Help with well casing corrosion/buildup 1

[waterwellguy]

I have a monitoring well the is 6" in diameter and 2000' deep. It produces water similar to seawater, except high SO4. A black, hard, sulfurry-smelling material has built up on the inside of the casing and choked off flow from the well. The well typically sits idle - pumped about one day a month. Any idea what the material that is building up is likely to be and how I might prevent furher buildup? Any help and a point in the right direction would be appreciated.

 

[unclesyd]

Sounds like you MIC. Get a sample and have it checked for bacteria. You probably have both SRB's and Iron Bacteria.
You need something done prior to the well becoming completely blocked.
Remediation of your well is going to be quite expensive.
Once the well is cleared it is extremely hard to keep the bacteria under control. I would make sure you get someone with expertise in this area.

Come back with a little more information about the conditions at the well head , like temperature and pressure.
Is the well free flowing?

 

[waterwellguy]

Temperature at the wellhead ranges from 35 to 95 degrees, probably averages 80 degrees. The well is artesian and probably has about 5 psi of pressure on it. Yes, remediation will probably run me $30,000 - not cheap.

Here is another one. I have a well that is used for disposal of secondary treated effluent - deep injection well. The well is 3,000 feet deep and 24" in diameter. The wastestream does have some salinity to it due to infiltration of seawater into the sewer pipes. A very rough, mineralized material has developed on the inside of the casing that has resulted in increased operating pressures. Temperature is about 70-90 degrees year-round. Operating pressure is about 40 psi and increasing as the material continues to buildup. The buildup seems to be worst on the shallow portions of hte well. Is this also a bacterial problem or am looking at something different?

 

[EdStainless]

Your second issue is probably a mineral scale. Remember some materials become more soluble with increasing temperature and some tend to precipitate faster. Find out what it is before you try to clean it.

Your first one may be MIC related, but the material is going to be mostly iron sulfides. Is the build up worse near the top? You may need to look at using lined casing for some sections of the well.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[unclesyd]

You are probably looking a different scenerio on your injection well. I would recommend again that you get an analysis of the material. The deposits formed by MIC can take on many forms depending on the local enviroment.

Here one of the test kits.

http://www.bti-labs.com/products.cfm

Here is a firm you send a sample to.

http://www.mic-testing.com

As your monitor well is seldom used and you have a place to reinject anything that might be purged from the well I would seriously think about the use of Chromates in this well after you get it cleaned. Chromates are one of the few chemicals that will deter MIC attack. Since your pressure is low it would be very easy to fill the monitor well with a Chromate solution. Our 3 injection wells are SS, both the casing and process, and have a Chromate solution in the annulus.

 

[waterwellguy]

I have had a sample of hte buildup material from the injection well analyzed. It is high in zinc, copper, lead, mickel, molybdomen, and arsenic. I suspect this is a scaling problem. Any idea how to prevent further buildup?

 

[EdStainless]

The two most common approaches:
1. pH control, lower (or raise as the case may be) the pH to keep everything soluble.
2. Use a disperant to keep the particles from sticking to each other and the walls.
There are even some chemicals that mess up the crystalization of the minerals.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[unclesyd]

What levels of the metals are in the process material you are injecting?
What are the Anions present?
What is the flow rate for the 24" pipe?.
Do you have any controls on the composition of the injected stream?

 

[0809]

Two answer could help:
o What is the material (kind of steel) when buildup grows?
o What exactly composition of water there is in such well, any result of analysis?
Waiting for reply

 

[waterwellguy]

Just injecting secondary treated wastewater, so metals levels are low. Zinc - 0.085 mg/L, copper - 0.005 mg/L, lead - 0.001 mg/L, nickel - 0.007 mg/L, molybdenum - unknown, pH is 7.3, chloride - 1200 mg/L, chemical oxygen demand - 26.4 mg/L, sulfate - 262 mg/L. I do not have information regarding anions present. Flow rate in 24" pipe varies from zero (not common) to 6 MGD or about 3 feet per second. Some kind of control on composition could probably be added (injection of chemical to prevent buildup - as long as regulators do not feel it is a hazardous material).
Steel casing is seamless, carbon steel conforming to ASTM API 5L, Grade B.
I really appreciate everyone's input - it is very helpful.

 

[0809]

It’s seams to be a scale, I suppose.
Some important questions more:
Does the buildup grows underwater, on surface of water, at splashed area or where condensation occurs?
Does acid dissolve it effectively?
How does it adhere to steel surface?
Waiting for reply

 

[waterwellguy]

Scale buildup is underwater.
I have not attempted to dissolve the material in acid.
The scale seems to bond to the well casing pretty well, does not come off real easily.

 

[unclesyd]

You Injection well presents an even tougher problem due to the size of the flow and the addition of periods of stagnation. Even though the metals are relatively low the presence of the sulfates are high enough to combine with all of them. I would get the services of waste water service, not the salesman but the chemist. The whole system needs to be analyzed to see if there is possibility of say treating one or two of the component streams to mediate the scaling. I can see several possible options, but a much more detail analysis of the both the physical system and chemistry is necessary.

Here is one company that has several different approaches to waste water treatment. They may not be able to help but can point you in the right direction.

http://www.proenv.com

I mentioned chromates in a previous post for the problems in the monitoring well but as you mention someone may not like this approach so here is an different approach to control bacteria if present. It is the use of ClO2. The website is in China but the information is very good.

http://www.clo2.net/en/thesis/thesis.phtml

I am digging through my files to see if I have any infromation left on the treatment of low level of metals in waste streams.

 

[0809]

I agree with „unclesyd” the problem is with periodical not contentious water receiving. There are at least four remedies.
1. (pointed out previously by unclesyd and others) is to find out sufficient and acceptable water treatment
2. you can also consider to find a minimal flow or maximal time intervals which “naturally” prevents buildup and in fact add simple equipment e.g. to recycle water once a week
3. also using an other material which would not allow to grow scale on it in such environment
4. design a special pre-using program including a rehabilitation of well directly before using it
Everything from above requires further examinations.
Best regards