Liquid purification or separation – Flow – fluid pressure or material level – responsive
Reexamination Certificate
2000-01-06
2001-09-18
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
C210S086000, C210S264000, C210S265000, C210S284000, C210S313000, C210S317000, C210S536000, C210SDIG005
Reexamination Certificate
active
06290842
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to a coagulator in which a coagulant is mixed into raw water, and suspended solids in the raw water are settled in a coagulated manner for separation in a coagulation tank, and more particularly to a coagulator having a packing medium accumulation layer(s) within the coagulation tank.
2. Background Art
Coagulators are known as water treatment apparatuses for use in cases where river water or the like, as raw water, is subjected to water treatment to obtain city water or industrial water, or where drainage such as public sewage and factory waste water is treated to meet regulatory limits. Among them, frequently employed is a so-called upward flow type coagulator, in particular, one having a packing medium accumulation layer in the interior of the coagulation tank because, for example, it has higher coagulating and filtering efficiencies and is easy to operate.
In such an upward flow type coagulator, a coagulant is first mixed into raw water. Raw water bearing the coagulant is then passed through the interior of the coagulation tank with upward flow to coagulatively separate flocculated flocs. In particular, within the coagulation tank there is provided a packing medium accumulation layer consisting of small pieces of packing medium with a large void ratio, through which the raw water bearing the coagulant flows with upward flow to thereby effectively flocculate and settle the suspended solids in the raw water.
Referring now to
FIGS. 5 and 6
, description will be given of a construction and an operation method of the conventional upward flow type coagulator.
FIG. 5
is a flow sheet showing the construction of the conventional upward flow type coagulator, and
FIG. 6
is a schematic diagram showing the construction of a coagulating tank.
The conventional upward flow type coagulator designated generally at
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 water, a coagulant dosing facilities
16
, a coagulant mixing tank
18
and a coagulation tank
20
.
The coagulant dosing facilities
16
includes a turbidimeter
22
for measuring the turbidity of the raw water, a coagulant tank
24
, and a coagulant pump
28
for injecting the coagulant from the coagulant tank
24
into a raw water supply pipe
26
downstream of the turbidimeter
22
so that a desired amount of coagulant is added into the raw water on the basis of 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 temporarily stays and is stirred by the stirrer
29
to rapidly mix the raw water and the coagulant. The raw water fully mixed with the coagulant is sent via an inflow pipe
30
to the coagulation tank
20
.
The coagulation tank
20
is a tank in which coagulative flocs containing suspended solids which have been aggregated by the coagulant are flocculated and filtrated and separated. The coagulation tank
20
consists of a raw water inflow zone
32
, a packing medium
34
and a water collection zone
36
which are partitioned in sequence from below as shown in FIG.
6
.
The packing medium zone
34
is partitioned by outflow prevention plates
38
and
40
which are porous mesh-like or perforated like partition plates provided in an upper part and lower part of the zone. In the region therebetween are accommodated a plurality of small packing medium with a large void ratio, e.g., plastic small packing medium
42
with a relatively small specific gravity in the shape of shortened tube as shown in FIG.
7
.
Upon the passage of the raw water, the packing medium
42
is accumulated below the upper outflow prevention plate
38
with the upward flow of the raw water to form a packing medium accumulation layer
44
, whereas a water flow region
45
is formed in between the packing medium accumulation layer
44
and the lower outflow prevention plate
40
, with no or little substances except the flowing water.
The water collection zone
36
is a region for collecting the treated water which has been treated through the packing medium zone
34
, the zone
36
consisting of a water collecting part
46
disposed immediately above the outflow prevention plate
38
of the packing medium zone
34
, a water collection trough
48
for collecting 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 the 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
which 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
for changing the direction of the downward flowing raw water to upward direction. 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 whose lowermost part 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 cleanse the packing medium
42
of the packing medium accumulation zone
34
.
In the coagulation tank
20
the raw water bearing the coagulant first flows into the inflow zone
32
. First settled and separated in the inflow zone
32
are relatively large flocs among flocs formed as a result of coagulation of the suspended solids in the raw water.
The raw water then flows into the packing medium zone
34
, in which micro flocs remaining in the raw water come into contact with the packing medium
42
and adhere onto the external surface of the packing medium and onto the inner surface of the packing medium or is captured in the interstices between the packing medium
42
and is separated from water. On the other hand, the raw water flows through voids of the packing medium
42
or flows through between the packing medium
42
, and is filtrated through the floc layer formed in the voids or between the packing medium, while simultaneously micro flocs in the raw water are captured by the floc layer.
The flocs which have adhered onto the packing medium
42
or have been captured between the packing medium grow gradually due to contact with the subsequent micro flocs or the like, resulting in an increase of the floc diameter. Then, accordingly as the flocs having a higher settlement velocity than the upward flow rate of the raw water become formed, those flocs are dislodged from the packing medium
42
due to the flow of raw water and further settle against the flow of the raw water and are retained in the sludge storage zone
58
, and then discharged from the sludge discharge pipe
60
.
In this manner, the suspended solids in the raw water are separated from the raw water and settled in the sludge storage zone
58
due to the coagulation function of the suspended solid flocs, filtration function thereof for the raw water, and separation and settlement function of the floc. On the other hand, the raw water flows as the treated water from the upper water collection zone
36
into treated water tank
52
.
This upward flow type coagulator enables a high speed treatment to be performed since the density of the coagulated flocs which have become thickly agglomerated is high with correspondingly higher settlement speed. Accordingly, the facilities become compact, resulting in a smaller facility area, with reduced dosages of chemical agents (coagulants, etc.), and with easy treatment and disposa
Miyanoshita Tomoaki
Ochiai Hisaaki
Cecil Terry K.
Drodge Joseph W.
Organo Corporation
Rosenthal & Osha L.L.P.
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