system requires a minimum of three tanks and advanced automation equipment to
control the cycle times and phases. The SBR control systems allows the operation
to be configured to operate as almost any other suspended floc physicochemical
reactor by adjusting the cycle phases between fill phase, react phase (chemical
precipitation/coagulation, flocculation), separation phase (either sedimentation or
flotation clarification), and decant phase. The physicochemical SBR system
involving the use of either sedimentation or flotation in the separation phase is
invented by Dr. Lawrence K. Wang, Dr. Lubomyr Kurylko, and Dr. Mu-Hao
Sung Wang in 1994 (US Patent 5354458).
Short circuiting: Shortening of hydraulic detention time, such as when plant flow
exceeds design flow.
Shredding: It is a unit operation for reducing the particle size of objects or debris in
the influent wastewater, also termed grinding or comminuting. These devices may
be installed with a screen directly in the wastewater flow or separately out of the
wastewater flow, with the shredded particles returned to the flow downstream of
the screen. Only those shredding and grinding devices that are installed directly in
the influent channel are termed comminuting devices.
Sidestreams: Sources of inflow from within the wastewater treatment facility, such
as supernatant return from digesters, centrate from centrifuge thickening, filtrate
from filter presses, etc. These sidestreams may be high in solids, BOD, or
nutrients and may add to the plant organic or hydraulic loading.
Single-sludge activated sludge system: It is a biological activated sludge process
system involving the use of one suspended activated sludge solids going through
aerobic and anoxic zones for carbonaceous oxidation, nitrification, denitrification, and phosphorus removal. The single-sludge activated sludge system is
commonly a continuous flow system using sedimentation clarification. The
Lenox Institute of Water Technology (LIWT) has developed three innovative
single-sludge activated sludge systems all for carbonaceous oxidation, nitrification, denitrification, and phosphorus removal: (a) continuous flow single-sludge
system using flotation clarification; (b) sequencing batch reactors (SBR) using
sedimentation for carbonaceous removal and nutrient removal; and (c) SBR using
flotation for carbonaceous removal and nutrient removal.
Sludge age (SA): SA is the length of time a particle of activated sludge stays in the
biological treatment plant, measured in days. In a biological phosphorus removal
plant, sludge age is the amount (pound or kilogram) of mixed liquor suspended
solids in all the biological reactors divided by the suspended solids withdrawn
from the system per day (pound per day of waste activated sludge or kilogram per
day of waste activated sludge).
Sludge dewatering: Sludge dewatering is the second step of sludge handling, after
sludge thickening. Sludge dewatering is required for all facilities that do not
dispose of their sludge in liquid form. It is a physical (mechanical) process to
reduce the moisture content of sludge. The purpose is to reduce sludge volume, in
turn, to reduce subsequent sludge digestion costs and/or final sludge disposal
(land disposal or incineration) costs. Dewatering is usually required prior to
3 Biological Processes
157
control the cycle times and phases. The SBR control systems allows the operation
to be configured to operate as almost any other suspended floc physicochemical
reactor by adjusting the cycle phases between fill phase, react phase (chemical
precipitation/coagulation, flocculation), separation phase (either sedimentation or
flotation clarification), and decant phase. The physicochemical SBR system
involving the use of either sedimentation or flotation in the separation phase is
invented by Dr. Lawrence K. Wang, Dr. Lubomyr Kurylko, and Dr. Mu-Hao
Sung Wang in 1994 (US Patent 5354458).
Short circuiting: Shortening of hydraulic detention time, such as when plant flow
exceeds design flow.
Shredding: It is a unit operation for reducing the particle size of objects or debris in
the influent wastewater, also termed grinding or comminuting. These devices may
be installed with a screen directly in the wastewater flow or separately out of the
wastewater flow, with the shredded particles returned to the flow downstream of
the screen. Only those shredding and grinding devices that are installed directly in
the influent channel are termed comminuting devices.
Sidestreams: Sources of inflow from within the wastewater treatment facility, such
as supernatant return from digesters, centrate from centrifuge thickening, filtrate
from filter presses, etc. These sidestreams may be high in solids, BOD, or
nutrients and may add to the plant organic or hydraulic loading.
Single-sludge activated sludge system: It is a biological activated sludge process
system involving the use of one suspended activated sludge solids going through
aerobic and anoxic zones for carbonaceous oxidation, nitrification, denitrification, and phosphorus removal. The single-sludge activated sludge system is
commonly a continuous flow system using sedimentation clarification. The
Lenox Institute of Water Technology (LIWT) has developed three innovative
single-sludge activated sludge systems all for carbonaceous oxidation, nitrification, denitrification, and phosphorus removal: (a) continuous flow single-sludge
system using flotation clarification; (b) sequencing batch reactors (SBR) using
sedimentation for carbonaceous removal and nutrient removal; and (c) SBR using
flotation for carbonaceous removal and nutrient removal.
Sludge age (SA): SA is the length of time a particle of activated sludge stays in the
biological treatment plant, measured in days. In a biological phosphorus removal
plant, sludge age is the amount (pound or kilogram) of mixed liquor suspended
solids in all the biological reactors divided by the suspended solids withdrawn
from the system per day (pound per day of waste activated sludge or kilogram per
day of waste activated sludge).
Sludge dewatering: Sludge dewatering is the second step of sludge handling, after
sludge thickening. Sludge dewatering is required for all facilities that do not
dispose of their sludge in liquid form. It is a physical (mechanical) process to
reduce the moisture content of sludge. The purpose is to reduce sludge volume, in
turn, to reduce subsequent sludge digestion costs and/or final sludge disposal
(land disposal or incineration) costs. Dewatering is usually required prior to
3 Biological Processes
157