Seawater Desalination RO Membranes
Water temperature is critical because it is an important quality in environmental parameters. It is important to measure water temperature. By doing so, we can see the characteristics of the water such as the chemical, biological, and physical properties of the water, as well as the possible health effects. Water temperature is an important factor in determining whether a body of water is acceptable for human consumption and use.
The temperature in water governs the kinds and types of aquatic life that live in it.
It regulates the maximum dissolved oxygen concentration of the water.
Temperature influences the rate of chemical and biological reactions.
It affects the dissolved oxygen level in water, photosynthesis of aquatic plants, metabolic rates of aquatic organisms, and the sensitivity of these organisms to pollution, parasites, and disease.
In the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document -Temperature it is stated that “temperature is currently defined by the ‘International Practical Temperature Scale of 1968, amended edition 1975’ in terms of the electrical resistance of a standard platinum-resistance thermometer at three calibration points. (The triple point of water, the boiling point of water at one standard atmosphere, and the freezing point of zinc).”
The aesthetic objective for water temperature in the Guidelines for Canadian Drinking Water Quality is 15°C. This is because most consumers complain about tap water at 19°C or higher. The intensity of taste is greatest for water at room temperature and is significantly reduced by chilling or heating the water. Increasing the temperature will also increase the vapour pressure of trace volatiles in drinking water and, therefore, could lead to increased odour. It is also possible that micro fungi can grow inside the internal plumbing systems of buildings, leading to complaints of musty, earthy, or mouldy tastes and odours if the temperature rises above approximately 16°C. It is advisable to keep the growth of such organisms to a minimum by using cold water because certain organic growths have been shown to protect bacteria from the effects of chlorination.
In the Water Quality Guidelines, it states, “the temperature dependence of most chemical reactions stems from the activation energy associated with them. The rates of chemical reactions decrease with decreasing temperature. The relative concentrations of reactants and products in chemical equilibria can also change with temperature... Temperature can, therefore, affect every aspect of the treatment and the delivery of potable water.”
In the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Temperature it is stated that “Measurement for water treatment purposes may be made with any good-grade mercury-filled Celsius thermometer. As a minimum requirement, the thermometer should have a scale marked for every 0.1°C and should be checked against a thermometer certified by the U.S. National Bureau of Standards.”
It is not economically feasible to alter the temperature of the water at the drinking water treatment plant. Therefore, the temperature is largely determined by the selection of the raw water source and the depth of the intake. In Canada, surface water temperature shows a wide seasonal variation in most localities (2ºC – 25ºC). Algal growth in surface water normally becomes noticeable only at temperatures above 15 ºC. Groundwater has a more constant seasonal temperature. The temperature of deep wells varies only by 2ºC - 3ºC. Larger variations occur in shallow ground water.
When chemical treatment is involved, generally the rates of chemical reactions decrease with decreasing temperature because the temperature dependence of most chemical reactions stems from the activation energy associated with them. In addition, the relative concentrations of reactants and products in chemical equilibria can also change with temperature. Therefore, temperature can affect every aspect of the treatment and the delivery of potable water.
The efficiency of one of the key water treatment steps, coagulation, is greatly dependent on temperature. Also, the optimum pH for the coagulation process decreases as temperature increases. Furthermore, as temperature decreases, the viscosity of water increases, and the rate of sedimentation decreases. As a longer settling time is not available in a plant with a fixed flow rate and basin capacity, the efficiency of colour and turbidity removal by coagulation and sedimentation may be less in winter than in summer. Due to the stratification of warmer water over cooler water in the treatment basin, very small increases in the temperature (<1ºC) of the raw water source have been reported to decrease the efficiency of the flocculation-sedimentation process. However, appropriate plant and process design can defeat this problem.