[Community_garden] response to question about biosolids - plus antimicrobial contaminants

Fri Mar 14 16:11:38 EDT 2008

Thanks Kriste and others for the clear and interesting discussion - 
there is another issue that is considered an emerging problem with 
biosolids and is related to domestic as well as commercial sources. That 
being the accumulations of antimicrobials found in the sludge component 
and the high percentage of those compounds that survive both anaerobic 
and aerobic processes.

"Whats known and whats unknown" about this small molecule contamination 
is what stopped me personally from using biosolids in my own garden, and 
I think needs to be part of everyone's considerations. My particular 
concern is introducing and accumulating antimicrobial into the soil 
colony while not knowing the effects those introduced compounds have on 
soil bacteria (particularly the nitrogen fixing varieties), or knowing 
the effects (or lack of) of soil bacteria on the introduced compounds - 
which are designed to remain stable and functional.

I have included a partial quote and some links for those interested in 
pursuing the trail into current research.

regards,

Darrol

A quote from: Science Observer Jan-Feb 2007 issue
http://www.americanscientist.org/template/AssetDetail/assetid/54434

"/More than a million pounds of antimicrobial chemicals from soap and 
other products flow into the nation's sewers every year. Do these 
compounds pose a risk? Product manufacturers say no, pointing to data 
that show only traces of the two most common antibacterials, triclosan 
and triclocarban, in treated wastewater. What happens to the remainder 
is less certain. The stock explanation has been that the majority is 
broken down during the treatment process. The fraction released into 
surface water was thought to meet the same fate sooner or later. Thus, 
much of the claim that these products are safe rested on the fact that 
they were rendered harmless in treatment plants or just beyond. /

/New data puncture that conclusion: 50 percent of triclosan and 76 
percent of triclocarban remain unchanged by aerobic and anaerobic 
digestion in a typical wastewater facility, according to a pair of 
recent reports. This large intact fraction isn't going out with the 
treated water---the old estimates are correct in that respect. Rather, 
it is trapped in the sludge at the bottom of the treatment tanks. Most 
of that sludge gets spread on the ground to fertilize pasture, forests 
and human food crops./"

http://toxics.usgs.gov/regional/emc/municipal_biosolids.html
http://pubs.acs.org/subscribe/journals/esthag-w/2006/sep/science/nl_composting.html
http://toxics.usgs.gov/highlights/earthworms.html

Kristen McIvor wrote:
> Hi all,
>
> I'm writing in response to the question about the safety of biosolids  
> for community garden plots.
>
> Yes, biosolids is the polite term for the solids left over after the  
> wastewater treatment process.  Prior to the Clean Water Act's passage  
> in 1971, most solids (poop) went out into nearby bodies of water.   
> Now, federal regulations require that municipalities separate and  
> treat their biosolids, and there is almost 40 years of research on  
> how to do it well.  They are tightly regulated by the EPA for  
> pathogens, vector attractants (how bad it stinks), and heavy metals.
>
> In 1993, there was an amendment to the law that created different  
> classes of biosolids:  Class B, Class A, and Class A "Exceptional  
> Quality".  Class B is subject to regulations and requires a permit to  
> use, but is routinely applied to farmland (true, not organic farms).   
> It is rich in organic matter and serves to replace petroleum-based  
> fertilizer at low cost to farmers.  Class A is treated to a higher  
> standard (often processed twice), is free of pathogens, and approved  
> for home use by residential customers.  Class A "Exceptional quality"  
> biosolids are an even higher class - free of pathogens and also  
> adhering to even stricter standards for reduction of heavy metals.   
> (Both Class B and Class A meet heavy metals standards that are  
> already quite low - and certainly safe).
>
> The research shows thats the prescription drugs, solvents, etc. that  
> end up in the wastewater system break down rapidly in an aerobic soil  
> environment.  The bacteria that "digest" sewage are really  
> remarkable, and can break down the complex molecules that form many  
> of the "compounds of concern" - endocrine disruptors from birth  
> control pills, for example.  The real problem with environmental  
> toxins in wastewater treatment is in the wastewater.  Because things  
> in water are in an anaerobic environment, they don't break down as  
> quickly, and can cause problems for fish and other wildlife.  We want  
> those compounds to end up in the biosolids because the bacterial life  
> that exists in biosolids (and in healthy soil) knows how to take them  
> apart.  (Heavy metals can't be taken apart, then must be kept out in  
> the first place, which requires a good source control program).
>
> Sewer treatment plants act as the liver of the city, digesting many  
> of the compounds that we humans, in our love of chemistry, have  
> released into the environment.  There is much research taking place  
> on how to improve the work, but the process as it stands today is  
> remarkable and under-appreciated by most.
>
> I am not familiar with the wastewater treatment program in your area,  
> but Class A biosolids are safe for home use, including vegetable  
> gardens.  Yes, biosolids as a category are excluded from the National  
> Organic Standards Act, but by using biosolids you are recycling a  
> local product, and in a very real sense, closing the loop in the  
> local food system.
>
> In live in Seattle, WA, and work in Tacoma, WA, where I use the Class  
> A "Exceptional quality" biosolids from the City of Tacoma, (TAGRO -  
> short for Tacoma Grow) in my work with the community gardens of  
> Tacoma, and at home to grow my own food.  The heavy metals in Tagro  
> are lower than background level soil in the Puget Sound region, and  
> levels of lead and arsenic are lower than our region's yard waste  
> compost. (Levels of zinc and copper are higher in Tagro, because  
> those are in your pipes...)  But all are comparable to the soil in my  
> backyard.  Check out www.tagro.com.  It is so popular, that it is not  
> uncommon for demand to outpace supply by mid-summer.
>
> (Yard waste compost is not necessarily heavy metal free, and it is  
> not subject to the strict testing that biosolids are.  Still, it's a  
> good product to reuse for all the same reasons one should use reuse  
> biosolids)
>
> As cities work to become more sustainable, it seems to me that the  
> beneficial reuse and recycling of organic matter close to home is an  
> important step.  We won't always have someone else's backyard in  
> which to dispose of our messes, and transporting it far away is  
> getting more and more expensive every day.
>
> I hope this didn't turn into a soapbox!  I'm happy to answer any more  
> questions that you have.  Email me at kristenmcivor at mac.com.
>
>
> I strongly recommend against it. "Bio-solids" is nice talk for  
> treated human
> waste from the sewer plant. (What's "Class A"? Poop from expensive
> neighborhoods?!)
>      This stuff is rife with the residues of prescription drugs (at much
> higher levels than the current drinking water scandal, especially
> antibiotics) and its contaminated with motor oil, solvents heavy  
> metals and
> other bad things idiots and criminals pour down the drain.
>      I don't think its safe.
>      I would not let children or people with any kind of illness near  
> it; and
> it is forbidden for use in organic agriculture. See if you can get  
> that yard
> waste they mix it with, but all by itself; that's the best kind of
> compost...
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