The expanding reach and continued impact of our magazine is attributed in part, to our vast knowledge of the water industry. WC&P brings the cutting edge of technology to water industry professionals in over 114 countries who rely on our expertise and accuracy. We receive letters from around the world and members of WC&P’s Technical Review Committee are always happy help. This month, we’ve expanded our Ask the Expert forum to include questions on a variety of topics. If you have a question, concern, or comment, we welcome your input.

Seawater purifiers

Question: We are based on the island of Malta in the central Mediterranean Sea. Please give me some contacts of company’s that sell large purifying machines for water.

Coralline Stone, contact for Victor Galea
1 Industrial Zone
Valletta Road
Attard p/code bzn 03

Answer: You will need seawater reverse osmosis because the borehole is probably brackish.

C.F. Chubb Michaud, CWS-VI
Systematix Co. Inc.
Buena Park, Calif.

Editor’s Note: Michaud also provided a list of manufacturers and products that would work. We receive questions just like this all the time. Readers can find manufacturers and distributors in our Buyer’s Guide at For those without easy internet access, send us a postcard and we’ll be happy to research the Guide for you.

User manual needed

Question: We have been offered a water-purifying machine but it has no owner’s manual and we have not found any info on the net. The only thing we can copy off the machine itself is that it’s made by Inter-American Development Water Purification Systems with and address in Florida and is a Model V-100. If you could give us a hand, with an email address for this company we would greatly appreciate it.

Guillermo Ortega Chiriboga
Centro Comercial Las Vitrinas
Local 1
Ciudadela Kennedy Vieja

Editor’s Note: Readers, we need your help. Can you identify this company?

Is UV suitable?

Question: My company is looking to install a UV system as a final polishing of treated drinking water prior to final filtering and chlorination. I have found a varying amount of recommended suggestions of the UV dosage required to obtain correct disinfection. Are any U.S. EPA or EU directives or standards that need to be followed or are all standards related to a minimum final water microorganism count? Is 40mJ/cm2 the minimum accepted standard for drinking water or will a lower UV dosage be sufficient? How can one obtain the minimum UV dosage required and are there any standards to follow?


[email protected]

Answer: I recommend against using UV in this application because (1) UV will compromise the effectiveness of chlorine by removing the residual; (2) I believe that with the ozone and chlorine, your disinfection regimen should be sufficient.

Peter Cartwright, P.E.
Cartwright Consulting
Minneapolis, Minn.

Answer: Adenovirus has greater resistance to UV light disinfection than any other known waterborne agent (Meng and Gerba, 1996; Gerba et al., 2002; Gerba et al., 2003). Recent work by researchers at the University of Arizona indicates that as much as 226mW/cm2 is required for inactivation of 00.00 percent of adenovirus type 40 (Thurston-Enriquez et al., 2003).

Kelly A. Reynolds, MSPH PhD
The University of Arizona
Environmental Research Laboratory
Tucson, Ariz. 85706
Lab tests in question

Question: We are having a difficult time securing a clean test for coliform bacteria on a new school site with city-supplied water from a well in Ceres, Calif. We are on test number six and haven not narrowed the scope of the problem yet. Any input or direction would help.

Dan Suegav
McFadden Construction
Stockton, Calif.

Answer: If you are having a problem with positive E. coli results, there are two possibilities: (1) there is E. coli in the water; or (2) there is no E. coli in the water but the test is not being done properly. I would suggest that you have a certified lab come out and take the test for you.

C.F. Chubb Michaud, CWS-VI
Systematix Co. Inc.
Buena Park, Calif.

Answer: If the laboratory performing the testing is using MMO MUG test, there is a potential for false positives. There are a few species that will cause this false positive. I would recommend speciating the bacteria when you get a positive. By speciating, a microbiologist will be able to determine if the organisms in the water are actually coliforms.

Marianne R. Metzger
Blue Marsh Labs
Douglassville, Pa.
Water reuse

Question: Is there a way to wash clothes and re-use/filter the water so that each load doesn’t require fresh water? What about using rain water or drain water?

Dana Bushouse
Waste Reduction Educator
Clackamas County Recycling Partnership
NWSA Americorps Member

Answer: Certainly rainwater could be used for both the washing and rinsing. Because it is naturally soft, it would not require softening. Depending upon how dirty it gets from falling through the air or during collection on the ground, it may required some filtration with cartridge liners. It is possible to reuse the wash water (you may recall older washers that had that capability); the efficacy of this approach depends on the amount of contamination picked up in the wash cycle. Additionally, solids (such as fibers, dirt and soap scum) should be filtered out between wash cycles. To properly rinse the clothes, fresh water should be used in the rinse cycle. One approach would be to use spent rinse water as the wash water for the next load. The barriers are not as much technical as practicality and convenience.

Peter Cartwright, P.E.
Cartwright Consulting
Minneapolis, Minn
Algae problems

Question: In the last five years, we have had volvox appear at our lake and the property owners around it are quite concerned. We are hoping you have some information on volvox that you could pass along.

Kathy Harvey
Office Manger
International Ultraviolet Association
P. O. Box 1110, Ayr, ON Canada N0B 1E0

Answser: Although I’m far from an expert in algae problems in lakes, my guess is that it’s a seasonal problem. I’m sure have the equivalent of county extension agents in Canada and I would get one of them involved. This person would have much more expertise than I have. One of the ways to minimize runoff is to allow about a one-meter barrier of natural weed growth at the shoreline. This not only absorbs most of the runoff, but supposedly inhibits Canada geese from walking onto the property.

Peter Cartwright, P.E.
Cartwright Consulting
Minneapolis, Minn.
Testing for chlorides

Question: We manufacture stainless steel tubes used in heat exchangers for water applications. During the manufacturing process, the tubes are pickled with acids and washed with water. There is a likelihood of traces of dissolved chlorine salts being retained on the tube walls as residual. We want to measure the quantity of these salts inside and out, per square feet area of the tube. Can you guide us on how to perform such tests and how to measure in milligrams per square meter surface?

K. J. Jain
[email protected]

Answer: Fill the heat exchanger with deionized water. Recirculate the DI water through a two-bed deionizer until the water reaches a constant state of purity. The residual chlorides that rinse off of the heater exchanger will be accumulated onto the anion component of the two-bed demineralizer. Chloride analysis of an anion resin is a common test and we routinely offer anion resins with extremely low chlorides to begin with. This scenario will only work if there is enough chloride present in the system to be detected by the accuracy of this method. The anion resin volume would have to be set to gather a measurable amount of the chlorides for analysis.

Larry Gottlieb
ARIES Filter Works
West Berlin, N.J.

Answer: What you are apparently concerned about is the presence of chloride salts that can cause corrosion in stainless steel tubes. The concentration of chlorides can be measured by wiping a known area of the surface (or immersing it) to extract the salts and then analyzing the water for chloride concentration. To be completely sure of chloride removal during rinsing, you may want to use a purified water stream.

Peter Cartwright, P.E.
Cartwright Consulting
Minneapolis, Minn

RO versus filtration

Question: Is there any study or authoritative research available to determine which system is superior for purifying water, RO or regular sediment/carbon filtration?

Amin Amlani
Coolstream Water Systems
Ottawa, Ontario, Canada

Answer: These are two distinctly different processes for two different qualities. With normal tap water, sediment plus carbon will give a better taste but does nothing for TDS. If there are nasties in the TDS, RO offers tremendous advantages. Is RO Necessary? NO. But there are times when it will be better. Is filtration plus GAC adequate? NOT ALWAYS. It all really depends on what is in the water and why it is being treated.

C.F. Chubb Michaud, CWS-VI
Systematix Co. Inc.
Buena Park, Calif.

Answer: The problem is that this is like comparing apples to oranges. Filtration technologies are very effective in removing suspended solids (sediment removal) and activated carbon is equally effective in removing many low-molecular weight organic compounds and gasses. RO is primarily used to remove dissolved ionic contaminants, which neither sediment filtration nor activated carbon adsorption will accomplish. As a matter of fact, sediment filtration and activated carbon filtration are usually used as prefiltration for RO.

Peter Cartwright, P.E.
Cartwright Consulting
Minneapolis, Minn

Answer: There are a number of projects that are out there regarding the purification of water. However to my knowledge, there are no direct comparison studies between RO and filtration for the purification of water, just test reports and results on varying technologies and their ability to purify water.

One example is the EPA / ETV projects for homeland security. There are a number of reports that are currently out there for POU and POE testing for microbial and chemical contaminants in the water. Watts Premier has been involved in this project.  There are a few other companies that have been involved in these projects as well.

In short it has demonstrated that RO membranes provide an excellent barrier for bacteria, virus and cysts.  It also indicated that the RO membrane performed better after 3 – 4 weeks of operation.  There has also been studies conducted on mechanical filtration.  Where standard sediment / carbon block filtration is not capable of obtaining the required log reduction for “purifier” status for bacteria and viruses – there have been advances made in carbon block technology.  Two examples of this is the Watts Premier Purifier block and the Kinetico filter that is in their Purefecta.  

I know through the testing that we have done on our modified carbon block system, we have been able to claim “Purifier” in the state of California with a single stage mechanical filtration system. I know that the Purefecta has also been Cal DHS Certified, however that utilizes a combination of the mechanical filtration block and the RO membrane.

As a side note – where RO membranes have demonstrated excellent reduction for microbial contaminants in the water, it falls short on VOC’s and mercury.  If you look at the chemical reduction test reports on the EPA ETV site, you will see that the addition of a VOC grade carbon block after the RO is needed in order to reduce these VOC’s and mercury. (Where I say RO membranes – I mean those that have been tested for this program, or carry the certification – as not all membranes are created equally)

An additional source of information recently came out – I have attached this below for your information.

National Geographic Germany and Bayer AG challenged research scientists last year to come up with innovative ideas to protect drinking water, committing a total of EUR 250,000 in financial support through the “Global Exploration Fund”.
From the 94 suggestions submitted, nine research projects have been selected to receive funding. The aim of the Global Exploration Fund for “Freshwater” is to supply more people with clean drinking water. The projects to be supported are concerned with research into water recovery and treatment and water studies.

The projects selected for support through the Global Exploration Fund show that a great deal can be achieved with very little investment. “The so-called “slanting hose process” is amazingly simple. This mobile water treatment unit can be rapidly deployed in disaster areas and turns filthy water into drinking water within a few hours,” says Klaus Liedtke, Editor-in-Chief of National Geographic Germany. The process developed by a research scientist from Karlsruhe is based on the chemical treatment of water in a plastic hose that stands on a slanting base. “We have been particularly impressed by simple solutions such as these that protect people from illness and thirst.”

Dr. Wolfgang Plischke, member of the Board of Management of Bayer AG responsible for Innovation, Technology and Environment, is also delighted that the two partners can support new methods of protecting drinking water. “No matter whether the projects we support treat water chemically, biologically or physically, the main criterion at the end of the day is that help is given to people who have no direct access to clean drinking water,” says Plischke. “By promoting innovative research into drinking water protection we can help to solve this global problem.”

94 research scientists with projects in Europe, Africa, Asia and South America applied for the funds. A scientific committee comprising experts from Bayer, National Geographic Germany and the National Geographic Society in Washington selected the nine winners in a multi-stage process. The funds are divided up among the following:

– Hans Jürgen Hahn, University of Koblenz: research into groundwater as a habitat
– Dietrich Maier, Center for Water Research in Karlsruhe: development of a mobile water treatment unit (slanting hose process)
– Heinrich Hühnerfuss, University of Hamburg: cleaning of drinking water with UV light and ultrasound, Pakistan
– Andreas Kappler, University of Tübingen: microbiological removal of arsenic from drinking water, Bangladesh
– Rainer Mohn, University of Münster: rainwater and freshwater management, Ethiopia
– Karsten Schittek, University of Trier: research into water-conserving plant communities, Argentina
– Kai Tiedemann, RWTH Aachen: design of mist catchers, Peru
– Jörg F. Venzke: plant filtration systems for permafrost soil, Siberia
– Herbert Weingartner, University of Salzburg: optimization of ancient systems (quanats) for groundwater distribution, Greece

Shannon Murphy
Watts Premier, Inc.
Phoenix, AZ

RO chemical dosing

Question: I have come across various queries about RO systems and its maintenance and sanitation chemicals. I would like to know more information about these treatment chemicals (how and when to dose, what are the advantages, etc.).

Atul Sonar
Mumbai, India

Answer: Only chemicals such as antiscalants or those used for pH adjustment are continuously dosed in RO systems. Cleaning and disinfection chemicals are used in separate operations when the unit is shut down for cleaning/disinfection. Continuous dosing is accomplished with chemical feed pumps designed for this activity. Virtually all large RO systems require antiscalant dosing and most require pH adjustment (lowering pH with an acid to about 6.0).

Peter Cartwright, P.E.
Cartwright Consulting
Minneapolis, Minn


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