RO fouling in Tanzania
Question: I’m having problem with our RO system. We process brackish well water, TDS 890 ppm to pure drinking water. The system is designed to process 5,000 liters of purified water per hour. In the beginning it did, but after processing 200,000 liters, permeate output has been reduced to 2,000 liters. The suppliers have done chemical cleaning on the membrane and also a phosphoric acid cleaning for manganese, but the output has still remained the same. In my opinion, I think we have a case of membrane fouling. What are the possible causes of membrane fouling and please advise if you think it is otherwise?
Murtaza Jessa, Operations Manager
A-One Products & Bottlers Ltd.
Answer: You may need some form of pre-treatment to protect your RO unit. Activated carbon can remove organics, and organics and other waterborne contaminants can foul RO. Possibly an activated carbon adsorption system in front of your RO would solve your problem. Additional pre-treatment may be required, such as sediment filters, to create a graduated reduction process. In the end though, because of the cost of RO membranes, you want to reduce the full load on the membrane to preserve it as long as possible. It’s cheaper, usually, to replace pretreatment filters.
Copper often the culprit
Question: Mechanical Systems, a Cheyenne, Wyo., contractor installed the plumbing in a new house approximately three years ago. Since the beginning, the homeowner has experienced blue/green staining of their plumbing fixtures and their daughter’s hair. The house is on city water, which has a pH of approximately 7.4. None of the other houses in the area are experiencing similar problems. A water analysis was done and it showed slightly elevated levels of copper. We have checked for potential electrolysis and everything is isolated. The anode rod in the water heater is magnesium. Any idea of what the problem may be and how to fix it? Everything was OK with the homeowner until green hair for teenagers went out of style.
Answer: We ran an article on this topic in our January 2000 issue (“Solving Blue-Green Water: What It Is and How to Deal with It,” by Larry Henke). We also ran in March 2001 a related article, “Copper Pipe Leaching and Proper Electrical Grounding,” by Pete Ostwald, who we ran a “Dealer Profile” on in our July 2000 issue. If you have further questions other than what the articles provide, Ostwald is from Albuquerque, N.M., and can be reached at Peteostwal@aol.com; Henke, senior technical director at Minneapolis’ Robert B. Hill Co., is on WC&P’s Technical Review Committee and can be reached at firstname.lastname@example.org