一位顾客的问题: We are a zinc-chloride plater and flow 15,000 gallons per day through a membrane system. 我们努力保持细胞膜正常运转. We average between 36 and 48 hours of run time before we must stop and clean the membranes. 我们可以做些什么来改进运行时?
废水专家: “这是个好问题, and in my personal experience as a MF membrane wastewater operator for over 15 years, I have found that the best way to improve MF process run time is to adapt and execute a full offensive approach with a focus on the upstream production processes.”
This offensive approach would include the evaluation of all negative impact factors that are being introduced into your waste stream. The goal is to remove these components from the waste stream to the best of our ability before they are introduced to the filters. 这些负面影响因素包括:
- Organic components and or other surfactants are usually found in heavily chelated cleaners;
- 光亮剂/润湿剂;
- 油基生产工艺.
If this offensive approach is not an option for you — and for any number of different reasons that may be out of the operator’s control — we can also achieve improved run time by focusing on three main MF cleaning processes. 三个主要的清洗过程包括一个淡水推冲洗, 清洗液浸泡, 清洗液循环.
淡水推洗
A freshwater push rinse is a process of pushing freshwater through the filters — and each train — from front to back. Most of these systems have a freshwater feed already designed into the system for this reason. 如果您没有此选项, it can also be manually pumped through the system from a separate freshwater tank. This will allow most of the heavily concentrated solution sitting in the filters to be pushed from front to back and through each train. 这个过程从开始到结束只需要几分钟, and its benefits could potentially help work to fight fouling and or promote more consistent and efficient cleaning results
清洗液浸泡
实际清洗过程的第一步是将清洗液浸泡, which is designed to attack and help break up the concentrated solution that has built up on the membrane surface. A successful soak for many hours will help ensure a proper circulation process that will follow. 作为锌板, I would start with a 5% to 8% hydrochloric acid solution that would be pumped through the filters until each train was completely full. I would recommend a soak time of 8 to 12 hours based on the daily flow of 15,000 GPD. 如果可能的话, it is also a good idea to drain the spent hydrochloric acid solution and replace it with fresh HCL if time allows after a freshwater push rinse is again executed.
清洗液循环
The next step is the cleaning solution circulation process that allows you to circulate fresh cleaning solution that is feeding from the clean holding tank through the membrane filters inside to out under a small amount of desired pressure by adjusting the drain values slightly. 不超过MF供应商的规格. If this circulation process is executed correctly and the proper equipment is available, the circulation can run automatically and safely for extended amounts of time and free up the operator to do other things. If time allows — and you are able to do so — it is always beneficial to drain the spent cleaning solution and conduct a freshwater push rinse before replacing it with a fresh cleaning solution.
Once both the initial acid circulation and soak processes have been completed, I would then recommend specifically targeting other components that are common in the waste stream, 比如其他金属或有机成分. It is also typical for plating facilities to follow the HCL solution with other acids such as sulfuric to ensure that other trace metals do not build up in the filters.
I would again recommend multiple freshwater push rinses to flush out the system if it is possible. I have learned that the extra push rinses also help in the removal of foreign material that may not have been visible to the naked eye during processing. Once you have determined the acidic portion of the cleaning process is completed, I would then safely and properly repeat both the soak and circulation processes with cleaning receipts such as peroxide or bleach to target the organics surfactants that have built up inside the filters from the plating processes additives. The organic cleaning is just as important as the metal cleanings; if the organic and metal concentrations have not been properly and completely cleaned out, they will assist in further fouling of the filters and a reduction in discharge flow and run time.
I have found that in the world of wastewater, a one-size-fits-all approach is never successful. Every MF system is different in its design and capabilities; therefore, the above recommendations will need to be tailored to fit your specific situation. The implementation of these techniques and good practices will help promote improved MF process run times while reducing the number of cleaning cycles per week.
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