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[GreenYes] Re: Best way to deal with sewage sludge


At 10:52 AM 7/8/2006 -0700, you wrote:

>I am asking the group for the thoughts and ideas on the best way to
>handle sewage sludge, have been reading how Toronto can't ship there
>sludge to the USA landfill after Aug. 1st. so please send your thoughs
>and ideas on the best way to handle sewage sludge from Canada and the
>USA. Thanks Keith

I don't think there is a "one size fits all" answer to this
question. The most common means of large-scale sludge disposal are
dumping (landfilling), various forms of "land application," and incineration.

Sludge is full of useful nutrients. But it can also have levels of
metals and chemical toxins that make it inappropriate for use as a
soil amendment/fertilizer. Or, at least, limit such use. Infectious
agents (bacteria, viruses....) are also of concern. The sensible
thing to do is to "close the loop" by managing the quality of the
sludge, by keeping metals and other toxins out of the sewer system.

The "beneficial reuse" thing has to be looked at carefully. For
example, in my city/county (Wilmington, Delaware) sludge is mixed
with coal ash. By magic, mixing two undesirable things creates
something good. The mixture passes some tests related to leaching of
constituents, but of course the metals are still there. Since nobody
actually wants the stuff, it is dumped illegally at a
supposedly-closed landfill under the pretext of landscaping. It is a
scam, but it works because the utility (Conectiv Energy) and the City
together have more political power than regulatory agencies have integrity.

Milwaukee, since 1925, has been selling it's sludge as fertilizer
(Millorganite). It is sold to homeowners as OK for vegetable gardens
and suchlike. (<http:///>http://www.milorganite<http:///>.com Take a
look at the history page and the MSDS.).

Note this data on Millorganite from the state of Washington
(http://agr.wa.gov/PestFert/Fertilizers/ProductDatabase.htm )

Arsenic 7.2
Cadmium 6.1
Cobalt 5.4
Mercury 2.7
Molybdenum 15
Nickel 40
Lead 120
Selenium 5.8
Zinc 760

This article, "Sewage Sludge, Pros & Cons,"
(http://www.mindfully.org/Pesticide/Sewage-Sludge-Pros-Cons.htm)
(Environ. Sci. Technol. A-Pages; 2000; 34(19); but not available
there without a password) is interesting. "When it comes to
spreading sludge on agricultural land, the United States has the most
relaxed standards for metals among developed nations."

Incineration seems obviously undesirable. Is it better to
concentrate the contamination in one place (a landfill) or dilute it
by spreading it all around, creating a lower-level hazard for more
people? I think the only reasonable answer is to clean up the sewer
systems themselves, but eliminating discharges into them that
contaminate the sludge, and flushing out the residual
contamination. But this is no small project for old cities.


Alan Muller



Alan Muller, Executive Director
Green Delaware
Box 69
Port Penn, DE 19731 USA
(302)834-3466
fax (302)836-3005
greendel@no.address
www.greendel.org

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