed-bed reactors Combined Suspended & Attached Growth Activated Biofilter Process Trickling filter-solids contact process Biofilter-AS process Series trickling filter-AS process

Activated Sludge Process The aeration tank contains a suspension of the wastewater and microorganisms, the mixed liquor. The liquor is mixed by aeration devices (supplying also oxygen) A portion of the biological sludge separated from the secondary effluent by sedimentation is recycled to the aeration tank Types of AS Systems: Conventional, Complete-Mix, Sequencing Batch Reactor, Extended Aeration, Deep Tank, Deep Shaft

Advantages/Disadvantages Flexible, can adapt to minor pH, organic and temperature changes Small area required Degree of nitrification is controllable Relatively minor odor problems Disadvantages High operating costs (skilled labor, electricity, etc.) Generates solids requiring sludge disposal Some process alternatives are sensitive to shock loads and metallic or other poisons Requires continuous air supply

Trickling Filters The trickling filter or biofilter consists of a bed of permeable medium of either rock or plastic Microorganisms become attached to the media and form a biological layer or fixed film. Organic matter in the wastewater diffuses into the film, where it is metabolized. Periodically, portions of the film slough off the media

Advantages/Disadvantages Good quality (80-90% BOD5 removal) for 2-stage efficiency could reach 95% Moderate operating costs (lower than activated sludge) Withstands shock loads better than other biological processes Disadvantages High capital costs Clogging of distributors or beds Snail, mosquito and insect problems

Rotating Biological Contactors It consists of a series of circular disks of polystyrene or polyvinyl chloride that are submerged in wastewater and rotated slowly through it The disk rotation alternately contacts the biomass with the organic material and then with atmosphere for adsorption of oxygen Excess solids are removed by shearing forces created by the rotation mechanism

Advantages/Disdvantages Short contact periods Handles a wide range of flows Easily separates biomass from waste stream Low operating costs Short retention time Low sludge production Excellent process control Disadvantages Need for covering units installed in cold climate to protect against freezing Shaft bearings and mechanical drive units require frequent maintenance

Major Anaerobic Biological Processes Type of Growth Common Name Use Suspended Growth Anaerobic Contact Process Carbonaceous BOD removal Upflow Anaerobic Sludge-Blanket (UASB) Attached Growth Anaerobic Filter Process Carbonaceous BOD removal, waste stabilization (denitrification) Expanded Bed Carbonaceous BOD removal, waste stabilization

Anaerobic Contact Process Untreated wastewater is mixed with recycled sludge solids and then digested in a sealed reactor The mixture is separated in a clarifier The supernatant is discharged as effluent, and settled sludge is recycled

Advantages/Disadvantages Methane recovery Small area required Volatile solids destruction Disadvantages Heat required Effluent in reduced chemical form requires further treatment Requires skilled operation Sludge to be disposed off is minimal

Upflow Anaerobic Sludge Blanket Wastewater flows upward through a sludge blanket composed of biological granules that decompose organic matter Some of the generated gas attaches to granules that rise and strike degassing baffles releasing the gas Free gas is collected by special domes The effluent passes into a settling chamber

Advantages/Disadvantages Low energy demand Low land requirement Low sludge production Less expensive than other anaerobic processes High organic removal eficiency Disadvantages Long start-up period Requires sufficient amount of granular seed sludge for faster start-up Significant wash out of sludge during initial phase of process Lower gas yield than other anaerobic processes

Major Anoxic and Combined Biological Processes Type of Process Type of Growth Common Name Use Anoxic Suspended Growth Suspended Growth Denitrification Denitrification Attached Growth Fixed-film Denitrification Combined Aerobic, Anoxic, and anaerobic Processes Single- or multi-stage processes, various proprietary processes Carbonaceous BOD removal, nitrification, denitrification, phosphorus removal Single- or multi-stage processes

Pond Treatment Processes Common Name Comments Use Aerobic Stabilization Ponds Treatment with aerobic bacteria; oxygen is supplied by algal photosynthesis and natural surface reaeration; depth of 0.15 to 1.5 m Carbonaceous BOD removal Maturation (tertiary) Ponds Use aerobic treatment; applied loadings are low to preserve aerobic conditions Secondary effluent polishing and seasonal nitrification Facultative Ponds Treatment with aerobic, anaerobic and facultative bacteria; the pond has 3 zones: a surface aerobic zone, a bottom anaerobic zone, and an intermediate zone partly aerobic-anaerobic Anaerobic Ponds Treatment with anaerobic bacteria; depths of up to 9.1 m to conserve anaerobic conditions Carbonaceous BOD removal (waste stabilization)

Examples from the Mediterranean Region (1) Country Name of the Plant Capacity m3/day Treatment Technology Reuse Application Spain Vitoria 55,000 Secondary treatment (screening, sedimentation, nitrification-denitrification) + tertiary treatment (coagulation-flocculation, sand filters, chlorine disinfection) Irrigation of orchards Tenerife 90,000 Secondary treatment (activated sludge), tertiary treatment Irrigation of banana, potatoes, and tomatoes Greece Chalkis 9,000 Pretreatment, clarification, aeration tanks, final clarifiers, advanced treatment Irrigation of trees and bushes

Examples from the Mediterranean Region (2) Country Name of the Plant Capacity m3/day Treatment Technology Reuse Application Palestine Dan Region Project 330,000 Secondary treatment (activated sludge, or stabilization lagoons), soil aquifer treatment Irrigation of field crops, fruit plantations, vegetables, flowers Italy Grammich-elle 1,500 Activated sludge, chlorine contact tank, tank storage Irrigation of orange, olive trees, crops for caning industry, and vegetables to be eaten cooked Clatagiron-e 5,200 Activated sludge, sand filtration, reservoir storage Cyprus Larnaca 8,500 Oxidation ditches, sand filtration, chlorination Irrigation of corn, alfalfa, in addition to gardens, parks and fields

Examples from the Mediterranean Region (3) Country Name of the Plant Capacity m3/day Treatment Technology Reuse Application Jordan Al Samra 150,000 3 trains of ponds: 2 anaerobic, 4 facultative, 4 maturation Irrigation of olive trees, forest area, fodder crops and non-restricted vegetables for experiments Morocco City of Drargua 600 Primary treatment (anaerobic basins), secondary treatment (sand filters), tertiary treatment Irrigation of alfalfa, tomatoes, zucchini, corn and grass Turkey Gaziantep 200,000 Primary treatment, secondary treatment (Activated Sludge) Irrigation of edible crops, vegetables and nearby fields

Examples from Lebanon Lebanon has been rebuilding its water and wastewater infrastructure since 1992; in this context, the Government initiated the construction of large-scale WWTPs employing AS and Biofilter treatment systems mainly Except for the Ghadir pre-treatment station, no single large-scale plant achieving secondary treatment has started to operate Some community-based plants funded by NGOs are achieving secondary treatment; however, these are small-scale plants and rarely function properly

Technology to be used inside WWTPs proposed by the Government Coarse Screening Fine Screening Grit and Grease Removal Tank Pumping Primary Settling Tank Degassing Tank Pumping Aeration Tank or Biofilter Treated Water Pumping Station Venturi Flume Distribution Structure Secondary Settling Tank

Ghadir Preliminary Treatment Station Serves the Greater Beirut Southern Wastewater Collection Basin (population of 977,000) Maximum instantaneous flow: 2.6 m3/s; average: 1.6 m3/s; expected minimum: 1.1 m3/s Accepts also septic tank septage and leachate from the Naameh landfill Effluent is discharged into the sea at a distance of 2.6 km away from the shore and at a depth of 60 m In periods of overflow, the plant partially or completely shuts down, and the effluent is discharged into the sea at a distance of 500 m from the shore GHADIR STATION

Treatment Steps At Ghadir LIFTING SCREENING DEGRITTING

Baalbeck WWTP Completed in summer 2000 Not yet functional because the collection network is not yet finished Serves a population of 130,600, and has a daily capacity of 19,600 m3/day Will achieve secondary treatment

Treatment Technologies in Community-based WWTPs There are 42 plants as shown by the table Process NGO CHF CAI MCI YMCA PM Extended Aeration 1 2 7 Activated Sludge 5 6 Anaerobic Digestion 17 Aerobic Digestion Mixed Treatment Total 18 10 8

EXTENDED AERATION ACTIVATED SLUDGE

ANAEROBIC DIGESTION AEROBIC DIGESTION MIXED TREATMENT

EXTENDED AERATION KAWS AKKAR YMCA

ACTIVATED SLUDGE KFEIR YMCA

ANAEROBIC DIGESTION HASBAYA MCI

AEROBIC DIGESTION MARJ EL ZOUHOUR YMCA

WASTEWATER PONDS SYSTEM MIXED TREATMENT ADVANCED INTEGRATED WASTEWATER PONDS SYSTEM AIN HARSHA YMCA

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