Liquid treatment apparatus

The apparatus includes a tank of steel, or concrete, into which the liquid to be treated is introduced vertically through a centrally located inlet at the tank bottom. Disposed inside the tank, above said inlet, are a tubular venturi-type eductor member and a conical partition member which defines a liquid mixing, coagulating, flocculating and sludge recirculating zone. As the entering liquid flows through the eductor, it draws in a very large volume of surrounding sludge to establish a high degree of sludge recirculation and mixing.

This invention relates to an apparatus for the treatment of liquids to 
remove suspended solids. 
In the purification of water or waste liquid (domestic sewage or industrial 
waste water) it is customary to add certain chemical flocculants (e.g. 
alum) to the liquid being treated to produce a mass of gelatinous 
suspended particles commonly called "floc particles". These particles are 
encouraged to grow in size during a period of mixing, coagulation and 
flocculation. The "floc particles" combine with suspended matter in the 
liquid being treated to produce a dense floc which can be removed by 
gravity settling in a clarifier. 
Normally, the liquid being treated is conveyed from its source (e.g. river, 
lake, industrial plant, municipal sewer) to the treatment facility by 
conventional pumping equipment. However, since the liquid must be 
relatively quiescent in the clarifier all of the energy imparted to the 
liquid by the pumping equipment must be completely disipated before it 
enters the clarifier. 
The United States patent literature contains several examples of liquid 
treatment apparatus in which flocculation and gravity settling are said to 
take place in the same tank. An early example of this type of apparatus is 
shown in U.S. Pat. No. 2,268,726 to Tark. In that case, flocculation is 
induced by means of a high speed paddle-type mixer. Scraper chains are 
employed to remove settled sludge from the bottom of the tank. U.S. Pat. 
Nos. 3,473,665 (Duff) and 3,929,640 (Dohnert) show examples of water 
treating apparatus in which rotary scraper assemblies are used for 
scraping settled sludge from the bottom of a settling tank. In each case, 
the scraper assembly includes a vertical shaft for driving scraper arms 
which sweep over the bottom wall of the tank. Water is introduced through 
a series of annular nozzles arranged around the shaft. However, it is 
believed that this annular nozzle arrangement would not be effective in 
producing the vigorous mixing action which is required to induce 
satisfactory flocculation. 
An object of the present invention is to provide an improved liquid 
treatment apparatus in which flocculation and gravity settling can take 
place in the same tank and in which the vigorous turbulent mixing required 
for efficient flocculation can be achieved by taking advantage of the 
energy ordinarily available in the influent water. 
The apparatus provided by the invention includes a tank for containing a 
body of liquid and having a floor. An inlet is provided for liquid to be 
clarified and is disposed in said floor of the tank and is arranged to 
direct influent liquid generally vertically upwards into the tank. Liquid 
outlet means disposed generally at the level of the surface of the body of 
the liquid, through which clarified liquid can leave the tank. Sludge 
outlet means is also provided in the floor of the tank through which 
settled particles can be removed as sludge. Sludge conveyor means is also 
provided and is operable to convey settled particles towards said sludge 
outlet means. A generally conical partition member is disposed in the tank 
above said inlet and defines a circulation zone therebelow. A tubular 
eductor member having open upper and lower ends is disposed in an upright 
position below the partition member and generally in aligment with the 
liquid inlet. The eductor member is arranged relative to said liquid inlet 
so that liquid entering the tank from the inlet flows upwardly in said 
member and enters said circulation zone through its open upper end, and 
liquid and suspended floc particles surrounding said open lower end of the 
eductor member are entrained by said upward flow of liquid, establishing a 
recirculation of liquid and suspended particles below said partition 
member for promoting flocculation of said particles. The portion of the 
tank outside the partition member defines a relatively quiescent zone for 
gravity settling of suspended particles.

The apparatus shown in the drawings has been designed primarily as part of 
a water purification plant; accordingly, the description which follows 
will relate specifically to this application of the invention although it 
is to be understood that the principles involved will be applicable to the 
purification of other liquids. 
Referring first to FIGS. 1 and 2, the apparatus includes a concrete tank 20 
of generally square shape for containing a body of water to a level 
indicated by reference character L. Water to be clarified enters the tank 
through a raw water inlet pipe 22 from a pumping installation (not shown). 
Pipe 22 terminates at a vertically arranged nozzle 24 inside the tank. 
Clarified water leaves the tank by way of an inner launder 26 or an outer 
launder 28. The launders are interconnected by a pipe 30 and a treated 
water outlet pipe 32 extends outwardly from the outer launder 28. Floc 
particles which settle from the water in the apparatus are removed as a 
sludge through a sludge outlet pipe 34 connected to a central sump 36. A 
sludge scraper assembly conveys settled sludge towards sump 36 and 
includes two scraper arms 38 and 40 mounted for rotation about a vertical 
axis denoted X--X in FIG. 1. An electric drive unit 42 is provided for 
rotating the scraper arms as will be described. 
A generally conical partition member 44 extends about axis X--X and is 
disposed in tank 20 above inlet nozzle 24, defining a liquid recirculation 
zone below the member. Member 44 is referred to as a reaction cone and 
defines a mixing, coagulation and flocculation zone 45 therebelow. 
Disposed inside cone 44 is a tubular eductor member 46 which also extends 
about axis X--X and which is positioned generally in alignment with nozzle 
24 so that water entering the tank through the nozzle will flow upwardly 
in the eductor. The eductor has an open upper end 48 through which water 
enters zone 45 and an open lower end 50. The open lower end 50 of eductor 
46 is disposed relative to inlet nozzle 24 so that water entering the 
eductor from the nozzle entrains surrounding water and suspended particles 
and a circulation pattern is established below the clarifier reaction cone 
44 as indicated by the arrows 51 in FIG. 1. In this particular embodiment 
a deflection baffle (see later) is provided above the open upper end 48 of 
the eductor member for laterally diverting liquid leaving the member into 
said circulation pattern as will be more specifically described later. 
At its lower end, eductor 46 has a generally conical inlet 52 to which the 
scraper arms 38 and 40 are attached as will be described. A tubular 
driving member 54 extends vertically upwardly from eductor 46 and is 
attached at its upper end to drive unit 42. Thus, it will be appreciated 
that the eductor forms part of the sludge scraper assembly and that rotary 
motion imparted to member 54 by unit 42 will be transmitted to the scraper 
arms by way of the eductor. 
The water entering tank 20 through inlet pipe 22 will be delivered from a 
pumping installation (not shown) by which the water will have been pumped 
from a river, lake or other source. Pipe 22 includes an inlet port 58 
through which chemical flocculating agents such as alum can be added to 
the raw water. Complete mixing is accomplished as the flocculating agent 
and water flow at high velocity through nozzle 24 into the tank. The 
eductor 46 and reaction cone 44 are designed to allow substantially 
unrestricted recirculation of the water below the reaction cone and 
promote a high degree of mixing and sludge recirculate which in turn 
maintains a high level of floc particles under the cone. Cone 44 confines 
the turbulent water to the liquid recirculation zone defined by the cone 
while the water in the remainder of the tank is in the relatively 
quiescent state required for good settling. 
Long chain hydrocarbons known as "polyelectrolytes" can be added through a 
chemical feed pipe 60 located at the top of the reactor cone. 
Polyelectrolytes tend to cause pin point floc particles to adhere to one 
another to form larger particles. A high concentration of floc particles 
under the cone 44 is required for efficient coagulation and flocculation. 
This is accomplished by effective turbulent mixing and a high degree of 
sludge recirculation obtained through the eductor assembly 46. This 
combined with the addition of polyelectrolytes will promote the formation 
of large floc particles which have good settling characteristics. A high 
level of sludge recirculation is required for efficient coagulation and 
flocculation. 
As raw water continuously enters tank 20 from inlet pipe 22 a mixture of 
floc particles and water flows out around the bottom edge of cone 44, as 
indicated by arrow 62 in FIG. 1. Heavier, larger particles settle out and 
fall to the bottom of tank 20. The lighter, smaller particles will rise as 
indicated by arrows 64. Because of the shape of cone 44 the area available 
for settling increases as the smaller particles rise. This increase in 
settling area reduces the upward velocity of the smaller, lighter floc 
particles and permits them to settle out at a higher level in tank 20. 
This action effectively forms a suspended blanket of clarified floc 
particles with the larger heavier particles at the bottom and the smaller, 
lighter particles at the top. This blanket, denoted 65 is referred to as a 
suspended sludge blanket. 
The suspended sludge blanket 63 acts as a filter medium through which the 
water is clarified as it flows upward through an array of tube settlers 68 
towards the launders 26 and 28. Coagulation and entrapment of smaller 
particles continues to take place within the suspended sludge blanket 63 
and causes them to grow in size and improves their settling ability. 
Through this action the smaller particles find their way to the bottom of 
the suspended sludge blanket to the point where they settle out on the 
floor of tank 20, where they are removed by sludge scraper 38 and 40 to 
the sump. Those pin point floc particles which are not trapped or 
coagulated in the "suspended sludge blanket" will continue to rise towards 
the tube settlers. The tube settlers will be more specifically referred to 
in connection with FIG. 4. For the present it is sufficient to note from 
FIG. 4 that the tube settlers cover the entire clarifier surface from 
inside tank 20 to the outside of cone 44. In this particular embodiment 
cone 44 occupies a diameter of only 5'0" to maximize the number of tube 
settlers that can be fitted into a given clarifier area. 
Having described the principal components of the apparatus and its 
operation, the apparatus will now be described in more detail. Referring 
first to FIGS. 1 and 2, tank 20 has a floor 70, the top surface of which 
slopes towards the central sump 36. Sidewalls 72 extend vertically 
upwardly from floor 70 to define the generally rectangular shape of the 
tank as can best be seen in FIG. 2. It will be noted that the corners of 
the tank are flattened slightly as indicated at 74 in order to avoid sharp 
internal corners. Floor 70 includes relatively steeply inclined arcuate 
portions 76 which can best be seen in FIG. 1 and which are indicated by 
dotted lines in FIG. 2. It will be seen from this latter view that these 
arcuate corner portions define a generally circular central area 78 of 
floor 70 which is relatively flat although nevertheless dished slightly 
towards sump 36. Only this central portion 78 of floor 70 is swept by the 
scraper arms 38 and 40 as the sludge scraper assembly rotates in use. 
Gravity feed is relied on in the case of particles which settle onto the 
arcuate corner portions of the floor. These particles will form a sludge 
which will travel down the corner portions into the path of scraper arms 
38 and 40. 
Adjacent their upper ends, each of the sidwalls 72 is formed with an 
integral channel-shaped formation 80 having an outer limb 82 and a lower, 
inner limb 84. The channel-shaped formations 80 merge with one another to 
define a continuous trough around the top of the tank which forms the 
outer launder 28. Weir plates such as those indicated at 86 in FIGS. 1 and 
4 are bolted to the inside surfaces of the inner limbs 84 of the 
formations 80 so as to protrude above the tops of the limbs and define the 
water level in the tank. The weir plates 86 are of conventional form and 
have saw-tooth shaped upper edges over which the water spills. This edge 
shaping has been found to be preferable since it avoids levelling problems 
which are found to occur with straight edged weir plates. The treated 
water outlet pipe 32 extends through the outer limp 82 of one of the 
formations 80 for conveying treated water from the apparatus. 
A main support beam 88 extends across tank 20 from one side to the other 
generally on the relevant center line of the tank (see FIG. 2) and is 
supported on the limbs 82 of the channel-shaped formations 80 of sidewalls 
(see FIG. 1). Beam 88 is in the form of two longitudinally extending boxed 
section members 90 disposed at respectively opposite sides of the beam and 
covered by top and bottom plates, one of which is visible at 92 in FIG. 2 
so that the beam overall has a closed rectangular cross-section. Beam 88 
supports the sludge scraper assembly and the clarifier reaction cone 44 of 
the apparatus as will be described. The beam also provides a walkway for 
maintenance personnel across the top of the tank. Suitable handrails will 
be provided for safety purposes but are not shown in the drawings. Beam 88 
also supports the inner launder 26. It will be seen that this launder is 
of square shape in plan and is suspended below beam 88 so as to be 
immersed in the water in tank 20 to a level corresponding substantially to 
the level of the weir plates 86 of the outer launder. The inner launder is 
fabricated from four channel-shaped metal sections one of which can 
clearly be seen at 94 in FIG. 4. Two pairs of launder support arms 96, 
(each of C-shaped in section) are welded to the underside of the main 
support beam 88 so as to project outwardly to both sides of the beam 
substantially at right angles thereto at positions corresponding to the 
intended position of the inner launder as can best be seen in FIG. 2. 
Transverse support brackets 98 (FIG. 4) are welded to the underside of the 
channel members 94 at appropriate positions and are coupled to the launder 
support arms 96 by tie rods 100. Weir plates 102 of similar shape to the 
weir plates 86 of the outer launder are bolted to the outer sides of the 
channel members 94. As indicated previously, the launders are connected by 
a pipe 30. This pipe connects at its inner end into the channel member 98 
of the inner launder and at its outer end into the outer launder 28 so 
that water collected in the inner launder will travel to the outer launder 
and, from there, to the treated water outlet pipe 32. 
The raw water inlet pipe 22 of the apparatus passes through the bottom wall 
of the tank to the sump 36 and includes a 90.degree. elbow 104 which is 
upwardly directed inside the sump 36. Nozzle 24 is fitted to elbow 104 and 
is in the form of a straight pipe section having a slightly inwardly 
bevelled upper end 24a. Nozzle 24 terminates inside the generally conical 
inlet portion 52 of the eductor of 46. The eductor is a sheet metal 
fabrication designed to provide a venturi-like throat just downstream of 
nozzle 24. This throat is formed by a generally cylindrical section 106 of 
the eductor which is of constant cross-sectional shape throughout its 
length. At its lower end, section 106 is connected to the conical inlet 
portion 52 of the eductor, while at its upper end the section is connected 
to an upwardly flared top section 108. 
It will be appreciated from the foregoing that as water is discharged from 
nozzle 24 into the eductor, it enters the throat formed by section 106 at 
high velocity and causes water and suspended floc particles in the 
vicinity of the eductor inlet to be entrained and drawn up through the 
eductor with the incoming water to establish a recirculatory flow as 
described previously. 
Eductor 46 is symmetrical about axis X--X. The vertical driving member 54 
from the drive unit 42 is also disposed on axis X--X and extends down a 
substantial distance into the top eductor section 108. Member 54 is 
coupled to section 108 by three plates, two of which are indicated at 110 
in FIG. 1 which are equiangularly disposed about axis X--X and are 
disposed in planes which radiate outwardly from the axis. The plates are 
welded both to member 54 and to the inner surface of section 108. 
The support plates 110 project a substantial distance above eductor section 
108 and terminate at a top member 112 (see FIG. 3) which defines the 
deflection baffle referred to above. Member 112 is of inverted conical 
shape and has a downwardly inclined lip 114 around its periphery. Due to 
its inverted conical shape member 112 serves to deflect outwardly water 
and floc particles rising in the top eductor section 108 and assists in 
establishing the recirculatory pattern below the clarifier reaction cone 
as discussed above. In other words, water travelling upwardly in the 
eductor will pass between the support plates 110 and be deflected 
outwardly through the space between the top member 112 and the upper edge 
of the top eductor member 108. 
Extending vertically downwardly through the tubular driving member 54 is a 
control rod 116 for a flow adjuster device 118 which is disposed within 
the open upper end of the water inlet nozzle 24 for varying the rate at 
which water enters the tank through the nozzle and hence the turbulence of 
the mixing which takes place below cone 44. Device 118 has the shape of 
two cones placed with their bases in contact and is positioned on rod 116 
so that the device is generally in the mouth of nozzle 24. The portion of 
rod 116 below the device is received in a collar 120 coupled by a bracket 
122 to the sidewall of the nozzle. At its upper end, rod 116 terminates 
within a coupling tube 124 bolted at a flange 126 to the top end of 
driving member 54. A cross member 128 is attached to the upper end of rod 
116 so as to extend transversely therefrom and protrude through two 
aligned vertical slots in tube 124, one of which is visible at 130. Cross 
member 128 is welded to a plate 132 which is loosely fitted around tube 
124 and which is coupled by two bolts 134 to a similar plate 136 welded to 
tube 124. The bolts 134 are adjustable to vary the spacing between the two 
plates 132 and 136 and hence the vertical position of device 118 and the 
extent of the annular water inlet opening between the member and the wall 
of inlet 24. 
Drive unit 42 is mounted on the main support beam 88 of the apparatus and 
includes an electric motor 138 coupled to a speed reducing gear box 140 
having an output shaft 142. Shaft 142 is connected to the upper end of the 
coupling tube 124 by means of a flange type coupling 144. The drive unit 
is mounted on beam 88 by way of a support bracket 146. The drive unit is 
designed to rotate the driving member 54 of the sludge scraping assembly 
at a relatively slow speed so as to cause the scraper arms 38 and 40 to 
sweep slowly over the bottom wall of tank 20. 
As indicated previously, eductor 46 forms part of the sludge scraper 
assembly and the scraper arms 38 and 40 are connected to the generally 
conical inlet portion 52 of the eductor. 
Referring primarily to FIG. 3, it will be seen that inlet portion 52 slopes 
downwardly from section 106 of the eductor to a depending flange 148. In 
FIG. 3, part of scraper arm 40 is visible in an exploded position adjacent 
the eductor. Since the two scraper arms are essentially the same only arm 
40 will be described. The arm includes a frame 150 constructed from 
seamless black iron pipe and including three main longitudinal members 
152, 154 and 158 arranged in a triangular configuration with two of the 
longitudinal members (152 and 154) defining the base of the triangle and 
the third member 158 at the top. Bracing struts generally denoted 160 
extend between the longitudinal members. At their inner ends, the 
longitudinal members are each fitted with attachment flanges 162. 
Frame 150 carries three scraper blades, one of which is visible at 164, and 
each of which is attached to the frame by mounting plate such as that 
indicated at 166 welded to one of the bottom longitudinal members of the 
frame. Each blade will in fact be provided with two mounting plates welded 
one to each of the bottom longitudinal frame members. The mounting plates 
are disposed in oblique positions with respect to the frame members on 
which they are mounted so that the scraper blades are angled with respect 
to the length of the arm in the direction such that the blades will tend 
to convey settled sludge towards the central sump 36 of the tank. Only one 
of the scraper blades of arm 40 is visible in FIG. 3 although it will be 
understood that the other two arms will be similarly angled. Those arms 
are denoted 168 and 170 in FIG. 1. Scraper arm 38 is essentially of 
similar construction and includes three scraper blades 172, 174 and 176. 
Referring back to FIG. 3, the scraper arms are attached to the conical 
member 52 of eductor 46 by two attachment members 178 and 180 which 
project outwardly from opposite sides of the flange 148 of eductor inlet 
52, generally radially with respect to axis X--X. Each of the members 178 
and 180 has a flange 182 and 184 respectively at its outer end which mates 
with the corresponding flange on the top longitudinal member of the 
relevant scraper arm. Thus, flange 184 mates with the flange 162 of the 
top longitudinal member 158 of scraper arm 40 and flange 182 mates with a 
corresponding flange on arm 38. The mating flanges are coupled together by 
bolts (not shown). 
The bottom longitudinal members 152 and 154 of scraper arm 40 are coupled 
to the corresponding members of arm 38 (one of which is visible at 186 in 
FIG. 1) by means of a coupling unit generally indicated at 188 in FIG. 3. 
Unit 188 includes two parallel tubes 190 and 192 which extend between the 
bottom longitudinal members of the two scraper arms and which have flanges 
194 and 196 at their respective ends. These flanges are bolted to the 
corresponding flanges on the longitudinal members of the scraper arms. The 
two tubes 190 and 192 are joined by a plate 198 having an upwardly 
extending sleeve 200 on its top surface. 
As can best be seen in FIG. 1, in the assembled apparatus, coupling unit 
188 is positioned around nozzle 24 and above the tank sump 36, at a level 
just slightly above the top surface of the bottom wall 70 of tank 20. Unit 
188 is in fact attached to eductor 46 by three generally triagnular 
plates. Two of which are visible at 202 and 204 in FIG. 1. These plates 
radiate outwardly from sleeve 200 in equally angularly spaced planes 
passing through axis X--X. The plates have vertical inner edges which are 
welded at their lower ends to sleeve 200 and the upper inclined edges of 
which are welded to the underside of eductor inlet 52. Thus, it will be 
appreciated that the coupling between eductor 46 and sleeve 200 is such 
that coupling unit 188 will turn when the eductor is turned. The scraper 
arms 38 and 40 are attached to coupling unit 188 and will therefore also 
turn with the eductor. As indicated previously, the eductor itself is 
coupled to the member 54 which depends from drive unit 42 and will 
therefore be rotated when the drive unit is operated. 
Sleeve 200 of coupling unit 188 also serves as a bearing housing for 
maintaining the scraper arms rotationally centered with respect to axis 
X--X. Referring back to FIG. 3, a bearing sleeve 206 is provided for 
mounting inside the sleeve 200 of coupling unit 188. Bearing sleeve 206 
has an external diameter substantially less than the internal diameter of 
sleeve 200 and is held inside sleeve 200 by three bolts 208 which project 
inwardly through sleeve 200 in equiangularly spaced positions, and the 
inner ends of which bear against and frictionally retain bearing sleeve 
206. The inner diameter of sleeve 206 is selected so that the sleeve is 
freely turnable on an inner metal sleeve 210 (see FIG. 1) welded around 
the external surface of water inlet nozzle 24. Bearing sleeve 206 is made 
of an elastomeric bearing material sold under the trade mark THORDON and 
available from Thomson Gordon Limited of Hamilton, Ontario. It will be 
appreciated that, as eductor 46 is turned, the coupling unit 188, and with 
it bearing sleeve 206 will also turn with respect to nozzle 24 while the 
bearing arrangement represented by sleeves 206 and unit 188 will maintain 
the eductor and scraper arms centered with respect to axis X--X. 
Coupling unit 188 additionally serves to provide a mounting for three 
scraper arms for the sludge collection sump 36 of tank 20. Two of these 
arms are visible at 212 and 214 in each of FIGS. 1 and 3. Referring 
particularly to FIG. 1, it will be seen that the sleeve 200 of coupling 
unit 188 extends below plate 198 of coupling 188. The cone scraper arms 
are attached to the sleeve 200 by lugs, one of which is visible at 216 
welded to sleeve 200 below plate 198, and to each of which one of the cone 
scraper arms is bolted. Each of these arms is formed by an angle section 
strut which projects outwardly and downwardly from sleeve 200, and to the 
outer end of which is transversely welded a blade of similar 
cross-sectional shape. In FIG. 3, the strut and blade of arm 212 are 
denoted respectively 218 and 220. The arms are angled and arranged so that 
their blades scrape the inner surface of sump 36 as the sludge scraper 
assembly rotates, causing sludge which may have adhered to said surface to 
be dislodged and moved down by gravity to the sludge outlet 34. 
The clarifier reaction cone 44 is a sheet metal fabrication and is in fact 
in the shape of a pyramid having an octagonal base (see FIG. 2). At its 
upper end, the cone is supported by an octagonal sleeve 222 which is 
coupled to the cone by angle section coupling elements generally indicated 
at 224 attached respectively to the cone and to the sleeve and welded to 
one another. At its upper end, sleeve 222 is fitted with angle section 
brackets 226 which in effect define a flange around the top of the sleeve 
and by which the sleeve is bolted to the main support beam 88. Guy rods, 
two of which are indicated at 228 and 230 in FIG. 1 also extend between 
beam 88 and the cone for stabilizing the cone. Each guy rod includes a 
turnbuckle 232 and 234 respectively by which the length of the associated 
rod can be adjusted for adjusting the installed position of the cone. 
The apparatus includes an array of tube settlers generally indicated at 68 
in FIG. 1 disposed in tank 20 just below the level L of the liquid 
therein. FIG. 4 shows part of this array in detail. The array is made up 
of a plurality of tube settler sections which cover the whole of the 
surface area of the tank with the exception of the area occupied by the 
reaction cone support sleeve 222. The arrangement of the sections is 
indicated by the lines denoted 236 in FIG. 2. Each tube settler section is 
in the form of a plastic extrusion comprising a plurality of square 
section tubes 238 disposed in a tightly packed arrangement with each tube 
disposed at a relatively shallow inclination to the vertical. The sections 
are supported on cross beams, one of which is indicated at 240 in FIG. 4. 
As water in tank 20 rises in the tank towards the outlet launders, it will 
enter the settler tubes in the generally vertical direction, but due to 
the inclination of the tubes, will be deflected laterally to some extent. 
This will cause floc particles in the water to fall down onto the lower 
sides of the tubes generally as indicated by reference numeral 242 in FIG. 
4. These particles will thus collect inside the tubes and form a sludge 
which will tend to slide out of the tubes by gravity as indicated by 
reference numeral 40. 
By way of further explanation, when pin point floc particles settle in a 
vertical direction the rate of fall is governed by Stokes Law. However, if 
they settle in an incline tube the vertical distance that they must settle 
is reduced to 2-3 inches. Once the particle reaches the inclined tube 
surface it slides down the tube to form a fine sludge. When this fine 
sludge is discharged from the bottom of the tubes it will have sufficient 
mass to settle into the suspended sludge blanket 63 below where it will 
gradually agglomerate and coagulate to a point where it is large enough to 
reach the floor of tank 20. The application of tube settlers to remove pin 
point floc particles will permit the clarifier to produce a sparklingly 
clear effluent. 
The tube settlers also have the advantage that they allow the apparatus to 
be operated at a higher rise rate (throughput of water) than would 
otherwise be possible. Thus, the tube settlers will remove relatively 
light floc particles which would otherwise settle out only if the water in 
which the particles are suspended was allowed to remain quiescent in the 
tank for a much longer period than is necessary with the present 
apparatus. A further advantage of the present design is that it allows a 
large area of tube settlers to be provided as discussed previously. 
To summarize, in the apparatus shown in the drawings mixing, coagulation, 
flocculation and gravity settling take place in the same tank, while at 
the same time, the extensive gentle turbulant mixing and sludge 
recirculating required for efficient coagulation and flocculation can be 
achieved. This is accomplished by taking advantage of the energy 
ordinarily available in the incoming liquid. Thus, the overall efficiency 
of the chemical treatment system is dependent on the combined efficiency 
of each of the individual unit process that make up the system (e.g. 
mixing, coagulation, flucculation and clarification). The system 
efficiency increases tremendously if the settled floc particles can be 
gently recirculated within the coagulation and flocculation zone. This 
action induces chemical coagulation and flocculation to take place on the 
surface of already formed floc to produce large, denser particles having 
better settling characteristics. The apparatus provided by one inventor is 
designed to maximize the operating efficiency of each of the four basic 
unit processes which make up the overall chemical treatment system. 
The relatively quiescent area (outside the cone) allows for gravity 
settling and is designed for maximum utilisation of tube settlers for 
efficient removal of pin point floc and production of a sparklingly clear 
effluent. In this area, not only does gravity settling take place, but 
also floc "blankets" tend to form as discussed previously which act to 
filter small floc particles from the water as it rises in passing to the 
launders. Also, the tube settlers provide for final removal of fine floc 
particles which have not already settled out by the time the water 
approaches the launders. Both inner and outer launders are provided for 
the purpose of assuming a reasonably uniform flow of water through the 
tube settlers across the entire area of the tank. 
The intensity of the mixing imparted by the water inlet nozzle 24 can be 
adjusted by varying the position of the device 118 in the nozzle as 
discussed previously. Thus, the optimum mixing effect for any particular 
liquid input will depend to some extent on the amount of solids present in 
the liquid. Generally speaking, a more turbulent mixing action is required 
for liquids having a high solid content than for liquids containing less 
solids. In other words, the apparatus is adjustable according to the 
nature of the liquid being processed. 
It will of course be appreciated that the preceding description relates to 
a particular embodiment of the invention and that many modifications are 
possible within its broad scope. For example, while the specific 
description refers to a sludge scraper assembly, it is to be noted that 
other forms of sludge conveyor means may be employed. In another 
embodiment, a screw type sludge conveyor could be employed, for example, 
as disclosed in U.S. Pat. No. 4,005,019. Another possibility would be to 
use a slat-type chain conveyor as disclosed in the Tark U.S. patent 
discussed above. 
With continued reference to the sludge removal means, it should also be 
borne in mind that it is not essential to employ a vertical drive shaft 
for operating the sludge conveyor. In the case of a slat-type conveyor, 
for example, no such shaft would be required. In other cases, a 
submersible motor could be employed for driving the sludge conveyor means. 
In most applications of the apparatus, the influent liquid will be pumped 
to the apparatus at a velocity sufficient to ensure that liquid entering 
the tank will flow through the eductor and recirculate as described. Thus, 
it is intended that the apparatus will ordinarily take advantage of the 
relatively high energy level imparted to the liquid by pumping equipment. 
However, in the event that the velocity of the liquid should be 
insufficient, it would of course be possible to provide auxiliary pumping 
means in association with the apparatus for achieving the required 
velocity. Also, it should be noted that the deflection baffle 112 is not 
essential. In an alternative embodiment the top of the clarifier reaction 
cone could be closed or fitted with means to laterally deflect liquid 
leaving the eductor member. In other cases, no physical baffle may be 
needed. 
Other detail modifications include the possibilities that tank 20 may be 
made of steel and that the sludge scraper assembly may include one or more 
scraper arms. 
Finally, it should be noted that the apparatus provided by the invention 
can be used not only for water purification, but also for removing 
suspended particles from other liquids, e.g. in the treatment of domestic 
sewage or industrial waste waters. The term "particles" is to be 
interpreted broadly as including not only solids but also colloidal 
suspensions.