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The present invention relates generally to removing contaminants from an
influent, such as wastewater or water. More particularly, it relates to a
systematic tertiary treatment process (step) for such influents that
results in an effluent that has much lower levels of contaminants, such as
biochemical oxygen demand (BOD), total suspended solids (TSS), nitrogen
and phosphorous than achieved in any known prior art tertiary treatment
process.
In addition, the systematic treatment process has been found to have three
subprocesses and units. One subprocess is used to reduce BOD and TSS, the
second subprocess is used to reduce BOD, TSS and nitrogen, and the third
subprocess is used to reduce BOD, TSS and phosphorous.
The present systematic treatment process and its subprocesses are flexible
enough to adapt to existing wastewater and water treatment facilities, and
can be modified in order to achieve desired purposes, such as removal of
BOD and TSS, or removal of BOD, TSS, nitrogen, phosphorous, bacteria and
viruses.
BACKGROUND OF THE INVENTION
Reducing the undesirable solids and analytes in raw wastewater has been
tried for a number of years. The raw wastewater or influent would enter a
primary treatment facility to remove the large particle contaminants in
the raw wastewater. The primary treated wastewater would then be sent to a
secondary treatment facility in order to lower the total suspended solids
(TSS) and reduce the biochemical oxygen demand (BOD) in that wastewater.
In the primary and the secondary treatments, nitrogen and phosphorous are
coincidentially reduced.
However, eutrophication caused by nitrogen and phosphorous has resulted in
serious environmental degradation of many lakes, rivers and even large
bodies of water, such as, for example, the Long Island sound. The known
secondary treatment facilities, except when needed for microbiological
metabolism, do not normally direct themselves to the reduction of nitrogen
(N) and phosphorous (P).
More recently, a tertiary treatment or third treatment step that employs
physical-chemical or biological process followed by chemical precipitation
has been used to lower the concentration of these analytes. To remove the
nitrogen and phosphorous in the known tertiary treatment processes has
been found costly. The tertiary treatment processing units have also been
found to require a significant area in a facility.
The present tertiary process increases the amount of TSS, BOD, and the
analytes nitrogen and phosphorous, removed from influent over known
tertiary treatment units and processes. The present tertiary treatment
process can also remove bacteria and viruses much more effectively than
present systems.
The present treatment unit can be used as a wastewater enhanced treatment,
drinking water treatment, industrial wastewater enhanced treatment, and
in-lake revitalization. It is versatile and requires a very small area as
compared to the prior art treatment units. It is adaptable and can fit
existing plant operations, as well as complying with present government
regulatory or permit requirements.
The prior art treatment units fail to provide the combination of treatment
units or stations provided in the present treatment unit. Furthermore, the
precise steps of the present treatment process are absent in the prior art
processes.
For example, some prior art units and processes provide breakpoint
chlorination or superchlorination that is accomplished by the addition of
chlorine to the effluent or wastewater stream in an amount sufficient to
oxidize the ammonia-nitrogen to nitrogen gas. After sufficient chlorine is
added to oxidize the organic matter and other readily oxidizable
substances present, a stepwise reaction of the chlorine with ammonium
takes place. Such breakpoint chlorination is shown in U.S. Pat. No.
3,733,266 titled: Waste Water Purification By Breakpoint Chlorination and
Carbon Adsorption, which issued on May 15, 1973 to D.F. Bishop, et al.
This patent is directed to a method of purification of wastewater in which
sodium hypochlorite or chlorine is used to oxidize the ammonia in raw,
secondary lime clarified wastewaters using breakpoint chlorination. The
sodium hypochlorite or chlorine is added to the influent and mixed therein
by a mixer-reactor, then the influent, now effluent, passes a carbon
adsorption station or step to provide the resultant effluent.
U.S. Pat. No. 3,760,829 titled: Automatic Control System For The Safe and
Economical Removal of NH3 by Breakpoint Chlorination, which issued on Sep.
25, 1973 to W.W. Schuk, et al., is directed to an automatic system for
controlling the chlorine feed in a breakpoint chlorination process. See
also, U.S. Pat. No. 4,435,291 titled: Breakpoint Chlorination Control
System, which issued on Mar. 6, 1984 to T.N. Matsko.
U.S. Pat. No. 4,948,510 titled: Biological Phosphorous Removal From
Wastewater Using Multiple Recombinable Basins, which issued on Aug. 14,
1990 to M.D. Todd, et al., is directed to a process for removing
phosphorous, as well as lowering the amounts of ammonia, TSS and BOD
levels. The treatment cycle of this process provides multiple basins that
may be individually controlled to achieve anaerobic, anoxic or aerobic
conditions to optimize the growth of phosphorous storing microorganisms,
and thus cause the uptake of phosphorous by the organisms and also provide
for the microbiological nitrification of ammonia.
U.S. Pat. No. 4,366,064 titled: Treatment of Blast Furnace Wastewater to
Mihelic, et al., is directed to a method used to treat blast furnace and
other wastewater containing ammonia, cyanide and phenol by a breakpoint
chlorination. An activated carbon step is provided to remove residual
contaminants.
Japanese citation No. 61-39877 provides a method for treating
phosphate-containing water by placing the water in contact with calcium
phosphate-containing seed crystal and with activated alumina.
Thus, the prior art fails to address the combined removal of BOD, TSS,
nitrogen and phosphorous in a single system. The prior art also fails to
provide the combination and sequence of operations in the treatment unit
and steps in the present systematic tertiary treatment process. In
addition, the prior art fails to provide the versatility of the
subprocesses of the present process.
Against the foregoing background, it is a primary object of the present
invention to provide a treatment system or unit and process that reduces
in influent the levels of TSS, BOD, nitrogen, phosphorous, bacteria and
viruses.
The preferred treatment unit and process is a systematic tertiary treatment
unit and process that also removes bacteria and viruses.
The present invention provides a tertiary treatment unit and process that
are versatile.
The present invention further provides a tertiary treatment system or unit
that requires a relatively small area, and is adaptable so that it can
readily fit into existing plants.
An alternative embodiment of the present invention is a tertiary treatment
unit and process therefore to remove TSS and BOD from an influent which
unit and process include two filtration units and an adsorption unit.
Another alternative embodiment of the present invention is a tertiary
treatment unit and process therefore to remove TSS, BOD and nitrogen from
an influent which unit and process include two filtration units, means for
supplying chemicals, an in-line mixer for mixing the chemicals into the
effluent in the unit, a reactor and an adsorption unit.
SUMMARY OF THE INVENTION
To the accomplishments of the foregoing objects and advantages, the present
invention, in brief summary, comprises a treatment unit, preferably a
tertiary treatment unit, that includes first filtration means operatively
connected to an influent stream for filtering solids therefrom to form an
effluent, second filtration means operatively connected to said first
filtration means to receive the effluent and to filter finer solids and
bacteria and viruses from the effluent, supply means operatively connected
to the effluent to provide chemicals that are mixed into the effluent, and
a reactor that receives the effluent and removes nitrogen and some
phosphorous therefrom to form a treated effluent. The treatment unit
further has first adsorption means that receives the treated effluent and
adsorbs additional nitrogen, BOD and TSS and certain chemicals from the
treated effluent, and second adsorption means that receives the treated
effluent from said first adsorption means and adsorbs additional
phosphorous from the treated effluent to form the finally treated
effluent. The finally treated effluent achieves between about 2 and about
3 parts per million BOD, about 0.1 parts per million TSS, between about
zero and about one part per million of nitrogen, and between about zero
and about one-half of one part per million of phosphorous.
A first alternative embodiment of the present invention is a tertiary
treatment system or unit that removes TSS and BOD from an influent which
system comprises first filtration means operatively connected to an
influent stream for filtering solids therefrom to form an effluent, second
filtration means operatively connected to said first filtration means to
receive the effluent and to filter finer solids, bacteria and viruses, and
first adsorption means that receives the treated effluent and adsorbs
additional BOD and TSS from the treated effluent to form the finally
treated effluent.
A second alternative embodiment of the present invention is a tertiary
treatment system or unit that removes TSS, BOD and nitrogen from an
influent which unit comprises first filtration means operatively connected
to an influent stream for filtering solids therefrom to form an effluent,
second filtration means operatively connected to said first filtration
means to receive the effluent and to filter finer solids, bacteria and
viruses, supply means operatively connected to the effluent to provide
chemicals that are mixed into the effluent, and a reactor that receives
the effluent and removes nitrogen therefrom to form a treated effluent.
The treatment system further comprises adsorption means that receives the
treated effluent and adsorbs additional nitrogen, BOD and TSS and certain
chemicals from the treated effluent to form the finally treated effluent.
A third alternative embodiment of the present invention is a tertiary
treatment system or unit that removes TSS, BOD and phosphorous from an
influent which unit comprises first filtration means operatively connected
to an influent stream for filtering solids therefrom to form an effluent,
second filtration means operatively connected to said first filtration
means to receive the effluent and to filter finer solids, first adsorption
means that receives the effluent and adsorbs additional BOD and TSS and
certain chemicals, and a second adsorption that receives the effluent from
said first adsorption means and adsorbs phosphorous to form the finally
treated effluent.
The foregoing and still other objects and advantages of the present
invention will be more apparent from the following detailed explanation of
the preferred embodiments of the invention in connection with the
accompanying drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a systematic tertiary treatment process of
the present invention;
FIG. 2 is a schematic view of a systematic bench scale tertiary treatment
unit of the present invention;
FIGS. 3A through 3F are charts of the data summary of a study of the unit
of FIG. 2;
FIGS. 4 through 6 are schematic layouts of test units of the first
alternative process of the present invention; and
FIGS. 7A through 7C are Tables summarizing the results of the test units
shown in FIGS. 4 through 6.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the figures and, in particular, FIG. 1, there is provided a
tertiary treatment system or unit generally represented by reference
numeral 10. The system 10 includes a first filter or filtration unit 20, a
second filter or filtration unit 30, a supply tank 40, a reactor 50, a
first adsorption unit or tank 60, and a second adsorption unit or tank 70,
as the main components. Pipes or tubes, as will be discussed below,
operatively connect the main components. The pipes have provisions so that
each of the above components can be bypassed for maintenance, backwashing,
recharging or replacing.
The main components, except the supply tank 40, are operatively connected
to backwash and unit process drains represented by reference numeral 90.
The system 10 receives influent wastewater from a supply pump 5 connected
to a secondary treatment plant. The influent is connected by the pipe 80
from the pump 5 to the first filtration unit 20.
The first filtration unit 20 can be of any conventional material that
removes coarse solids from secondary treatment effluents. Preferably, the
first filtration unit 20 is either a mixed media filter or filtration
sand. The influent is treated at the first filtration unit 20 to remove
coarse solids from the flow stream. The first filtration unit 20 is
connected via pipe 82 to a backwash. The backwash from the first
filtration step is directed back to the head of the treatment plant.
The filtered effluent that emits from the first filtration unit 20 then
proceeds through pipe 80 to the second filtration unit 30. The second
filtration unit 30 removes finer solids, e.g. it filters TSS and BOD, and
bacteria and viruses from the effluent. The second filtration unit 30
includes diatomaceous earth alone as the preferred filter medium. However,
the filter medium can include fly ash, powdered activated carbon, clay or
any mixture thereof mixed with diatomaceous earth. The fly ash and the
powder activated carbon are known adsorbers and therefore are mixed with
diatomaceous earth when improved adsorption is desired. Clay is a known
ion exchange medium and, therefore, is mixed with diatomaceous earth when
the ability to remove dissolved metals is desired.
The wash and drain from the second filtration unit 30 moves via pipe 83 to
station 90. The second filtration media is renewed by conventional means
to slough off the media from the internal support system. Such
conventional means are pure mechanical, auto mechanical, hydraulic,
pneumatic or any combination thereof. Returning flow back into the second
filtration unit hydraulically redeposits the second filtration media back
on the supports in the filtration unit. Accordingly, the second filtration
media is capable of trapping additional solids over several regeneration
cycles before it must be replaced. The second filtration media that is
spent can be disposed of along with other process sludges in a digestion
or thickening or dewatering process.
Thus, the two filtration units 20, 30 remove successively finer solids from
the flow stream. The two filtrations units or steps remove solids from the
effluent and, in addition, protect the remaining process steps from
premature blinding.
The filtered effluent is then moved by pipe 80 through mixer 45 to the
reactor 50. Along pipe 80, the supply tank 40 is equipped with a chemical
feed pump that provides a chemical, such as chlorine, sodium hypochlorite
or calcium hypochlorite, into the treated effluent. The preferred chemical
is calcium hypochlorite. The chemical feed pump actually forces a chemical
into the filtered effluent. The effluent is then moved to a mixer, most
preferably an in-line mixer 45. The mixer 45 is a static mixer that mixes
the chemical into the filtered effluent. An in-line mixer 45 provides
improved efficacy since it avoids loss of chemicals and provides direct
mixing of the chemicals in the effluent.
The mixed, filtered effluent is then forwarded via pipe 80 to the reactor
50. The reactor 50 removes a significant portion of the nitrogen from the
influent and precipitates part of the phosphorous which is then removed in
the backwash. The removed precipitates are sent via pipe 84 to its
backwash 90.
The combination of supplying the calcium hypochlorite from the supply tank
40, the mixing of the calcium hypochloride by the mixer 45 and the
reaction caused in reactor 50 results in the oxidization of
ammonia-nitrogen in the effluent to nitrogen gas.
The effluent is then forwarded via pipe 80 to the first adsorption unit 60.
The first adsorption unit 60 includes granulated activated carbon as the
adsorption medium. It adsorbs from the effluent some additional nitrogen,
additional BOD and TSS, and some other chemicals including any residual
chlorine compounds.
The effluent is then forwarded via pipe 80 to the second adsorption unit
70. The second adsorption unit 70 has activated alumina as its adsorption
medium. However, alumina can also be used. The second adsorption unit 70
adsorbs additional phosphorous.
The vessels for the reactor 50, the first adsorption unit 60 and the second
adsorption unit 70 each require backwashing. The backwash from the first
adsorption unit 60 and the second adsorption unit 70 is directed by pipes
85 and 86, respectively, back to the backwash and unit process drains 90
and then to the treatment influent.
It is believed that backwashing in the various units will vary. For
example, the first filtration unit 20 will need to be backwashed the most
of all units, perhaps daily in normal use. The second filtration unit 30
will need to be renewed periodically. The filtration media will probably
need to be replaced once a week in normal use. The reactor 50 will need to
be backwashed less than the first filtration unit 20, while the first
adsorption unit will need to be backwashed less than the reactor. The
second adsorption unit 70 will need to be backwashed the least, i.e. less
than the first adsorption unit 60.
The ultimate tertiary treatment unit and process is directed to the total
or almost total removal of nitrogen and phosphorous BOD, TSS, bacteria and
viruses. This ultimate tertiary treatment unit and process includes the
first and second filtration, the chemical supply, the reactor and the
first and second adsorption units and steps.
Domestic wastewater normally has the following typical characteristics in
parts per million (ppm) which equals one milligram per liter (mg/L) when
it is a raw influent, after primary treatment, e.g. a primary treatment
effluent, and a second treatment effluent:
______________________________________
Primary Secondary
Treatment Treatment
Analyte Raw Influent Effluent Effluent
______________________________________
BOD 250 ppm 175 ppm 25 ppm
TSS 250 ppm 100 ppm 25 ppm
nitrogen 40 ppm 35 ppm 25 ppm
phosphorous
10 ppm 8 ppm 5 ppm
______________________________________
The prior art tertiary treatment processes and units have achieved the
following values from the secondary treatment effluent again measured in
parts per million (ppm) which equals one milligram per liter (mg/L):
______________________________________
Secondary Tertiary
Treatment Treatment
Analyte Effluent Effluent
______________________________________
BOD 25 ppm 5 ppm
TSS 25 ppm 5 ppm
nitrogen 25 ppm 3 ppm
phosphorous 5 ppm 1 ppm
______________________________________
The present tertiary treatment unit and process, that also uses secondary
treated effluent as its influent or flow source, results in the following
treated or final effluent:
______________________________________
STEP
Secondary Tertiary
Treatment Treatment
Analyte Effluent (Influent)
Effluent
______________________________________
BOD 25 ppm 2 to 3 ppm
TSS 25 ppm 0.1 ppm
nitrogen 25 ppm 0 to 1.0 ppm
phosphorous
5 ppm 0 to 0.5 ppm
______________________________________
The treatment process operates under pressure. Preferably, it operates at
approximately under 30 psi pressure. The resultant or finally treated
effluent looks and smells like drinking water. The finally treated
effluent will meet present and anticipated future regulatory or government
regulations.
The treatment process set forth in FIGS. 1 and 2 is much more economical
than any other tertiary treatment process since it minimizes space and
components needed while achieving maximum removal of TSS, BOD, phosphorous
and nitrogen which, heretofore, had not been considered in one treatment
process.
FIG. 2 is a schematic of an actual pilot plant operation of the full
systematic tertiary treatment process of the present invention that was
performed earlier this year. A wastewater storage tank 2 is connected to
the supply pump 5 that, as described in FIG. 1, provides wastewater
influent through pipe 80 to the treatment unit 10. The influent passes
through the twin filtration units (not shown) and is moved to the in-line
mixer 45 while calcium hypochlorite is pumped by pump 48 from the supply
unit 40 also to the in-line mixer. From the in-line mixer 45, the effluent
passes to the reactor 50 and then to a reactor effluent tank 52 and via
pump 55 is forwarded to the first adsorption unit 60. The first adsorption
unit 60 has granular activated carbon as the first adsorption medium. The
effluent is then forwarded to the second adsorption unit 70 that has
alumina as the second adsorption medium. The laboratory results of this
pilot plant operation are set forth in FIGS. 3A through 3F.
The versatility of the present treatment system and process allows for
installation of separate steps in order to attain different effluent
requirements. The resultant effluent has a combination of low levels of
BOD, TSS, nitrogen and phosphorous, that have not, heretofore, been found
in other tertiary treatment processes. In addition, the present tertiary
treatment process removes bacteria and viruses from the effluent.
A first alternative embodiment of the present process is shown in FIGS. 4
through 6. These figures illustrate the schematic layout of pilot plant
systems that were placed in experimental use from Oct. 15, 1991 through
Jan. 15, 1992. The goal of these pilot plant systems was to provide
granular activated carbon (GAC) as an absorption/adsorption system to
function as a polishing filter after twin filtration, but prior to
chlorination. The first filtration unit had mixed media (MM) as the
filtration medium, while the second filtration unit had diatomaceous earth
(DE) as the second filtration medium. The first and second filtration
mediums were installed lapstream of the adsorption unit. They prevented
premature plugging and also removed TSS from the flow stream before it
advanced to the adsorption unit. DE filtration removes particulates down
to microbe size.
MM was comprised of 50 lbs. of high rate sand No. 1/2 (0.45 mm-0.55 mm) and
approximately 35 lbs of anthracite (0.9 mm-1.1 mm, 1.4 UC). The surface
area of the filter was 1.4 sq.ft. and the design surface loading rate
using clean water was 25 gpm/sq.ft. DE filter was 72 individual tube
assemblies that had a surface area of 11.8 sq.ft., and a design surface
loading rate of 4.23 gpm/sq.ft. when operating with clean water. The GAC
had a recommended maximum flow rate of 10 gpm and the detention time at
that flow was five and one-half minutes. The loading rates for the
treatment units were:
______________________________________
Treatment Loading Rate Applied Loading
Unit with Clean Water
with Treated Effluent
______________________________________
MM 25 gpm/sq.ft.
3.5 gpm/sq.ft.
DE 4.23 gpm/sq.ft.
0.423 gpm/sq.ft.
______________________________________
Detention Time
at 10 gpm at 5 gpm
______________________________________
GAC 51/2 min. 11 min.
______________________________________
The typical operating pressures were in the range of 30 psi for treated
effluent vs 6 to 12 psi for clean water.
The carbon drum used in the experimental pilot system contained 200 lbs. of
activated carbon. The BOD adsorption capacity of the carbon is 25% of its
weight so that the carbon could remove 50 lbs. of BOD before it is spent.
FIG. 4 is a schematic of the first and second operating modes of the pilot
plant system. This first operating mode includes a MM filter, a DE filter
and a GAC filter or absorption medium. The results are set forth in Table
1 in FIG. 7A. The results demonstrated overall removal efficiencies of
66.8% and 92.4% of BOD and TSS, respectively. The removal of TSS through
MM and DE filters is very effective, namely 72%, however BOD removal
through the same filters is only 8.4%. When the flow reaches the GAC, BOD
removal occurs at 63.8%. The deep bed of GAC further reduced TSS by 72% of
that applied.
The second operating mode includes the MM filter followed by the GAC
filter. The results of the second operating mode are set forth in Table 2
also in FIG. 7A. The MM filter alone achieved 55% removal of the TSS
applied. However, mode 2 used different and more frequent cleaning and
backwashing so that the higher TSS removal demonstrated the effectiveness
of frequent backwashing. Operating mode 2 also demonstrated that the
majority of the BOD removal took place in the GAC filter or unit, and that
operating without the DE filter reduced the level of TSS and BOD removals
by about 14% and 15%, respectively, as compared to mode 1.
The third operating mode is shown schematically in FIG. 5. In this
operating mode two DE filters in series were used. The purpose of this
operating mode was to determine whether there would be any significant
additional solids removed prior to the GAC filter using two DE filters.
The results of this third operating mode are shown in Table 3 in FIG. 7B.
TSS removal efficiency of 80.4% was demonstrated by this combination of
MM+DE+DE filtration. The series operation of the two DE filters did not
significantly lower the BOD applied. An average reduction of 16.9% was
noted in Table 3. The overall BOD removal of 77.9% was greater than that
reported in operating mode 1 (66.8%) and mode 2 (51%). The removal of
80.4% of the TSS applied in the third (MM+DE+DE) filtration, is greater
than that noted in mode 1 (MM+DE), 72.3% and that of mode 2 (MM alone),
55.3%. Those results further demonstrated that effluent polishing through
sequential filtration units reduces both TSS and BOD to lower levels than
single units alone.
The fourth operating mode is shown schematically in FIG. 6. In this
operating mode, a second GAC filter or unit was used. This fourth
operating mode included the MM filter, two series DE filters and two
series GAC filters. The results of this third operating mode are shown in
Table 4 in FIG. 7C. BOD reductions did not improve over that of mode 3
even though two GAC filters or units were used. BOD effluent
concentrations near 2 ppm appear to be refractory levels below which GAC
can not go.
The BOD removal efficiency of all four operating modes are shown in Table 5
in FIG. 7C. Effluent polishing for TSS removal does entrance BOD removals
as well, as evidenced by comparing modes 1 through 3. The elimination of
DE filtration in mode 2 resulted in a deterioration of BOD removal
efficiency, however the addition of a second DE filter in mode 3 increased
BOD removal efficiency. These results show that increased removal of TSS
via DE filtration will also remove some non-soluble BOD in the flow
stream. Thus, mechanical filtration by means of MM and DE will lower both
BOD and TSS levels. Those processes followed by GAC will further lower BOD
levels so that regulatory permit levels are consistently met. Operation of
sequential DE filtration units and sequential GAC units did not enhance
the effluent to the degree that either mode would be further considered.
Thus, the three month operation demonstrated that the process of effluent
polishing, i.e. MM+DE+GAC, can reduce both BOD and TSS to less than permit
levels.
The second alternative embodiment of the present process (not shown in the
drawings) is used for the removal of TSS, BOD and nitrogen. This
embodiment is the same as that shown in FIGS. 1 and 2, except that the
second adsorption unit 70 is eliminated. Accordingly, phosphorous is not
removed to the level achieved by the use of a second adsorption unit 70.
The third alternative embodiment of the present invention process (not
shown in the drawings) is used for the removal of TSS, BOD and
phosphorous. This embodiment is the same as that shown in FIGS. 1 and 2
except that units 40, 45 and 50 are eliminated. Accordingly, nitrogen is
not removed.
Having thus described the present invention with particular references to
the preferred forms thereof, it will be obvious that various changes and
modifications may be made therein without departing from the spirit and
scope of the invention as defined by the appended claims.
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