Water Treatment
Chapter 11
Sewage Treatment• Rationale• More than 500 pathogenic bacteria, viruses, and
parasites can travel from human or animal excrement through water.
• Natural Processes• In many areas, outdoor urination and defecation is
the norm.• When population densities are low, natural processes can
quickly eliminate waste.
• Artificial Wetlands Are a Low Cost Method • Natural water purification
• Effluent can be used to irrigate crops or raise fish for human consumption.
Lincoln Wastewater FacilitiesUnderneath and throughout Lincoln are over 1,000 miles of sanitary sewer lines and 16 pumping stations114 employees at solid waste and wastewater facilities
Theresa Street Facility27th & Cornhusker20 million gallons of water daily
Northeast Facility5 million gallons of water daily
Combined this would fill Holmes Lake in 3.5 days
Lincoln Northeast Treatment Facility
3. aeration basin
1. screening and grit basin
2. primary clarifiers
4. secondary clarifiers
5. disinfection
6. solids digestion7. solids dewatering
Municipal Sewage Treatment
1. Primary Treatment - Physical separation of large solids from the waste stream
• screening, pumping, grit removal• get the big stuff out• material collected hauled to
landfill• primary clarification
• removes settleable solids• removes floatable
materials like grease• 2-4 hrs
primary clarifier
2. Secondary Treatment - Biological degradation of dissolved organic compounds
• Biological Treatment• Aeration basin• removes pollutants with
bacteria and protozoans• must be aerated• 8 hrs
• Secondary clarification• separates treated
wastewater from microorganism (from aeration basin)
• Disinfection• chlorination or UV light
Municipal Sewage Treatment
2. Solids processing - Biological degradation of dissolved organic compounds
• solids digestion• anaerobic digesters to
stabilize organic solids• produce methane gas
(CH4) which can power turbine to generate electricity
• 18-20 days• solids dewatering
• removes excess water• solids (organ rich
material)
Municipal Sewage Treatment
Belt Filter Press Dewatering
Anaerobic Digesters
2. Solids processing - Biological degradation of dissolved organic compounds
• land application• soil amendment and
fertilizer• alternatively dewatering is
replaced by collecting liquid and using it as fertilizer on city owned land
Municipal Sewage Treatment Subsurface Biosolids Injection
Municipal Sewage Treatment3. Tertiary Treatment - Removal of plant nutrients (nitrates and phosphates) from secondary effluent.
• Chemicals, or natural wetlands
• Lincoln does not have tertiary treatment
• In many US cities, sanitary sewers are connected to storm sewers.• Heavy storms can overload
the system, causing by-pass dumping of raw sewage and toxic runoff directly into watercourses
Unusual Pollutants are Now Being Detected in Surface Waters
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