Introduction

Quality is the standard of something as measured against other things of a similar kind; the degree of excellence of something.

Pollution is the presence/introduction of a substance which has harmful or poisonous effects in an environment. Pollution can loosely be defined as the deterioration of an existing state.

Water Pollution

Understanding the source of pollution is necessary for eliminating, minimising, reusing or treating their negative effect on the environment.

Classification of the sources of water pollution (Water Quality control Handbook)

Water Quality

Maintaining high water quality or keeping water systems safe is a continuous real-world challenge.  

The key to a successful water quality system in today’s environment is using established parameters to measure change over time at varying locations in the network on a continuous basis. These measurement parameters include pH, conductivity, free chloride, monochloramine, dissolved oxygen, ammonium, turbidity, fluoride, ozone, temperature.  Read more…

Water quality is determined by its physical (temperature, colour, taste, odour, etc), chemical and microbiological properties. These properties are are characterised with wide variability.

The quality of water is measured according to different needs. Different types of production demand water with a typical quality. The greatest quality requirement of water is when it’s used for drinking.

It follows here that the natural quality of water in streams and rivers is formed by the following groups of factors that work simultaneously: climatic conditions, hydrological conditions, hydrodynamic conditions, hydrobiological and biological processes in the water flow. On the other hand, the hydrophysical processes that affect the quality of stream and river water include transportation of solid particles, heating and cooling, evaporation, freezing (formation of ice), absorption, diffusion, and dispersion of the light in water flows.

There are several ways of classifying pollutants in order to predict their effect on water quality and the means of their removal.

• Classification according to their physical condition: solid, a liquid or gas
• Classification according to their sources: agriculture, urban areas

Water Quality Modelling

Modelling is a continuous process of developing models for describing a real process as more information and knowledge about a system became available.

A model is a simplified approximation of a real system. A model is a schematic description or representation of something, especially a system or phenomenon, that accounts for its properties and is used to study its characteristics.

A model is a system of equations, relationships and observed monitoring data, created for the description of a natural system and demonstration/checking system behaviour under different conditions and time.

Water quality models try to simulate changes in a pollutants concentration as they move through the environment. A pollutant entering an environment may increase or decrease its concentration due to a large variety of mechanisms.

Mathematical models are a means for relevant stakeholders to gain the best social and economic solutions of water problems.

Mathematical models are used to:

• simulate the effects of different scenarios on water quality
• choose solutions where and how to invest for water quality improvement
• assess the value of parameters, for which there is limited information.

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Purpose of water quality modelling

• to develop a clear conceptual model based on all available information
• to understand more fully the transport regime of pollutant
• to test hypotheses, to ensure that they are consistent with governing principals and observations, and to quantify the dominant controlling processes.
• to reconstruct the history of pollutant transport
• to establish time ranges within which an event could have begun, or within which contaminants could have reached specified level in certain areas
• to calculate future contaminant distributions

The fundamental principles for water quantity and quality modelling are:

• conservation of energy states (first law of thermodynamic);
• conservation of mass states (mass balance models) and
• conservation of momentum states (Newton’s first law of motion).

The process of model building is an iterative process, it starts with expression of a working hypothesis, typically based on a priori knowledge about the system in the form of mathematical model.

An experiment is like a window through which the nature is viewed. Our view is never perfect. Interaction between experimental data collection and data analysis provides the opportunity for improving precision by shifting emphasis to different variables, making repeated observations, and adjusting experimental conditions. The assessment of water quality is always related with the determination of water flow characteristics. It is not possible to assess water quality without evaluation of the water quantity. That is why the water quality modelling includes as a main part the water quantity modelling, which gives the answer how water movement affects the concentration of the dissolved and suspended constrains.

The creation of a water quality model involves the following two stages:

• Analysis of the system – this may be theoretical, observational, or experimental;
• Synthesis of a mathematical replica of the system.