Liquid purification or separation – With means to add treating material – Plural distinct separators
Reexamination Certificate
1999-08-17
2002-08-06
Cintins, Ivars (Department: 1724)
Liquid purification or separation
With means to add treating material
Plural distinct separators
C210S262000, C210S265000, C210S284000
Reexamination Certificate
active
06428698
ABSTRACT:
TECHNICAL FIELD
The present invention relates a coagulator, and more particularly it relates to a coagulator in which an inorganic coagulant such as an aluminum-based coagulant is added to raw water to coagulate and separate suspended solids in the raw water.
BACKGROUND ART
Coagulators are apparatuses used to treat water for use where water from a river or the like is treated so that it can be used as municipal or industrial water, and where waste water such as public sewage or factory waste water, is treated to meet regulatory limits. In particular, an upflow type coagulator is often employed because such a coagulator has high coagulating and filtering efficiencies and is easy to operate.
In an upflow coagulator, raw water to which a coagulant is added is passed upward through the interior of a packing medium accumulation layer formed by stacking small pieces of packing medium having a high void ratio to thereby flocculate and settle suspended solids in the water.
Referring now to
FIG. 5
, description will be given of a configuration and an operation of a conventional upflow type coagulator
10
.
This typical conventional upflow type coagulator
10
comprises, as shown in
FIG. 5
, a raw water tank
12
, a raw water pump
14
for pumping raw water from the raw water tank
12
to feed the raw water, coagulant adding facilities
16
, a coagulant mixing tank
18
and a coagulation tank
20
.
The coagulant adding facilities
16
include a turbidimeter
22
for measuring the turbidity of the raw water, a coagulant tank
24
, a coagulant pump
28
for injecting the coagulant from the coagulant tank
24
into a raw water supply pipe
26
on the downstream side of the turbidimeter
22
so that a desired amount of the coagulant may be added to the raw water on the basis of a measured value of the turbidimeter
22
.
The coagulant mixing tank
18
is a container fitted with a stirrer
29
, in which the raw water bearing the coagulant is temporarily stored and stirred by the stirrer
29
to rapidly mix the raw water and the coagulant. The water bearing the coagulant is then sent via an inflow pipe
30
to the coagulation tank
20
.
The coagulation tank
20
is a tank in which the suspended solids in the water which have been aggregated by the coagulant are coagulated, flocculated, filtered and separated. As shown in
FIG. 6
, the coagulation tank
20
consists of a water inflow zone
32
, a packing medium accumulation zone
34
, and a water collection zone
36
which are partitioned in sequence from the underside.
The packing medium accumulation zone
34
is partitioned by perforated outflow prevention plates
38
,
40
which are provided in an upper part and a lower part of the zone. In this packing medium accumulation zone
34
, many small packing media having a small specific gravity and a high void ratio are accommodated, and a packing medium accumulation layer
44
is formed below the upper outflow prevention plate
38
with the upflow of the water. As the small packing media for forming the packing medium accumulation layer
44
, for example, there are employed short tube-shaped plastic small packing media
42
having a relatively small specific gravity as shown in FIG.
7
.
The water collection zone
36
is a region for collecting the treated water which has been treated through the packing medium accumulation zone
34
, and this zone
36
consists of a water collecting part
46
disposed immediately above the outflow prevention plate
38
of the packing medium accumulation zone
34
, a water collection trough
48
for collecting the treated water overflowing from the upper end of the water collection part
46
, and an outflow pipe
50
, connected to the water collection trough
48
, for sending the treated water to a treated water tank
52
(see FIG.
5
).
The raw water leaving the coagulant mixing tank
18
flows via the inflow pipe
30
into the inflow zone
32
. The inflow pipe
30
extends to the middle of the inflow zone
32
, and has at its tip a downward opening. An inverted umbrella-shaped baffle plate
54
is provided under the opening of the inflow pipe
30
to change the direction of flow of the raw water from downward to upward. An alkaline agent injection pipe
56
is also connected to the inflow pipe
30
so as to inject an alkaline solution, if desired, for the control of the pH of the raw water.
In the lower part of the inflow zone
32
, that is, below the baffle plate
54
, there lies a hopper-shaped sludge storage zone
58
for storing the sludge, to the lowermost part of which is connected a sludge discharge pipe
60
for discharging the sludge.
Above the inflow zone
32
is disposed an air supply pipe
62
having a plurality of air nozzles for jetting air upward, so as to eject air fed by the air blower
64
to thereby stir and wash the packing media
42
of the packing medium accumulation zone
34
.
In the coagulation tank
20
, the water bearing the coagulant first flows into the inflow zone
32
. In this inflow zone
32
, among flocs formed as a result of coagulation of the suspended solids in the raw water, relatively large flocs are first settled and separated.
The water then flows into the packing medium accumulation zone
34
, in which micro-flocs remaining in the water come into contact with the packing media and adhere onto the external surfaces of the packing media, or are captured in the interstices between the respective packing media
42
and are separated. Water flows upwardly through voids of the packing media
42
or flows through between the respective packing media, and is filtered through the floc layer formed in the voids or between the packing media, while simultaneously the micro-flocs in the raw water are captured by the floc layer.
Flocs which have adhered onto the packing media
42
or have been captured between the packing media
42
gradually grow due to contact with the subsequent micro-flocs or the like, resulting in flocs of increased diameter. Then, accordingly as the flocs having a higher settlement velocity than the upward flow rate of the raw water become formed, these flocs are dislodged from the packing media
42
by the flow of the water, settle against the flow of the water, retained in the sludge storage zone
58
, and then discharged via the sludge discharge pipe
60
.
In this manner, suspended solids in the raw water are separated from the water and settled in the sludge storage zone
58
by the agglomeration of the suspended solid flocs, the filtration of raw water through the layer of flocs, the separation and settlement of the agglomerated flocs, and the like. On the other hand, raw water thus treated flows out from the water collection zone
36
into the treated water tank
52
.
When the packing medium accumulation layer
44
of the packing medium accumulation zone
34
clogs, air jets through the air nozzles of the air supply pipe
62
to stir and wash the packing medium accumulation layer
44
.
This upflow type coagulator enables treatment to be performed at a high speed because the density of the coagulated flocs which have become thickly agglomerated is high as is settlement speed. Accordingly, the facilities become compact, so that facility installation area can be reduced, the amounts of chemical agents can be decreased, and the treatment and disposal of the generated sludge can be simplified.
While upflow type coagulators have many advantages, for the purpose of further heightening its treatment efficiency, various improvements have been made.
For example, it has been attempted to prolong water treatment time between the respective wash treatments by the use of packing media having a large size in place of the small packing media which constitute the packing medium accumulation layer, but this results in a problem that the turbidity of the treated water increases. Conversely, when the packing media having smaller sizes are used in order to decrease the turbidity of the treated water, the wash frequency of the packing medium accumulation layer increases, so that there arises a problem that the raw water trea
Miyanoshita Tomoaki
Ochiai Hisaaki
Cintins Ivars
Fish & Richardson P.C.
Organo Corporation
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