[GreenYes] Re: Question about grinding of C&D Waste for landfill cover

["gevrenov_epa" <gevrenov.julie@no.address>]

Debra,
The short answer to your question is that this can be very risky.  It's
a complicated issue.  See the following message from my colleague,
Ramon Mendoza, in reponse to your question.


The use of grounded up C&D debris containing gypsum as  alternative
daily cover has the potential for generation of hydrogen sulfide gas if
certain actions are not taken by the landfill operators.   People can
smell hydrogen sulfide at low levels in the air, ranging in
concentration from 0.0005 to 0.3 parts of hydrogen sulfide in 1 million
part of air (parts per million or ppm).  However, at high
concentrations (100 ppm and above), the sense of smell becomes rapidly
fatigued and cannot be relied upon to warn of continous presence of
H2S. Exposure to low concentrations of hydrogen sulfide may cause
irritation to the eyes, nose, or throat. It may also cause difficulty
in breathing for some asthmatics. Brief exposures to high
concentrations of hydrogen sulfide (greater than 500 ppm) can cause a
loss of consciousness and possibly death. In most cases, the person
appears to regain consciousness without any other effects. However, in
many individuals, there may be permanent or long-term effects such as
headaches, poor attention span, poor memory, and poor motor function.
No health effects have been found in humans exposed to typical
environmental concentrations of hydrogen sulfide (0.00011-0.00033 ppm).


This problem is not a new one and has been encountered in Massachusetts
and New Hampshire:

http://www.wasteinfo.com/news/stories/archives/2003/12/NA/N03CB1.htm

http://www.greenquill.com/portfolio/Passing%20the%20Smell%20Test.htm


Gypsum has been identified as a leading contributor of H2S production
in landfills where it is disposed.   H2S is produced in a landfill when
sulfur compounds decompose in the presence of moisture and absence of
oxygen (Ref. 3).  Under anaerobic (absence of air) conditions, sulfate
reducing bacteria produce H2S from the sulfate (SO4-2) in gypsum and
the organic carbon waste materials as follows:

SO4-2 + 2CH2O = 2HCO3-1 + H2S

>From the above reaction, 100 tons of landfilled sulfate has the
potential to produce 35 tons of H2S gas .

Other materials in a landfill can contribute sulfate ions for SRB to
reduce to H2S.  Human and animal waste, wastewater treatment sludge,
paper mill sludge and a variety of items that are commonly thrown away
in  household trash all contain some concentration of sulfate.

The following conditions are necessary for H2S gas to form:

·	Sulfate Reducing Bacteria (SRB) must be present (SRB are widespread
throughout nature, in sewage, pulp mill effluent and landfill garbage).

·	Gypsum (sulfate source)  must be present:  Gypsum board enters
landfills from several different locations, including manufacturing
facilities, construction sites, renovation activities, building
demolitions, disaster debris, and manufactured housing plants.

·	Organic nutrition must be present (carbon source):  Decaying gypsum
board leaches enough sulfate ions and organic matter (e.g. paper
backing on wall board)  for SRB to generate large H2S concentrations.

·	Anaerobic conditions (no oxygen) must be present: Anaerobic
conditions can be produced within landfills when large amounts of waste
are placed together and compacted.  Oxygen will kill SRB .

·	Liquid Water: The biological conversion of sulfate to H2S gas must
occur in saturated or wet conditions.   Water can be present from the
waste and from precipitation.  Surface water run on and run off and
ponding also contribute to a wet environment.

·	 Ideal pH conditions:   SRB thrive in environments with pH between 4
and 9, but the optimum pH is 7.
·	Temperature between 30 and 38 C (86 and 100.4 F) :  There are a few
sulfate reducers that can operate in more extreme conditions, but most
sulfate reducers optimum temperature is in the range of  30 to 38 C
If the above conditions are all present , the SRB break down the gypsum
and H2S gas is formed.  The rate at which H2S is generated depends on
the aforementioned conditions.    When any one of these conditions is
absent, the SRB cannot live and therefore, H2S will not be produced .



The New Hampshire Dept. of Environmental Services (NHDES) has published
(Nov.2004) an Interim Best Management Practices (please contact
mendoza.ramon@no.address for a copy)  which provides recommendations to
control hydrogen sulfide emissions.   NHDES found that using C&D fines
alone as ADC results in significant increase in hydrogen sulfide
generation within an MSW landfill environment.   NHDES recommends
mixing the C&D fines at a 50:50 ratio and/or coal ash to control
hydrogen sulfide generation.

We would also recommend that the C&D fines containing gypsum be kept
from being saturated with water in an anaerobic environment.  USEPA
Region 5 and our Office of Research in Development (CI, Ohio) is
currently drafting a guidebook tell help disposal facilities which
accept C&D debris containing gypsum fines, prevent and control hydrogen
sulfide emissions.    This document should be available by the end of
the spring in 2006.  This document is being put together in partnership
with Bill Turley of the Construction Materials Recycling Association, &
the C&D Association of Ohio, amongst others.

Should you have any further questions on this matter, please contact me
at:  mendoza.ramon@no.address



Ramon C. Mendoza, Environmental Engineer
Waste Management Branch (DW-8J)
Waste, Pesticides, and Toxics Division
USEPA Region 5
77 W. Jackson Blvd. Chicago, IL. 60604
Tel: 312-886-4314, fax: 312-353-4788
mendoza.ramon@no.address


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