How does water quality lose its stability? How to tell?

The main reasons for unstable water quality are； (1) Rising water temperature, water evaporation, the release of carbon dioxide from water, or the introduction of excessive calcium and magnesium ions into the water can all lead to scaling ； (2) In the cooling water system, algae and bacteria grow and reproduce; in particular, the growth of iron-bacteria and sulfate-reducing bacteria produces colloidal substances. Additionally, dust from the atmosphere settles in, and suspended particles accumulate over time during the circulation process, thereby causing fouling ； (3) Chemical corrosion is caused by hydrogen sulfide and carbon dioxide dissolved in water, while electrochemical corrosion occurs when metal comes into contact with water. The methods for determining whether water quality is stable are as follows: (1) Critical pH method. Sodium hydroxide is added to the water sample until precipitation occurs; at this point, the pH value is the critical pHc. If the pH of the water is higher than pHc, scaling will occur. (2) Method for determining limiting carbonate hardness. Through small-scale simulation tests, the critical point at which circulating water does not precipitate calcium carbonate at a specific temperature was determined; if the carbonate hardness of the water exceeds this critical point, scaling occurs. (3) Saturation index method. The difference between the measured pHd value of water and the pHd value when water is saturated with calcium carbonate is generally referred to as the saturation index (SI). When SI > 0, it indicates that the water is a supersaturated solution of calcium carbonate, with a tendency to form scale ； When SI=0, it is in an equilibrium state, with no scaling or corrosion ； When SI < 0, there is a tendency to dissolve calcium carbonate and cause corrosion. Furthermore, the degree of scaling and corrosion can also be determined practically through direct observation or by attaching metal sheets.

The main reasons for unstable water quality are: 1. Rising water temperature, leading to water evaporation； 2. Growth and reproduction of algae and bacteria in the cooling water system ； 3. Contact between metal and water causes electrochemical corrosion. The methods for determining whether water quality is stable are as follows: (1) Critical pH method. Sodium hydroxide is added to the water sample until precipitation occurs; at this point, the pH value is the critical pHc. If the pH of the water is higher than pHc, scaling will occur. (2) Method for determining limiting carbonate hardness. Through small-scale simulation tests, the critical point at which circulating water does not precipitate calcium carbonate at a specific temperature was determined; if the carbonate hardness of the water exceeds this critical point, scaling occurs. (3) Saturation index method. The difference between the measured pHd value of water and the pHd value when water is saturated with calcium carbonate is generally referred to as the saturation index (SI). When SI > 0, it indicates that the water is a supersaturated solution of calcium carbonate, with a tendency to form scale ； When SI=0, it is in an equilibrium state, with no scaling or corrosion ； When SI < 0, there is a tendency to dissolve calcium carbonate and cause corrosion. Furthermore, the degree of scaling and corrosion can also be determined practically through direct observation or by attaching metal sheets.

The main reasons for unstable water quality are: 1. Rising water temperature, leading to water evaporation； 2. Growth and reproduction of algae and bacteria in the cooling water system ； 3. Contact between metal and water causes electrochemical corrosion. The methods for determining whether water quality is stable are as follows: (1) Critical pH method. Sodium hydroxide is added to the water sample until precipitation occurs; at this point, the pH value is the critical pHc. If the pH of the water is higher than pHc, scaling will occur. (2) Method for determining limiting carbonate hardness. Through small-scale simulation tests, the critical point at which circulating water does not precipitate calcium carbonate at a specific temperature was determined; if the carbonate hardness of the water exceeds this critical point, scaling occurs. (3) Saturation index method. The difference between the measured pHd value of water and the pHd value when water is saturated with calcium carbonate is generally referred to as the saturation index (SI). When SI > 0, it indicates that the water is a supersaturated solution of calcium carbonate, with a tendency to form scale ； When SI=0, it is in an equilibrium state, with no scaling or corrosion ； When SI < 0, there is a tendency to dissolve calcium carbonate and cause corrosion. Furthermore, the degree of scaling and corrosion can also be determined practically through direct observation or by attaching metal sheets