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 Facilities Underneath and throughout Lincoln are over 1,000 miles of sanitary sewer lines and 16 pumping stations 114 employees at solid waste and wastewater facilities Theresa Street Facility 27 th & Cornhusker 20 million gallons of water daily Northeast Facility 5 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 digestion 7. 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 (CH 4 ) which can power turbine to generate electricity 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 Treatment 3. 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