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WATER QUALITY MODELING AND
PREDICTION
>> Muhammad bin Ramlan
CONTENT AN ALGAL BIOMASS PREDICTION MODEL
Introduction Nutrient Cycling The Nitrogen Cycle Phosphorus Cycle Silica Cycle Summary of Nutrient Cycles
Simulation Method Introduction Numerical Accuracy Traditional Approach Backtracking Approach Model Uncertainty
CONTENT AN ALGAL BIOMASS PREDICTION MODEL
Introduction Nutrient Cycling The Nitrogen Cycle Phosphorus Cycle Silica Cycle Summary of Nutrient Cycles
Simulation Method Introduction Numerical Accuracy Traditional Approach Backtracking Approach Model Uncertainty
INTRODUCTION
Simulation model: DELWAQ-BLOOM
This model is used to predict algae growth and mortality, oxygen concentrations and nutrient dynamics
This model process can be grouped into: nutrient cycling, algae modeling, and oxygen-related process.
NUTRIENT CYCLING
The DELWAQ-BLOOM model assumes that algae consumes ammonia and nitrate in the water column.Optionally the model includes algae species with the ability to take up atomic nitrogen and detritus.
THE NITROGEN CYCLE
The nitrogen cycle consider the water-column components• e.g. ammonia, nitrite and
nitrate, algae, suspended detritus and suspended (non-dertitus) organic nitrogen.
Two important reaction in the nitrogen nutrient cycle • Nitrification and
denitrification• nitrification
(production of nitrate in system) and denitrification (nitrate is removed from the system).
• These reaction affect the flux of ammonia and nitrate in the water column.
PHOSPHORUS CYCLE
A simplified version of the nitrogen cycle
The specified reaction of this cycle is the absorption / desorption of particulate inorganic phosphorus
SILICA CYCLE
A simplified version of the nitrogen cycle
The specified reaction of this cycle is there is no absorption of silica to inorganic suspended solids.
SUMMARY OF NUTRIENT CYCLE
The nutrient cycle just described are based on the assumption that
nutrients can be recycled an infinite number of times without any loses
other than due to transport, chemical absorption, denitrification
and burial.
CONTENT AN ALGAL BIOMASS PREDICTION MODEL
Introduction Nutrient Cycling The Nitrogen Cycle Phosphorus Cycle Silica Cycle Summary of Nutrient Cycles
SIMULATION METHOD Introduction Numerical Accuracy Traditional Approach Backtracking Approach Model Uncertainty
INTRODUCTION
Simulation Method – water quality models
Numerical
Accuracy
Traditional Approach
Backtracking
Approach
NUMERICAL ACCURACY
Water quality simulation models based on physical,
biological and chemical processes typically include time rate of change terms
as dC/dt.
TRADITIONAL APPROACH
Most water quality simulation models
simulate quality over a consecutive series of discrete time periods.
Time is divided into discrete intervals and the
flows are assumed constant within each of
those time period intervals.
Each water body is divided into segments or
volume elements, and these are considered to
be in steady state conditions within each simulation time period.
At the end of each period, mixing occurs
within each segment or volume element to obtain the concentrations in the
segment or volume element at the beginning
of the next time step.
BACKTRACKING APPROACH
Backtracking approach eliminates the need to consider the simulation time-step duration restriction. The backtracking approach permits any simulation time-step duration to be used along with any segmenting scheme.
Unlike the traditional approach, water can travel through any number of successive segments or volume elements in each simulation time step.
Instead of following the water in a segment or volume element downstream, the system tracks back upstream to find the source concentration of the contaminants.
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