Strontium in wastwater - why are there limits?

[BmaninMN]

I've run into an issue where Strontium was found in a wastewater. The wastewater permit (State of CT) has a limit of 2 mg/L.

We found that Strontium is naturally occurring in the diatomaceous earth that we use to precoat our wastewater filter press.

My main question is why would the state regulate Sr? If we cannot obtain a variance for Sr, we will have to investigate other precoat materials. Any ideas there?

 

[RWF7437]

Here is some general information on Sr. It would probably be best to find a different source for the filter precoat ? Would some other diatamaceous earth work just as well?



Strontium
For nuclear batteries in buoys.

Atomic Number: 38
Atomic Symbol: Sr
Atomic Weight: 87.62
Electron Configuration: [Kr]5s2

History
(Strontian, town in Scotland) Isolated by Davey by electrolysis in 1808; however, Adair Crawford in 1790 recognized a new mineral (strontianite) as differing from other barium minerals.

Forms
Strontium is found chiefly as celestite and strontianite. The metal can be prepared by electrolysis of the fused chloride mixed with potassium chloride, or is made by reducing strontium oxide with aluminum in a vacuum at a temperature at which strontium distills off. Three allotropic forms of the metal exist, with transition points at 235 and 540oC.

Properties
Strontium is softer than calcium and decomposes in water more vigorously. It does not absorb nitrogen below 380oC. It should be kept under kerosene to prevent oxidation. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish color with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart a beautiful crimson color to flames, and these salts are used in pyrotechnics and in the production of flares. Natural strontium is a mixture of four stable isotopes.

Isotopes
Sixteen other unstable isotopes are known to exist. Of greatest importance is 90Sr with a half-life of 29 years. It is a product of nuclear fallout and presents a health problem. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxilliary Power) devices. These devices hold promise for use in space vehicles, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is needed.

Uses
The major use for strontium at present is in producing glass for color television picture tubes. It has also found use in producing ferrite magnets and in refining zinc. Strontium titanate is an interesting optical material as it has an extremely high refractive index and an optical dispersion greater than that of diamond. It has been used as a gemstone, but is very soft. It does not occur naturally.

Cost
Strontium metal (98% pure) in January 1990 cost about $5/oz.

Isotope

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Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.


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Last Updated: 12/19/97, CST Information Services Team


Russ Faust,PE
Salem, OR, USA

 

[prodeng]

Try looking it up in the FDA or EPA websites. They have a whole list of chemicals and usually an article or two on research done on that chemical. If it is regulated, it probably shows up in one or both of their lists.

 

[GarySCWSVI]

The following is taken from the EPA web site:

How can strontium-90 affect people's health?
Strontium-90 is chemically similar to calcium, and tends to deposit in bone and blood-forming tissue (bone marrow). Thus, strontium-90 is referred to as a "bone seeker." Internal exposure to Sr-90 is linked to bone cancer, cancer of the soft tissue near the bone, and leukemia.
Risk of cancer increases with increased exposure to Sr-90. The risk depends on the concentration of Sr-90 in the environment, and on the exposure conditions.
What is EPA doing about strontium-90?
EPA protects people and the environment from Sr-90 by establishing standards for the clean-up of contaminated sites, by setting limits on the amount of Sr-90 (and other radionuclides) that may be released to the air, and by setting limits on the amount of strontium-90 (and other radionuclides) that may be present in public drinking water.
EPA uses its authority under the Comprehensive Environmental Response, Compensation, and Liability Act (commonly known as "Superfund&quot to set standards for the clean-up of existing contaminated sites. Cleanups must meet all environmental requirements that are relevant or applicable, including state regulations and regulations issued in connection with other federal environmental laws.
When these types of regulations are unavailable, or not protective enough, EPA sets site-specific cleanup levels. Site-specific standards limit the chance of developing cancer because of exposure to a site-related carcinogen (such as strontium-90) to between one in 10,000 and one in 1,000,000.
EPA's Superfund Radiation Webpage
EPA's Superfund Hotline: 1-800-424-9346 or 1-800-535-0202

 

[aspearin1]

Have you looked at zeolites instead of diatomaceous earth? I have looked at both in my applications, and I found zeolites to be cleaner for the ion exchange benefits.

http://www.stcloudmining.com

is a tremendous supplier of natural zeolite (and it's cheap). Metals analysis on my effluent using the zeolite shows low ppb levels of stronium that we later scavenged with ion exchange resins. Also, I am in the process of using laumontite, another zeolite form (

http://www.magicmineral.com).

These are all dirty entities, and I suggest that you flush your filter press material well before you use them. Make sure it's only the ion exchange that's putting the Strontium and other metals into your waste stream, and not the fines (sub-micron particles and colloids) of your filter press.
-aspearin
P.S.- CT huh? Me too. Good to see a local online! Go Huskies!

 

[saxon]

Bmanin, It's probably due to the problem of bio-accumulation. You see, most municipal treatment plants take the sludge that is generated and reuse/resell it for land application such as fertlizer (wouldn't you just love to eat the strontium uptake from your farm produce?) or fill. When the Heavy metals in this sludge reaches a max. as determined by the USEPA, it must be handled as a Hazardous Waste. In some cases it increase the cost of operating the treatment plant by several million dollars per year. Hence the regulations to regulate it at the source. It's all covered under the Federal Pretreatment Guidelines.

Hope this clarifies the issue.

saxon

 

[chymer]

A possible, inexpensive alternative to Sr. for filter precoating may be bentonite clay. It cost $.12/lb and is readily available. Contact Cetco-Hydron at 1-800-721-3006 for more info.

 

[Muggle]

Bentonite clay you refer to contains lanthanum - which is the flocculating agent for the strontium. Easier to use lanthanum chloride direct - cheaper and takes very little - Orenda Technologies 800-322-1648 supplies most of the lanthanum in the U.S.

Once the lanthanum bonds, you get a large particulate that can easily by mechanically removed using bag or other micron filtration. There are various metalltury firms that will buy the waste material, as the strontium and lanthanum are used in various specialized glass and fiber-optic systems.
Dave/Aquatic Technologies

 

[EScC]

I know this question is nearly fully answered, but i'd like to connect the final few dots of the picture.

First, on the main vector that saxon points out in sludge often finding itself as landspread. The main problem route is the same as the main route for our calcium intake. When dairy cattle extract the vast amount of caluim for milk production from vegetation they'll bring in the strontium right along with it. Milk being a major source of Ca for our population.

There is also the issue of Sr ions entering drinking water downstream, given the rarity of a municipal water system removing this Ca mimicer during treatment.

The insidious thing about Sr is that generally the younger the person the more calcium, per body mass, is absorbed. This is true right back to the fetus stage and nursing infants, that get their calcium from their mother's diet (or formula, that often uses dairy milk as a base). Since it heads into bones and bone marrow, and given the 30 year halflife of Sr90, any Sr90 ingested can easily become a source of radiation you carry with you for a lifetime....however long that lifetime then becomes.