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Management of Non-Point
Source Pollution
CE 296B
Department of Civil Engineering
California State University, Sacramento
Lecture #12, March 17, 1998
Monitoring - Part I
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail?
This is not just an academic question. The
management of non-point source pollution differs
substantially from the management of point source
pollution such as municipal wastewater. With
municipal wastewater, it is possible to assess
performance and compliance by sampling and
testing effluent. A mindset surrounding non-point
source pollution management is that performance
and compliance can be assessed primarily by
sampling and testing effluent.
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
A. What are the characteristics of point vs. nonpoint source pollution that influence how we
will define monitoring?
1. Point source pollution:
• Management efforts take place primarily in one
location.
• Management efforts are primarily technological
in nature and allow for process control.
• As the discharge is relatively steady, constant in
composition and takes place in one point, the
impact on receiving waters is relatively easy to
assess.
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Schematic of Point Source Pollution
At single outfall:
• steady flow
• constant conc.
POTW
Receiving Water
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
A. What are the characteristics of point vs. nonpoint source pollution that influence how we
will define monitoring? (cont.)
2. Non-point source pollution:
• Management efforts take place in countless
locations spread throughout a large area.
• Management efforts are diverse in type.
• As the discharge is highly variable and takes
place in many locations, the impact on
receiving waters is difficult to assess.
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Schematic of Non-Point Source Pollution
Urban
Flow
Suburban flow:
Irrigation
Storm Flow
Receiving Water
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
B. As a point of comparison, how is monitoring
accomplished for point source pollution?
Three primary areas of work:
1. Monitoring of process control
2. Monitoring of effluent quality
3. Monitoring of downstream impacts of
discharge
In each case, the central technique is sample
collection and analysis.
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Monitoring of Process Control at a POTW
• Consider a flow diagram of a typical POTW:
• Sample and analyze influent characteristics to:
– Obtain ongoing characterization profile of influent,
BOD strength, solids content, flow rate.
– Identify specific constituents that source control
programs could help control.
• Sample and analyze influent and effluent from unit
processes to obtain performance data.
Use data to optimize performance of a
technological system.
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Monitoring of Effluent Characteristics at a POTW
• Requirements in the Porter-Cologne Act and Clean
Water Act require point source dischargers, the real
kind, to monitor effluent quality as part of any
NPDES permit. There are multiple purposes to this
and include:
– Identifying the presence and amount of particularly
troublesome constituents. (e.g., Hg, Pb, synthetic
organics)
– Meeting concentration based numerical effluent limits
– Assessing the load, typical units - mass per day, of
conventional and exotic constituents released to the
receiving water.
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Monitoring of Downstream Impacts of POTW
Discharge
Because of the well defined nature of point source
discharge, both in terms of steady flow and consistent
constituent concentrations, it is relatively ease to
determine the impact of that discharge downstream.
• By sampling downstream effluent, one can assess
the amount of dissolved oxygen depletion due the
the noted BOD concentration in POTW effluent as a
good example.
• Because of the well defined characteristics of
POTW effluent, one can easily assess the magnitude
of the loading of many different constituents
associated with the facility.
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
C. What are some of the objectives of a
monitoring program an effort to manage nonpoint source pollution?
1. For a specific BMP, one would certainly
like to establish effectiveness of that BMP
in managing pollutants. Because the very
nature of non-point source pollution, such
an evaluation would have to be done for a
large number of circumstances. Low-flow,
high-flow. Seasonal differences.
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
C. What are some of the objectives of a
monitoring program an effort to manage nonpoint source pollution? (cont.)
1. BMP effectiveness testing - more:
Additionally, in assessing BMP effectiveness,
there is also the difference between source control
type measures and treatment type measures.
While it is possible, although not easy, to measure
the pollutant removal from a detention basin, how
do you determine if stenciling drain inlets has
reduced pollution?
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
C. What are some of the objectives of a
monitoring program an effort to manage nonpoint source pollution? (cont.)
2. An effort to manage non-point source
pollution might involve the implementation
of over 100 different BMPs, some of which
are implemented in thousands of locations.
One would certainly like to know how
complete the effort has been or is to
implement those BMPs.
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
C. What are some of the objectives of a
monitoring program an effort to manage nonpoint source pollution? (cont.)
3. One would like to know how much nonpoint source effluent there is and what is in
it. Major problem, there may be countless
points of discharge and many different
conditions under which that discharge takes
place.
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
C. What are some of the objectives of a
monitoring program an effort to manage nonpoint source pollution? (cont.)
4. One would like to know what the effect on
receiving waters is of non-point source
discharges in the sense of chemical
characteristics.
5. One would like to know how the realization
of beneficial uses is affected by non-point
source discharges.
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I. With respect to the management of non-point
source pollution, what does the term Monitoring,
entail? (cont.)
C. What are some of the objectives of a
monitoring program an effort to manage nonpoint source pollution? (cont.)
In summary, it is desirable to monitor to meet
the following objectives:
•
•
•
•
•
BMP effectiveness
BMP implementation
Effluent quality
Affect on water quality objectives
Affect on beneficial uses
All the while, the cost of the management
program needs to be assessed
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Discussion Break
Say you are designing a monitoring element of a
non-point source management plan. You have a
modest amount of money to do this and need to
spend your money wisely.
On what would you spend money first? Assume that
the regulators will give you freedom to chose.
•
•
•
•
•
BMP effectiveness
BMP implementation
Effluent quality
Affect on water quality objectives
Affect on beneficial uses
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level?
A. First distinction is the difference between a grab
and composite sample. Consider the classic
hydrograph: Q
A grab sample
take place at a
point in time.
Time
The goal of a composite sample is to collect a
sample containing the average concentration
experienced over a period of time.
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
B. How are grab samples collected? Physically,
this could be complicated, but conceptually it is
simple. A portion of the flow at the moment in
time one is interested in, is placed in an
appropriate sample container.
C. How are composite samples collected? Two
primary different possibilities exist:
1. Flow splitting
2. Flow proportioned samples
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Collection of Composite Samples - Basics
• Note that on a hydrograph, the area under the curve
represents total flow volume of the time period in
Area = Q (vol./unit time)
question. Q
x Time = Volume
Time
• The true average concentration for the specified time
period would be the total mass (load) divided by the
total volume (area).
• With an accurate estimation of the average
concentration, coupled with total flow measurement
yields the mass loading.
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Composite Samples - Flow Splitting Method
• Recall the classic hydrograph:
Q
Area to be sampled:
Time
• If an equal fraction of the flow, as an example
1/100th Q, is diverted into a sample container
throughout the sample time, one has a composite
sample. This works best when the flow and
concentrations are relatively constant. Then, it
works great!!
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Composite Samples - Flow Proportioned Method - I
• Recall the classic hydrograph, made much bigger:
Q
A3 A
A
4
A 2
1
If A1=A2=A3=…=A8,
Then,
V1=V2=V3=…=V8
A7
A8
A5
A6
to
t2 t4 t6
t1 t t
3 5
t7
t8
Time
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Composite Samples - Flow Proportioned Method - II
• If equal sized samples are taken at t1, t2, t3, …,t8 and
mixed together, then a good approximation of the
average concentration under the hydrograph has
been collected.
• For such a system to work, the following
information must be accurate:
– The estimate of storm size, or dry weather flow
– The estimate of total run-off from the storm size
– The measurement of flow
• If the above items are true, fancy equipment exists
to help in the process.
Fringe Benefit of Flow-Proportioned Sample Pollutograph
• If individual samples taken at t1, t2, t3,…t8 are
analyzed separately, a picture of the constituent
concentrations with time can be established.
• Currently, this is called a pollutograph, and on the
rare occasions they have been collected, they have
served to study the phenomena of first flush.
• Another possible use is to correlate constituent
concentrations with flow rate.
• It would be nice if more of these existed.
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
D. What are well collected composite samples
from storm events called?
Event Mean Concentration (EMC) Samples
E. If one is dealing with storm water run-off, the
size of the catchment can influence the results.
Consider hydrographs from a large and small
catchment.
Large
Catchment,
> 20 sq. mi.
Small
Catchment,
< 100 acres
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Discussion Break
Based on what you have just seen, what kind of
caveats would you put on EMC concentrations taken
at:
Large catchments?
Small catchments?
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
F. When sampling for constituents, which ones are
appropriate for grab samples and which ones for
composite samples?
1. Grab: Anything that is perishable
• Samples associated with indicator organism
analysis or pathogen identification
• Volatile organic compounds
• NOT BOD. Icing will preserve these samples
2. Composite: Anything else
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Discussion Break
Why do you think there is a basic preference for
composite samples?
Could this ignore the impact of concentration effects
at moments in time during an event?
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
G. What are some of the major pitfalls in actually
collecting samples for non-point source
pollution? Several categories, among them:
1. The extreme difficulty of collecting sheet
flow samples. Problem is though, one might
be real interested in collecting sheet flow
samples. Examples include:
• Erosion at different points on the slope.
• Flow from streets before the piping system is
encountered.
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
G. What are some of the major pitfalls in actually
collecting samples for non-point source
pollution? Several categories, among them:
2. If one is collecting from a conveyance
system (pipe, channel, etc.), it’s usually
from a point in the flow cross-section,
question is, is it representative of the crossSample collection
section?
tube and device
Turbulent Flow
Helps
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
G. What are some of the major pitfalls in actually
collecting samples for non-point source
pollution? Several categories, among them:
3. Avoidance of backwater effects, this can be
a particular problem with treatment type
BMP’s
Sampler and sample line
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
G. What are some of the major pitfalls in actually
collecting samples for non-point source
pollution? Several categories, among them:
4. When the non-point source pollution is
storm water in the western U.S. capturing a
representative storm can be problematical.
Regulations can dictate how representative a
storm is based on among others:
• Storm size
• Storm duration
• Storm intensity • Antecedent dry period
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II.With respect to sample collection and analysis
type monitoring of water, what is involved at a
nuts and bolts level? (cont.)
G. What are some of the major pitfalls in actually
collecting samples for non-point source
pollution? Several categories, among them:
5. When the non-point source pollution is
storm water the logistics of the sample
collection and analysis are substantial:
•
•
•
•
•
Deciding if the storm is going to be a good one
Getting people to the site
Getting perishable samples to the lab
Making sure the lab people are there
and on, and on , and on!!!!