Chemistry: analytical and immunological testing – Nitrogen containing – Amine and quaternary ammonium
Reexamination Certificate
1999-04-23
2001-06-19
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Nitrogen containing
Amine and quaternary ammonium
C436S112000, C436S113000, C436S181000, C422S062000, C422S068100, C422S075000, C422S081000
Reexamination Certificate
active
06248595
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for measuring amounts of NO
x
(nitrate (NO
3
) and/or nitrite (NO
2
)) and nitrification/denitrification rates in liquid and controlling the treatment thereof, more particularly, to apparatus and methods for real time measuring the amount of NO
x
in liquids and nitrification/denitrification rates of liquids in a biochemical process and using the results of such measurement to control and/or adjust selected aspects of the process.
BACKGROUND OF THE INVENTION
The prior art has employed many devices and systems to process and purify water from industrial operations and municipal sources prior to discharging the water. Wastewater treatment plants (WWTP's), which are well known in the art, have been most often utilized to address this problem. Additionally, many industrial and municipal water treatment plants utilize biological systems to pre-treat their wastes prior to discharging into the usual municipal treatment plant.
Microorganisms used in the sludge break down or degrade contaminants for the desired water treatment in these processes. Efficient process performance and control requires quick and accurate assessment of information on the activity of the microorganisms. This has proven to be a difficult task in view of the wide variety of materials and contaminants that typically enter into treatment systems. Also, variations in the quantity of wastewater being treated, such as daily, weekly or seasonal changes, can dramatically change numerous important factors in the treatment process, such as pH, temperature, dissolved oxygen, nutrients and the like, alteration of which can be highly detrimental to proper wastewater treatment. Improperly treated wastewater poses serious human health dangers.
Various biological nutrient removal (BNR) processes are often used in biochemical systems/plants/processes. “BNR” is used hereinafter in a very generic sense, namely any biochemical process that uses microorganisms to remove nutrients. In BNR processes, contaminants in liquids such as wastewater, particularly carbon sources (measured as biochemical oxygen demand or BOD), ammonia, nitrates, phosphates and the like are digested by activated sludge in anaerobic, anoxic and aerobic (oxic) stages, also known in the art. In the anaerobic stage, wastewater, with or without passing through a preliminary settlement process, is mixed with return activated sludge (RAS), sometimes hereinafter referred to as “mixed liquor.”
It is, of course, important to quantify the various contaminants in the wastewater. One of those contaminants that is important to quantify is the amount of NO
x
. This is because quantification of the amount of NO
x
provides valuable information about nitrification and denitrification processes. Also, it is important to determine the nitrification or denitrification rate to facilitate adjustment of various system parameters, such as retention time, to enhance the treatment process and increase treatment system efficiency in response to this important information.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide apparatus and a method for measuring the amount of NO
x
in biochemical systems to maximize the efficiency of the treatment process.
It is a further object of the present invention to provide apparatus and a method for measuring nitrification and/or denitrification rates to enhance control of biochemical processes, to maximize process performance in response to transient and other conditions.
Other objects of the present invention will be apparent to those of ordinary skill in the art based on the following drawings, detailed description of preferred embodiments and the appended claims.
SUMMARY OF THE INVENTION
One aspect of the invention includes a method of measuring the nitrification rate for a liquid including isolating a first liquid sample at t
0
; recording a value of ammonia [NH
3
]
1
present in the first sample at a predetermined time t
1
; isolating a second liquid sample and introducing air into the second liquid sample after another predetermined time t
2
; terminating the introduction of air into the second liquid sample and adjusting the pH of the second sample at t
3
; recording another value of ammonia [NH
3
]
2
in the second sample at a predetermined time t
4
; and determining the nitrification rate of the liquid according to the following formula:
NR
=
Δ
[
NH
3
]
Δ
t
wherein NR is the nitrification rate, &Dgr;t is t
2
−t
3
and &Dgr;[NH
3
] is [NH
3
]
1
−[NH
3
]
2
.
Another aspect of the invention includes another method of measuring a nitrification rate for liquids including isolating first and second liquid samples and introducing air into the second liquid sample at t
0
;recording a value of ammonia [NH
3
]
1
present in the first sample and terminating introduction of air into the second sample at t
1
; recording a value of ammonia [NH
3
]
2
present in the second sample at t
2
; and determining the nitrification rate of the liquid according to the following formula:
NR
=
Δ
[
NH
3
]
Δ
t
wherein NR is the nitrification rate, &Dgr;t is t
1
−t
2
and &Dgr;[NH
3
] is [NH
3
]
1
−[NH
3
]
2
.
The words “ammonia” ([NH
3
]) and “ammonium” ([NH
4
+]) are hereafter often used interchangeably regarding the concentration of ammonia in the aqueous phase. This is because at a given pH, there exists a chemical equilibrium between ammonia molecules and ammonium ions in the aqueous phase. This equilibrium is described in the following form with the equilibrium constant equal to one, at pH=9.25.
NH
3
+H
2
O←→NH
4
+
+OH
−
The measurements of ammonia [NH
3
] and ammonium [NH
4
+
] are substantially equivalent so long as the pH value of the solution is known. It is advantageous to measure ammonium concentration, [NH
4
+
], at a lower pH(pH<6), while the measurement of ammonia concentration, [NH
3
], is more convenient at an elevated pH(pH>8). The discussion of this invention often refers to the ammonia concentration as [NH
3
] measured with an ammonia selective probe, with the understanding that at a lower pH, it can be replaced by [NH
4
+
] measured with an ammonium ion selective probe.
The invention also includes a method of measuring NO
x
in liquids, especially wastewater. This method is different from other analyzing methods in that there is no need to prepare the sample by filtration or other method of solids removal. The method includes isolating a wastewater sample; adjusting the pH and/or ionic strength of the sample to a predetermined level for a predetermined time interval t
1
; recording a value of [NO
x
]
1
present in the sample with an NO
x
selective probe(s); recording another value of [NO
x
]
2
present in the sample after another predetermined time interval t
2
; determining NO
x
concentrations in the sample at each predetermined time interval t
1
and t
2
according to the following formula:
[NO
x
]=10
a·mV+b
wherein a and b are linear coefficients of the NO
x
probe and mV reading is from the NO
x
ion selective probe(s); determining the changes in NO
x
according to the following formula:
&Dgr;[NO
x
]=[NO
x
]
2
−[NO
x
]
1
; and
determining the NO
x
concentration of the sample according to the following formula:
[
NO
x
]
=
[
NO
x
]
1
-
Δ
[
NO
x
]
Δ
t
·
t
1
.
In yet another aspect of the invention, the rate of denitrification may be determined. The denitrification rate (DR) may be determined as follows: isolating a liquid sample at t
0
; recording a value of [NO
x
]
1
present in the sample at a predetermined time t
0
; recording a value of [NO
x
]
2
presen
Kolb Marcus E.
Lee Jaw Fang
Maneshin Sergey K.
Yang Xin
Biochem Technology, Inc.
Schnader Harrison Segal & Lewis LLP
Soderquist Arlen
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