Re: radioactivity in sewer sludge

[High Plains Drifter <magna1@jps.net>]

scott dennerlein wrote:
> 
> People are correct in assuming the majority of the radioactivity input
> to Publicly Owned Treatment Works (POTW's) is from drinking
> water/irrigation, however this material is by nature soluble, i.e. it
> entered the system as water and it leaves as water. The POTW's job is to
> remove biosolids, kill pathogens, and let as much water as possible pass
> through the system. The problem is insoluble material being "screened
> out" in settling ponds and clarifiers,  reconcentrated, and removed as
> dewatered sludge. Hence, the NRC'c prohibition on insoluble,
> non-dispersible discharges. The sludge is either ashed and landfilled,
> or applied to land as fertilizer.

Non dispersible and soluble is two different things.  Given
time and the right circumstances soluble materials will
disassociate with water.  The NRC solubility requirement is
questionable, since a certain amount of uranium oxide can be
discharged by a licensee.  I don't remember uranium oxides
being all that soluble.

>     The NRC's "Site Decommissioning Management Plan" (NUREG-1444) has a
> good summary of the contamination at the NE Ohio Sewer District. Levels
> of Co-60 in soil ranged up to 9,000 pCi/g. Nothing to sneeze at for
> those of us working to attain levels of 5 pCi/g at many environmental
> sites!

Yes, they range up to!  With the majority being relatively
low.  Note that if no action were taken the final
disposition of the material makes 9,000 picoCuries per gram
an insignificant contributor to the over all radioactivity
of landfills or agricultural lands due to dilution with
other materials.

> There has been ten to fifteen incidents of contamination at
> POTW's over the last few decades, most of which were readily traced back
> to the "offending" company. This may or may not be alot depending on
> your point of view.

Really an insignificant problem from a radiation protection
perspective and reoccurrence rate.

> However, all of these sites were discovered by
> "accident" setting of alarms at the landfill, or during remediation of
> nearby licensed sites. 

Evidently our release limits are way to low.  It is common
knowledge that waste site radiation detectors are set way to
low for the risk presented by putting some NORM or cobalt-60
in a Class-C landfill. Its the NIMBY reaction.

>That is why a nationwide screening program is a
> good proactive approach to determine the extent of the problem.

Yeah, just like the Radon screening program.  Its a knee
jerk reaction to a few poor performers.  

> As far as regulatory control is concerned, regards the Ohio incident,
> the contaminee? was a manufacturor of Co-60 therapy units. The
> requirements for their decommissioning fund may have been too low.
> Rather than lower discharge limits, perhaps requiring greater amounts of
> money to be set aside for decommissiong, to include cleanup of the local
> POTW, may be appropriate.

The source has been removed! The POTW will eventually clean
its self up by natural means without human intervention. 
Keeping discharges ALARA will go farther to reduce the
future burden on cleanup, which by the way will eventually
include background levels of radioactivity.  If a true risk
perspective is not applied, instead of knee jerk reactions,
to cleanup and radiation protection practices the Helen
Caldicott's and Alex Baldwins will dictate the limits.

Doe anyone know what decommissioning criteria they are using
for the Ohio site.  It sounds like they are using the old
cobalt requirement which was pre-Marssim(?).  

High Plains Drifter (aka Devils Advocate)
magna1@jps.net
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