Request on facts and figures regarding MIC in water stagnant systems 3

[Farzin1342]

Dear Colleagues,

As you know, in systems such as hydrants or dead ends of pipeline as well as pipes and vessels exposed to relatively prolonged hydrostatic testing and/or those that use extremely poorly treated water for hydrotesting, a case of internal corrosion can be developed that is called as “Microbiologically Influenced Corrosion”, or briefly, MIC.

In these situations, a widely expected scenario to explain MIC is as follows: as the water used in these cases is more often under-¬¬ treated or even non-treated and thus contain many types of micro-organisms including anaerobic sulphate reducing bacteria (SRB), the out-diffusion of the water which is kept stagnant in these systems, makes the environment become gradually depleted from oxygen. This will be advantageous to the growth conditions by SRB and therefore, due to their activity, corrosion starts-or if due to any reason it has already started, it will be enhanced. The outcome, of course, is inducing locaised corrosion, manifested as pitting and loss of mechanical integrity of the equipment.

In systems such as fire water (hydrants), not only the loss of mechanical integrity is important, due to the formation of pits, the water kept in these systems for fire fighting purposes, will be leaking out and therefore in a case of emergency, the system will not be able to function as expected.

For a research project I am preparing, I am after facts and figures that will support my casem that is how stagnant water and the induced MIC have been able to cause damage and economical as well as ecological problems.

Any help will be as always highly appreciated.

Dr. Reza Javaherdashti

MTU

Qatar University

 

[metengr]

Farzin1342;
Have you conducted a search on the internet for this information?

 

[Metalguy]

Check with EPRI. They have lots of data on MIC. BTW, SRB's can cause damage even when the bulk water is high in oxygen. They live underneath slime layers where the O is low, and are among the worst bacteria for MIC.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[EdStainless]

Here is a group that you can contact for more information also.

http://www.s-p-l-a-s-h.com/index.cfm/ci_id/13651/la_id/1.htm

The are a number of groups that work with the integrity of water systems

http://www.awwa.org/index.cfm?showLogin=N

This is the first one that comes to mind.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[blacksmith37]

I think NACE has a section devoted to SRB/MIC. As pointed out, you sure don't need stagnant conditions for MIC.

 

[unclesyd]

You might want to contact these people for information about your system as compared to a FPS (Fire Protection System).

http://www.bti-labs.com/assets/images/features/Guide to MIC in FPS 2005v2.pdf

 

[hkerfoot]

I believe that sulfate reduction actually _consumes_ H+. (SO4 + 8 H+ = S-- + 4 H2O)
However, anaerobic fermentation of organic matter typically proceeds through the production of organic acids. The onset of such fermentation can promote the production of organic acids before a microbial population to consume the acids exists and the pH goes down. Either sulfate reduction or fermentation of organic matter could be limited by addition of nitrate (depending on your water usage)

 

[unclesyd]

hkerfoot,
I have to disagree with your post when it comes to Nitrates.

Our CTW has one of the worst MIC problems in the country, with the primary bacterial nutrients being , organics, organic acids, nitrates from HNO3 oxidation reactions. Every water treatment company and their brother have suggested nitrates as an preventive additive, it does not work as we already have them, maybe too much at times.
Since we removed the addition of Chromium in the 70's I've seen a periodic table of compounds tried in our system without any success. Our only success has come from changes in the MOC of our heat exchanger.

 

[Farzin1342]

hkerfoot

Nitrates (actually Nitrogen) is a nutrient for all microoragnisms including SRB and I don't understand how your consultants in the past advised using it. Perhaps these consultanst may have thought of something that is technically called as "Bio-competitive exclusion" where by adding nitrate, nitrate-reducing bacteria which are probably present (although 9n relatively l;ow numbers w.r. to SRB) will outnumber sulphate reducing bacteria by using this nutrient, thus leaving the "bad guys", that is SRB, deprived of food. However nice the theory may sound, in practice it may not work well (I have explained it in my book, "Microbiologically Influenced Corrosion-An Engineering Insight", Springer, 2008). The problem can arise if 1) you have no nitrate reducing bacteria in your system and thus you are actually feeding your SRB and add more into already troubled system or 2)the outnumbering NTB will start to produce nitric acid and make corrosion even worse.

Regards,

RJ

 

[rconner]

While I’m not real sure of the context of this inquiry and the specific “systems” referred to, conventional hydrant leads are quite often constructed of cement mortar lined ductile iron pipe. Among the reasons for this choice is the need for dependable supporting and pressure/ restraint strength in these locations, as well as the fact that this piping withstands the quite high flow velocities of fire testing and fighting demands when required. For other good reasons as well, the axial length of the leads [that are contemporarily often of 6” pipe (~150 mm), and thus often smaller in flow diameter than many main lines to which they are now affixed] is typically no longer than absolutely necessary.

Under these conditions, I believe cement mortar lining has generally done a pretty good job for quite a long time in minimizing or preventing the corrosion threat mentioned in even low flow velocities, as well as tuberculation that can accompany same in water conditions amenable to its formation. The mechanisms of this protection have been explained in many references, including a 1985 AWWA RESEARCH FOUNDATION and DVGW-Foschungsstelle am Engler-Bunte-Institut report, “Internal corrosion of water distribution
systems”, as well as

http://www.dipra.org/pdf/cementMortarLinings.pdf

etc.

I guess it should be mentioned as well that “dead ends” at least for common combined potable water/fire protection systems are generally dissuaded in favor of “loops”, e.g. by AWWA Manual M31 and other publications. While I believe this is primarily to offer increased flow capability (where e.g. hydrants etc. can be fed from both directions) as well as more reliability/redundancy in disasters, it also might be argued loops basically keep the water moving at least to some extent virtually all around the loops (and regardless of demand).

 

[blacksmith37]

Maybe there was a miscommunication : NITRITE is a fair corrosion inhibitor (as I remember) in relatively clean water systems.

 

[DefenderJ]

We have practical experience of MIC on our combined fire protection and potable water system, circa 30 years old. Our plant is in Ireland so ambient temperatures typically range from 0-20°C. The piping system is not buried, but on raised supports about 8m high

We get leaks from MIC in ASTM A106 carbon steel piping, typically 6" standard wall. This is most common in:
- dead legs to hydrant valves
- water lines within buildings even thought they are flowing, but perhaps the warmer temperatures accelerate.

The immediate problem of the leak is easily dealt with by a clamp fitted over the pipe. We have had to replace several sections of lines over the past 10 years. When you see a lot of clamps in one area you know it's time to replace the pipe.

The leaks also start fairly small and do not affect the ability of the hydrant to deliver the required amount of water. As the piping is above ground we spot any leaks quite easily.

Our biggest worry is a leak inside a building over electrical equipment - this has the potential to bring the plant down.

 

[bimr]

Actually, hkerfoot is correct.

Sulfate reduction or fermentation of organic matter may be limited by addition of nitrate (depending on your water usage). Nitrogen fertilizer (sodium nitrate) is sometimes added to wastewater force mains to control hydrogen sulfide odors.

http://www.webs1.uidaho.edu/ce432/H2S-NEWEA.pdf

http://www.water.siemens.com/en/app...casestudy_mutiple_odor_control_treatment.aspx

http://www.water.siemens.com/en/pro...rocess_bioxide_odor_control_product_page.aspx

However, this phenomenon is something that occurs in wastewater, not pure water and would be inappropriate for this application.

 

[Guest102023]

I have done a couple of F/A investigations involving MIC, including a plant emergency water system very similar to the system described.
Capturing live bacteria is very difficult, and analysis requires very specialized handling and lab techniques. I was able to conclude SRBs were the culprit only by inference, from the scale analysis and the known (anaerobic) operating conditions (or NON-operating, as the case may be).