Water Purification and Water Purification and Wastewater TreatmentWastewater Treatment
Water PurificationWater Purification
• ScreeningScreening
• Chlorination, fluoridationChlorination, fluoridation
• Chemical applicationChemical application– Aluminum sulfate (“alum”)Aluminum sulfate (“alum”)• CoagulationCoagulation
– Activated charcoalActivated charcoal• Removes objectionable tastes and odorsRemoves objectionable tastes and odors
Water PurificationWater Purification
• Mixing BasinsMixing Basins– Alum chemically reacts to form “floc”Alum chemically reacts to form “floc”• Gelatinous particles Gelatinous particles
– Water in mixing basins is stirredWater in mixing basins is stirred• Promotes collisions betwen floc particlesPromotes collisions betwen floc particles
– Floc particles grow in sizeFloc particles grow in size• Entrain bacteria and sedimentEntrain bacteria and sediment
Water PurificationWater Purification
• Settling BasinsSettling Basins– Flocculated material settles out and is Flocculated material settles out and is
piped to wastewater treatment plantpiped to wastewater treatment plant
• Sand FiltersSand Filters– Hydrated lime added to minimize Hydrated lime added to minimize
corrosioncorrosion– Polishing operationPolishing operation
Water PurificationWater Purification
• Temporary storage in clear wellsTemporary storage in clear wells
• Filtered-water reservoirFiltered-water reservoir– ChlorinationChlorination– Caustic soda to minimize corrosiveness Caustic soda to minimize corrosiveness
of polished waterof polished water– Gravity flow to pumping stationsGravity flow to pumping stations
Wastewater TreatmentWastewater Treatment
• Septic Tanks Septic Tanks – Bacteria in sewage degrade organic Bacteria in sewage degrade organic
mattermatter– Tank buried in ground to treat sewage Tank buried in ground to treat sewage
from an individual homefrom an individual home– Wastewater flows into tankWastewater flows into tank
Septic Tank SystemSeptic Tank System
Wastewater TreatmentWastewater Treatment
• Septic Tanks Septic Tanks – Solid material (“sludge”) settles to Solid material (“sludge”) settles to
bottom of tankbottom of tank– Cleaner water flows out of tank into Cleaner water flows out of tank into
ground through subsurface drainsground through subsurface drains
Wastewater TreatmentWastewater Treatment
• Lagoons (Stabilization Ponds)Lagoons (Stabilization Ponds)– 3-5’ deep3-5’ deep– Sunlight, algae, oxygen interact to clean Sunlight, algae, oxygen interact to clean
wastewaterwastewater
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• CollectionCollection• TreatmentTreatment
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• CollectionCollection
– SewersSewers• CombinedCombined• SeparateSeparate
Stormwater and Sanitary Sewer SystemStormwater and Sanitary Sewer System
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• CollectionCollection
– Combined SewersCombined Sewers• Carry stormwater and wastewaterCarry stormwater and wastewater
– Separated SewersSeparated Sewers• Sanitary SewersSanitary Sewers• Storm SewersStorm Sewers
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• CollectionCollection
– Household sewerHousehold sewer– Lateral sewerLateral sewer– Main sewersMain sewers– InterceptorsInterceptors– Wastewater treatment plantWastewater treatment plant
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• CollectionCollection
– High rainfall eventsHigh rainfall events• Some wastewater may be diverted to Some wastewater may be diverted to
receiving streamsreceiving streams
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• TreatmentTreatment
– FunctionFunction• To speed up natural processes by which To speed up natural processes by which
water purifies itselfwater purifies itself• DO is the key!DO is the key!
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• TreatmentTreatment
– ProcessesProcesses• Primary Primary • SecondarySecondary• AdvancedAdvanced
The Wastewater Treatment ProcessThe Wastewater Treatment Process
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Primary TreatmentPrimary Treatment
– Mechanical processMechanical process• ScreeningScreening• GrindingGrinding• Grit Chamber (heavy particles - “grit”)Grit Chamber (heavy particles - “grit”)• Sedimentation Tank (suspended solids - Sedimentation Tank (suspended solids -
“sludge”) “sludge”) • Chlorination of effluentChlorination of effluent
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Secondary TreatmentSecondary Treatment
– Biological processBiological process• Uses bacteria to removed ODW and lower Uses bacteria to removed ODW and lower
BODBOD– TypesTypes
• Trickling FilterTrickling Filter• Activated SludgeActivated Sludge
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Secondary Treatment With Trickling Filters Secondary Treatment With Trickling Filters
– Effluent leaves sedimentation tank and flows Effluent leaves sedimentation tank and flows through through trickling filterstrickling filters• Bed of stones 3-10’ deep through which Bed of stones 3-10’ deep through which
sewage passessewage passes• Bacteria gather on stones and multiply, Bacteria gather on stones and multiply,
consuming ODWconsuming ODW• Cleaner water trickles through pipes at Cleaner water trickles through pipes at
bottom of filter for additional treatmentbottom of filter for additional treatment
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Secondary Treatment With Activated Secondary Treatment With Activated
SludgeSludge– Effluent leaves sedimentation tank and is Effluent leaves sedimentation tank and is
pumped to an pumped to an aeration tank aeration tank – Effluent is mixed with air and sludge loaded with Effluent is mixed with air and sludge loaded with
bacteria (bacteria (“activated sludge”“activated sludge”))– Sludge contacts with raw sewage, and bacteria in Sludge contacts with raw sewage, and bacteria in
the sludge then decompose the raw sewage, the sludge then decompose the raw sewage, lowering ODW and BODlowering ODW and BOD
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses
• Secondary Treatment With Activated SludgeSecondary Treatment With Activated Sludge– Activated sludge-sewage mixture is called Activated sludge-sewage mixture is called mixed mixed
liquorliquor– Mixed liquor leaves aeration tank and flows to Mixed liquor leaves aeration tank and flows to
another sedimentation tank where suspended another sedimentation tank where suspended solids settle out for reuse as activated sludgesolids settle out for reuse as activated sludge
– Effluent is chlorinatedEffluent is chlorinated– Activated sludge in sedimentation tank is reusedActivated sludge in sedimentation tank is reused
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Advanced (Tertiary) Wastewater TreatmentAdvanced (Tertiary) Wastewater Treatment
– Physical and chemical processes that specific Physical and chemical processes that specific pollutants left in wastewater after primary and pollutants left in wastewater after primary and secondary treatmentsecondary treatment
– Extremely costly! Extremely costly! • It cost twice as much to build a tertiary It cost twice as much to build a tertiary
treatment plant compared to a secondary treatment plant compared to a secondary treatment planttreatment plant
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Advanced (Tertiary) Wastewater TreatmentAdvanced (Tertiary) Wastewater Treatment
– ProcessesProcesses• Bleaching to remove colorationBleaching to remove coloration• Disinfection to kill pathogensDisinfection to kill pathogens• Coagulation-sedimentation with alumCoagulation-sedimentation with alum• Adsorption using activated charcoalAdsorption using activated charcoal• Electrodialysis for salt removalElectrodialysis for salt removal
Wastewater TreatmentWastewater Treatment
• Conventional Sewage TreatmentConventional Sewage Treatment– ProcessesProcesses• Sludge DisposalSludge Disposal
– LandfillsLandfills– IncinerationIncineration– Land applicationLand application– Anaerobic digestion Anaerobic digestion
Wastewater TreatmentWastewater Treatment
• Water Quality ProtectionWater Quality Protection– Federal LawsFederal Laws• Clean Water Act (1977)Clean Water Act (1977)• Water Quality Act (1987)Water Quality Act (1987)• U.S. Safe Drinking Water Act (1974)U.S. Safe Drinking Water Act (1974)
Wastewater TreatmentWastewater Treatment
• Water Quality ProtectionWater Quality Protection– Clean Water ActClean Water Act• To restore and/or maintain the chemical, To restore and/or maintain the chemical,
physical, and biological integrity of the physical, and biological integrity of the nation’s surface watersnation’s surface waters
Wastewater TreatmentWastewater Treatment
• Water Quality ProtectionWater Quality Protection– Safe Drinking Water ActSafe Drinking Water Act• Required USEPA to establish drinking water Required USEPA to establish drinking water
standards (“Maximum Contaminant Levels”) standards (“Maximum Contaminant Levels”) for any pollutant that MAY have adverse for any pollutant that MAY have adverse effects on human healtheffects on human health
• No MCLs established for some SOCs, No MCLs established for some SOCs, radioactive materials, toxic metals, and radioactive materials, toxic metals, and ptahogensptahogens
Wastewater TreatmentWastewater Treatment
• Water Quality ProtectionWater Quality Protection– Natural Resources Defense Council Natural Resources Defense Council
StudyStudy• Drinking water of > 50 million Americans Drinking water of > 50 million Americans
exceeds one or more MCL standardsexceeds one or more MCL standards
• Most people have not been notified when Most people have not been notified when their drinking water was contaminatedtheir drinking water was contaminated
• Contaminated drinking water is responsible Contaminated drinking water is responsible for > 7 million ilnesses and 1200 deaths per for > 7 million ilnesses and 1200 deaths per yearyear
Wastewater TreatmentWastewater Treatment
• U.S. Water Quality FactsU.S. Water Quality Facts– 44% of lakes, 37% rivers, 32% estuaries 44% of lakes, 37% rivers, 32% estuaries
still unsafe for fishing, swimming, other still unsafe for fishing, swimming, other recreational usesrecreational uses