Case
Study 7-St. Johns County Municipal Wastewater Treatment
Facility
St. Augustine, Florida
Wastewater Treatment |
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Background Data: |
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Case Study: Wastewater Treatment |
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Location: St. Johns County Municipal Wastewater Treatment Facility
St. Augustine, Florida |
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The St. Johns County Municipal Wastewater Treatment Facility,
located in St. Augustine, Florida. with a design flow of 4 MGD,
treats an average of 1.8 MGD of both industrial and domestic
wastewater. Bill Young, St. Johns County Director of Utilities,
had become alarmed at the rising cost of sludge transport and
disposal. Greg Hartley, Wastewater Superintendent, contacted
Natural Resource Protection Corporation to discuss use of PX-700TM
at the St Johns County Municipal Wastewater Treatment Facility.
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This aerobic wastewater treatment facility was generating an
average of 192 tons per month of sludge. The sludge generated at
the municipal wastewater treatment facility is dewatered and
disposed of at the St. Johns County Landfill. |
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Sludge disposal costs for the St. Johns County Municipal
Wastewater Facility were above $100,000.00 per year and rising.
This figure does not take man hours, sludge press maintenance, or
polymer usage into account. According to Greg Hartley, Wastewater
Superintendent, the true sludge disposal costs may be over
$225,000.00 per year. |
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Scope: |
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It was determined that the use of PX-700TM could reduce the
quantity of sludge generated at the St. Johns County Municipal
Wastewater Treatment Facility, thus reducing overall sludge
disposal costs. |
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PX-700TM, a microbial bio-catalyst, was to be used as an additive
at the St. Johns County Municipal Wastewater Treatment Facility. |
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The anticipated result from the use of PX- 700TM was to be an
overall reduction of sludge generated by the St. Johns County
Municipal Wastewater Treatment Facility; thereby reducing costs
associated with sludge disposal. |
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Facility personnel were to gather pertinent data to analytically
determine the effectiveness of PX- 700TM .Records were maintained
for Mixed Liquor Suspended Solids (MLSS), Mixed Liquor Volatile
Suspended Solids (MLVSS), Waste Activated Sludge (WAS), Fecal
Coliform, Tons of Sludge Generated, Belt Press Run Hours, Man
Hours to Press and Dispose of Sludge, Amount of Polymer Used,
Sludge Transport and Disposal Charges. |
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Treatment Procedures: |
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On October 2, 1998, PX-700TM was introduced into the digester at
the St. Johns County Municipal Wastewater Treatment Facility.
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Since the only objective was to eliminate the amount of sludge
generated, and thereby reduce the cost associated with sludge
disposal, the digester was chosen as the injection point
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62.7 ounces were injected on a flow proportional bases into the
digester during each 24 hour period, this converts into 0.25 mg/l. |
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At the time of this writing, the dosage amount and location has
not changed. |
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Results: |
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The Operatons Log at the St. Johns County Municipal Wastewater
Treatment Facility notes a drastic change in both the facility
settling time and turbidity during the first 24 hours of use. Due
to the quicker settling time and clearer water, it was determined
by facility personnel to reduce the amount of polymer introduced
into the treatment works. |
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Facility records indicate that on average, 192.39 tons of sludge
was generated and disposed of each month from January 1997-
September 1998. This compares to an average of 68.44 tons of
sludge generated after the use of PX-700TM. This decrease in the
amount of sludge generated represents a reduction of over 64%.
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Facility records also indicate a better running and smelling
wastewater treatment facility after the use of PX-700TM. Man hours
associated with sludge dewatering and disposal have been reduced.
The amount of polymer used at the St Johns County Wastewater
Treatment Facility, along with equipment run hours has also been
reduced proportionately. |
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In order to substantiate the results attained, Greg Hartley, St
Johns County Wastewater Treatment Facility Superintendent, began a
detailed study on PX- 700TM, and the microbiology at the
wastewater treatment facility. His study concluded that PX- 700TM
contributed to the growth, reproductive, and metabolic rate of the
microorganisms at the facility .This increased growth,
reproductive, and metabolic rate contributed directly to the
reduction in the amount of sludge generated. |
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It quickly became apparent to all involved, that the use of
PX-700TM significantly reduced the amount of sludge generated by
the St. Johns County Municipal Wastewater Treatment Facility.
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City personnel decided to permanently keep PX-700TM on line. The
St. Johns County Municipal Wastewater Treatment Facility has
continued to purchase and use PX-700TM through the date of this
writing. |
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Total Cost of Sludge Transport and Disposal |
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Prior to Use of PX-700 |
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$225,000.00 Annually |
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With Use of PX-700 |
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$68,500.00 Annually |
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This amounts to a 70% reduction in the total annual cost
of transport and disposal of sludge. |
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$300,000.00
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Prior to Use of
PX- 700 |
With Use of PX-
700 |
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$250,000.00
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$200,000.00
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$150,000.00
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$100,000.00
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$50,000.00
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Total Cost of Sludge Generated |
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Prior to Use of PX-700 |
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2309 Tons Annually |
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With Use of PX-700 |
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821 Tons Annually |
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This amounts to a 64% reduction in the total amount of
sludge generated |
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2,000 Tons
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Prior to Use of
PX- 700 |
With Use of PX-
700 |
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1,500 Tons
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1,250 Tons
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1,000 Tons
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750 Tons
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500 Tons
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250 Tons
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