1. IB Sewage Treatment and BOD
Where does YOUR waste go???

2. Sewage Treatment/Cultural Eutrophication

3. Biological Oxygen Demand (BOD)
BOD: Oxygen is removed from water when organic matter is consumed by bacteria.
Low oxygen conditions may kill fish & other organisms!
Sources of organic matter
Natural inputs: bogs, swamps, leaf fall, and vegetation aligning waterways.
Human inputs: pulp and paper mills, meat-packing plants, food processing industries, and wastewater treatment plants.
Nonpoint inputs: runoff from urban areas, agricultural areas, and feedlots.

4. Fish Die!

5. Wastewater Treatment Objectives
Wastewater treatment systems:
take human and industrial liquid wastes and make them safe enough (from the public health perspective) to return to the aquatic or terrestrial environment.
In some cases, wastewater can be clean enough for reuse for particular purposes.
use the same processes of purification that would occur in a natural aquatic system only they do it faster and in a controlled situation.

6. Sewage or Wastewater Treatment
Sewage or wastewater is composed of sewage or wastewater from:
Domestic used water and toilet wastes
Rainwater
Industrial effluent (Toxic industrial water is pretreated)
Livestock wastes
** microbes degrade organic compounds
** elimination of pathogens occurs

7. Wastewater Treatment
Types of treatment systems include: Septic Tanks or Wastewater Treatment Plants (WWTPs).
Septic Tanks typically treat small volumes of waste (e.g., from a single household, small commercial/industral)
WWTPs typically treat larger volumes of municipal or industrial waste.

8. BOD Effects on Water Quality
All streams have some capability to degrade organic waste. Problems occur when stream is overloaded with biochemical oxygen-demanding waste.

9. SEPTIC TANKS
Septic tanks are used in areas where there are no combined sewers.
Septic tanks (cesspools) must be emptied each year. Old tanks can crack and leak coliform bacteria into surrounding soil, groundwater, and surface waters.

10. Figure 9-28 Page 196 Septic tank with manhole (for cleanout)
Non-perforated pipe
Household
wastewater
Distribution box (optional)
Drain
field
Gravel or
crushed
stone
Vent pipe
Perforated pipe

11. Septic Tanks
Approx. 22 million systems in operation ( 30% of US population)
Suitability determined by soil type, depth to water table, depth to bedrock and topography
Commonly fail due to poor soil drainage
Potential contaminants: bacteria, heavy metals, nutrients, synthetic organic chemicals (e.g. benzene)

12. Decentralized Alternatives
In rural areas or in particular urban communities in the U.S., human wastewater will be treated through individual septic tank systems (pumped or leachfield varieties)
Wastewater is filtered, microorganisms killed and chemicals adsorbed and/or diluted in its passage through the soils and rocks of the leachfield
In developing countries, urban wastewater is seldom treated and instead flows raw through collectors to receiving water bodies (like in the US 100 years ago)
The solution for many developing nations is centralized oxidation lagoon systems (but this needs space) or the use of individual ventilated pit-latrines, especially for shanty towns and rural villages

13. SEWAGE TREATMENT
Sewage treatment means removing impurities so that the remaining waste water can be safely returned to the surface waters (river, bay, ocean) and become part of the natural water cycle again.
sewage treatment separates solids from liquids by physical processes and purifies the liquid by biological and chemical processes

14. IMPACTS FROM ORGANIC WASTE
8 ppm
Types of
organisms
Clean
Zone
Recovery
Zone
8 ppm (mg/L)
Septic
Zone
Dissolved
oxygen
(ppm)
Decomposition
Zone
Clean Zone
Biological
oxygen
demand
Normal clean water organisms
(Trout, perch, bass,
mayfly, stonefly)
Trash fish
(carp, gar,
leeches)
Fish absent,
fungi, sludge
worms,
bacteria
(anaerobic)
Trash fish
(carp, gar,
leeches)
Normal clean water organisms
(Trout, perch, bass,
mayfly, stonefly)

15. Eutrophication = Algae Blooms from Fertilizers!
Accelerated results with human input of nutrients to a lake
© Brooks/Cole Publishing Company / ITP Water Resources and Water Pollution by Paul Rich

16. Primary
Secondary
Grit
chamber
Chlorine
disinfection tank
Bar screen
Settling tank
Aeration tank
Settling tank
To river, lake,
or ocean
Raw sewage
from sewers
(kills bacteria)
Sludge
Activated sludge
Air pump
Sludge digester
Sludge drying bed
Disposed of in landfill or
ocean or applied to cropland,
pasture, or rangeland
(Sludge cake or pellets)

18. PRIMARY TREATMENT
Solids like wood, paper, rags and plastic are removed by screens, washed, dried and taken away for safe disposal at a licensed waste tip. Grit and sand, which would damage pumps, are also removed by settling tanks and disposed of in a similar way.

19. PRIMARY TREATMENT
The remaining solids are separated from the liquid by passing the sewage through large settlement tanks, where most of the solid material sinks to the bottom. About 70% of solids settle out at this stage and are referred to as sludge. The sludge is used on farms after further treatment called sludge treatment.

20. Sewage Treatment Primary Treatment (Physical Process)
Wastewater or sewage treatment is a multistep process:
Primary Treatment (Physical Process)
Removal of large objects using grates and screens
Settling to remove suspended solids (primary sludge)
flocculating chemicals are added to enhance sedimentation

21. SECONDARY TREATMENT
The rate of this process can be increased by pumping air into tanks of sewage where the aerobic digesters float freely and feed on the bacteria. These treatment units are called aeration tanks.
Following either form of secondary treatment, the waste water is settled in tanks to separate the biological sludge from the purified waste water.

22. SECONDARY TREATMENT
a biological process which relies on naturally occurring microorganisms acting to break down organic material and purify the liquid.
In a simple sewage treatment process, micro-organisms are encouraged to grow on stones over which the sewage is trickled. They feed on the bacteria in the sewage and purify the water. These treatment units are called percolating filters.

23. Sewage Treatment Secondary Treatment (Microbial Process)
Supernatant or primary effluent contains high levels of dissolved organic load (Biological Oxygen Demand)
Aeration to stimulate aerobic degradation
activated sludge reactor
trickling filter reactor
bacteria degrade organic
carbon to CO2

24. Extra treatment is needed to give the waste water a final "polish"
Extra treatment is needed to give the waste water a final "polish". This is known as tertiary treatment. Various methods may be used, including sand filters, reed beds or grass plots (artificial treatment wetlands). Disinfection, using ultra violet light to kill bacteria, is another method, and is being used at a number of coastal sewage treatment plants.
TERTIARY TREATMENT

25. Sewage Treatment Tertiary Treatment (Physicochemical Process)
Precipitation
Filtration
Chlorination
Treated water is discharged to waterways
Used for irrigation
Recycled into drinking water
expensive process, sharply reduces inorganic nutrients (PO4, NO3)

26. Sewage Treatment Pathogen Removal by Activated Sludge
More than 90% of E.coli. and Salmonella are destroyed
Bacteria are removed by inactivation, grazing by ciliated protozoa, and adsorption to sludge solids.
Viruses are removed mainly by adsorption process.

27. Anaerobic Digestion of Sludge
Sludges from the primary and secondary treatment settling tanks are pumped into an anaerobic digester
Sludges contain cellulose, proteins, lipid and other insoluble polymers
Anaerobic bacteria digest the sludge to methane and carbon dioxide

28. Rotating Drum Treatment

29. Sand Filtration

30. Carbon Filtration
There are two principal mechanisms by which activated carbon removes contaminants from water; absorption, and catalytic reduction, a process involving the attraction of negatively charged contaminant ions to the positively-charged activated carbon. Organic compounds are removed by absorption and residual disinfectants such as chlorine and chloramines are removed by catalytic reduction.

31. MONITORING SEWAGE
Standard test for for total coliform (TCOL) and fecal coliform (FCOL) bacteria. The number of colonies formed are counted.
STANDARDS: (EPA)
Drinking Water – 1 coliform bacteria:100 mL of water
Swimming Water – 200 coliform bacteria: 100 mL of water

32. DISPOSAL OF SEWAGE SLUDGE
ANAEROBIC DIGESTION – anaerobic bacteria break down organics into methane gas (NH4) and CO2. Methane is trapped and used to heat the digester to 95F.
END PRODUCT = Soil conditioner for gardens (humus).
2. FERTILIZER – sludge is rich in plant nutrients and can be dried (pelletized) and sold as a fertilizer.
PROBLEM: Combined sewer (industrial, residential and storm water combined may be high in heavy metals and PCB’s (NYC SLUDGE!)

33. WATER POLLUTION CONTROL LAWS
1988 – Ocean Dumping Ban Act – barred ocean dumping of sewage sludge at the 200 mile marker. All cities were in compliance by 1988 EXCEPT for NYC, who were permitted to dump until June, 1992.
1972 – Water Pollution Control Act – EPA established regulations for the discharge of pollutants in the USA. It gave the EPA authority to implement pollution control programs and set ambient water quality standards for all contaminants entering surface waters. It also funded the construction of sewage treatment plants.

34. WATER POLLUTION CONTROL LAWS
The Federal Water Pollution Control Act was amended in 1977 and came to be known as the Clean Water Act. The ACT does NOT address water quantity or groundwater, ONLY water quality. Initially addressed point source, since the 1980’s has come to address nonpoint source issues as well.

35. Spotsylvania County Water Treatment Plants
Massaponax Wastewater Treatment Plant – The wastewater division operates and maintains the County’s expanded and upgraded 8 million gallons per day (MGD) Wastewater Treatment Plant.  This facility is a state-of-the-art biological nutrient removal facility.  The plant is staffed 24-hours a day, 365 days a year. The plant is currently under expansion to 9.4 MGD.
FMC Wastewater Treatment Plant – The wastewater division operates and maintains the County’s 4 MGD Wastewater Treatment Plant.  The plant is staffed 24-hours a day, 365 days a year.  Of the 4 MGD capacity, the City of Fredericksburg has a 1.5 MGD reserve.  Operations costs are allocated to the City based upon the City’s proportion of sewage flow to the facility.  These facility costs are billed directly to the School Board.
Thornburg Wastewater Treatment Plant – the wastewater division operates and maintains 345,000 gallons per day (GPD) Wastewater Treatment Plant.  The plant is staffed 12 hours each weekday and 10 hours each weekend day. 
Laboratory Services – The division supplies laboratory support for the water, wastewater and field divisions.  The laboratory performs bacteriological and chemical analysis to ensure compliance with regulatory agencies and to help the operations staff make informed decisions in optimizing the water and wastewater treatment processes.  The laboratory also provides timely data to help optimize drinking water quality in the distribution system. Additionally the laboratory services division responds to customer contacts regarding water quality.

36. Wastewater Virtual Tours
Blue Plains Treatment Plant Wash DC