Mixing & Mass Transfer Technologies, LLC v. HDR Engineering, Inc. et al

Filing 80

MEMORANDUM AND ORDER that the disputed terms and phrases identified by the parties in filing 50 are construed in accordance with the foregoing memorandum opinion. Ordered by Senior Judge Richard G. Kopf. (ADB)

IN THE UNITED STATES DISTRICT COURT
FOR THE DISTRICT OF NEBRASKA

MIXING & MASS TRANSFER
TECHNOLOGIES, LLC,
and PETER KOS, Ph.D.,
Plaintiffs,
v.
CITY OF LINCOLN, NEBRASKA,
and HDR ENGINEERING, INC.,
Defendants.

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4:11CV3068

MEMORANDUM
AND ORDER

U. S. Patent 5,811,009 (“the ’009 Patent”), concerning a “Method and System
for Improved Biological Nitrification of Wastewater at Low Temperature,” was issued
to the inventor, Peter Kos, Ph.D., in 1998. The patent is licensed (by an assignment
executed in 2001) to Mixing & Mass Transfer Technologies, LLC (“m 2t”). Dr. Kos
and m 2t allege that HDR Engineering, Inc., designed a wastewater treatment facility
for the City of Lincoln, Nebraska, which infringes the ’009 Patent. Specifically, the
plaintiffs contend HDR and the City have infringed Claim 18 of the ’009 Patent,
which requires:
18. An activated sludge biological wastewater treatment process
having enhanced biological nitrification comprising the steps of:
(a) directing wastewater through a mainstream nitrification
process including at least one aerobic treatment zone and a final clarifier
that separates purified supernatant from settled sludge;
(b) returning at least a portion of the settled sludge from the final
clarifier to the mainstream treatment process;
(c) producing supplemental biological nitrifiers in a sidestream
by directing a stream having a relatively high concentration of ammonia
into a sidestream biological nitrification system and nitrifying the same

and in the process producing the supplemental biological nitrifiers in the
sidestream biological nitrification system;
(d) transferring the supplemental biological nitrifiers produced in
the sidestream nitrification system to the mainstream nitrification process
where the supplemental nitrifiers assist in nitrifying the wastewater
passing through the mainstream nitrification process; and
(e) m[a]intaining sludge age within the mainstream nitrification
process at a value of less than 200% of the critical sludge age of a
conventional nitrification process.
(’009 Patent, 14:10-34 1 (filing 58-2 at 13)) (underlining supplied).2
On October 22, 2012, the court held a Markman 3 hearing regarding certain
terms and phrases used in Claim 18 the ’009 patent that were identified by the parties
in filing 50 as being disputed. Now, after considering the parties’ evidence, briefs,
and oral arguments, and applying accepted claim-construction principles, the court
construes the disputed terms and phrases as follows:

Disputed Terms and Phrases

Court’s Construction

“mainstream nitrification process”

“The portion of the mainstream treatment
process in which mainstream wastewater is
nitrified, meaning ammonia nitrogen in the
mainstream, NH 3—N, is converted to nitrite
or nitrate, both referred to NO x. This portion
of the mainstream treatment process takes
place in the aerobic treatment zone(s).”

1

References are to column and line numbers in the patent.

2

The meaning of underlined terms and phrases are disputed by the parties.

3

Markman v. Westview Instruments, Inc., 517 U.S. 370, 373 (1996) (holding
that claim construction is a matter of law for the court).
-2-

Disputed Terms and Phrases

Court’s Construction

“mainstream treatment process”

“a biological suspended growth wastewater
treatment process designed to treat a
wastewater stream and produce treated or
purified effluent, which may include a
series of treatment zones, but which
excludes any sidestream or sidestream
treatment process”

“return activated sludge”

Not construed

“sludge”

Not construed

“sidestream biological
nitrification system”

“a system in which nitrification occurs (i.e.,
ammonia nitrogen, NH 3—N, is converted to
nitrite or nitrate, both referred to as NO x)
that is separate from the zone in which
nitrification occurs during the mainstream
treatment process”

“sidestream”

“The ‘mainstream’ is the wastewater stream
flowing through the wastewater treatment
plant. Any stream other than the
mainstream, auxiliary to treatment of the
wastewater stream, is a ‘sidestream.’”

“relatively high concentration of
ammonia”

Not construed

“sludge age”

Not construed

“sludge age within the mainstream
nitrification process”

“the average amount of time nitrifying
bacteria remain in the oxic (aerated) portion
of the mainstream reactor tank, determined
by dividing the mass of suspended solids in
the oxic (aerated) portion of the mainstream
reactor tank by the mass of suspended
solids discharged from the overall system
per day”

-3-

Disputed Terms and Phrases

Court’s Construction

“maintaining sludge age within
the mainstream nitrification
process”

Not construed

“critical sludge age of a
conventional nitrification process”

“the minimum solid retention time (sludge
age) in days at which conventional
nitrification ceases for a given pH,
temperature and dissolved oxygen level,
which is equal to 1 divided by the
difference between the maximum daily
nitrifier growth rate for conditions and the
decay rate.”
The equation is as follows:
è cm =
ì

1
Í - kd

where:
è cm = minimum solids retention time, days,
for nitrification at pH, temperature and
dissolved oxygen (mg/L);
ì
Í = maximum possible nitrifier growth
rate, per day, for environmental conditions
of pH, temperature and dissolved oxygen
(mg/L) (as calculated by equation 5 of U.S.
Patent No. 5,811,009); and
k d = endongenous decay coefficient”
“conventional nitrification
process”

Not construed

-4-

DISCUSSION
“[A] patent must describe the exact scope of an invention and its manufacture
to ‘secure to [the patentee] all to which he is entitled, [and] to apprise the public of
what is still open to them.’” Markman, 517 U.S. at 373 (quoting McClain v. Ortmayer,
141 U.S. 419, 424 (1891)). These objectives are served by two distinct elements of
every patent application: (1) “a specification describing the invention ‘in such full,
clear, concise, and exact terms as to enable any person skilled in the art . . . to make
and use the same’”; and (2) “one or more ‘claims,’ which ‘particularly poin[t] out and
distinctly clai[m] the subject matter which the applicant regards as his invention.’”
Markman, 517 U.S. at 373 (quoting 35 U.S.C. § 112). A patent “claim” defines the
scope of a patent and serves to prohibit exact copies of an invention, as well as a
product that goes to “‘the heart of an invention but avoids the literal language of the
claim by making a noncritical change.’” Id. (quoting H. Schwartz, Patent Law and
Practice 1, 82 (2d ed. 1995)).
In order to prevail in a patent infringement lawsuit, a patent “claim” must
“‘cover[] the alleged infringer’s product or process,’ which in turn necessitates a
determination of ‘what the words in the claim mean.’” Markman, 517 U.S. at 374
(quoting Schwartz, supra, at 80). Here, the parties dispute the meaning of several
terms used in the claims of the ’009 Patent. The court, and not the jury, must resolve
claim-construction disputes. Markman, 517 U.S. at 388-89; O2 Micro Intern. Ltd. v.
Beyond Innovation Tech. Co., Ltd., 521 F.3d 1351, 1362 (Fed. Cir. 2008) (“When the
parties present a fundamental dispute regarding the scope of a claim term, it is the
court’s duty to resolve it.”).
Claim Construction Principles
In construing claims of a patent, the court examines intrinsic evidence,
including the language of the claims themselves, the specification, and the prosecution
history. Phillips v. AWH Corp., 415 F.3d 1303, 1314 (Fed. Cir. 2005). Words of a
-5-

claim are generally given their “ordinary and customary meaning,” which “is the
meaning that the term would have to a person of ordinary skill in the art in question
at the time of the invention.” Id. at 1312-13. Further, the claim terms must be read
“in the context of the entire patent, including the specification.” Id. at 1313. While
a patentee may give special definitions to claim terms in the patent’s specification,
“the specification cannot support a definition that is contrary to the ordinary meaning
of a claim term unless it communicates a deliberate and clear preference for this
alternative definition.” Kumar v. Ovonic Battery Co., Inc., 351 F.3d 1364, 1368 (Fed.
Cir. 2003).
The prosecution history, which is part of the “intrinsic evidence” to be
considered by the court in construing patent terms, “consists of the complete record
of the proceedings before the PTO [Patent and Trademark Office] and includes the
prior art cited during the examination of the patent.” Phillips, 415 F.3d at 1317. Like
the specification, the prosecution history “was created by the patentee in attempting
to explain and obtain the patent,” and this history “provides evidence of how the PTO
and the inventor understood the patent.” Id. However, “because the prosecution
history represents an ongoing negotiation between the PTO and the applicant, rather
than the final product of that negotiation, it often lacks the clarity of the specification
and thus is less useful for claim construction purposes.” Id.
Finally, a district court may also consider “extrinsic evidence” consisting of “all
evidence external to the patent and prosecution history, including expert and inventor
testimony, dictionaries, and learned treatises.” Id. (internal quotation marks omitted).
However, extrinsic evidence “is less significant than the intrinsic record in
determining the legally operative meaning of claim language” because (1) such
evidence “is not part of the patent and [was not] created at the time of patent
prosecution for the purpose of explaining the patent’s scope and meaning”; (2)
“extrinsic publications may not be written by or for skilled artisans and therefore may
not reflect the understanding of a skilled artisan in the field of the patent”; (3) “there
is a virtually unbounded universe of potential extrinsic evidence of some marginal
-6-

relevance that could be brought to bear on any claim construction question” from
which each party will select the evidence that most favors them, leaving the court
“with the considerable task of filtering the useful extrinsic evidence from the fluff”;
and (4) “undue reliance on extrinsic evidence poses the risk that it will be used to
change the meaning of claims in derogation of the indisputable public records
consisting of the claims, the specification and the prosecution history, thereby
undermining the public notice function of patents.” Id. at 1318-19 (internal quotation
marks omitted).
A district court may decline to construe a patent term for the reason that it
carries its plain and ordinary meaning; however, failing to construe a patent term for
this reason “may be inadequate when a term has more than one ‘ordinary’ meaning
or when reliance on a term’s ‘ordinary’ meaning does not resolve the parties’ dispute.”
O2 Micro, 521 F.3d at 1361 (in deciding that “only if” needed no construction because
term was well-understood, district court failed to resolve parties’ dispute, which
centered upon the scope that should be encompassed by the claim language; proper
claim construction required district court to determine what claim scope was
appropriate in context of patents-in-suit).
“Ultimately, the interpretation to be given a term can only be
determined and confirmed with a full understanding of what the
inventors actually invented and intended to envelop with the claim. The
construction that stays true to the claim language and most naturally
aligns with the patent’s description of the invention will be, in the end,
the correct construction.”
Phillips, 415 F.3d at 1316 (quoting Renishaw PLC v. Marposs Societa’ per Azioni,
158 F.3d 1243, 1250 (Fed. Cir. 1998)).

-7-

Overview of the ’009 Patent
“The present invention entails a method and system for enhancing biological
nitrification in a wastewater treatment process” (’009 Patent, abstract (filing 58-2
at 1)).

Depicted below is “a schematic illustration of the enhanced biological

nitrification process and system of the present invention” (’009 Patent, 3:29-31
(filing 58-2 at 8)), which is identified in the ’009 Patent as Figure 1:

(’009 Patent, Figure 1 (filing 58-2 at 2)).
“[T]he biological nitrification process of the present invention is indicated
generally by the numeral 10” in Figure 1 (’009 Patent, 4:15-17 (filing 58-2 at 8))
(boldface in original).

-8-

In this process influent wastewater is directed along a mainstream 12
through a mainstream biological treatment process 14. The mainstream
biological treatment process can include a series of various treatment
zones including one or more anaerobic zones, one or more aerobic (oxic)
zones, or one or more anoxic zones. However, it is contemplated that in
the present process, the mainstream biological treatment process 14
would include at least a nitrification zone for converting ammonia
nitrogen NH 3—N to NO x. Basically, the mainstream biological treatment
area or zones 14 would produce a treated or purified effluent that could
be discharged into a creek, river, lake, etc.
(’009 Patent, 4:17-28 (filing 58-2 at 8)) (boldface in original).
In addition to the mainstream biological treatment area or zones, “the present
invention entails a sidestream nitrification system indicated generally by the numeral
16” (’009 Patent, 4:36-37 (filing 58-2 at 8)) (boldface in original).
Basically, the sidestream nitrification system 16 produces supplemental
nitrifiers that are conveyed or transferred to the mainstream 12 where the
supplemental nitrifiers aid or assist in the mainstream nitrification
process.
To produce the supplemental biological nitrifiers, the present
invention entails directing a sidestream 15 into a sidestream nitrification
zone or reactor 13. It is contemplated that the sidestream being fed or
directed into the sidestream nitrification zone 13 would have a relatively
high ammonia concentration compared to the ammonia concentration
found in the influent wastewater being directed into and through the
mainstream process.
(’009 Patent, 4:38-49 (filing 58-2 at 8)) (boldface in original).
Figure 2 of the ’009 Patent is “a schematic illustration of the enhanced
biological nitrification process and system of the present invention showing a
particular process and system design” (’009 Patent, 3:32-39 (filing 58-2 at 8)). It is
depicted below:
-9-

(’009 Patent, Figure 2 (filing 58-2 at 3)).
The patent specification describes this particular process and system design in
the following manner:
Now turning to FIG. 2 and the process shown therein, it is seen
that wastewater is directed into inlet line 50 which leads to a primary
clarifier 52. Primary clarifier 52 produces settled sludge and primary
clarifier effluent which is directed into a mainstream inlet line 54. From
inlet line 54 the primary clarifier supernatant is directed into a
mainstream treatment area or a series of mainstream treatment zones.
In the case of the present disclosure, the mainstream treatment area
includes at least one aeration tank 56. This of course is utilized for
mainstream nitrification. As pointed out above, it should be appreciated
that the mainstream treatment area could include any number of other
treatment zones such as anaerobic, aerobic, or anoxic. From the main
-10-

treatment area or the main treatment zone or zones, the treated
wastewater is directed through a secondary clarifier 60 that directs a
treated or purified effluent out outlet line 62. Separated sludge is directed
out the bottom of secondary clarifier 60 and a portion of it is returned to
the mainstream via a return activated sludge line 64. The return activated
sludge is mixed with the incoming influent wastewater in line 54 to form
a mixed liquor that is subsequently treated in the mainstream treatment
area or the mainstream treatment zone or zones (in this case the aeration
tank 56).
Some of the sludge directed from the secondary clarifier 60 is
referred to as excess activated sludge or waste sludge and that is directed
through line 68 to a digester 70 or another sludge stabilization process.
Also, primary sludge collected by the primary clarifier 52 is directed
into line 66 and into the digester 70. . . . Once the digestion process has
been completed the digested sludge is directed to a sludge dewatering
station 72. There the sludge is separated into dewatered sludge which is
directed out line 74 and dewatering liquid which is directed through line
76 to a sidestream nitrification system or zone 78. There the dewatering
liquid is subjected to nitrification and . . . would have a high
concentration of ammonia nitrogen and would typically be at an elevated
temperature compared to the influent wastewater passing through the
mainstream of the process. . . . [S]upplemental biological nitrifiers are
produced in the sidestream nitrification system 78 and these
supplemental nitrifiers are conveyed to the mainstream via line 84.
There the supplemental nitrifiers combined with nitrifiers produced in
the aeration tank 56 and the combined nitrifiers act to effectuate
complete and effective nitrification in the mainstream and particularly in
aeration tank 56 of the example shown. It should be also noted that
excess biological sludge full of nitrifiers held in the sidestream
nitrification system 78 can be conveyed to the mainstream and
particularly through the aeration tank 56 via line 80.
. . . [I]n the event there is a need to dilute the solution contained
in the sidestream nitrification system 78 or need additional organic
substrate that a portion of the primary supernatant leaving the primary
clarifier or treated effluent can be directed into the sidestream
nitrification system 78 via line 86. As also discussed in the preceding
-11-

example [FIG. 1], it is appreciated that chemicals can be directed into
the sidestream nitrification system 78 for the purpose of controlling
pH and alkalinity.
(’009 Patent, 5:39-6:33 (filing 58-2 at 9)) (boldface in original).
Overview of Claim 18
Before explaining the court’s construction of each of the disputed terms and
phrases contained in Claim 18 of the ’009 Patent, it may be helpful to discuss the
patent claim more generally. It will be seen that the claim promises to “reduce the
size of nitrification treatment basins and . . . accordingly reduce the overall cost of
building adequate treatment facilities for nitrification” in a wastewater treatment
process (’009 Patent, 2:43-46 (filing 58-2 at 7)).
“[T]he nitrification step [in a wastewater treatment process] basically entails
converting the ammonia nitrogen, NH 3–N, to nitrite or nitrate, both referred to as
NO x.” (’009 Patent, 3:57-60 (filing 58-2 at 8)). “[M]any conventional activated sludge
wastewater treatment processes accomplish nitrification in an aerobic or oxic
treatment zone” where “the wastewater containing the ammonia nitrogen is subjected
to aeration and this gives rise to a microorganism culture that effectively converts the
ammonia nitrogen to NO x.” (id.).4 The ’009 Patent utilizes this nitrification method.
Thus, paragraph (a) of Claim 18 specifies that the so-called “mainstream nitrification
process” must include “at least one aerobic treatment zone” (’009 Patent, 14:13-16
(filing 58-2 at 13)).

4

“Once the ammonia nitrogen has been converted to NO x. then the NO x.
containing wastewater is typically transferred to an anoxic zone for the purpose of
denitrification. . . . Here, a different culture of microorganisms operate to consume
the oxygen from the NO x. and thereby freeing [sic] the nitrogen to escape to the
atmosphere” (’009 Patent, 3:66-4:8 (filing 58-2 at 8)).
-12-

In addition to the mainstream nitrification process, the invention calls for a
“sidestream process” which “includes directing a liquid stream . . . having a high
ammonia concentration at an elevated temperature into a sidestream nitrification
zone which is operated at conditions which maximize production of nitrifiers [i.e.,
nitrifying bacteria] therein” (’009 Patent, abstract (filing 58-2 at 1)). This process is
described in paragraph (c) of Claim 18 (and in subsequent dependent claims).5
“Afterwards, the resulting nitrifiers produced in the sidestream nitrification
zone are directed into the mainstream where the nitrifiers function to enhance
nitrification in the mainstream and allows [sic] operation at low sludge retention time
conditions where nitrification otherwise could not be sustained” (id.). Paragraph (d)
of Claim 18 describes this step.
“Normally, the process design for sludge age [i.e., average retention time] in a
conventional nitrification process calls for the sludge age to be designed to be at least
200% of the critical or minimum sludge age [for nitrification]” (’009 Patent, 2:50-53
(filing 58-2 at 7)). The present invention allows a wastewater treatment system to be
designed using a smaller safety factor because “the sidestream process produces an
abundant supply of supplemental nitrifiers that . . . assist[ ] in carrying out the
nitrification process in the mainstream” (’009 Patent, abstract (filing 58-2 at 1)).
“Thus, in the case of the present process, the upper boundary line for design sludge
age is fixed at 200% of the critical or minimum sludge age for a conventional
nitrification process operated under the same temperature conditions” (’009 Patent,
12:1-5 (filing 58-2 at 12)). In other words, the minimum design sludge age for a
5

The “temperature within the sidestream nitrification system [is maintained]
higher than the temperature of the wastewater passing through the mainstream
nitrification system” (’009 Patent, Claim 20, 14:40-41 (filing 58-2 at 13)) and
“chemicals are added] to the sidestream biological nitrification system for controlling
pH and alkalinity” (’009 Patent, Claim 22, 14:45-47 (filing 58-2 at 13)). “[B]iological
nitrification is carried out in the sidestream through any conventional nitrification
process” (’009 Patent, 5:13-15 (filing 58-2 at 9)).
-13-

conventional nitrification process becomes the maximum design sludge age for the
present invention. This improvement is reflected in paragraph (e) of Claim 18.
Figure 5 of the ’009 Patent is “a graphic illustration showing various
relationships between sludge age and temperature for a conventional nitrification
process” (’009 Patent, 3:44-46 (filing 58-2 at 8)). It is depicted below:

(’009 Patent, Figure 5 (filing 58-2 at 6)). The values plotted in Figure 5, “show[ing]
the minimum sludge age (i.e. critical or minimum sludge age or SRT [sludge retention
time]) and design sludge age for a conventional nitrification process as a function of
temperature” (’009 Patent, 10:24-27 (filing 58-2 at 11)), are also listed in the first
three columns of Table 3 of the ’009 Patent:
-14-

(’009 Patent, Table 3, 10:31-43 (filing 58-2 at 11)). These values were obtained using
equations 5, 6, and 7 as set out in the patent specification.

(’009 Patent, 8:20-51 (filing 58-2 at 10)).6
6

The subtrahend “k d ” shown in equations 6 and 7 is an “endogenous decay
coefficient” (’009 Patent, 8:11 (filing 58-2 at 10)).
-15-

The significance of this data, and its relationship to paragraph (e) of Claim 18,
is explained in the patent specification as follows:
Table 3 and the graph illustration of FIG. 5 explores the critical or
minimum sludge age at various temperatures for conventional
nitrification processes. As discussed herein, the determination of critical
or minimum sludge age for a conventional mainstream nitrification
process, such as that disclosed in the Barnard patent (U.S. Pat. No.
3,964,998), is highly dependent upon temperature. As Table 3 aptly
illustrates, in a conventional nitrification process, the minimum sludge
age increases with temperature. For example, at a wastewater design
temperature of 5° C., the minimum or critical sludge age for a
conventional nitrification process is 9.4 days. On the other hand, for a
wastewater design temperature of 15° C., the minimum or critical sludge
age for the mainstream of a conventional nitrification process is 3.5 days.
These are critical or minimum sludge ages—not design sludge ages. It
is well-accepted in the wastewater industry that one cannot base a
nitrification process design on minimum or critical sludge age. A safety
factor (SF) must be applied. Universally, the applied safety factor (SF)
is typically 2.0 or at least 1.5.
Turning to FIG. 5, there is shown a plot of critical or minimum
sludge age (critical SRT) as a function of temperature. As Table 3
illustrates, the critical or minimum sludge age for a conventional
nitrification process decreases as the wastewater design temperature
increases. Taking the minimum acceptable safety factor of 1.5, and
assuming an effluent ammonia concentration of 2 mg/l, a shaded region
is formed below the design sludge age line of FIG. 5 based on a 1.5
safety factor. Consequently, beginning with design wastewater
temperatures of 5° C., the design sludge age for conventional
nitrification processes begins at 17.6 days. For wastewater temperatures
of 10° C., the design SRT for a conventional nitrification process begins
at approximately 10.7 days. Similarly for a wastewater design
temperature of 15° C., the design sludge age for a conventional
nitrification process begins at approximately 6.6 days. It is important to
appreciate that this is the lower boundary line (i.e. a safety factor of 1.5
or 150%) for design criteria relating to design sludge age in conventional
nitrification processes. It can be seen that for each temperature, that
-16-

these design sludge age values are approximately twice (200%) of the
critical or minimum sludge age.7
Thus, in the case of the present process, the upper boundary line
for design sludge age is fixed at 200% of the critical or minimum sludge
age for a conventional nitrification process operated under the same
temperature conditions. In many cases, the design sludge age of the
present invention would be substantially below this boundary line.
Accordingly, the facilities for handling the wastewater influent to be
treated by the present process will be substantially less in size and cost
than the facilities that would be required in cases involving conventional
nitrification processes.
(’009 Patent, 11:5-12:10 (filing 58-2 at 12)) (boldface in original).
Construction of Disputed Terms and Phrases
The disputed terms and phrases will be addressed in the same order in which
they are listed in the table set forth in the introductory section of this opinion.
1.

“Mainstream nitrification process”

This term appears in paragraphs (a), (d), and (e) of Claim 18 of the ’009 Patent.
Because it establishes the measuring point for the “sludge age” value which paragraph
(e) says must be maintained at “less than 200% of the critical sludge age of a
conventional nitrification process,” the meaning of this term could be crucial to the
outcome of this litigation.
The defendants contend a “mainstream nitrification process” is “[a] process for
treating wastewater by directing it through any combination of (a) a primary settling
7

It is mathematically possible for a safety factor of 150% to result in design
sludge ages that approach 200% of the critical sludge age because the maximum
possible nitrifier growth rate (ìÍ) is reduced by a fraction in equation 7.
-17-

or clarifying tank, (b) a Mainstream Treatment Process, (c) a secondary settling or
clarifying tanks [sic], and circulating Return Activated Sludge” (filing 50 at 2). The
“Mainstream Treatment Process” which is identified as item (b) of this definition is
a disputed term which appears in paragraph (b) of Claim 18. It is defined by the
defendants to mean “[a] portion of the Mainstream Nitrification Process where
wastewater is treated by directing it through any combination of aerobic, oxic,
anaerobic, and anoxic zones” (filing 50 at 3). “Return Activated Sludge” is another
disputed term, although it does not appear anywhere in Claim 18. The defendants
define it as “[s]ludge produced in the Mainstream Treatment Process that is recycled
as a part of the Mainstream Nitrification Process” (filing 50 at 6). The defendants add
that “during recycling, the Sludge may be subjected to additional treatments” (id.).
The defendants also explain that “[a] Sidestream or Sidestream Biological
Nitrification System (as defined in this patent) is not a part of a Mainstream
Nitrification Process” (filing 50 at 2).
Referring to the particular process and system design illustrated in Figure 2 of
the ’009 Patent, the defendants’ definition of “mainstream nitrification process”
would include at least the following items: (1) the primary settling tank 52; (2) the
aeration tank 56; (3) any mainstream anaerobic or anoxic treatment zone (not shown
on Figure 2 but permitted by the accompanying description); (4) the secondary settling
tank 60; and (5) the return activated sludge line 64. By contrast, the plaintiffs would
include only the aeration tank 56 within the “mainstream nitrification process.”
The plaintiffs contend the “mainstream nitrification process” is “[t]he portion
of the mainstream treatment process in which mainstream wastewater is nitrified,
meaning ammonia nitrogen in the mainstream, NH 3—N, is converted to nitrite or
nitrate, both referred to NO x” (filing 50 at 2). The plaintiffs further specify in their
definition that “[t]his portion of the mainstream treatment process takes place in the
aerobic treatment zone(s)” (id.)

-18-

The plaintiffs’ proposed construction of “mainstream nitrification process”
will be adopted by the court. The defendants’ argument “that the ’009 Patent uses the
term ‘mainstream nitrification process’ broadly to encompass all of the mainstream
portions of the wastewater process, and the term ‘mainstream treatment process’ to
describe only a portion of the ‘mainstream nitrification process’” (filing 62 at 11)
defies common sense. Simply put, “nitrification” is part of wastewater “treatment,”
not the other way around.
For example, the description of Figure 2 states that while “the mainstream
treatment area could include any number of other treatment zones such as anaerobic,
aerobic or anoxic,” it must include “at least one aeration tank 56,” which “of course
is utilized for mainstream nitrification” (’009 Patent, 5:46-48 (filing 58-2 at 9))
(boldface in original). This description expressly recognizes that the mainstream
nitrification process occurs within the aeration tank(s), and is a subpart of the
mainstream treatment process (which could include other treatment zones). The
defendants’ proposed construction reverses this relationship.
As a practical matter, if settling tanks, anaerobic or anoxic treatment zones, and
the return activated sludge line were to be considered part of the “mainstream
nitrification process,” as proposed by the defendants, then the “sludge age within the
mainstream nitrification process” (referenced in paragraph (e) of Claim 18) would be
skewed upward. The ’009 Patent specifies that only sludge located in mainstream
aerobic treatment zones should be included in the calculation of sludge age:
Processes which employ biological phosphorous removal and/or
denitrification require anaerobic or anoxic zones and proportional
increases in sludge age to account for sludge in these anaerobic and
anoxic zones. All of the descriptions and specifications herein of the
sludge age refers to the so-called oxic sludge age, that is the sludge age
necessary for nitrification in the oxic or aerated zones only.
(’009 Patent, 12:11-17 (filing 58-2 at 12)) (emphasis supplied).

-19-

The first step of the treatment process described in Claim 18 involves “directing
wastewater through a mainstream nitrification process including at least one aerobic
treatment zone and a final clarifier that separates purified supernatant from settled
sludge” (’009 Patent, 14:13-16 (filing 58-2 at 13)). The defendants contend this
language (paragraph (a) of Claim 18) indicates that a final clarifier must be included
in the “mainstream nitrification process.” While it is possible to read paragraph (a)
in this manner, it is more sensible to parse the language as requiring that wastewater
be directed through two things: (1) a mainstream nitrification process that includes at
least one aerobic treatment zone and (2) a final clarifier. The final clarifier (or settling
tank) is simply a physical operation that uses gravity to separate purified effluent from
sludge; it is distinct from the biological and chemical process of nitrification. (See Kos
Depo., 50:15-51:5, 53:1-9, 60:23-61:14, 63:22-64:25 (filing 58-4 at 10-16)). It should
also be noted that Claim 18 does not require a primary clarifier or settling tank.8
Claim 18 does require (in paragraph (b)) “returning at least a portion of the
settled sludge from the final clarifier to the mainstream treatment process” (’009
Patent, 14:17-18 (filing 58-2 at 13)). The defendants claim this requirement serves
to reinforce their argument that the “mainstream treatment process” is part of a larger
“mainstream nitrification process,” but a more reasonable interpretation is that the
settled sludge is directed into a “sidestream” when it leaves the final clarifier. This
is made clear in the description of Figure 2, which states that “[s]eparated sludge is
directed out the bottom of secondary clarifier 60 and a portion of it is returned to the
mainstream via a return activated sludge line 64” (’009 Patent, 5:54-57 (filing 58-2

8

The particular process and system design illustrated in Figure 2 includes a
primary settling tank, but the description of this drawing states that the “[p]rimary
clarifier 52 produces settled sludge and primary clarifier effluent which is directed
into a mainstream inlet line 54 . . . [and from there] into a mainstream treatment area
or a series of mainstream treatment zones . . . includ[ing] at least one aeration tank
56.” (’009 Patent, 5:41-47 (filing 58-2 at 9)) (boldface in original). The specification
thus indicates that the primary clarifier shown in Figure 2 is an operation that occurs
prior to the mainstream treatment and mainstream nitrification processes.
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at 9)) (emphasis supplied). The same point is made in independent Claim 11 of the
’009 Patent, which includes these steps: “(a) directing influent wastewater into and
through a mainstream; (b) treating the influent wastewater in the mainstream by
nitrifying the same in an aerobic zone; (c) directing the nitrified wastewater into a
final clarifier and forming purified supernatant and settled sludge; [and] (d) returning
a portion of the settled sludge back to the mainstream where it is mixed with the
influent wastewater.” (’009 Patent, 13:25-34 (filing 58-2 at 13)). The settled sludge
would not need to be “returned” to the mainstream unless it had left the mainstream.
It follows that the return activated sludge line is not a part of either the “mainstream”
or the “mainstream nitrification process.”
2.

“Mainstream treatment process”

This term appears in paragraph (b) of Claim 18, which requires “returning at
least a portion of the settled sludge from the final clarifier to the mainstream treatment
process” (’009 Patent, 14:31-34 (filing 58-2 at 13)). For the reasons discussed in the
preceding section, the court rejects the defendants’ definition, which would subsume
the treatment process under the nitrification process.
The ’009 patent provides that “[t]he mainstream biological treatment process
[identified as 14 in Figure 1] can include a series of various treatment zones including
one or more anaerobic zones, one or more aerobic (oxic) zones, or one or more anoxic
zones,” but, at a minimum, for purposes of the present invention would “include at
least a nitrification zone for converting ammonia nitrogen NH 3—N to NO x.” (’009
Patent, 4:17-26 (filing 58-2 at 8)). The specification further provides that “[b]asically,
the mainstream biological treatment area or zones 14 would produce a treated or
purified effluent that could be discharged into a creek, river, lake, etc.” (’009 Patent,
4:26-28 (filing 58-2 at 8)) (boldface in original).
Consistent with this specification, the plaintiffs’ proposed construction states
that a “mainstream treatment process” is “a biological suspended growth wastewater
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treatment process designed to treat a wastewater stream and produce treated or
purified effluent, which may include a series of treatment zones, but which excludes
any sidestream or sidestream treatment process” (filing 50 at 3). The court will adopt
the plaintiffs’ proposed construction.
3.

“Return activated sludge”

This term does not appear in Claim 18 and does not require any construction.
The construction proposed by the defendants, discussed above in connection with the
term “mainstream nitrification process,” is inaccurate.
4.

“Sludge”

This term appears several times in Claim 18, but never on its own. Instead, the
claim preamble refers to “activated sludge,” paragraphs (a) and (b) refer to “settled
sludge,” and paragraph (e) refers to “sludge age.” Each usage is different.9
The defendants propose to define “sludge” as “semi-liquid waste with some
solid concentrations including biological nitrifying bacteria used to decompose waste
and purify the wastewater” (filing 50 at 2). While it might be useful to define “sludge”
for the jury, the defendants’ proposed definition is not accurate. For example, sludge
in the primary clarifier would not contain nitrifiers. As Dr. Kos testified, “that’s [a]
different kind of sludge.” (Kos Depo. 115:8-9 (filing 58-4 at 30)). For another
example, dewatered sludge cannot be described as “semi-liquid.”
9

The term also appears in other contexts within the patent. For example, the
portion of the specification describing Figure 2 identifies six different things that are
referred to as sludge: primary sludge from the primary settling tank; return activated
sludge from the secondary settling tank; excess activated sludge from the secondary
settling tank; digested sludge from the digester; dewatered sludge for disposal from
sludge dewatering; and excess biological sludge from the sidestream biological
nitrification zone. (’009 Patent, 5:41-43, 5:54-57, 5:62-6:7, 6:19-22 (filing 58-2 at 9).
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In addition to being inaccurate, the defendants’ proposed construction would
not assist the jury in understanding the meaning of “settled sludge” or “sludge age.”
It is not necessary to define “settled sludge” in order to understand Claim 18 because
paragraph (a) states that the final clarifier “separates purified supernatant from settled
sludge” and paragraph (b) states that “at least a portion of the settled sludge from the
final clarifier” is returned to the mainstream treatment process (Ex. B at 14:13-18).
There is no need to know the composition of the sludge in order to understand this
step in the treatment process. The meaning of “sludge age,” a disputed term which
will be discussed subsequently, likewise can be understood without knowing the
composition of the sludge.
For these reasons, the court will not accept the defendants’ definition. The
plaintiffs’ request that the term “sludge” not be construed will be granted.
5.

“Sidestream biological nitrification system”

This term appears twice in paragraph (c) of Claim 18. Paragraph (d) uses a
similar term, “sidestream nitrification system.” The proposals for construing this term
do not vary significantly.
The defendants propose: “A system used to create Supplemental Biological
Nitrifiers10 separate from the Mainstream Nitrification Process” (filing 50 at 3). This
would be acceptable were it not for the defendants’ overly inclusive definition of
“Mainstream Nitrification Process.” (See the discussion above.)
The plaintiffs’ proposed definition of a “sidestream biological nitrification
system” is “a system in which nitrification occurs (i.e., ammonia nitrogen, NH 3—N,
is converted to nitrite or nitrate, both referred to as NO x) that is separate from the zone
10

“The parties agree that “supplemental biological nitrifiers” are “nitrifying
bacteria produced outside of the mainstream nitrification process” (filing 50 at 1).
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in which nitrification occurs during the mainstream treatment process” (filing 50 at
3). This definition will be adopted by the court because it is consistent with the
previously adopted definitions of “mainstream treatment process” and “mainstream
nitrification process.”
6.

“Sidestream”

This stand-alone term appears in paragraph (c) of Claim 18 (which requires
“producing supplemental biological nitrifiers in a sidestream”). The court will adopt
the plaintiffs’ proposed construction, which is that a “sidestream” refers to “[a]ny
stream other than the mainstream, auxiliary to treatment of the wastewater stream”
(filing 50 at 3), and that the “mainstream” is “the wastewater stream flowing through
the wastewater treatment plant” (id.). Basically, the “mainstream” is the top line of
the particular process and system design illustrated by Figure 2; the other lines shown
in Figure 2, including the return activated sludge line 64,11 are sidestreams.12
7.

“Relatively high concentration of ammonia”

Although identified as a disputed term in filing 50, the parties stipulated during
the Markman hearing that it is not necessary for the court to construe “relatively high

11

The defendants’ proposed construction would specify that “[a] Return
Activated Sludge Line is not a ‘sidestream’ as defined in this patent” (filing 50 at 3).
As previously explained, this is incorrect because the settled sludge that is conveyed
by this line is being returned to the mainstream.
12

In the biological nitrification process of the present invention, as illustrated
in Figure 1, “influent wastewater is directed along a mainstream 12 through a
mainstream biological treatment process 14” to “produce a treated or purified
effluent” (’009 Patent, 4:17-27 (filing 58-2 at 8)), while “a sidestream 15 [is directed]
into a sidestream nitrification zone or reactor 13” (’009 Patent, 4:43-44 (filing 58-2
at 8)) which “produces supplemental nitrifiers that are conveyed or transferred to the
mainstream 12”(’009 Patent, 4:38-41 (filing 58-2 at 8)).
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concentration of ammonia” as used in paragraph (c) of Claim 18 (describing the
stream which is directed into a “sidestream biological nitrification system.”).
8.

“Sludge age”

Paragraph (e) of Claim 18 requires “m[a]intaining sludge age within the
mainstream nitrification process at a value of less than 200% of the critical sludge
age of a conventional nitrification process” (’009 Patent, 14:31-34 (filing 58-2 at 13)).
The parties agree that the phrase “a value of less than 200%” means “a value of less
than twice” (filing 50 at 2), but otherwise they are in disagreement. Five of the
disputed terms and phrases which have been identified by the parties are found in this
paragraph: (1) “sludge age,” (2) “sludge age within the mainstream nitrification
process,” (3) “maintaining sludge age within the mainstream nitrification process,” (4)
“critical sludge age of a conventional nitrification process;” and (5) conventional
nitrification process.”
The defendants propose that the term “sludge age” be defined as “[t]he average
amount of time Sludge remains in the system determined by dividing the total active
microbial mass in the entire treatment system by the quantity of active microbial mass
discharged per day” (filing 50 at 4). The plaintiffs contend it is unnecessary for the
court to construe the term “sludge age.” They also take issue with the defendants’
formula because it calculates the average retention time of active sludge “in the entire
system” rather than just “within the mainstream nitrification process” as required by
paragraph (e) of Claim 18.
As previously discussed, the ’009 Patent expressly states that “[a]ll of the
descriptions and specifications herein of the sludge age refers to the so-called oxic
sludge age, that is the sludge age necessary for nitrification in the oxic or aerated
zones only” (’009 Patent, 12:14-17 (filing 58-2 at 12)). The defendants’ proposed
definition of “sludge age” does not conform to this specification.

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The court agrees with the plaintiffs that it is not necessary to construe “sludge
age” outside of the specific context in which it used in paragraph (e) of Claim 18.
Providing the jury with a generic definition of “sludge age” would likely cause
confusion, especially since paragraph (e) also uses the term “critical sludge age,”
which is a distinct concept (requiring calculation of a minimum solids retention time
instead of an average time).
9.

“Sludge age within the mainstream nitrification process”

The plaintiffs would calculate “sludge age within the mainstream nitrification
process” by “dividing the mass of suspended solids in the oxic (aerated) portion of the
mainstream reactor tank by the mass of suspended solids discharged from the overall
system per day” (filing 50 at 4). The defendants, on the other hand, would calculate
this average solids retention time by “dividing the total active microbial mass in the
Mainstream Nitrification Process by the quantity of active microbial mass discharged
from the Mainstream Nitrification Process per day” (id).
The parties’ briefs establish that their dispute centers on the meaning of the
term “mainstream nitrification process,” with the plaintiffs contending that it only
includes “the portion of the mainstream treatment process in which mainstream
wastewater is nitrified . . . in the aerobic treatment zone(s)” (filing 50 at 2), and the
defendants contending that the “mainstream nitrification process” also includes
mainstream settling tanks and anaerobic treatment zones, plus the return activated
sludge line.13 The court has already resolved this dispute in the plaintiffs’ favor. For
this reason, the court also adopts the plaintiffs’ proposed construction of “sludge age
within the mainstream nitrification process” as meaning “the average amount of time
nitrifying bacteria remain in the oxic (aerated) portion of the mainstream reactor tank,
determined by dividing the mass of suspended solids in the oxic (aerated) portion of
13

As discussed previously, the parties dispute whether the return activated
sludge line is on the mainstream.
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the mainstream reactor tank by the mass of suspended solids discharged from the
overall system per day” (filing 50 at4).14
10.

“Maintaining sludge age within the mainstream nitrification process”

The defendants argue that the term “maintaining” in paragraph (e) of Claim 18
“connotes an average over at least some period of time” (filing 62 at 27), and they
propose that the phrase “maintaining sludge age within the mainstream nitrification
process” be construed as “[o]perating the Mainstream Nitrification Process so that the
thirty-day average age of all Sludge in the Mainstream Nitrification Process is within
a predetermined range” (filing 50 at 4). The defendants have failed to provide a
rational explanation for their proposal, and, in particular, have failed to justify using
a 30-day average in connection with sludge age calculations.15
The court finds that “maintaining” is a common word which is used in its
ordinary sense in paragraph (e) of Claim 18. Accordingly, the court will not construe
the phrase “maintaining sludge age within the mainstream nitrification process.”
14

The plaintiffs explain “it is essential that the denominator refer to the mass
‘discharged from the overall system.’ As illustrated by Figure 2 of the ’009 patent,
excess activated sludge may be discharged from a system after being separated in the
secondary settling tank, rather than being directly wasted from the aeration tank.
Thus, in the system illustrated by Figure 2, one controls sludge age in the aeration
tank by varying the amount of activated sludge returned to the system via the return
activated sludge line 64 versus the amount treated as excess activated sludge or waste
sludge and directed through line 68 for further treatment and disposal. Accordingly,
the definition should not specify that the suspended solids be discharged from a
particular component of the mainstream system.” (Filing 57 at 53) (record citations
and footnote omitted). The defendants do not contest these statements.
15

The defendants reference the “Barnard ’998 Patent,” but the measurements
described in that patent concerned concentrations of nitrogen and phosphorous in the
effluent, not sludge age. (Filing 58-7, Fig. 6 & 14:27-44) Moreover, there was no
calculation of a 30-day average.
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11.

“Critical sludge age of a conventional nitrification process”

The defendants argue that “[t]his term is ambiguous as a matter of law and
cannot be defined” (filing 69 at 37). The same argument was made by the defendants,
and rejected by the court, in connection with a motion for summary judgment based
on an affirmative defense of indefiniteness. See the court’s Memorandum and Order
entered on August 17, 2012 (filing 75).
In filing 50, the defendants proposed that the “critical sludge age of a
conventional nitrification process” be construed as “the minimum amount of time,
given various temperatures, that Sludge can remain in a Conventional Nitrification
Process to achieve sufficient nitrification” (filing 50 at 5). This proposed construction
is inaccurate because “critical sludge age” actually measures “the minimum solids
retention time at which conventional nitrification ceases” (’009 Patent, 8:34-41
(filing 58-2 at 10)).
As discussed earlier, the specification of the ’009 Patent includes an equation
for calculating the “critical sludge age of a conventional nitrification process.” The
jury will be provided the detailed equation along with a simplified explanation that
the critical sludge age of a conventional nitrification process for environmental
conditions of pH, temperature, and dissolved oxygen is equal to 1 divided by the
difference between the maximum daily nitrifier growth rate for conditions and the
decay rate. (See filing 57 at 61)
12.

“Conventional nitrification process”

Finally, the defendants propose that the court separately construe the term
“conventional nitrification process” to mean “[a] Mainstream Nitrification Process
utilizing Return Activated Sludge, such as the Bardenpho process and the processes
disclosed in U.S. Pat. Nos. 3,964,998; 4,056,465; and 4,874,519” (filing 50 at 5). For
several reasons, the court will not adopt this proposal.
-28-

First, this construction relies on the defendants’ proposed construction of the
term “mainstream nitrification process,” which the court has rejected. Second, the
jury’s understanding of the term would not be enhanced by mere references to the
“Bardenpho process” or to a series of patents. Third, and perhaps most importantly,
the jury does not need to identify the components of a “conventional nitrification
process” in order to calculate the critical sludge age of the process in accordance with
the equation set out above. The only variables in the equation are environmental
conditions (i.e., pH, temperature, and dissolved oxygen levels).
The court agrees with the plaintiffs’ assessment that it is not necessary to
construe the term “conventional nitrification process.” If clarification were needed,
however, the court would instruct the jury that it is “a suspended growth biological
nitrification process that does not utilize supplemental biological nitrifiers produced
outside of the mainstream reactor(s) during ongoing operations” (filing 67 at 52).
+++
IT IS ORDERED that the disputed terms and phrases identified by the parties
in filing 50 are construed in accordance with the foregoing memorandum opinion.
November 8, 2012.

BY THE COURT:
Richard G. Kopf
Senior United States District Judge

*This opinion may contain hyperlinks to other documents or Web sites. The U.S. District
Court for the District of Nebraska does not endorse, recommend, approve, or guarantee any third
parties or the services or products they provide on their Web sites. Likewise, the court has no
agreements with any of these third parties or their Web sites. The court accepts no responsibility
for the availability or functionality of any hyperlink. Thus, the fact that a hyperlink ceases to work
or directs the user to some other site does not affect the opinion of the court.

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