Filtration system

A filtration system for cleaning contaminated fluids having input means disposed tangentially of a cylindrical filter surface and simultaneously sweeping said surface and providing a fluid flow therethrough and backwash means having one or more nozzle bearing standpipes adapted to simultaneously rotate within and axially reciprocate spray nozzles relative to a cylindrical filter assembly to dislodge particulates therefrom either concurrently or independently of the flow of contaminated fluid therethrough.

The present invention relates generally to in situ filtration of untreated 
water for industrial and domestic use and more particularly to a novel 
filtration system which is especially useful for, but not limited to, 
water recharge. 
BACKGROUND OF THE INVENTION 
While not universal, many segments of the world's population suffer from 
the lack of an adequate water supply at some time during the year. When 
this occurs, crops fail for want of irrigation and major health problems 
arise, both from dehydration and from the compulsive, albeit imprudent, 
use of contaminated water supplies to satisfy human thirst. 
Throughout history efforts have been directed to the creation of back-up or 
auxiliary water supply sources such as reservoirs or tanks, strategically 
placed dams in river beds, canals and the like. However, as is well known 
each has failed to totally resolve the problem and as a result, a need 
still exists for insightful means and methods to manage nature's water 
supply in such a way that mankind can have a ready source of usable water 
throughout the year regardless of general climate, terrain or the 
idiosyncrasies of local weather patterns. 
One area which typifies those geographical areas which have heretofore been 
subject to great heat and highly cyclical and frequently unpredictable 
rainfall is the Sonora desert which extends from the Southwest United 
States into Northern Mexico and includes Phoenix, Arizona, the ninth 
largest city inn the U.S. 
In the Phoenix Metropolitan area, the Salt River Project (SRP) is the 
largest raw water purveyor, founded basically to serve agricultural users 
and communities which do not have their own water supply. SRP delivers 
primarily through canals but, in addition, has approximately 250 wells to 
supplement its extensive surface water supply during dry periods and peak 
demand time. It is believed that these wells, which are located adjacent 
to SRP's canal conveyance system, could be further used for artificial 
ground water recharge if means could be developed to filter and treat the 
canal water to render it compatible with the wells and thereafter 
introduce that compatible water into the wells during idle ground water 
pumping periods. 
A pilot project was commenced in 1991 to evaluate the feasibility of using 
the SRP wells for artificial ground water recharge in the alluvial aquifer 
of the Salt River Valley. A test injection station was established in a 
well site which was found to possess all the desirable characteristics, 
including a monitoring well. An innovative injection system was installed 
and evaluated. This system used a rotating microscreen for filtration, and 
chlorination of canal water prior to its injection into the well (Gorey et 
al. 1989, Lluria et al. 1991). Although this system proved to be effective 
in reducing particulates, it was incapable of providing an adequate flow 
rate, was costly to erect and operate, and required considerable 
maintenance. The drawbacks encountered in this approach motivated SRP to 
announce a need for alternative solutions to the problem. The filtration 
system of the present invention was devised in response to that 
announcement. 
The use of idle production wells for ground water recharge is an attractive 
idea. However, such a well must be characterized by favorable geohydrology 
and ground water quality characteristics. Furthermore, the recharge water 
must be compatible with the well or else irreversible well damage may 
result. Three mechanisms exist that can plug and permanently damage a 
well: chemical, entrained air, and suspended particulates. Chemical 
plugging occurs when the water chemistry of the water used for recharge is 
significantly different than that of the water in the aquifer because it 
causes an ionic/chemical reaction to occur which closes up the pores of 
the well, and reduces its permeability. Air entrainment also adversely 
affects a well because air bubbles, driven by capillary action, become 
lodged in the formation and reduce its permeability. Indeed, the damage 
from air bubbles can be so extensive that well redevelopment, that is, 
pumping all water out of the well, may not be able to reverse the damage. 
Suspended particulate (organic and mineral) plugging is probably the major 
cause of reduction of recharge rates in injection wells because the 
clogging of the intergranular pores in medium and fine grained sediment 
aquifers substantially reduces their permeability. If the suspended solids 
concentration is large and the time of injection with this type of water 
is considerable, permanent damage to the well may also result. Well 
redevelopment, using pumping and surging, is the only method presently 
known which can improve well recharge performance. If the source for well 
recharge is untreated water, frequent redevelopment will be required at 
very short time intervals, elevating the cost of the recharge operation 
and reducing the long-term injection rate. 
In dealing with canal water, mineral particulates did not present a 
problem. On the other hand, the canal water was rich in organics, 
primarily algae, and that presented a major challenge to the filtration 
system. 
The desiderata leading to the present invention was the quest for a 
filtration system which has the ability to remove large particulates and 
organics, provide high flows, keep air from being entrained, and which 
would be relatively inexpensive to build and operate. 
In our pursuit, it was learned that filters which work well in the water 
treatment business are not necessarily feasible for recharge. For 
instance, the centrifugal separator, an excellent means to remove sand and 
heavy particulates, could not be used for water recharge because the 
suspended particulates in canal water are primarily organic and have a 
density close to that of water. As a result, centrifugal forces cannot 
differentiate between the organic particulates and water. 
Further, the cost of the filter must be relatively low since present 
economic incentives for recharge are modest. This also means that the cost 
to build and operate the system must be low, and to be cost-effective, the 
system must be able to produce large flows. It is toward accomplishment of 
these goals that the present invention is directed. 
Of course, there are also many prior art patents which deal with fluid 
filtration systems and their associated backwash or filter cleaning 
mechanisms developed to attempt to improve filtering efficiency. Among 
such disclosures are Vandercook (U.S. Pat. No. 1,139,825) who discloses a 
filter system in which a rotating nozzle assembly is used to spray a 
solid-liquid mixture against a horizontal filter. This spraying action not 
only facilitates the filtration, but also helps to keep the filter free 
from excessive buildup of unfiltered solids. A backwash process is also 
disclosed in which either water or air is forced up through the filter 
from below and coacts with a stream of water or air from the rotating 
nozzle assembly to dislodge debris from the filter surface. 
Morino (U.S. Pat. No. 2,851,164) discloses a swimming pool filter in which 
a filter element is suspended in concentrical relationship about a fixed 
spray head which consists of a vertical tube having a plurality of holes 
disposed therein. Whether filtering or backwashing, incoming water is 
flowed into and through the fixed spray head. A valve is provided to 
increase the flow pressure during backwashing to create a "jet" to clean 
the filter element. 
Snyder (U.S. Pat. No. 3,193,103) discloses a submersible pond filter having 
a cylindrical metal mesh strainer which contains a cleaning mechanism 
comprising a plurality of flexible, elastomeric hoses disposed 
therewithin. Fluids such as water, air, or both are forced under pressure 
into the elastomeric hoses which causes them to whip and flail about and 
direct a stream of fluid against the inner surface of the filter to 
dislodge debris therefrom. 
Everroad (U.S. Pat. No. 3,236,249) discloses a free-standing filter 
cleaning device for cleaning individual cylindrical filters which are 
imported into the cleaning device. The device also includes a rotatable 
spray head arrangement comprising a cylindrical inner spray standard 
having a plurality of spray heads formed thereon, and two outer spray 
pipes, each having a plurality of spray heads which face radially 
inwardly. The inner sprays deliver a cleaning fluid radially against the 
interior of the filter, while the outer sprays spray the exterior. The 
outer pipe spray heads are positioned at a slight lateral angle thereby 
causing the entire spray head arrangement to rotate about its cylindrical 
axis during the cleaning operation in response to the "jet propulsion" 
created thereby. 
Knieriem (U.S. Pat. No. 3,337,052) teaches a filter apparatus comprising an 
outer housing having a detachable top, and an inner cartridge assembly 
having a sintered filter element as a substantial part of its side wall. 
Fluid to be filtered flows into the housing, through the filter element on 
entering the cartridge and then flows out of the housing. The filter 
element is a porous, electrically conductive, sintered material that has a 
substantial electrical resistance. To clean this filter of clogged debris, 
an electrical current is passed through the filter element to heat the 
filter and burn any material caught on the filter. Gas purge means are 
then provided to blow the resulting ash from the assembly. 
MacFarlane (U.S. Pat. No. 4,759,846) discloses a rotatable filter drum with 
a permeable filter element. The fluid to be filtered is passed through the 
filter element to the interior of the filter drum from which the filtrate 
then exits. To backwash the filter element, a plurality of hollow backwash 
arms are disposed outside of and operably bear against the filter element 
to provide a backwash seal. The backwash arms are preferably positioned so 
that they will sweep the entire surface of the filter element during one 
full rotation of the filter drum. 
In the use of this device, backwashing and filtering can occur 
simultaneously. As the filter drum rotates, most of the fluid flows 
through the filter and out the filtrate outlet. However, a small 
percentage of filtrate is simultaneously forced back through the filter 
element into the backwash arms. A lower pressure is preferably maintained 
in the backwash arms to suction the limited back flow into the arms. 
Contaminants are dislodged by the back flow and carried out through the 
backwash arms. Rotating spray arms that sweep the inside surface of a 
filter drum may also be used to help loosen the debris. 
Wilkins, et al. (U.S. Pat. No. 4,822,486) teaches a cylindrical, rotatable 
self-cleaning strainer or filter having a fixed nozzle structure mounted 
within the filter. The nozzle structure is supplied with water from an 
independent source and the water is forcefully discharged against the 
filter to dislodge trapped debris from the outside of the filter. 
As is readily apparent, none of the prior art teaches a filtration system 
which achieves all of the aforestated goals. It is toward the realization 
of those goals that the present invention is directed. 
BRIEF SUMMARY OF THE INVENTION 
The present invention relates to a novel and unique water recharge 
filtration system which is gravity fed and can operate with heads as low 
as the height of the filter. A novel filter comprising a synthetic filter 
fabric or screen mounted on the outside of a cylindrical, skeletal frame 
and fitted within a cylindrical tank comprises one salient element of the 
new system. 
Still another important aspect of the present invention is the provision of 
an off-center tangentially disposed feed inlet which during the filtering 
mode, not only maintains a full charge to the filter but by its induced 
turbulence sweeps across the filter screen and dislodges accumulated 
particulates therefrom thereby enabling each filter cycle to be 
substantially extended and reduces the incidence of major independent 
backwashes. The vortical effect of the raw water inflow also settles out 
heavier particulates and keeps lighter contaminants afloat to delay their 
impingement on and in the filter screen. 
Another important feature of the present invention is the provision of a 
backwash and filter cleaning system in which a plurality of strategically 
placed jet-stream nozzles are assembled on a shaft which simultaneously 
rotates about and reciprocates along the vertical axis of the shaft to 
provide full disgorgement of all particulates lodged within filter screen 
openings while, either independently backwashing or simultaneously 
cleaning some filter screen openings during continued filtering of the 
input fluid. 
In practice, untreated raw water is fed tangentially to an annulus defined 
between the filter tank and the cylindrical filter frame from whence it is 
passed through the filter and is delivered into a storage tank, where, 
when desired, it can be disinfected by chlorination or by using other 
suitable chemicals and prepared for its ultimate consumptive use. The 
storage tank allows uninterrupted flow to the ultimate user, even while 
the filter unit is being independently backwashed. When a storage well is 
the immediate destination for the processed water, the storage tank also 
minimizes the possibility of air entrainment in that well because of its 
configuration such that the air bubbles float to the surface of the tank 
and dissipate. The filter screen is either simultaneously cleaned during 
filtering mode or independently backwashed by selectively directing 
filtered water from the storage tank through a plurality of rotating and 
reciprocating nozzles located in the center of the frame. The filter frame 
structures are preferably fiberglass. Tests have demonstrated peak flows 
in the preferred embodiment in excess of four m.sup.3 /min, with the 
average flow depending on the quantity of algae present and the frequency 
or duration of backwash. 
Accordingly, a primary object of the present invention is to provide a 
novel and unique water filtration system which is capable of removing 
large particulates, provides high flow, avoids air entrainment, is self 
purging and which is relatively inexpensive to build and operate. 
Another object of the present invention is to provide a novel and unique 
water filtration system which is especially useful in processing water for 
recharging domestic wells. 
Still another object of the present invention is to provide a novel filter 
system having a unique backwash and filter cleaning system adapted to 
simultaneously vertically reciprocate while rotating to selectively 
dislodge particulates from ever-changing target areas of the screen. 
Still a further object of the present invention is to provide a novel and 
unique filtration system having an off-center tangentially disposed inlet 
so positioned to enable the inlet flow to swirl and circulate around the 
filter frame to create a vortex which simultaneously settles out heavier 
particulates and sweeps debris from the filter screen. 
These and still further objects as shall hereinafter appear are readily 
fulfilled by the present invention in a remarkably unexpected fashion as 
will be readily discerned from the following detailed description of an 
exemplary embodiment thereof especially when read in conjunction with the 
accompanying drawings in which like parts bear like numerals throughout 
the several views.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention relates to a novel filtration system which, as shown 
in FIG. 1, is identified by the general reference 10. The system, 
denominated "Cylindrical Filter System" or "CFS" has been developed 
especially for recharge applications but is not so limited in its use. For 
illustrative purposes only, the present invention will be described in a 
setting with a rechargeable well. 
As shown in FIG. 1, unfiltered or raw fluid such as water is taken from a 
raw water source such as canal 12 and suitably transported, either by 
gravity feed or pump activation through inlet conduit 14 and inlet valve 
16 into filter assembly 18 which removes foreign particulates from the 
fluid. From filter assembly 18, the filtered or clean fluid is passed 
through outlet conduit 20 into storage tank 22 (where chlorination may 
take place as desired) from which, inter alia, it can be withdrawn through 
storage tank valve 24 and directed to the ultimate destination such as 
adjacent recharge well 26. 
System 10 is especially designed for, but is not limited to water recharge 
installations. When thus used, however, the contaminated fluid, that is 
canal water, is fed from its source 12 through inlet valve 16 into annulus 
27 substantially tangentially to filter screen 28 as shown in FIG. 2. 
Annulus 27 is the open space disposed around cylindrical filter screen 28 
Which is itself mounted on the perimeter of generally cylindrical skeletal 
filter frame 30 (which is preferably 1.52 m high and 0.81 m in diameter). 
Frame 30 and screen 28 as thus attached are centrally and preferably 
coaxially mounted within cylindrical tank 33 (preferably 0.91 m in 
diameter). 
As shown in FIG. 3, skeletal frame 30 comprises a plurality of annular 
rings 31 disposed in vertically spaced generally parallel relationship to 
each other and interconnected by a plurality of spaced vertically 
extending generally parallel slat members 32. As constructed, the frame 30 
is circumscribed by a suitable filter fabric screen 28 to complete the 
filter assembly 18. 
The fluid, once passed through filter screen 28 into the area within frame 
30 exits through a bottom opening 34 of tank 33 into outlet conduit 20 and 
hence to storage tank 22. In operation, the hydrostatic head across the 
screen 28 forces the fluid through screen 28 while particulates are 
trapped in the screen mesh. FIG. 1 shows a schematic of the complete 
installation. Water is introduced tangentially as shown more particularly 
in FIG. 2, into cylindrical filter assembly 18 and produces a turbulent 
flow which swirls around, across and through screen 28. The sweeping 
action across the screen surface serves to remove some of the particulates 
previously deposited on the screen 28. 
The level of fluid in annulus 27 circumscribing screen 28 is maintained by 
modulating inlet valve 16. Preferably, this level is maintained close to 
the top of the filter assembly 18 to maximize head and hence flow. The 
level of the water can be monitored by means of a see-through slit window 
(not shown) defined on the side of the filter tank 33. In the event that 
valve 16 is not closed fast enough during a rising head, unfiltered water 
overflows through eight 0.10 m diameter holes on top of the filter tank 
where it spills to the ground. 
In another embodiment (not shown) a plurality of pressure or other water 
level sensors are used to activate automated inlet and backwash valves 16 
and 35 to operate an independent backwash mode described below. Preferred 
locations for such sensors are in either the storage tank 22 or the filter 
tank 33 of preselected levels to sense either a specific low level in 
storage tank 22 or a predetermined excess level or head in filter tank 33. 
After a period of operation, which may include continuous backwashing 
during water inflow filtering, and depending on the turbidity of the 
water, enough particulate matter will attach to the filter screen 28 to 
plug screen 28 and essentially stop the flow of fluid through filter 28. 
When this occurs, the fluid level in tank 22 lowers an appreciable amount 
as the fluid flow through conduit 20 falls below a predetermined 
threshold, either of which indicates that filter 28 needs to be fully and 
independently backwashed. Independent backwash is accomplished by closing 
inlet valve 16, opening backwash valve 35, and activating a preferably two 
hp swimming pool type pump (1 hp=0.7457 Kw) 36. Pump 36 moves previously 
filtered water from storage tank 22 through a computer-controlled valve 37 
which directs the flow sequentially to one or more standpipes 38 through a 
stationary supply pipe 39. This fluid then exits standpipes 38 through a 
series of nozzles 40 mounted thereupon which direct backwash water 
radially outward toward the inner surface 41 of filter screen 28, and 
thereby dislodge particulates lodged in the filter screen 28. FIGS. 4(a) 
through 4(d) show schematically the sequence of this backwash operation. 
In particular, FIG. 4a shows peak operation with inlet valve 16 open and 
backwash valve 35 closed. Also shown, are a high head in annulus 27 and 
optimum flow through screen 28 shown by the curved arrows. A corresponding 
high operating head is shown in storage tank 22. At some subsequent point 
in time, during which screen 28 has been clogged by particulates, FIG. 4b 
shows a reduced flow rate through screen 28 by the use of fewer curved 
arrows. As a result, the fluid levels inside both filter frame 30 and 
storage tank 22 begin to drop. Then, as is shown in FIG. 4c, by either 
manual or automated means, inlet valve 16 is closed, backwash valve 35 is 
opened, and clean fluid is sprayed from nozzles 40 in standpipe(s) 38 
against screen 28 from the interior of filter frame 30 as shown by the 
arrows. Note also that filtered fluid continues to exit storage tank 22 
through valve 24. FIG. 4d shows the completion state just before 
re-initiating the filtering mode shown in FIG. 4a. Finally, note that 
although this independent backwash procedure involves shutting down inlet 
valve 16 and opening backwash valve 35, the same process of running 
backwash sprays from the nozzles 40 of standpipe(s) 38 as shown in FIG. 
4c, can also be used to simultaneously clean filter screen 28 during the 
filtering mode shown in FIG. 4a. 
Furthermore, each time that particular nozzles 40 are activated by valve 
37, standpipe(s) 38 rotate a partial revolution such as 1/18 of a 
revolution. Also because the independent backwash mode is initiated while 
the fluid level in the storage tank is sufficiently high, flow continues 
from storage tank 22 to its ultimate destination 26 throughout the 
backwash cycle. A flow meter 42 downstream of storage tank 22, measures 
the flow and can be automated using conventional technology, to prevent 
storage tank 22 from emptying prematurely. In practice, the jet sprays 
from nozzles 40 will cover the entire filter surface 41 in about two 
minutes. 
Preferably, system 10 will embody the backwash arrangement illustrated in 
FIG. 5 which comprises a singular standpipe 38 and nozzle array 40, as 
previously described, but also in which standpipe 38 is simultaneously 
reciprocated along its longitudinal axis and rotated to spray the entire 
interior surface 41 of the filter screen 28. This movement is accomplished 
by pull/turn mechanism 42 which suspends standpipe 38 from the top of 
filter tank 33. The backwash fluid is fed to standpipe 38 as previously 
described through the bottom from a pump 36 through a stationary supply 
pipe 39. Note, a stronger pump 36 may be used to maintain a high pressure 
level within standpipe 38 and thereby eliminates the need for computer 
controlled valve 37. A lip seal 44 surrounds standpipe 38 without leakage. 
In still another practice of the present invention, as shown in FIGS. 6 and 
7, standpipe 38 is replaced by a plurality of standpipes 138 (usually 
four), each of which is independently fed by pump 36 through computer 
controlled valve 37 to assure each standpipe is equally pressurized. Each 
standpipe 138 has a plurality of lateral extensions 139 (usually three per 
standpipe) to each of which a retractable nozzle assembly 140 is attached. 
Assemblies 140 function in response to the water pressure generated by 
pump 36 to extend upwardly from lateral extensions 139 whereupon nozzle 
head 141 pops up and commences spraying the inner wall 41 of filter screen 
28. Lateral extensions 139 are offset from each other at a plurality of 
lateral angles as is particularly shown in FIG. 7. These angles permit 
both the physical vertical orientation of nozzle assemblies 140 to be 
close together without pop up interference, and the ability to spray the 
full interior surface 41 of screen 28 including those areas hindered by 
stationary standpipes 138. Also shown in FIG. 6 is computer controlled 
valve 37 which intermittently supplies each of standpipes 138 with fluid 
as shown by dashed lines 141. One of such dashed lines 141 leads to an 
alternatively includable spray ring 142 circumscribing the top of screen 
28 to spray down along screen 28 during the independent backwash modes. 
Computer controlled valve 37 is programmed using conventional technology 
to periodically interrupt the flow of water to each standpipe 138 and 
consequently each nozzle assembly 140 whereupon each nozzle head 141 
retracts and in retracting rotates in its seat so that when the water 
pressure is resumed, the nozzle head pops up to produce a spray having an 
orientation different from that obtained previously. 
During the backwash process, using either embodiment described, the 
particulates, once dislodged, will fall onto beveled tank floor 46 from 
whence they are transported through backwash valve 35 to an off-site grey 
water storage 50 designated for agricultural or golf course use. 
While any of the conventional filter screen materials can be used in the 
practice of the present invention, the preferred filter screen will be 
formed of polypropylene monofilament fabric. Because of its durability and 
its high resistance to chemical attack, it is also very durable and is 
available in a variety of fabric constructions and pore sizes. Pore size 
is selected based on the size of the particulates in the raw fluid supply. 
Furthermore, the other components of the present invention are made from 
conventional materials using conventional assembly techniques. However, 
the preferred materials for filter assembly 28 include fiberglass frame 
members and PVC pipe for their lightweight durable properties. 
The ultimate destination, represented in the preferred embodiment as 
recharge well 26 can alternatively be an industrial plant or, when health 
standards are met, a community water supply. 
From the foregoing, it is readily apparent that a useful embodiment of the 
present invention has been herein described and illustrated which fulfills 
all of the aforestated objectives in a remarkably unexpected fashion. It is 
of course understood that such modifications, alterations and adaptations 
as may readily occur to the artisan confronted with this disclosure are 
intended within the spirit of this disclosure which is limited only by the 
scope of the claims appended hereto.