CLEANING UP THE RIVERS

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CLEANING UP THE RIVERS

• 4.11

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• For many years our rivers were used to carry
  wastewater away from the cities.
• The industrial revolution and the invention of
  the w.c. (water closet) increased the rivers
  load of wastes.
• The rivers smelled of sewage and water-borne
  diseases diseases cause by organisms in the
  water were common

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Thames River-London, England

• In the mid 1800s 25000 people living near the
  river died of cholera
• Caused by Vibrio cholerae bacteria in wastes in
  the water.
• Sewers were built to take the waste out to the
  sea did not solve problem only moved the
  problem
• Sewage plants were built in1960s and river is
  clean again.

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Americas Rivers

• Americas rivers were once like the Thames.
• The first sewers were constructed in NYC during
  18th century. They carried untreated sewage and
  dumped in rivers.
• During 1970s, 290 million gallons of raw sewage
  flowed into the Hudson and East Rivers.
• Now the city has 14 sewage treatment plants

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• Charles River of Boston is still polluted by raw
  sewage and storm water runoff but it is steadily
  improving.
• In 1950, the Delaware River had a DO of zero.
  Fish either died or migrated back to ocean.
  States along the river have issued fish
  consumption advisories because of fish
  contaminated with toxins.

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Fishable Swimmable Rivers

• No river is too small or too polluted that it is
  not worth saving.
• Water in ALL rivers should be fishable and
  swimmable.
• Thus the 1972 Clean Water Act was passed
  Requires cities to treat their sewage before
  dumping it into rivers and streams.

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• The 2004 National Water Quality Inventory reports
  that
• 44 of streams
• 64 of lakes
• 30 of estuaries
• were not clean enough to support fishing and
  swimming.
• Less than 30 of all water bodies were assessed
  for the report.

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Sewage Treatment Plants

• 1. As sewage enters, it flows through a vertical
  bar screen that removes rags, sticks, and other
  large solids. The trash is scraped from bars and
  taken to a landfill
• 2. Primary Treatment physical separation of
  liquids and solids.
• 1/3rd of the suspended solids (organic matter)
  settles out to the bottom of the tank and called
  sludge. Floating grease and oils are skimmed off
  the surface of the water. The sludge and the
  effluent, the partially treated wastewater, are
  piped to separate tanks for further treatment.

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• Secondary Treatment a biological process that
  increases the oxygen in the wastewater and allows
  time for organisms to remove organic matter.
• 2 Processes for this
• 1. Activated sludge process-air is pumped into
  the tank which supplies bacteria with the oxygen
  they need to break down the organic matter. Then
  pumped to a second tank where remaining solids
  settle out.

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• 2. Trickling filters - a tank filled with a
  rock-like or grid system that is coated with
  slime, which contains algae, bacteria, and other
  pollutant tolerant organisms. The effluent is
  sprayed over the tank and as it trickles over the
  organisms, they remove most of the organic matter
  and nutrients from the wastewater.
• Primary and Secondary treatment can remove 85 of
  the organic matter and nutrients from the sewage.

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• 4. Digesters- sludge from the primary and
  secondary settling tanks is piped to large tanks
  that re heated to 95F. Sludge held 15-20 days so
  anaerobic bacteria in waste can digest more
  organic material. Natural gas or methane is a
  waste product. Some is burned to provide heat
  for digesters and also heat for buildings nearby.
  

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BIOSOLIDS

• Sludge biosolids
• WHAT DO WE DO WITH IT?
• EPA approved sites off the coast
• Farmers can use as fertilizers but must be tested
  for disease-causing agents and nutrient content
  (N P K)
• Used to make
• compost

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Pretreatment

• Industries must pretreat wastewater before
  dumping it into the sewers to reduce the levels
  of heavy metals.
• Required to pretreat wastewater so toxic wastes
  dont interfere with the treatment process.

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Chlorination

• After secondary treatment, wastewater is
  disinfected through an outfall pipe into a body
  of water nearby.
• Chlorination sodium hypochlorite is added to
  kill any disease-causing bacteria that might
  remain in the water.
• Disadvantage chlorine reacts with organic
  compounds to form trihalomethanes, a
  carcinogenic. Chlorine is also toxic to some
  aquatic organisms.

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Chlorination (cont.)

• Before the water is released thru the outfall
  pipe into the river,
• Sulfer dioxide is added to burn off the chlorine
  to minimize effects on fish and other aquatic
  organisms

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Combined Sewers

• Carry both sewage and storm water.
• During average rainfalls the volume of water is
  5-15 times greater than normal.
• Sewage treatment plants are not designed to
  process this massive volume of water.
• During storms, untreated sewage and storm water
  may flow directly into river.
• Ex. Potomac River, Washington D.C.

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Lagoons Aquaculture

• Another method for primary and secondary
  treatment that requires large amounts of land and
  less expensive to build/maintain.
• A lagoon is a shallow pond where sewage is held
  for 20-30 days.
• In warm climates, algae and bacteria in a series
  of lagoons provide acceptable primary and
  secondary sewage treatment.

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Lagoons

• In warmer climates, Hyacinths are added to
  lagoons to control odors, they use nitrates and
  phosphates, and roots filter the water.
• In cooler climates, duckweed, watercress or
  cattails are used.
• To control mosquitoes, fish that eat the larvae
  and bats that eat the adults are introduced.

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On-site Sewage Treatment

• Septic Tank a large tank buried in the ground
  to treat sewage from an individual home or
  business.
• Solids settle to the bottom, bacteria break down
  organic matter, and the effluent flows through
  piles into the soil absorption field (drain
  field).

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Septic Tanks

• Bacteria normally digest about 50 of the solids
  that remain in the tank. The remainder will
  accumulated in the bottom as sludge.
• The mixture of fluids and solids pumped from the
  tank is called septage. Septage contains
  disease-causing organisms. It us usually
  disposed as spray on farmland.

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• Livestock do not feed on crops sprayed with
  septage for at least 60 days.
• Septage should not be used on home gardens or
  commercial production of food that will be eaten
  raw.
• Septage applied on dairy farms must be plowed
  down before crops are planted.

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• Effective wastewater
• treatment is essential
• for human health.
• Effective treatment
• of wastewater and proper
• disposal of sludge is essential to meet the goal
  of fishable, swimmable waters.