Water Quality Problems

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Outline

• Water Quality Problems Indicators
• Sediment
• Nutrients
• Pathogens
• Aquatic Health
• Water Quality Solutions
• Agriculture
• Forestry
• Urban

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Stream Impairment Causes (EPA, 2000)

• Sediment
• Pathogens
• Nutrients
• Metals
• Dissolved Oxygen
• Habitat Alterations
• Temperature
• pH
• Impaired Biology
• Pesticides
• Flow Alterations
• Mercury

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Major Pollutants Causing Stream Use Impairment in
North Carolina
Source USEPA
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Estuary Use Impairment
Source USEPA
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Nonpoint Sources
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Sediment

• Natural erosion
• Also referred to as geologic erosion -- is
  relatively slow
• Most rapid along shorelines and stream channel
• Vital factor in maintaining environmental balance
• Produces about 30 of all sediment in U.S.
• Accelerated erosion
• Refers to erosion occurring at increased rate
  usually because of removal of natural vegetation
  or alteration of ground contour
• Accounts for 70 of all sediment generated in
  U.S.
• Construction and agriculture are main causes

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Impacts of Sedimentation

• Annually about 8 billion metric tons of sediment
  will reach ponds, rivers and lakes in the US
• Roughly two-thirds comes from agriculture and
  forestry practices
• One-third comes from active construction or land
  development

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Impacts of Sediment

• Screens out sunlight/ reduces clarity
• Fills channels and reduces capacity
• sediments can fill up ponds and reservoirs
• sedimentation can plug culverts and storm drains
• Pollutants attach to sediment particles
• legal action
• additional costs and penalties
• delays in schedule
• Property damage from flooding

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Total Suspended Sediment - TSS

• TSS Concentration of sediment in water measured
  in mass per unit volume (mg/L)
• TSS Load Product of concentration and stream
  discharge (tons per day)
• TSS can be related to Turbidity for each watershed

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Example Problem
In the Wages Creek watershed, a 2-L sample of
water was collected from a stream with a
discharge of 10 cfs. The dry weight of sediment
in the sample was 48 mg. Calculate TSS
concentration and TSS load.
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Example Problem
In the Wages Creek watershed, a 2-L sample of
water was collected from a stream with a
discharge of 10 cfs. The dry weight of sediment
in the sample was 48 mg. Calculate TSS
concentration and TSS load. Given Volume 2
L Mass 48 mg Discharge 10
cfs Calculate TSS 48 mg / 2 L 24
mg/L TSS load 24 mg/L X 10 cfs
0.65 tons/day
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Turbidity

• An expression of the optical property that causes
  light to be scattered and absorbed rather than
  transmitted in straight lines through the water
  (the measure of relative clarity) measured in
  NTUs Nephelometric Turbidity Units
• Turbidity can be related to TSS

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Example from Wages Creek
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Relationship of Turbidity and TSS(must be
determined for each watershed)
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Relationship of TSS and Discharge(must be
determined for each watershed)
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Example Problem
In the Wages Creek watershed, a 2-L sample of
water was collected from a stream with a
discharge of 10 cfs. The measured turbidity was
20 NTU. What is the expected TSS concentration?
What is the expected TSS load? As the discharge
increases to 50 cfs, how does TSS load change?
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Example Problem
In the Wages Creek watershed, a 2-L sample of
water was collected from a stream with a
discharge of 10 cfs. The measured turbidity was
20 NTU. What is the expected TSS concentration?
What is the expected TSS load? As the discharge
increases to 50 cfs, how does TSS load
change? From the graphs, we expect the TSS
concentration to range from 30 to 60 mg/L and the
TSS load to range from 0.1 to 1.0 tons/day. At
50 cfs, the expected TSS load increases to 3 to
10 tons/day.
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• Soil Erosion Two Phases
• Detachment individual particles are loosened
  from the soil mass.
• Rainsplash gt running water gt wind
• Transport water or wind carries the detached
  particles downslope or downwind.
• Flow in rills is the most important.

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Expected Erosion Rates(Tons/Acre/Year)

• Forest Land 1 to 5
• Farm Land 10 to 40
• Construction Sites 100 to 200

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• Factors in Soil Losses
• Rainfall intensity, duration, and energy.
• Soil Erodibility texture, structure, organic
  matter content.
• Topography slope length, steepness.
• Surface Condition vegetation, mulch, bare, etc.
• Erosion Control Practices contours, terraces,
  silt fences, basins, etc.

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Soil Erodibility All Soils Are Not Created
Equal

• Texture or Particle Size Distribution
• Silt is the most easily eroded component.
• Clay tends to remain bound in the soil structure.
  Once in runoff, it is very difficult to settle.
• Sand promotes infiltration, reducing runoff
  volume, and tends to settle quickly.
• Organic Matter increases infiltration so runoff
  volumes are lower.

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• Definitions
• Erosion Control
• Techniques that keep soil from leaving its
  original location
• Sediment Control
• Techniques that capture soil after it has been
  displaced from its original location

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Sedimentation Size Matters
Coarse Clay
Silt
Fine sand
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Nutrients

• Can lead to algal blooms in surface waters which
  then result in low DO and fish kills
• Can cause drinking water to be unsafe (nitrate)
• Freshwater usually P limited
• Estuarine usually N limited

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Too Much of a Good Thing Nutrients and Water
Quality

• Algal mats cause problems with
• recreational uses
• aesthetics
• smell
• low oxygen
• toxins
• shade submerged vegetation
• change fish populations

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Sources Processes

• Nutrients come from
• Rainfall dry deposition
• Wastewater discharges
• Fertilizer runoff
• Animal human waste

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Lower Neuse River Basin
Raleigh News and Observer, 1995
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Nitrogen

• Nitrogen Forms Nitrate, Ammonium, Organic N
• Total N TKN NO3-N NO2-N
• TKN Organic N Ammonium-N
• Indicator of animal or human waste
• Nitrate soluble in water
• Unpolluted water lt1 mg/L of NO3-N
• Drinking water standard 10 mg/L of NO3-N

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Ammonia Concentrations and Fish Kills

• Lethal concentrations of ammonia range from 0.2 -
  2.0 ppm
• trout most sensitive
• carp least sensitive

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Neuse River Basin Sources of Nitrogen (1995
estimates)
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Surface Runoff vs Subsurface Leaching Nitrogen
Losses
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Nitrate and water movement
Nitrate losses due to buffer
Aquitard
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Buffer Width Affects Nitrogen Removal
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Source Deanna Osmond, NCSU
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Example Problem
For a 1,000-hectare farm in the Neuse River
Basin, it is determined that the total nitrogen
loss to the river is 20 kg/ha/year. What is the
change in nitrogen load if the farmers installs
the following BMPs which? BMP hectares
affected Vegetative Buffer gt 30
ft 100 Vegetative Buffer gt 20
ft 100 Tree/shrub Buffer gt 20ft 100 Water
control structures 200
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Example Problem
Solution The current N load is 20,000 kg/year.
The total load reduction is calculated in the
table below as 5,200 kg/year, or
26. BMP hectares reduction load
reduction Vegetative Buffer gt 30
ft 100 65 1300 Vegetative Buffer gt 20
ft 100 40 800 Tree/shrub Buffer gt
20ft 100 75 1500 Water control
structures 200 40 1600 Total 500 5200
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Stormwater BMPs for N Reduction

• Wet ponds and wetlands
• Bioretention (rain gardens)
• Level spreaders
• Permeable pavement
• Green roofs

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ConstructedWetlands
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Bioretention Areas
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Bioretention Areas
Source Bill Hunt, NCSU
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Example Problem
What is the expected nutrient load reduction if a
properly-designed bioretention area is installed
to treat runoff from a 10-acre commercial
development in central North Carolina where the
current loading is estimated to be 20 lb/ac/year
of nitrogen and 0.5 lb/ac/year of phosphorus?
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Example Problem
What is the expected nutrient load reduction if a
properly-designed bioretention area is installed
to treat runoff from a 10-acre commercial
development in central North Carolina where the
current loading is estimated to be 20 lb/ac/year
of nitrogen and 0.5 lb/ac/year of
phosphorus? Solution Current loading is 200
lb/year of N and 5 lb/year of P. The expected
removal efficiencies are at least 40 for N and
at least 50 for P, resulting in reductions of at
least 80 lb/year of N and 2.5 lb/year of P.
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Phosphorus EPA Water Quality Criteria

• Background Levels
• 0.01-0.03 ppm

• Standards
• 0.05 ppm
• stream that discharges into lake or reservoir
• 0.025 ppm
• lake or reservoir
• 0.1 ppm
• streams that do not discharge
• 0.01-0.03 ppm
• to stop algae blooms

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Transport of Soil P
Rainfall
Total Surface P LossParticulate Dissolved P
Soil Erosion(Particulate P)
Surface Runoff(Dissolved P)
Infiltration Percolation
Release of soluble soil P to Runoff
InteractionZone (lt2 in)
P Leaching
Subsurface Lateral Flow
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Phosphorus
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Buffer Width Affects Runoff of P
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Example Problem
For inorganic fertilizer applied to farmland in
North Carolina, the expected total loss to
receiving waters is 0.55 lb/ac/year. What buffer
width is needed to reduce this loss to 0.25
lb/ac/year?
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Example Problem
For inorganic fertilizer applied to farmland in
North Carolina, the expected total loss to
receiving waters is 0.55 lb/ac/year. What buffer
width is needed to reduce this loss to 0.25
lb/ac/year? Solution The buffer will reduce
erosion losses and surface runoff losses, which
currently total 0.45 lb/ac/year. This value must
be reduced 0.15 lb/ac/year, meaning that a
delivery ratio of 0.3 is required. The minimum
buffer width required is 30 ft.
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Dissolved Oxygen

• Decreases
• As temperature increases
• Daily/seasonal cycles
• Affected by thermal pollution
• With depth
• DO stratification
• With Biological Oxygen Demand (BOD)
• Decomposition of organic matter
• Possible fish kills

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Dissolved Oxygen
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Water Temperature

• Lower than air temp and slower to change
• Daily/Seasonal cycles
• Stream temp affected by shade depth
• Affects
• Waters physical and chemical properties
• Feeding, reproduction, and metabolic rates of
  organisms
• DO levels

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Pathogens Sources (Direct and Indirect)

• Agricultural Runoff and Infiltration
• CAFOs
• Septic Systems
• Sewage Lines
• Straight Pipes
• Urban Runoff
• Wildlife Biosolids

Escherichia coli
Photograph courtesy of USDA-ARS
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Survival of Indicators in the Environment

• Longer survival in cool than warm temperatures
• Longer survival in clayey than sandy textured
  soil
• Longer survival in circumneutral than acid or
  alkaline pH
• Longer survival when moist than dry
• Longer survival when shaded than exposed to UV
  light

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What are benthic macroinvertebrates?

• Invertebrates (animals without backbones) that
  live on the stream bottom and are visible with
  the naked eye, such as aquatic insects,
  crustaceans, worms, clams, and snails

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Scale Issues
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