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Waste disposal and
decomposition
Options for sewage disposal
Landfills: problems with cost,
availability,
ground-water pollution,
liquid content,
methane production.
Incineration; problems with location, NIMBY,
Not In My BackYard
Oceans: the “Victoria” solution,
Seattle’s Lake Washington and
Puget Sound experience.
Some developments leading to recycling
In the 1950’s demonstration by Professor Tommy Edmondson
that the Lake Washington ecosystem had been substantially
changed due to discharge of effluent. Nitrogen pollution
In 1958 voters in Seattle and King County created Metro, an
agency charged with creating a regional wastewater treatment
system.
In 1966 construction of a primary treatment plant completed at
West Point with discharge into Puget Sound.
1972 Federal Clean Water Act
In 1972 first biosolids applications at Pack Forest
In 1991 Metro begins an expansion of the plant West Point plant
Recycling
The principle is: (1) to use a treatment plant to remove
soluble nitrogen from the effluent and kill pathogens,
and (2) to apply the solid processed from bacterial
matter to agricultural fields, forests, and land requiring
re-medial treatment
There are problems associated with:
Quantities and collection
Biology and engineering of treatment
Recycling through biosolids application
Quantities and Collection
In King County 95% of the wastewater is from homes and
businesses, with only 5% from industries
At the West Point plant:
Total Suspended Solids loading (average annual) 181,000 lbs/day
Biosolids produced 53,409 wet tons; 13,277 dry tons per year
Reclaimed water used 0.61 mgd
Electricity generated 7,437,972 kilowatt hours
Outfall 3,600 ft. offshore; 240 ft. deep; 500 ft. diffuser
Annual budget for King County: Operating, $82 million; Capital, $96 million
Two waste water treatment plants in King County
Average daily capacity of the West plant is
133 million gallons per day
Biology and engineering of treatment
Most organic matter is converted by micro–organisms to
inorganic forms. This process is called mineralization.
Large molecules will first be broken down to smaller ones by
bacterial exo-enzymes, enzymes that bacteria excrete.
The most important organisms involved in these conversions are
heterotrophic bacteria.
It is extremely difficult to identify bacterial genera, let alone
species, from water purification systems, but it is obvious that
the genera Flavobacterium and Pseudomonas are important.
Overview of treatment
West Point Treatment Plant
Screen
Primary
treatment
Skim
Grit
chamber and
settle
solids
O2 + bacteria + dissolved
and suspended organic
Nitrogen
matter
Secondary
treatment
removal into
High Purity Oxygen
activated sludge process biomass
Chlorination
Settled biomass
Methane
Blend
Centrifuge
Thicken
Solids
processing
Heat
Anaerobic
bacterial
digestion
Puget
Sound
Nitrogen is incorporated into microbial biomass. Two types
of bacteria process ammonium to nitrate
Nitrogen metabo;ism
residence times
mean cell
http://bark214-3.berkeley.edu/MCB290/illana.htm
Anaerobic sludge digester
http://bark214-3.berkeley.edu/MCB290/illana.htm
30% of power for the plant
Anaerobic methane production
Electricity sold to
Seattle City Light
Problems!
We do not know the precise composition of bacteria
in either the aerobic or anaerobic processes.
Plating out and culturing provides micro-organisms with a
very different environment than found in the tanks
There is some hope to use new DNA/RNA identification
techniques to identify bacteria and seek ways of improving
processing rates
Increased treatment capacity will be needed
What will happen in the future? A third plant will be added.
But there is resistance to expanding the processing area of
existing plants although their current capacity may be exceeded
350 feet deep processor
Temp and O2
control systems
A 350 feet deep processor is being investigated!!
Recycling through biosolids application
What we do not have!
Some regulations
Seattle Biosolids Applications
The “Cornell” recommendations
What we do not have!
What we need to avoid
Giardia lamblia trophozoites, as
they appear with the scanning
electron microscope. Original
image by Arturo Gonzalez,
CINVESTAV, Mexico.
http://www.biosci.ohio-state.edu/~parasite/giardia_sem.html
Some regulations
The EPA breaks down land application of biosolids into 4
categories: Agricultural lands, Forest lands, Reclamation sites,
and Public contact/Home lawns & gardens. Each land application
category has its own set of requirements according to WAC 173308-210, 220, 230, 240, and 250. Washington state has adapted the
federal EPA rule 40 CFR 503 standards to its own rule, Chapter
173-308 WAC.
A Plain English Guide to the
EPA Part 503 Biosolids Rule
http://www.epa.gov/owm/bio/503pe/
Different rules for different classes of biosolids.
Class A biosolids contain no detectible levels of pathogens and
and meet strict vector attraction reduction requirements and
have low levels of metals. Permits are required to ensure that
these standards have been met.
Class B biosolids are treated but still contain detectible
levels of pathogens. There are buffer requirements, public
access, and crop harvesting restrictions for virtually all
forms of Class B biosolids.
Class A Biosolids
Class A production processes include irradiation,
composting, heat drying, heat treatment,
pasteurization, thermophilic aerobic digestion, and
alkaline stabilization. Class A biosolids do not contain
pathogens in sufficient quantity to warrant restricted
access or special precautions and may be applied the
same way as commercial fertilizer.
Alternative 1: Thermally treated biosolids
Biosolids must be subject to one of the following four (4) timetemperature regimes:
7 percent solid or greater biosolids must be heated to 50 degrees
Celsius of higher for 20 minutes or longer.
7 percent solid or greater biosolids in the form of small particles
and heated by contact with either warmed gases or
immiscible liquid must be heated to 50 degrees Celsius or
higher for 15 seconds or longer.
Biosolids less than 7 percent solid must be heated for at least 15
seconds but less than 30 minutes using the following
equation:
D=131,700,000/100.14 t
Biosolids less than 7 percent solid must be heated to 50 degrees
Celsius of higher with at least 30 minutes of longer contact
time.
There are chemical alternatives for application of alkaline
K-S Nara Paddle Dryer/Cooler
Class B Biosolids
King County biosolids are anaerobically
digested at the treatment plant to meet Class
B pathogen reduction. Further reduction
does take place after application in what
King County (and other processors) refer to
as a hostile environment for microbes
In practice odor is a principal restriction to the
location where Class B biosolids can be applied.
This can be reduced by chemicals
EPA Class B biosolids site restrictions
Restricted Activity
Harvest of food crop touching ground
Harvest of root crop (see next condition)
Harvest of root crop if sludge on surface
Harvest of other food, feed, and fiber crops
Grazing of animals
Harvest of turf for high contact site,
e.g., golf course or lawn; or public access
to turf
Access to sites with high potential for
public exposure
Access to sites with low potential for
public exposure
Site Restriction
14 months after application
20 months after application
38 months after application
30 days after application
30 days after application
1 year after application
Restrict for 1 year
Restrict for 30 days
Biosolids Quality from the West Point Plant
2000 Average
By weight
Total Solids
24.8%
Ammonia Nitrogen 1.2%
Organic Nitrogen
5.5%
Phosphorus
1.9%
Potassium
0.3%
Sulfur
1.1%
Organic nitrogen provides a sustained release of N
Trace metals in West Point biosolids
West Point Plant
mg/kg
Arsenic
7.07
Cadmium
3.7
Copper
529
Lead
141
Mercury
2.71
Molybdenum 11.1
Nickel
35.1
Selenium
5.97
Zinc
804
National and State
Regulatory Standards
mg/kg
541
39
1500
300
17
under reconsideration
420
36
2800
“Dryland” soils program
Improved moisture retention
Increased growth – sometimes too much N
Forest Application
Reclamation
Bunker Hill Wetland, Idaho
Rapid establishment of vegetation
Issues – returning to ‘natural’
vegetation may be
retarded by high N
Four arguments against biosolids application
1. Odor and ‘unpleasantness’
2. EPA is not doing its job to ensure compliance
with its own regulations
3. Treatment and disposal should be local
4. Class B biosolids can cause illness to people
applying them
Cornell University site management recommendations
--Limiting applications to keep soil metals low;
--Testing soils before application;
--Applying only at agronomic rates;
--Supplying all landowners with biosolids quality
information;
--Monitoring downstream water bodies and wells;
--Calibrating application equipment;
--Maintaining setbacks and buffers;
--Avoiding application to areas prone to runoff;
--Imposing access restrictions for the public.
In practice most of these items are specified in Washington State
and EPA regulations
Conclusion
According to EPA estimates for 1993, approximately
33% of the 5.4 million dry metric tons of biosolids
generated annually in the US is land applied
This is increasing due to rising costs and less
available space in landfills, regulations banning
ocean dumping, and a move away from incineration.
So application to the land will increase
and must be placed on a sustainable basis
There is likely to be continued discussion as new
regions consider biosolids application
Courses that deal with this topic
ESC518, formerly Microbial
Degradation, to Bioremediation Science
CIVE 484 On-Site Wastewater Disposal
CIVE 482 Water and Wastewater Treatment