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API - Mixing Zone Modeling and Dilution Analysis for Water Quality Based NPDES Permit Limits


Quiz Questions

1.EPA water quality criteria guidance includes some components for each regulated pollutant. They are:
Magnitude (the allowed concentration in ambient water)
Duration (the averaging period over which the ambient pollutant concentration is compared to the allowed value)
Frequency (how often the criterion may be exceeded)
All of the above
2. Mixing zone implementation differs widely across the United States. Some states have very prescriptive policies and procedures for establishing mixing zones and calculating dilution factors.
True
False
3.What does USGS stand for?
United States Geological Survey
United Standard Geological Survey
None of the above
United States Geological Standard
4.The harmonic mean flow used to evaluate ambient water quality against human health criteria is a long-term mean value for the receiving water calculated according to procedures outlined by Rossman and EPA.
True
False
5.After determining effluent dilution under critical conditions for a bay or estuary,
EPA (1991) also recommends checking a non-critical condition (e.g., higher river inflow or lower stratification) that encompasses the period of maximum ambient velocity during a tidal cycle.
True
False
6.EPA’s minimum requirement is that water quality within mixing zones should result in lethality to migrating fish, drifting organisms moving through a plume, or sessile organisms that may attempt to reside within a mixing zone.
True
False
7.States fall into two categories with regard to the overall process of establishing mixing zones. In the first category, a state sets the dimensions of the mixing zone and calculates dilution factors for the discharger. The second category of states require the discharger to submit a mixing zone study which establishes the dilution factor.
True
False
8.What does table 2-1 illustrate about?
Mixing Zone Regulations of Selected States
Florida Department of Environmental Protection
Permitting Authority
None of the above
9.The results of the reasonable potential analysis are also used to determine the maximum size of the mixing zone.
True
False
10.The physics of effluent mixing and dilution involve the principles of conservation of mass, momentum, and energy.
True
False
11.What does figure 3-1 illustrate about?
Illustrations of Plumes and Jets
Pure Plume in uniform crossfire
Effects of ambient conditions on discharge
None of the above
12.Negatively buoyant discharges will rise regardless of discharge hydraulics until reaching the surface or entraining sufficient ambient water to equal the density of the receiving body
True
False
13.The term "outfall pipe" is typically used to refer to the pipe extending from the wastewater treatment plant to the first port.
True
False
14.Lateral mixing in rivers occurs over relatively longer distances and is dependent on factors such as current speed, channel morphology, and the presence or absence of bottom roughness and rapids.
True
False
15.For buoyant discharges, research has shown that the dilution of a multi-port diffuser in un-stratified waters increases in proportion to the length raised to the 2/3 powers, as indicated below

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What does Q stand for in the above equation?

Design discharge rate
Tube coefficient
Height of the tube
None of the above
16.Peak flow conditions must be evaluated to ensure that sufficient head exists to discharge effluent at the design high water level without adversely impacting treatment plant hydraulics.
True
False
17.Risk of infrastructure damage can come from causes including storms, currents, shipping, seismic failures, debris, sediment, and plant growth.
True
False
18.One-dimensional models consider changes in pollutant concentration over a single dimension in space, typically the axis of the discharge jet or plume
True
False
19.Steady state models predict receiving water concentrations in response to model inputs (e.g., effluent flows, concentrations) that remain constant over time.
True
False
20.A more rigorous tool is available for predicting maximum in-stream concentrations downstream of a discharge as well as attenuation due to ambient dilution. This desktop equation is:

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What does W stand for in the above equation?

Stream width
Discharge
Diameter of the tube
None of the above