Description

The QUAL-UFMG model is a comprehensive tool for simulating water quality in rivers, developed to assess the spatial distribution of pollutants and water quality parameters along watercourses. The model considers multiple biogeochemical processes and allows detailed analysis of the evolution of various water quality constituents.

 

The model offers 3 cross-sectional geometric configurations:

 

• Trapezoidal section: For natural channels with side slopes
• Rectangular section: For artificial channels with vertical walls
• Triangular section: For V-shaped channels

 

Modeled processes

The QUAL-UFMG model simulates the following processes:

• Oxygen cycle: Consumption by organic matter decomposition, nitrification, and atmospheric reaeration
• Nitrogen cycle: Conversion of organic nitrogen → ammonia → nitrite → nitrate
• Phosphorus cycle: Transformation between organic and inorganic phosphorus
• Coliform decay: Natural death of indicator organisms
• Sedimentation: Removal of particulate material by deposition

Fundamental equations

The model uses the following differential equations to describe temporal concentration variations:

Dissolved oxygen:

$\frac{dDO}{dt} = K_2(DO_{sat} - DO) - K_d \cdot BOD \cdot K_T - O2Namon \cdot N_{NH_3} \cdot K_{an} \cdot f_{nitr} - O2Nnitri \cdot N_{NO_2} \cdot K_{nn} \cdot f_{nitr}$

BOD:

$\frac{dBOD}{dt} = -K_r \cdot BOD$

where $K_r = K_d + K_s$

Organic nitrogen:

$\frac{dN_{org}}{dt} = -(K_{so} + K_{oa}) \cdot N_{org}$

Ammoniacal nitrogen:

$\frac{dN_{NH_3}}{dt} = K_{oa} \cdot N_{org} - K_{an} \cdot N_{NH_3} \cdot f_{nitr} + \frac{S_{NH_3}}{h}$

Organic phosphorus:

$\frac{dP_{org}}{dt} = -(K_{spo} + K_{oi}) \cdot P_{org}$

Temperature correction

All kinetic coefficients are corrected for temperature using:

$K_T = K_{20} \cdot \theta^{(T-20)}$

where $\theta$ varies between 1.024 and 1.080 depending on the process.

Channel hydraulics

For trapezoidal sections:

• Wetted area: $A = h(b + zh)$
• Wetted perimeter: $P = b + 2h\sqrt{1 + z^2}$

For rectangular sections:

• Wetted area: $A = bh$
• Wetted perimeter: $P = b + 2h$

For triangular sections:

• Wetted area: $A = zh^2$
• Wetted perimeter: $P = 2h\sqrt{1 + z^2}$

Depth is calculated using Manning's equation:

$Q = \frac{A}{n} \cdot R_h^{2/3} \cdot S^{1/2}$

Input data

Output data