【JST-016】One-on-one consultation office for experts in circulating water and wastewater treatment

I have a question for the senior colleagues: Our factory uses the contact oxidation method to treat wastewater, and the treated water meets the standards required for reuse as circulating water in power plants. However, why is the water yellow in color, albeit a light shade? The color becomes lighter after adjusting the pH value of the incoming water (it was originally between 7 and 8, and now it’s adjusted to between 8 and 9). What is the reason for this? If you want to remove color, what method should be used? Please give some guidance, thank you!

Wastewater from what industry? Yellow fades as pH increases; it might be due to iron ions, so it’s worth testing.

Great, it was time to have such a section. Recently, I was working on the ironmaking system of an steel plant. Since their system was severely scaled, I carried out cleaning operations, but there were still many residues remaining on the pipe walls, some green and some yellow. The green color is probably caused by slime or moss; then what causes the yellow color? According to experts, it’s not caused by rust, but they won’t tell me the real reason. So what could be causing it then?

There are two possibilities for the yellow color: 1. The sludge or algae have not been completely eliminated; as you mentioned, there is still green algae present, and this is the more likely scenario. In such cases, an algaecide should be used to kill or remove them. 2. After corrosion, iron mixes with sludge, scale, and the like. A small amount of these yellow substances can be taken and dissolved in acid; if they dissolve and the solution remains yellow, it is likely to be rust.

After biochemical treatment, since there is still some COD present in the wastewater, its color remains normal. As the pH value increases, its color fades, likely because its coloration is visible only in neutral or slightly acidic environments. Please explain what kind of wastewater it is

What is hot-state pre-film formation in circulating water? Should the hot medium be used first, and then the cold medium (circulating water)? Which is softer, demineralized water or deionized water? Cleaner (with fewer ions)?

Hello, senior. I have a question: in an aerobic biological tank, does intermittent intensive aeration have any impact on COD degradation? The process system flow is: hydrolysis + primary aerobic treatment + sedimentation tank + secondary aerobic treatment + MBR membrane unit. It is mainly used to treat phenol-containing wastewater; the COD of the raw water ranges from 8000 to 12000, while that of the treated water ranges from 800 to 3000. The COD level of the treated water is unstable

Hello, moderator! How to culture bacteria in PTA wastewater? Including anaerobic and aerobic bacteria? Thank you, moderator! :handshake

The purified water obtained after acid vapor stripping in the refinery wants to be reused. Its COD level is around 160. What level is required for it to be suitable for use in the circulating water system? What impact does a high COD level have on the quality of water? Thank you

The so-called hot-state pre-film formation with circulating water refers to the normal operation of the heat exchanger, with heat exchange taking place as usual, without the need to introduce a heating medium. The so-called cold pre-coating refers to the pre-coating of a heat exchanger in a state where no heat exchange takes place. Soft water refers to water that contains no or only a small amount of soluble calcium and magnesium compounds. Softened hard water refers to water that has had its calcium and magnesium salts reduced to levels of 1.0–50 milligrams per liter. So, soft water is mainly water that removes the cationic ions in water that tend to cause scaling. Demineralized water is the finished water obtained by using various water treatment processes to remove impurities in water such as suspended solids, colloids, and inorganic cations and anions. Desalinated water does not mean that all salts in the water have been completely removed; due to technical constraints and considerations related to production costs, trace amounts of impurities are allowed to be present in desalinated water depending on its intended use. The fewer impurities in the desalinated water, the higher its purity. Water with a conductivity of less than 5 us/cm (at 25°C) and a SiO2 content of less than 100 ug/L is referred to as primary deionized water, while water with a conductivity of less than 0.2 us/cm (at 25°C) and a SiO2 content of less than 20 ug/L is called secondary deionized water. The conductivity of demineralized water is lower than that of soft water.