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

Sewage Treatment/Cultural Eutrophication

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.

Fish Die!

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.

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

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.

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.

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.

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

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)

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

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

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)

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

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)

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.

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.

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

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.

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.

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

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

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)

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.

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

Rotating Drum Treatment

Sand Filtration

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.

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

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!)

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.

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.

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.

Wastewater Virtual Tours Blue Plains Treatment Plant Wash DC http://www.lcusd.net/lchs/mewoldsen/Water_Pollution_LCHS.ppt