WATER POLLUTION
BOD: WHAT IS IT?
• Biodegradable organic matter
• Excess is consumed by bacteria in the water
• They deplete the water of oxygen
• Example: Gold fish bowl
WHAT CAUSES A BUILDUP OF BOD
• Fall leaves
• Animal/human waste discharge
• Process plant discharge-especially in food manufacturing
CONDITIONS THAT CAN CAUSE ELEVATED
LEVELS
• Water temperature increases causing the bacterial
population to increase
• If sufficient organic material is present in the water
HOW CAN YOU MEASURE IT
• Chemists mix water with “organics” with oxygen and test
how long it takes for the oxygen levels to drop
• This test is typically 5 days at a lab
• COD testing is another route
• Much more cost effective
• Quicker results
• Can be done in house
MARCH 2016: FLORIDA FISH KILL
WHAT IS EL NINO?
• Climate cycle begins in the Pacific Ocean
• Warm water from the western tropical Pacific ocean shifts
eastward along the equator of South America
• Forcastors declare an official El Nino when they see both
ocean temperature and rainfall veer towards the east
• Happens every 3-5 years
2015-2016 EL NINO
• Super El Nino
• Hottest summer yet (2011-2015 warmest summers)
• Sea surface temperatures peak around December, impact is
usually seen a few months later as the global ocean heats up
• 2015 hottest year ever without El Nino, but El Nino caused a
8-10% increase in temps as well
EL NINO
• Causing massive algae bloom
• Pseudo-nitzschia genus produces a deadly neurotoxin
• Builds up in sediment and sea-life
• Warm water in the Pacific (The Blob) combined with nutrient
rich water of Pacific coast=perfect conditions
• Duration of algae blood precedented
ALGAE BLOOM COMPLICATIONS
• Fish kills
• Amnesic shellfish poisoning
• GI issues
• Vomiting and diarrhea after ingestion
• Must be monitored and communicated in the summer during
blooms
• Dungeness crab/clamming
HORMONE DISRUPTORS AND DRUGS
• Pulp mills release estrogen-like compounds in significant
amounts into lakes and rivers
• Changes the hormonal system of the animals that ingest
them
• When fish are exposed to these hormones, male fish develop
both male and female reproductive parts
• Female birth control pills
HORMONE DISRUPTORS AND DRUGS
• Paper mills release group of potentially harmful materials
know as dioxins
• High levels are carcinogenic
• Low levels will suppress the immune systems of
animals/humans
• Some have converted to chlorine free processes, but very
little have converted thus far
SEWAGE TREATMENT AND DISPOSAL
• Primary sewage treatment
• Secondary sewage treatment
• Tertiary treatment
PRIMARY SEWAGE TREATMENT
• Settling tanks (Clarifiers)
• Removes solids from water/fluid chlorinated and discharged
• Travel through screens when it enters the plant
• Sludge is pumped to the digester
• Bacteria feed on it
• Methane gas is produced-can be burned off
• Primary treatment removes 30-60% BOD
SECONDARY TREATMENT
• Aerobic bacteria to break down degradable organic
materials
• Removes ammonia to nitrates
• Activated Sludge Process
• Trickling Filter
ACTIVATED SLUDGE PROCESS
• Fluid is pumped out of the clarifier into another tank that is
aerated
• Aerobic bacteria breakdown
• BOD drops rapidly due to increase oxygen and aerobic bacteria
• Then transferred to settling tank
• Remaining suspended material and bacteria sink to the bottom
SLUDGE DIGESTER
• Sludge is transferred to the anaerobic digester
• It is broken down to activated sludge due to the lack of
oxygen
• Some is recycled back to aeration tank to seed the tank
• What is left is dried and can be used as a fertilizer or go to
the landfill
TRICKLING FILTER
• Sewage is sprayed by arms that are slowly rotating onto a
filter bed of stones
• Stones are covered with thin film to help dissolve organic
compounds
• Solids are transferred to sludge tank
• 80-85% of dissolved organics are removed
TERTIARY TREATMENT
• Removes nitrates and phosphates
• Not all waste water systems have tertiary treatments
• Four times as expensive to operate
• Currently 50% of treatment plants have tertiary treatment
RECYCLING WASTE
• Fuel
• Biogas used to run sewage
• Livestock feed
• Proteins and fats that are required
• Soil fertilizer
• Land apply