What should be the range of chloride ions in circulating water? Are ppm and mg/L the same concept?
Thread Content
Are ppm and mg/L the same concept? I’ve spent a lot of time searching online recently but still haven’t managed to understand these two units. I found on the internet that the chloride concentration in tap water is generally between 0.3–0.5 mg/L. Is that correct? The new system in my workplace requires that the chloride concentration in the circulating water be less than 700 mg/L. (Is that wrong? It can’t be that high, right?) Only a small amount of disinfectant and acid is added to the circulating water; so its chloride concentration can’t reach 700 mg/L, can it? I asked a friend from another factory, and he said that their facility’s circulating water has a chloride concentration of only 70–90 mg/L. I’m not an expert in this field, so I really don’t understand. I hope the experts here can explain it to me. Thank you
This post was last edited by qugd on 2022-5-30 09:07. The unit mg/L is an objective and practical unit, and the meaning of its dimension is quite clear. PPM is a ratio that is, in principle, dimensionless. In the absence of additional reference information or clear explanations, it may be difficult for some people to understand its true meaning. Therefore, when using the ppm unit, it is usually specified whether it refers to a volume ratio, a mass ratio, a molar ratio, or even a mass/volume ratio or a molar amount/volume ratio, so that readers, especially those unfamiliar with the ways in which units are expressed in chemical analysis, can more easily and accurately comprehend the true significance of this concentration or component content. For aqueous solutions, since the density of water is 1000 grams per liter, or for samples with a density similar to that of water, using mg/L or mass ppm has the same meaning. However, when the density of a liquid sample differs from 1000 grams per liter, or when its specific gravity (ratio to water) is not 1, it is necessary to use the density value for conversion. As for the limits on the chloride ion concentration in circulating water, they are related to the chemicals used in circulating water treatment as well as the materials of the pipelines, containers, valves, and other equipment involved. Since the specific conditions vary from one company to another, such values have limited usefulness as a reference for one another. However, for most circulating water systems, it is beneficial to keep chloride ions at low levels in order to prevent corrosion of the equipment. Since chloride ions in water cannot be naturally degraded or removed, high concentrations of them in circulating water can cause corrosion in various devices that come into contact with this water. Of course, if a company uses titanium or other chloride-resistant materials to manufacture the pipes and equipment in its circulating water system, it is possible to relax or even ignore the requirements regarding chloride concentration.
Thank you for the detailed explanation. I think I understand a bit now. In general, if it’s the chloride ions in circulating water, are PPM and MG/L roughly equivalent to each other? I just can’t figure it out: if the chlorine content in tap water is only 0.3, why does adding some chemicals after recycling it raise the cost by several hundred? If it really gets too high, will adding some fresh water lower it?
This post was last edited by qugd on 2022-5-30 at 12:39. The chlorine in tap water refers to free chlorine or active chlorine, which is used for disinfection and sterilization; it is added intentionally by the water treatment plants, and it is not the chlorine ions that are already present in the water.
Got it! Thank you so much! ! !