Energy Conservation Strategies Commission, Residential
Subcommittee
Guiding Principles (DRAFT)
Alachua County Energy Conservation Strategies
Commission
Waste and Energy Implications Subcommittee
Draft Biosolid Report: Supplement to the Biosolid
Motion
This is a draft of the sludge report. Comments in green are from Bob.
Comments in blue are from Dwight. Citations in blue refer to Dwight’s
list at the end of the paper, and will eventually be merged into the
endnotes. We still need to add a link to the Comprehensive Plan and
improve the organization.
1.1.Summary of Recommendations
The Energy Conservation Strategies Commission recommends
(AFTER THIS IS APPROVED BY THE FULL COMMISSION)
Anaerobic digestion of sewage sludge, which would have the benefits of
(a) providing an alternative source of energy through production of
methane, (b) reducing emissions of various greenhouse gases, (c)
destroying harmful microorganisms in the sewage sludge, and (d)
providing a valuable soil amendment or fertilizer, thereby reducing the
need for commercial fertilizers that are produced from natural gas.
Anaerobic digestion is recommended as a replacement for the current
practice of aerobic digestion and landspreading biosolids. An alternative
procedure, incineration (thermal oxidation) of biosolids, is not
recommended because (a) no energy is produced, (b) the carbon is
released into the atmosphere as carbon dioxide, a greenhouse gas, and (c)
the fertilizer value of the biosolids is lost.
1.2.Definitions and Process Description
The term biosolids was coined by the Water Environment Foundation,
formerly known as the Federation of Sewage Works Associations, to
lessen public objection to spreading sewage sludge on the land[i]. Now it
is used to differentiate between raw, untreated sewage sludge and treated
sludge (biosolids) that might be suitable as a soil amendment of fertilizer.
Anaerobic digestion is the process by which bacteria decompose
organic material into methane and carbon dioxide in the absence of air [ii].
The resulting solid product, called the digestate, has less odor and fewer
pathogens [iii]. When the process of digestion is conducted at
approximately 122–150 °F (50–60 °C), the thermophilic temperature
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Energy Conservation Strategies Commission, Residential
Subcommittee
Guiding Principles (DRAFT)
range, pathogens are killed and the biosolids can attain a Class A or even
Class AA rating [1] [2 I did not see content about the temperatures or
Class in the Warmer Bulletin #100 or the EPA factsheet OK, let’s use 3,
the GRU management plan has info on producing Class AA, also your
previous reference by Wilson et al., although Class AA is a FDEP
designation. ].
Another process for treating wastewater is aerobic digestion, which is
conducted at ambient temperatures and requires air to be pumped into the
water. Aerobic digestion typically requires less time and produces Class B
biosolids, which contain more pathogens than Class A or Class AA
biosolids.
Methane extracted from the anaerobic digestion process can be used to
generate electricity. A rough estimate of the methane produced from
wastewater is 18,250 kg per 1,000 persons per year [iv]. Another estimate
is that the wastewater from one person can produce enough methane to
generate 2.2 watts of electricity [v]. Within the thermophilic temperature
range, one study found that methane output is maximized at approximately
127 °F at which point methane output is approximately three times what it
would be at 135.5 °F and double what it would be at the 95 °F (35 °C)
second-stage temperature recommended by the GRU Biosolids
Management Plan in Exhibit 5-44, and also higher than the 42°C primary
digestion temperature recommended in by GRU in section 5.4.3 [vi, 3].
The large amount of methane produced from wastewater can be
problematic if released into the atmosphere because of its global warming
potential. Both the carbon dioxide and the uncaptured methane produced
during digestion can contribute to global warming, with each unit of
methane producing approximately 23 21 times the global warming
potential of the same amount of carbon dioxide over a 100-year period
[vii]. These gasses absorb relatively more solar radiation than other gasses
do, and the result is a relative warming of the atmosphere [2]. (This is not
correct explanation of the greenhouse effect and is best left out.
Presumably, the overall report will have some brief explanation. I could
give a brief explanation here if desired. See the IPCC Technical Summary
that I cited for that statement. Page 24 contains a brief description of the
global warming process. You can write a summary if you want to, or we
can quote that entire box on page 24 of the IPCC report [or quote another
summary]. We need ECSC direction on where to explain global warming)
The Intergovernmental Panel on Climate Change has determined that
these warming effects threaten to increase average temperatures, change
precipitation patterns, raise sea levels, and increase the frequency and
intensity of extreme weather events [viii].
When used as fertilizer, biosolids must be evaluated to determine
their levels of metals; organic compounds (such as PCBs, dioxin,
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Guiding Principles (DRAFT)
pharmaceuticals, and cleaners); and biological pathogens [ix]. In the
Clean Water Act of 1993, the EPA defined the standards for the allowable
levels of these contaminants [x]. The EPA also has additional reporting
guidelines [xi].
1.3.Management of biosolids in Alachua County
In Alachua County, biosolids are produced from sludge that is treated
by Gainesville Regional Utilities (GRU) at its Main Street and Kanapaha
Water Reclamation Facilities (commonly called wastewater treatment
facilities). The wastewater is collected from the City of Gainesville and
other portions of Alachua County that have GRU sewer service. GRU
provides biosolids treatment and handling for the University of Florida
and the small communities of Hawthorne, High Springs, and Waldo [xii].
The city of Alachua has its own wastewater treatment facility with final
disposal of biosolids on land owned by the city [xiii].
Once some of the wastewater has been separated from the solid sludge,
it has a water content of either 5.3 % or 16.0 %, for “thickened” and
“dewatered” sludge respectively [3]. Because of the difference in water
content, the quantity of sludge is given in dry tons per day, which for the
year 2006 was 13.9 tons per day for undigested sludge or 9.85 tons per day
once it has been digested [3 I can’t find the 13.9 vs 9.85 reference in the
GRU Biosolids Management Plan. what about pdf page 50: 12 tons vs 6
tons; also page 39 OK, it is: Attachment 2: GRU Wastewater Biosolids
Characteristics, GRU RFP 2007-135]. The decrease in mass can be
attributed to the conversion of biosolids to carbon dioxide, methane and
other gasses by the digestion process. The current GRU treatment process
is aerobic in which air is blown through the sludge and the digestion
process decomposes organic material into carbon dioxide and other gases.
After the Class B biosolids are processed by GRU at the wastewater
treatment facilities, they are trucked to Whistling Pines Ranch, a site near
Archer, and spread on the farmland for growing hay using conventional
farm equipment. Adding nutrients such as nitrogen and phosphorus
provided by the biosolids to the soil is considered a “beneficial use” unless
the quantity is too great or there are unacceptable levels of toxins in the
biosolids. A concern is that the nitrogen and phosphorus not exceed the
amount that can be absorbed by the crops being grown [xii].
For the past 25 years, GRU has been landspreading Class B biosolids
on 1175 acres of farmland at Whistling Pines Ranch [xii]. The present
contract expires in 2009 [xii]. Consequently, the City of Gainesville has
proposed to buy the property for GRU so that landspreading can continue
indefinitely [xiv]. Since the land is in unincorporated Alachua County,
application for a Special Exception has been made to the County to allow
this use.
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Guiding Principles (DRAFT)
Today, approximately half of all seven million tons of sewage sludge
produced in the US is applied to farmlands [5].I do not see where these
citations discuss the percent of sludge spread on land, I did find an old
reference from 1998, but I don’t think applies to today: Ok, this number is
not important to us http://tinyurl.com/2a2hgw] Frequently,
nearby residents object vigorously to the practice of landspreading sewage
sludge[yes, but does this apply to the rural area around Whistling Pines?
You betcha, read the newspaper; you could look up the reference to GSun
articles]. The safety of landspreading sewage sludge, which may be toxic
because of heavy metals, radio-nuclides, pathogens, and untreated organic
chemicals, is highly questionable [xv, xvi, xvii]. Some of the organic
chemicals in sludge are known endocrine disruptors such as those that
caused reproductive problems for alligators in Lake Apopka [xviii] . The
EPA regulates only ten pollutants out of many thousand found in sludge
[3]. Paul Gilman, EPA assistant administrator, stated on 60 Minutes that
there is no assurance that landspreading Class B sludge is safe.
The Florida Department of Environmental Protection (FDEP), which
has responsibility for administering EPA regulations in the state, is in the
process of revising its rule 62-640 for landspreading biosolids. A new
subsection, 62-640.100(1)(b), has been added in the 2007 draft that states,
“The Department [FDEP] intends to encourage the highest levels of
treatment, quality, and use for biodsolids” [7]. Although the GRU
Biosolids Management Plan states that new stricter regulations being
promulgated would require treatment to Class A or Class AA, at this point
the rule does not prohibit landspreading Class B biosolids.
1.4. Producing Class A or Class AA biosolids
1.4.1.Composting
The solid digestate produced in biological decomposition of sludge,
either by composting or anaerobic digestion is either Class A or Class AA
biosolids depending on the level of pollutants remaining after treatment.
Composting may be the simplest, low-cost, low-tech process that will
produce these classes [3]. In composting sludge, another component of
waste such as wood chips or yard waste is used as a “bulking agent” to
disperse the liquid sludge and allow air to be circulated through it. With
adequate aeration, the solids in sludge decompose into carbon dioxide and
water, with compost, a solid humus-like material remaining. If aeration is
inadequate, some methane is produced that is undesirable since it is a
greenhouse gas that the composting facility is not likely to capture.
The two most common methods for composting are “the static pile”
and “windrows” [xix]. For the static pile, aeration is achieved by blowing
air through pipes up through the pile. Aeration of windrows is provided
by frequent mechanical turning of the pile. For both of these methods
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Guiding Principles (DRAFT)
energy is required to accomplish the aeration. However, there is a useful
environmental benefit of carbon sequestration when the compost is used in
agriculture or plant growing [xx]. The EPA estimates that the net
greenhouse gas sequestration is 0.05 metric tons of carbon equivalents per
(standard) ton of wet organic material composted [5].
1.4.2.Anaerobic Digestion
The preferred option for managing biosolids is anaerobic digestion that
is carried out in a closed, heated vessel in the absence of oxygen.
Thermophilic anaerobic digestion is carried out at temperatures up to
130 0F with retention times of two to three weeks, which destroys
contaminants except for heavy metals. If industries discharge to the
wastewater, heavy metals may be present in unacceptable concentration
unless pre-treatment of the wastewater is used to remove them. The
presence of heavy metals in biosolids could limit their use to landscaping
and horticultural uses rather than for growing food.
The decomposition produces a gas of about 60% methane and 40%
carbon dioxide, a solid digestate, and “process liquor” [2, xxi]. The
methane might be used for power production at 80% efficiency using
combined heat and power, which EPA recommends []. The waste heat
can be used to heat the anaerobic digestion vessels. A net energy of about
100 kWh per ton is realized, as well as the digestate, which is Class AA
biosolids, a valuable soil amendment [, ].
Although GRU has objected to suggestions that they switch to anaerobic
digestion as not being “cost effective.” In contrast, Jacksonville Electric
Authority (JEA), changed to anaerobic digestion in 2002 [xxii]
Following the anaerobic digestion step, JEA dries the biosolids to produce
pellets, which are then taken by an Alachua County firm,
GreenTechnologies to make into GreenEdge, an organic fertilizer
marketed in various outlets [xxiii].
Anaerobic digestion of waste to produce methane is an increasingly
important way to provide an alternative to fossil fuel. It is being used in
various European cities to power city busses, on farms to supply power
need to operate the farm with energy left over to sell, in various locations
to produce energy from food waste, etc. [xxiv] [article] Live Oak, FL has
switched to anaerobic digestion to save almost one megawatt of electricity
that was previously used to operate the aeration pumps in the old aerobic
digestion process. [citation needed I gave out a copy of web article about
Live Oak at the Feb 12 meeting. It is important to keep this as an
indication of a small city that made the switch. ]
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Energy Conservation Strategies Commission, Residential
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Guiding Principles (DRAFT)
Anaerobic digestion of waste for energy with use of the digestate as a
fertilizer is a good example of fully closing the recycling loop on this
“problem” waste.
Thermophilic anaerobic digestion would have the following positive
effects relative to aerobic digestion currently being used.
1.5.Energy Analysis of Aerobic Digestion

1. Energy saved by avoiding aeration (~ 2-3 megawatts) [estimated from
].
2. Energy content of methane produced by anaerobic digestion using
combined heat and power (~1 megawatts) [9 the EPA fact sheet does
not tell us how much electricity can be produced at a given GRU
facility. Of course not, the fact sheet gives general information, which
applied to GRU gives 1 Mw.].
3. Savings in energy for thermophilic digestion using ground (or
wastewater) source heat pump for heating of up to 50% [14]. the
references here are about savings for home heating and cooling, not for
for heating sewate to 127 degrees F Heat pumps are devices that can
heat for whatever purpose, including water heating to well over 127
degrees. .Use: “Turning waste into gold in the future cityscape,” by
Stephen Salter, Watershead Sentinel Sept.-Oct. 2007, p 16, which has
a diagram with a heat pump heating sludge.
4. Reduction in carbon dioxide, methane and other greenhouse gases
released in aeration, at least 4 metric tons of carbon equivalents per
day. Assuming a global warming potential for methane of 23 23
(change other 23’s below) [2], and assuming that approximately 60%
of the gas is methane and 40% is carbon dioxide2:
23  4  .6  .4  4   56.8 metric tons per day of carbon equivalents
for greenhouse gasses produced.
5. Reduction in amonia and methane from landspreading of biosolids [xii
I didn’t see any occurence of “amonia” or “NH3” in the GRU BMP].
6. Savings and reductions in greenhouse gas emissions associated with
the burning of fossil fuels need to truck sludge to the Archer site and
spread the sludge [15]. [if you don’t make a specific claim about the
amount of the savings, we can skip the citation The number was not
large, but since Sean calculated it, I would include it.]
7. Savings from the capital cost of the trucks ($436,000) and spreading
equipment ($1,082,500) needed to haul the sludge and the rental of
another truck from Whistling Pinnes ($30 per hour) [3].
8. Production of Class AA biosolids would eliminate health concerns
with pathogens and other toxic substances in Class B biosolids.
9. Class AA biosolids would be useful for replenishing soil carbon for
landscaping, soil amendment and plant growing by the City, County or
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Guiding Principles (DRAFT)
private sector. and would reduce the need for artificial fertilizer
produced from natural gas.
The economics of anaerobic digestion should take into account the
$11.5 14.1 million [xii The difference in capital costs between Exhibit 511 and5-12 is 14.1 million, which would seem to be the cost of the land.
The differences in total capital cost from the last two pages is around 1012 million--is that what you used? Those numbers do include the capital
cost but the AND model does not include the cost of producing Class A
biosolids The cost of the land of $11.5 M has been given in newspaper
articles and in presentations by GRU to City commission.] saved by not
purchasing land for landspreading Class B biosolids. A few years ago,
JEA implemented anaerobic digestion with drying of biosolids to produce
Class AA granular fertilizer [11].
1.6.Class AA biosolids as a fertilizer, soil amendment, or planting
medium
(to be done)
1.7.Incineration (burning)
Incineration (burning) was presented by GRU consultants (using the
euphemism terminology “thermal oxidation” instead of incineration) as
an option for disposal of sewage sludge. A recent GRU Biosolids
Management Plan reviewed incineration and other waste disposal methods
but failed to consider the full impacts of greenhouse gassesError!
Bookmark not defined.. The plan for landspreading of biosolids might
also be affected by proposed changes in Chapter 62-640 of the Florida
Administrative Code that require registration of lands, restrictions on
when and where biosolids can be spread, prohibition of spray guns,
prohibition of some stockpiling, and requirements for redundancy of
equipmentxxv.
The request for proposal [16] by GRU, GRU RFP 2007-135 for a
planned biomass-burning generator includes sludge as a possible fuel and
City Commissioners have expressed considerable interest in using this
once the biomass burner is online. Burning sludge would be primarily a
disposal mechanism rather than an energy producing process (as opposed
to anaerobic digestion) since the heating value (Btu content) of sludge is
essentially zero because of the high moisture content. While supplying
little energy, burning the carbon in sludge would add it to the atmosphere,
producing 10-15 metric tons of carbon equivalents per day [3]. Thermal
oxidation, although allowed by environmental regulations is not advisable
since (a) no energy is produced, (b) the carbon is released into the
atmosphere as carbon dioxide, a greenhouse gas, and (c) the fertilizer
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value of the biosolids is lost. Because of the cost and the carbon output,
incineration is not recommended.
(OLD) References
1.
2.
3.
4.
5.
Private communication, Arthur Saarinen, P.E., Retired Environmental (wastewater) Engineer.
“Wastewater Fact Sheet,” EPA: epa.gov/chp/markets/wastewater_fs.html.
“Municipal Wastewater Treatment Facilities,” EPA:
www.epa.gov/chp/markets/wastewater.html.
Dr. Amir Varshovi, GreenTechnologies.
The solid content in GRU undigested sludge is currently 13.93 dry ton/d.
New references to add to yours (delete Saarinen reference, it is too
complicated to do and others suffice).
1. Wikipedia (your 1 also)
2. Anaerobic Digestion Information Sheet, Warmer Bulletin,
www.residua.com.[which issue? #100?]
3. GRU Biosolids Management Plan (there is an URL that can be listed).
4. (City of Alachua, same as your xii).
5. A. A. Rockefeller, Sewers, Sewage Treatment, Sludge: Damage Without End,
New Solutions, Vol. 12(4) 341, 343 (2002); Joel Bleifuss, Nightmare Soil, In
These Times, Oct. 12, 1995, at 13-14; Sheldon Rampton and John Stauber,
Toxic Sludge is Good For You: Lies, Damn Lies and the Public Relations
Industry, The Sludge Hits the Fan [PAGE] (1995) at www.riles.org/sludge.
6. (your xiv)
7. The Biocycle Guide to Yard Waste Composting, The JG Press, Inc, Emmasus,
PA, (1989).
8. Solid Waste Management and Greenhouse Gases, EPA (URL available).
9.
“Wastewater Fact Sheet,” EPA: epa.gov/chp/markets/wastewater_fs.html; “Municipal
Wastewater Treatment Facilities,” EPA: www.epa.gov/chp/markets/wastewater.html.
10. http://www.jea.com/business/services/prodandserv/byp
roducts/byproducts_sewer.asp].
11. Emil Varshovi, GreenTechnologies, presentation to WEIS, (check minutes
for date)
12. Stephen Salter, Modern Alchemy, Turning Waste into Gold, Watershed
Sentinel, Sept-Oct. 2007.
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13. GRU’s power consumption at its wastewater treatment facilities is 4 MW.
Although there is no separate data for aeration, over half is required for this.
(Public Records).
14. www.energystar.gov/index.cfm?c=geo_heat.pr_geo_heat_pumps;
www1.eere.energy.gov/geothermal/pdfs/26161a.pdf;
www1.eere.energy.gov/femp/procurement/eep_groundsource_heatpumps.html
15. (Sean did the calculation for energy used by sludge hauling truck)
16. GRU RFP 2007-135, Biomass Energy Supply.
i
Wikipedia (2008). Biosolids. Retrieved from
http://en.wikipedia.org/wiki/Biosolids
ii
Environmental Protection Agency (2006). Biosolids Technology Fact
Sheet: Multi-Stage Anaerobic Digestion. Retrieved from
http://www.epa.gov/owm/mtb/multi-stage.pdf
iii Water Environment Federation (2004). High Performance Anaerobic
Digestion (White Paper). Retrieved from http://www.wef.org/NR/rdonlyres/4D51F55C2CDD-42A0-AB9C-D77C4139F51C/0/AnaerobicDigestion.pdf
iv
Department of the Environment, Water, Heritage and the Arts (Australia;
1997) Methane Capture and Use–Waste Management Workbook. Retrieved from
http://www.environment.gov.au/settlements/challenge/publications/methanequickref.html
v
Environmental Protection Agency (2007). Wastewater Fact Sheet: Energy
Savings and Energy Reliability for Wastewater Treatment Facilities. Retrieved from
http://epa.gov/chp/markets/wastewater_fs.html
vi
C. A. Wilson, S. M. Murthy, Y. Fang, and J. T. Novak (2007) The Effect
of Temperature on the Performance and Stability of Thermophilic Anaerobic Digestion.
Conference paper from Moving Forward: Wastewater, Biosolids Sustainability:
Technical, Managerial, and Public Synergy. Retrieved from
http://tinyurl.com/246shu)
vii
J. T. Houghton, Y. Ding, D.J. Griggs, M. Noguer, P. J. van der Linden and
D. Xiaosu (Eds.) (2001) Contribution of Working Group I to the Third Assessment
Report of the Intergovernmental Panel on Climate Change (IPCC): Technical Summary.
Cambridge University Press, UK. Retrieved from http://www.ipcc.ch/pdf/climatechanges-2001/scientific-basis/scientific-ts-en.pdf
viii
Intergovernmental Panel on Climate Change (2007). Climate Change 2007:
Synthesis Report. Retrieved from http://www.ipcc.ch/ipccreports/ar4-syr.htm
ix
Suzanne R. Jenkins, Carl W. Armstrong, and Michele M. Monti (2007).
Health Effects of Biosolids Applied to Land: Available Scientific Evidence (Virginia
Department of Health white paper) Retrieved from
http://www.vdh.virginia.gov/epidemiology/DEE/documents/Biosolids.pdf
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x
Code of Federal Regulations. Standards for the Use or Disposal of Sewage
Sludge. Title 40, Volume 20, Parts 425 to 699. Retrieved from
http://www.cee.vt.edu/ewr/environmental/teach/gwprimer/group09/503reg.htm
xi
Environmental Protection Agency (2006) 2006 Integrated Report
Guidance. Retrieved from http://www.epa.gov/owow/tmdl/2006IRG/
xii
C2MHILL (2007). Draft Final Biosolids Management Plan. Retrieved
from
http://www.alachuacounty.us/assets/uploads/images/epd/documents/ECSC/GRU_Sludge.
pdf
xiii
City of Alachua (2007). Wastewater Treatment. Retrieved from
http://tinyurl.com/2aspyl
xiv
Gainesville City Commission (July 23, 2007). Meeting Minutes. Item
070232. Retrieved from http://tinyurl.com/2yjcqr
xv
Hillman, J. P., Hill, J, Morgan, J. E. & Wilkinson, J. M. (2002). Recycling
of Sewage Sludge to Grassland: A Review of the Legislation to Control the localization
and Accumulation of Potential Toxic Metals in Grazing Systems. Grass and Forage
Science 58, 101–111.
xvi
Topcuoglu, B. (2005) Effects of Repeated Applications of Sewage Sludge
and MSW Compost on the Bioavailability of Heavy Metals in Greenhouse Soil. Polish
Journal of Environmental Studies, 14(2) 217–222.
xvii
Bozkurt, M. A., Akdeniz, H, Keskin, B. & Yilmaz, I. H. (2006).
Possibilities of using sewage sludge as nitrogen fertilizer for maize. Acta Agriculturae
Scandinavica Section B-Soil and Plant Science, 56, 143–149.
xviii
Harrison E. Z. et al Sc. Total Env.367 (2006) 481-497.
xix
Biocycle (1989). The BioCycle Guide to Yard Waste Composting. JG
Press: Emmasus, PA.
xx
Environmental Protection Agency (2006). Solid Waste Management and
Greenhouse Gases: A Life-Cycle Assessment of Emissions and Sinks. Retrieved from
http://www.epa.gov/climatechange/wycd/waste/SWMGHGreport.html
xxi
Wikipedia (2008). Anaerobic Digestion. Retrived from
http://en.wikipedia.org/wiki/Anaerobic_digestion
xxii
Jacksonville Electric Authority (n.d.). Sewer Treatment Byproducts.
Retrieved from
http://www.jea.com/business/services/prodandserv/byproducts/byproducts_sewer.asp
xxiii Jacksonville Electric Authority (n.d.). GreenEdge-Fertilizer. Retrieved
from http://www.jea.com/community/stories/greenedge.asp
xxiv Salter, S. (2007). Modern Alchemy, Turning Waste into Gold. Watershed
Sentinal, September–October. Retrieved from
http://www.watershedsentinel.ca/documents/ModernAlchemyWS.pdf See also
http://www.georgiastrait.org/files/share/PDF/UVic-Waste-to-Gold.pdf
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xxv Florida Department of Environmental Protection (2008). Draft 62-640
Biosolids. Retrieved from
http://www.dep.state.fl.us/water/wastewater/dom/docs/draft_62-640_2-21-07.pdf
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