Municipal sewage sludge was placed in geo-textile bags
for the purpose of evaluating the dewatering and consolidation
capabilities of large geo-textile tubes and effluent water
quality. A proposed ASTM test method for determining the flow rate
of suspended solids from a geo-textile containment system for dredged
material was used to conduct tests to determine the efficiency of
different combinations of geo-textile filters. Prior to filling
the large geo-textile tube, two small geo-textile bags 48 inches in circumference
and 70 inches long were supported vertically in a wooden frame and
filled to a depth of about 60 inches or about 48 gallons of sewage
sludge from the primary sludge digester. As water passed through
the geo-textile bag, samples were collected during, immediately after,
and for several days to determine the total percent suspended solids (TSS),
heavy metals, and bacterial count. The test results indicated
significant consolidation or reduction in the form of the sludge volume
in the bag. There was also a significant reduction in the TSS,
heavy metals, and bacterial count in the effluent water. These
test results led to filling a large geo-textile tube 15 ft. wide, 30 ft.
long and filled to a height of 5 ft. with sewage sludge.
The quality of pore water or effluent passing through
the geo-textile container systems proved to be environmentally
acceptable for subsequent discharge into the Mississippi River and/or
return to the treatment plant.
This new and innovative technology has been
successfully used to dewater fine-grained, contaminated dredged material
that contains dioxins, PCB's, PAH's, pesticides and heavy metals for
Miami River and the Port of Oakland, CA. This is the first
successful use of geo-textile tubes for dewatering sewage sludge for
beneficial uses in the United States. Research using this process
for dewatering port and dairy farming waste, paper mill waste, fly ash,
mining waste, chemical sludge lagoons and several other waste streams
are being conducted.
This concept of containing sewage sludge has proven to
be construction-practical, technically and economically feasible and
environmentally acceptable.
