[compost_tea] Tea from biosolids

From: Ted Peterson <ted.peterson_at_tcsn.net>
Date: Thu, 29 Apr 2004 11:50:42 -0700

----- Original Message -----
From: Tim Kiphart
To: compost_tea_at_yahoogroups.com
Sent: Thursday, April 29, 2004 4:07 AM
Subject: RE: [compost_tea] Re: CTTF Report - Tests (and others)


Has anyone actually ever brewed using Class A biosolids? I have wanted to =
do this for the last couple of years but obviously haven't gotten around to=
 it. It quite possibly could be used to prove or disprove a great deal abo=
ut pathogen issues.

Yes. Class A biosolids or EQ biosolids are not a composted product. The d=
ried bulk biosolids are loaded with N and zero carbon. They will heat up j=
ust like compost but to work in a brewer, you need a carbon source. I brew=
ed a bunch of batches using dried biosolids and using composted (mixed with=
 greenwaste) biosolids. For both I used white sugar (carbon source), kelp,=
 and fish emulsion. We then tested the tea at the plant for biomass. The =
composted material showed some substantial growth of bacteria and very litt=
le fungi. The dried biosolids showed only bacteria.

Interestingly, the dried and composted biosolids did show a bunch of critte=
rs normally found in aerated supernate taken directly from an aerobic biodi=
gester. So the aeration of the treated sewage both reduces pathogen count =
to ND and favors aerobic bacteria and protozoa. Fungi was not a factor in =
the material taken from the biodigester.

This supernate (from the biodigester) is about 2 to 4 percent solids and is=
 pumped into drying beds. Testing is done at this time and during the time=
 this stuff is in the biodigester. The water is then decanted from the dry=
ing bed and reprocessed through the plant (secondary processing) where it i=
s eventually discharged into the ocean. As the material in the drying beds=
 dry and gel, tests are taken to ensure that fecal coloforms are not repopu=
lating the drying biosolids. The material in the beds is turned with a fro=
nt end loader or some type of mechanical implement that stirs up the drying=
 material so O2 can get to a lot of the material and exposing stuff buried =
under the crusty top to UV.

While tests showed that the dried material indicated ND for pathogens, the =
pathogens did spike when water was added to the dried biosolids. We noted =
this in our report and it was something new to the plant operators. EPA on=
ly requires they treat the material a certain way and test along the way. =
By the way, the operators were not happy with that finding because if misin=
treperted could lead to fears that existing processing does not adequately =
remove pathogens.

So dried biosolids tested ND but when water was introduced, the pathogen le=
vels spiked. Now this spike was still below EPA but not below British Colum=
bia pathogen limits which are higher. We took the drying material and comp=
osted it per EPA and applied compost tea AFTER the pasturization process wa=
s finished. This tea controled the spikes even though the biosolids were w=
et. I can summarize our findings:

Dried biosolids -- show ND when dried and show pathogen spike when wet.
Composted biosolids -- show ND when dry (< 40 moisture content) and showed =
a pathogen spike when wet.
Dried and composted biosolids treated with compost tea -- No subsequent spi=
ke even though water was added to the material.

The plant has changed how it operates and now is involved in a program to c=
ompost all biosolids. They are phasing in the amounts because we have extr=
eme weather conditions that can thwart composting operations for up to 4 an=
d 5 months at a time. They are brewing tea using a brewer and a recipe I c=
reated for them and using the previously composted biosolids as the compost=
 source. Pathogens are just as controlled using the compost tea, there are=
 no spikes even when the compost is watered or after a short rain. Adding =
inputs to the tea does not create a spike in pathogen growth in the tea. =
 

The compost, mixed with greenwaste, is then treated with PFRP (Processes to=
 Further Reduce Pathogens) according to EPA regulations and more tea is add=
ed after that process to revitalize the composted biosolids. So compost te=
a made from biology found in composted biosolids is used to control pathoge=
ns in newly processed and composting biosolids.

Ted Peterson
EW/SOE



Received on Thu Apr 29 2004 - 15:23:39 EDT

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