AGEC/FNR 406 LECTURE 33. Groundwater nitrate risk:. Low Medium High Very High. Source: http://pasture.ecn.purdue.edu/~frankenb/watershedmap.html. Types of water pollutants.
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AGEC/FNR 406 LECTURE 33
Groundwater nitrate risk:
Types of water pollutants
1. Organic wastes: degradable wastes, residuals, some chemicals (detergents, pesticides, oil).
2. Inorganic substances: toxic metals, salts, acids, nitrate and phosphorous compounds.
3. Nonmaterial pollutants: heat, radioactivity.
4. Infectious agents: bacteria, viruses.
Sources of water pollutants
1. Point sources: industry and municipal sewage treatment plants. “end of the pipe” typically continuous emission typically governed by Federal (EPA) standards
2. Nonpoint sources: agriculture, yard, and street runoff
hard to monitor episodic governed by states
1965 Water Quality Actrequired states to set ambient standards for water quality1972 Water Pollution Control Act Amendmentsset a “zero discharge” standard (inefficient!)set technology-based effluent standards and federal discharge permits1977Clean Water Actrequired Best Conventional Technology
Biological Oxygen Demand (BOD)
High quality water is usually associated with a high level of dissolved oxygen (DO).
DO is typically used up in the degradation process.Main source is treated municipal wastewater.One way to measure water quality is via “biochemical oxygen demand.”
Time or distance
Emission vs. Concentration
A transfer coefficient measures the per unit relationship between a level of emission at a source and a constant concentration of the pollutant at a receptor site.
ai Ei + B
KR = concentration at receptor site
ai = transfer coefficient
Ei = emission level of ith source
B = background emission, if any
Policy Goal: Obtain given concentration target (not emission target) at minimum cost.
Procedure: translate emission reduction into concentration reduction.
Concentration = emission x transfer coefficientMC of concentration reduction = MC of emission reduction / transfer coefficient
Two sources, one receptor site.
EA= 10/day, a = 0.50, MC = 100
EB= 10/day, a = 1.0, MC = 100
Concentration at R = 10*.5 + 10*1.0 = 15
MC of concentration reduction = 100/0.5 = 200 for A
MC of concentration reduction = 100/1.0 = 100 for B
Standards based on zone may be useful when monitoring costs are high
Goal: reduce damages at receptor site at lowest cost
How: balance the impact each polluter has(not on emission, but on concentration) with cost of reducing damages (in terms of concentration)
Key concept: Target concentration, not emission.