Sludge thickening and dewatering combined, belt filter press Conditioned
sludge is first placed on a gravity drainage section where it is allowed to thicken.
In this section, the bulk of the free water is removed from the sludge by gravity.
On some units, this section is equipped with a vacuum assist, which enhances
drainage and may help to reduce odors. Following gravity drainage, pressure is
applied in a low-pressure section, where sludge is squeezed between opposing
porous cloth belts. On some units, the low-pressure section is followed by a highpressure section where the sludge is subjected to shearing forces that induce the
release of additional quantities of water from the sludge. The final dewatered
sludge cake is removed from the belts by scrapper blades.
Sludge thickening/dewatering centrifuge, basket centrifuge They are suitable
for small plants. It is a semibatch type operation. Sludge cake is collected on the
sides of the spinning bowl, while the centrate (dilute effluent stream from the
centrifuge) overflows the bowl rim. Once solids have built up to a maximum
thickness, the feed sludge is stopped and scrapper blades peel the sludge from the
walls. The process is then resumed.
Sludge thickening/dewatering centrifuge, solids bowl centrifuge Sludge is fed at
a constant flowrate into the rotating bowl where it is separated into a dense cake
and a dilute stream called centrate. The units can be used with no prior chemical
conditioning, but solids caputer and centrate quality are improved considerably
when the sludge is conditioned with polymer.
Sludge thickening Sludge thickening is the first step of sludge handling. It is
employed prior to subsequent sludge dewatering processes to increase the efficiency of the sludge dewatering equipment. There are at least five types of sludge
thickening processes: gravity thickening, flotation thickening, centrifuge thickening, gravity belt thickening, and rotary drum thickening.
Sludge volume index (SVI) SVI is the ratio of the volume (in mL) of sludge settled
from a 1000 mL sample in 30 minutes to the concentration of mixed liquor
(in mg/L) multiplied by 1000. It indicates settling capabilities, compaction, and it
is an indication of filamentous organism overgrowth and several other indicators
of process problems.
Slurry It is a term used to describe the mixture of solids with a liquid (typically
water). In dredging, these solids can include silt, sand, gravel, clay, or coal.
Snowpack A seasonal accumulation of slow-melting snow.
Sodium hypochlorite It is a liquid sodium hypochlorite solution to be used as a
disinfectant for water or wastewater disinfection.
Soil carbon A major component of the terrestrial biosphere pool in the carbon
cycle. The amount of carbon in the soil is a function of the historical vegetative
cover and productivity, which in turn is dependent in part upon climatic variables.
Solar radiation Radiation emitted by the Sun. It is also referred to as short-wave
radiation. Solar radiation has a distinctive range of wavelengths (spectrum)
determined by the temperature of the Sun.
Solid wastes A solid waste is defined by the US Environmental Protection Agency
(USEPA) as the following: Any garbage, refuse, sludge from a waste treatment
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M.-H. S. Wang and L. K. Wang
sludge is first placed on a gravity drainage section where it is allowed to thicken.
In this section, the bulk of the free water is removed from the sludge by gravity.
On some units, this section is equipped with a vacuum assist, which enhances
drainage and may help to reduce odors. Following gravity drainage, pressure is
applied in a low-pressure section, where sludge is squeezed between opposing
porous cloth belts. On some units, the low-pressure section is followed by a highpressure section where the sludge is subjected to shearing forces that induce the
release of additional quantities of water from the sludge. The final dewatered
sludge cake is removed from the belts by scrapper blades.
Sludge thickening/dewatering centrifuge, basket centrifuge They are suitable
for small plants. It is a semibatch type operation. Sludge cake is collected on the
sides of the spinning bowl, while the centrate (dilute effluent stream from the
centrifuge) overflows the bowl rim. Once solids have built up to a maximum
thickness, the feed sludge is stopped and scrapper blades peel the sludge from the
walls. The process is then resumed.
Sludge thickening/dewatering centrifuge, solids bowl centrifuge Sludge is fed at
a constant flowrate into the rotating bowl where it is separated into a dense cake
and a dilute stream called centrate. The units can be used with no prior chemical
conditioning, but solids caputer and centrate quality are improved considerably
when the sludge is conditioned with polymer.
Sludge thickening Sludge thickening is the first step of sludge handling. It is
employed prior to subsequent sludge dewatering processes to increase the efficiency of the sludge dewatering equipment. There are at least five types of sludge
thickening processes: gravity thickening, flotation thickening, centrifuge thickening, gravity belt thickening, and rotary drum thickening.
Sludge volume index (SVI) SVI is the ratio of the volume (in mL) of sludge settled
from a 1000 mL sample in 30 minutes to the concentration of mixed liquor
(in mg/L) multiplied by 1000. It indicates settling capabilities, compaction, and it
is an indication of filamentous organism overgrowth and several other indicators
of process problems.
Slurry It is a term used to describe the mixture of solids with a liquid (typically
water). In dredging, these solids can include silt, sand, gravel, clay, or coal.
Snowpack A seasonal accumulation of slow-melting snow.
Sodium hypochlorite It is a liquid sodium hypochlorite solution to be used as a
disinfectant for water or wastewater disinfection.
Soil carbon A major component of the terrestrial biosphere pool in the carbon
cycle. The amount of carbon in the soil is a function of the historical vegetative
cover and productivity, which in turn is dependent in part upon climatic variables.
Solar radiation Radiation emitted by the Sun. It is also referred to as short-wave
radiation. Solar radiation has a distinctive range of wavelengths (spectrum)
determined by the temperature of the Sun.
Solid wastes A solid waste is defined by the US Environmental Protection Agency
(USEPA) as the following: Any garbage, refuse, sludge from a waste treatment
484
M.-H. S. Wang and L. K. Wang