In printing and dyeing wastewater, there are common characteristics such as high organic matter content, high alkalinity and deep color. If the staff handle it with liquid salt or ferrous sulfate, there are two possible causes of yellowing. 1.There are some inorganic metal ions that have not settled in the printing and dyeing wastewater; 2.The color of organic substances.
If the original color of the wastewater is yellow, the color will fade after ferrous treatment and then turn yellow again. This might be a color reversal phenomenon, which is related to some reactive dyes. It seems that the color has been removed at first glance, but the familiar color reappears at the back. Therefore, it is still recommended to deal with the sewage problem through biochemical treatment.
If ferrous sulfate is used to treat green and red wastewater, the effect will be relatively poor. However, as long as the reaction conditions are appropriate, the color intensity can generally be reduced to meet the discharge standards. Here are two suggestions for this situation:
1.Add sodium hydroxide at the front end and ferrous ions at the back end. After adding ferrous ions, keep the PH at around 9. After adding sodium hydroxide in this way, the pH can reach above 12. Under strong alkaline conditions, it can destroy the molecular structure of some colored groups, transforming difficult-to-treat colored groups into easily treatable ones.
Furthermore, at the beginning of the reaction with ferrous ions, the PH will be around 11. When the PH is above 11, the decolorization effect of ferrous ions will be better than that when the PH is around 8, especially for some difficult-to-treat colored groups.
2.Replacing sodium hydroxide with lime not only reduces the cost of chemicals but also has the effect of improving the treatment outcome.
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After the staff have treated the sewage, it still cannot be discharged immediately. It is necessary to use an online water quality meter to conduct real-time detection of various indicators in the water body to ensure that all indicators are qualified before discharging it! Which industries need to carry out sewage and wastewater discharge monitoring work? There are: medical wastewater online monitoring,drinking water online monitoring, industrial water online monitoring, monitoring of industrial process water, agricultural sewage monitoring, etc.
