Membrane treatment of printing and dyeing wastewater

Our company has carried out several projects for the reuse of printing and dyeing wastewater, using a dual-membrane process in which both ultrafiltration and reverse osmosis employ Dow membranes. Based on the operational results, the performance of some of these projects has not been ideal, mainly due to organic matter and microbial contamination; therefore, pretreatment is extremely important, particularly the efficiency of the biochemical treatment system at the initial stage.

Has anyone here done specific projects? I hope we can meet up and discuss it in detail!

Textile printing and dyeing wastewater is the sum of wastewater of different natures generated at various stages of this process. If membrane treatment is applied to this combined wastewater stream, there is no guarantee of operational stability, nor can economic efficiency be assured. Textile printing and dyeing wastewater mainly includes desizing water, rinsing water, etc., and there are significant differences in the properties of desizing water and rinsing water ； The water quality for rinsing after bleaching is different from that for rinsing after dyeing and printing ； Different companies use different sizing and dyeing processes, so the substances in their wastewater also vary ； The various printing and dyeing processes do not start simultaneously, so the water quality in the main canal remains unstable. All these increase the difficulty of operating the membrane. Moreover, the cost of membrane treatment for printing and dyeing wastewater is higher than that of biochemical treatment, and even by pricing the membrane-treated water, no competitive advantage can be achieved. If a valuable membrane treatment process is to be developed, desizing water is a good starting point. Alkalis, PVC, and modified starch are valuable substances in desizing water; concentrating and reusing them is what makes the application of membranes worthwhile from an investment perspective. Many people have conducted experiments in this area, but application is only possible in integrated textile printing and dyeing enterprises (the slurry concentrated by membranes must be transported to the weaving workshop to become valuable, and transportation costs will determine the feasibility of the project). This post was last edited by 1959dsf on 2009-2-8 08:18]

Reply to the original poster: The projects I have been involved in before were all related to the advanced treatment and reuse of comprehensive wastewater from printing and dyeing factories. As far as I know, many companies in China are engaged in such projects, and the actual performance of these systems is more or less average. A major drawback of this type of technology is that it hardly reduces the total amount of pollutants emitted; it only allows for the reuse of a portion of the water, thereby achieving a slight reduction in volume. Companies undertake such projects sometimes for economic reasons, while in other cases it’s merely a formality. What the friend upstairs mentioned regarding the recycling of these dyeing and printing auxiliaries is indeed very useful. If it can be implemented, it will not only allow for the recovery of valuable auxiliaries but also reduce pollutant emissions and the burden associated with subsequent biochemical treatment processes. Friend upstairs, are there any existing engineering examples for this?

I have not worked on dyeing and printing wastewater projects. My research on printing and dyeing wastewater took place in 2005 and 2006; due to the lack of suitable clients and being busy with other projects, I stopped working on this topic thereafter.

We are now able to achieve zero discharge of wastewater generated from denim padding and dyeing processes. We have not dealt with other types of printing and dyeing wastewater; those involved in denim production can get in touch with me. qq110468738

Both ultrafiltration and reverse osmosis utilize organic membranes and are applied in industries that require specialized separation processes, especially in projects related to the reuse of printing and dyeing wastewater. In such cases, organic matter and microbial contamination can be reduced by over 90%. Therefore, it is advisable to use alkaline cleaning agents, and to seek out professional composite membrane cleaning agents for regular maintenance. One should not wait until the contamination becomes severe before attempting to clean the membranes; cleaning should be carried out as soon as contamination levels are low, so that pollutants can be removed promptly. Otherwise, as contamination accumulates over time, the pressure difference increases and water production declines significantly, making it more difficult to carry out cleaning later on.