This tutorial document is based on a steady state problem from Thomann & Mueller (1987) “Principles of Surface Water Quality Modeling and Control” Sample Problem 6.10 (which was itself adapted from Driscoll et al., 1981).

The purpose is to provide new users of EE with a step by step tutorial to setup a simple hydrodynamic and water quality model that they can create themselves from scratch. At the same time, it provides the more advanced modeler the ability to make a comparison between analytical solution and the EFDC results.

This document will take the user through the following steps:

• building a grid

• setting hydraulic parameters

• setting initial conditions

• setting boundary conditions

• setting a conservative and non-conservative dye tracer

• creating data files for calibration data

• configuring calibration plots

The problem is taken from Thomann and Mueller (1987, p.356). A city of approximately 60,000 people discharges its wastewater into a relatively small river with an average annual flow of about 250 cfs. The city’s wastewater is presently treated by a trickling filter plant which provides about 85% BOD removal and has reached its design capacity of 7.5MGD. The population is expected to increase by 50% to 92,000 people by the year 2000. Expansion of the treatment plan to capacity of 11.5 MGD and provision of an activated sludge system for more efficient secondary treatment are proposed.

A calibration analysis at Qu = 100 cfs is done first to establish kinetic rated based on observed in stream data.

• Upstream and tributary boundary inflows of water and pollutants

• Initial conditions of water depth and pollutants in time and space

• Physical transport of water (velocity, travel time)

• Waterbody geometry (length, depth, area, volume)

• Pollutant fate reactions and interactions

• Sources/loading rates of flow & pollutants

Geometry

Relatively constant spatially over reach of interest. From three field surveys of different flows, the following area flow and depth flow relationships were derived:

• A = 19.5Q^0.6 ; A (ft²), Q (cfs)

• H= 0.312Q^0.5; H (ft), Q (cfs)

• W = A/H

Flow

• USGS gaging station upstream of WWTP

• Long term average summer flow = 100 cfs

• 7Q10 = 30 cfs (for min 7-consecutive day flow with return period of once in 10 years)

Open

Velocity

From time of travel studies at various flows, U = 0.0513Q^0.4; U (fps), Q (cfs)

Water Temperature

25 ^oC during low flow summer survey, 27 ^oC maximum monthly average temperature (August) to be used with 7Q10 to check conformance with standards.

H = 0.312 x (111.5)^0.5  = 3.3 ft

U = 0.0513 x (111.6)^0.4 = 0.34 fps = 5.6 mpd = 10.32 cm/s

K_a = [12.9 x 0.34^0.5 / (3.3)^1.5] x (1.024)^25-20 = 1.42 /day @25 ^oC

Upstream boundary