The city of Modesto, Calif., agreed to pay a $165,000 fine...
Two sludge treatment plants in Eatonton, Ga., find long-term solution for solids management
Miratech, a Division of Ten Cate Nicolon
3680 Mount Olive Road * Commerce, GA 30529
Solids management at municipal wastewater treatment plants
is crucial in maintaining operating efficiencies and permitted discharge
levels. Drying beds and mechanical methods of dewatering biosolids can be labor
intensive and inefficient for rapid solids removal.
In the spring of 2003, the city of Eatonton, Ga., faced
potential discharge permit violations due to increased solids levels that
hampered operations at their two activated sludge wastewater treatment plants.
Solids within the aeration lagoons were exceeding 900 on the Settling Meter
Test due to higher than usual rainfall and the inability to use their onsite
drying beds for solids wasting.
With a tight budget and labor limitations, the plant
superintendent was faced with the dilemma of taking immediate action to rapidly
reduce solids inventory in a short time, but without exceeding the operating
budget. The city was also searching for a long-term economical method for
solids management without capital expenditures.
Miratech’s Geotube Dewatering technology was chosen
for rapid removal of solids from the city’s two 350,000 gpd wastewater
treatment plants. The Geotube container is a 30-ft-circumference flexible
dewatering tube fabricated from specially designed, high-strength industrial
textiles. These engineered textiles allow for containment of fine particles of
solids yet are permeable to allow for rapid dewatering. The Geotube container
is tailored specifically for the municipal water and wastewater market to fit
within drying beds and other designated plant locations.
A total of eight sections of 50-ft-long Geotube containers
are being used at the Eatonton, Ga., wastewater plants per year to contain and
dewater three million gallons of biosolids with 1% solids.
Each of the two plants deployed four Geotube sections in
their existing drying beds. Once per week at each plant, 30,000 gallons of
biosolids are pumped from the digester into the Geotube container. As the waste
flows through an inline mixer, 15 ppm of a 0.5% solution of a cationic polymer
is injected into the waste stream to facilitate flocculation and precipitation
of the solids. The flocculated waste then flows into one of the Geotube
containers. Clean effluent flows through the porous surface of the textile as
the solids are contained. This dewatering process allows for 80-90% volume
reduction of waste. This process is repeated weekly until the container is
filled to capacity.
Performance stands out
Within 180 days following installation of the technology at
both plants, more than 1.5 million gallons of biosolids had been pumped from
the digesters into the Geotube containers and dewatered. Settlement meter tests
of solids taken from the aerator lagoons indicate levels below 350 at both
plants. Both locations are operating at well below permitted discharge levels
and within efficient parameters.
The plants are on track to remove and dewater a total of
three million gallons of waste before the end of 2003.
These results were achieved without capital expenditures and
without exceeding the city of Eatonton’s operating budget. Because of
this success, the Geotube Dewatering System has become their long-term solution
for solids management.