Page 63 - GRIHA Manual Volume IV - Introduction to National Rating System
P. 63
54 Griha Manual: Volume 4
Figure 3 Cross section of media and underdrain
materials are placed over a thick layer of plastic sheets, to prevent loss of wastewater. The wastewater
is repeatedly pumped on the top of the soil medium using a pipeline network. The treated water,
which is collected in the furrows between the soil bunds, is finally diverted to a collection well, which
also acts as an aeration tank. This water is pumped out and used for irrigation. Locally available wild
plants are grown on top of the soil to further enhance the treatment process. The system has a low
operation and maintenance cost, as it does not require any chemicals and energy is required only
for the purpose of pumping. The system effectively removes COD, ammonium, nitrates, suspended
solids, bacteria, color, and odour, and further, there is no sludge generation.
3. Uplow Anaerobic Sludge Blanket Reactor
The Upflow Anaerobic Sludge Blanket Reactor (UASBR) can be fitted into any base or corridor and
is shop assembled, hence, requiring minimal construction. In a UASB reactor, wastewater is fed
from the bottom. As it flows upward through the reactor, organic matter in the waste is degraded
anaerobically by micro-organisms resident in the sludge blanket. Besides converting organics to
cell mass, biogas rich in methane is produced as a by-product. A Gas Liquid Solid Separator (GLSS)
provided near the top of the reactor, enables the sludge to settle into the blanket, biogas to escape
into the dome at the top of the reactor, and treated supernatant to flow out of the reactor. High
sludge concentration in sludge blanket and low concentration of suspended solids in the reactor
over flow are characteristic features of a good UASBR.
Following are the basic advantages of a UASBR over aerobic treatment units.
# UASBR in a compact unit is ideal for economic space utilization and applicable at decentralized
scales.
# UASB treatment process requires no external input of energy. Even the required mixing is
achieved by upflowing wastewater and rising gas bubbles.
# Nutrient requirement (N and P) is much less than (about half that needed) for aerobic treatment.
# Residuals (sludge) generated by UASB treatment are much less in amount and well digested,
requiring reduced sludge handling, and causing much less odour problems.
# Biogas, rich in methane, is generated as a valuable by-product. Methane produced is about 0.15–
3
0.35 Nm /kg COD destroyed.
# Owing to the compactness of UASBR, absence of mechanical/moving components, energy
efficiency of the process, and reduced post-treatment and sludge handling requirements, both
Figure 3 Cross section of media and underdrain
materials are placed over a thick layer of plastic sheets, to prevent loss of wastewater. The wastewater
is repeatedly pumped on the top of the soil medium using a pipeline network. The treated water,
which is collected in the furrows between the soil bunds, is finally diverted to a collection well, which
also acts as an aeration tank. This water is pumped out and used for irrigation. Locally available wild
plants are grown on top of the soil to further enhance the treatment process. The system has a low
operation and maintenance cost, as it does not require any chemicals and energy is required only
for the purpose of pumping. The system effectively removes COD, ammonium, nitrates, suspended
solids, bacteria, color, and odour, and further, there is no sludge generation.
3. Uplow Anaerobic Sludge Blanket Reactor
The Upflow Anaerobic Sludge Blanket Reactor (UASBR) can be fitted into any base or corridor and
is shop assembled, hence, requiring minimal construction. In a UASB reactor, wastewater is fed
from the bottom. As it flows upward through the reactor, organic matter in the waste is degraded
anaerobically by micro-organisms resident in the sludge blanket. Besides converting organics to
cell mass, biogas rich in methane is produced as a by-product. A Gas Liquid Solid Separator (GLSS)
provided near the top of the reactor, enables the sludge to settle into the blanket, biogas to escape
into the dome at the top of the reactor, and treated supernatant to flow out of the reactor. High
sludge concentration in sludge blanket and low concentration of suspended solids in the reactor
over flow are characteristic features of a good UASBR.
Following are the basic advantages of a UASBR over aerobic treatment units.
# UASBR in a compact unit is ideal for economic space utilization and applicable at decentralized
scales.
# UASB treatment process requires no external input of energy. Even the required mixing is
achieved by upflowing wastewater and rising gas bubbles.
# Nutrient requirement (N and P) is much less than (about half that needed) for aerobic treatment.
# Residuals (sludge) generated by UASB treatment are much less in amount and well digested,
requiring reduced sludge handling, and causing much less odour problems.
# Biogas, rich in methane, is generated as a valuable by-product. Methane produced is about 0.15–
3
0.35 Nm /kg COD destroyed.
# Owing to the compactness of UASBR, absence of mechanical/moving components, energy
efficiency of the process, and reduced post-treatment and sludge handling requirements, both
