Management of Non-Point Source Pollution CE 296B

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Management of Non-Point Source PollutionCE 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.
  non-point 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.

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. non-point 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
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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 non-point
  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 non-point 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 non-point 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 non-point source pollution? (cont.)

• 3. One would like to know how much non-point
  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 non-point 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 non-point 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

A grab sample take place at a point in 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 question.

Area Q (vol./unit time) x Time Volume

• 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

Area to be sampled

• 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

If A1A2A3A8, Then, V1V2V3V8
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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.

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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.

Small Catchment, lt 100 acres
Large Catchment, gt 20 sq. mi.
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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.), its usually from a point
  in the flow cross-section, question is, is it
  representative of the cross-section?

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 BMPs

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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 intensity

• Storm duration
• 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!!!!