Liquid purification or separation – With alarm – indicator – register – recorder – signal or...
Reexamination Certificate
2001-10-09
2004-03-16
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
C210S096100, C210S142000, C210S143000, C210S202000, C210S257200, C210S321690, C210S500230, C210S605000, C210S614000, C210S739000
Reexamination Certificate
active
06706171
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to processes and systems for treating wastewater and more particularly to removing nutrients from wastewater in a wastewater treatment 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. Activated-sludge 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. In these processes, the microorganisms used in the activated sludge break down or degrade contaminants for the desired water treatment. Efficient process performance and control requires quick and accurate assessment of information on the activity of 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 currently used in wastewater treatment plants to assist in contamination degradation. In a typical BNR process, contaminants in the wastewater, such as carbon sources (measured as biochemical oxygen demand or BOD), ammonia, nitrates, phosphates and the like are digested by the activated sludge in anaerobic, anoxic and aerobic stages, also known in the art. In the anacrobic stage, the wastewater, with or without passing through a preliminary settlement process, is mixed with return activated sludge (RAS).
In many wastewater treatment plants one anaerobic stage is arranged in the BNR process. In the anaerobic stage poly-P microbial species take up short chain carbonaceous nutrient and store this nutrient intracellularly most commonly as polyhydroxybutyrate (PHB). Microorganisms must expend energy to accomplish this uptake of soluble organics and formation of intracellular storage products. The energy is obtained anaerobically through the cleavage of high energy phosphate bonds in stored long-chain inorganic polyphosphates. This process produces orthophosphate that is released from the cell into solution in the anaerobic zone. In a subsequent oxic stage, a rapid uptake of soluble orthophosphate provides for the resynthesis of the intracellular polyphosphates. Previously stored PHB is also aerobically metabolized to carbon dioxide, water, and new cells. When solids are wasted from the treatment process, the orthophosphate taken up by the poly-P microbes results in up to four times the phosphorus removal in comparison to a conventional treatment process without an anaerobic zone.
In most wastewater treatment plants, one or several anoxic stages are arranged in the BNR process. In the anoxic stages, denitrifiers, i.e., microbial species capable of denitrification, utilize nitrate and/or nitrite as electron acceptors and consume some of the available carbon sources during the denitrification process. NO
x
is reduced stepwise to nitrogen gas and released to the atmosphere in the following manner:
NO
3
−
→NO
2
−
→NO→N
2
O→N
2
The nitrate is usually supplied by recycling a certain volume of wastewater from the end of the oxic stage back to the beginning of the anoxic stage.
One or several oxic stages are typically employed in BNR processes. In the oxic stage, air which contains about 20% oxygen or pure oxygen, is supplied so that a desired dissolved oxygen level is maintained. Autotrophic organisms, i.e., microbial species capable of using ammonia as their energy source, convert ammonia to nitrite and nitrate under aerobic conditions. The poly-P microbial species in the wastewater uptake phosphate from the water phase and digest their intracellular PHB and PHV storage products converting it into polyphosphate, a compound for energy storage. The polyphosphate pool of the poly-P microbial species is thus replenished and phosphorous is removed from the water phase. The phosphorous is then removed from the system by sludge wasting, which is well known in the art. Under aerobic conditions, the remaining carbon sources in the water phase are further digested by aerobic organisms.
As the degradation of the contaminants nears completion, the microorganisms and the treated water are led through a solid/liquid separation process where the biosolids are separated from the liquid. The biosolids are then either recycled back to the anaerobic/anoxic/oxic treatment processes, or removed from the treatment process as waste biosolids. Common devices used in the solid/liquid separation are clarifiers where biosolids are settled to the bottom and withdrawn by recycling pumps while clear liquid flows over discharge weirs at the clarifier surface. Air flotation devices are also frequently used in the solid/liquid separation process. These are commonly known in the art.
However, many of the current wastewater treatment plants require clarifiers which increase the amount of space utilized by the wastewater treatment plant, add to the initial capital costs and increase operating and maintenance costs. Also, such systems oftentimes utilize significant operator input, which adds additional costs and, as mentioned above, utilize recycling/return systems which increase the capital costs, as well as the operating and maintenance costs. Finally, there is a significantly increased hydraulic retention time (HRT) in the overall treatment process.
SUMMARY OF THE INVENTION
In one aspect the invention relates to a system for removing BOD and NH
3
from wastewater including a first wastewater treatment tank T
1
having a first tank inlet I
1
and a first tank outlet O
1
with a first tank membranous filter F
1
, a second wastewater treatment tank T
n−1
operatively connected to tank T
1
to permit wastewater to flow between tanks T
1
and T
n−1
, and an Nth wastewater treatment tank T
n
having an Nth tank inlet I
n
and an Nth tank outlet O
n
with an Nth tank membranous filter F
n
operatively connected to tank T
n−1
to permit wastewater to flow between tanks T
n−1
and T
n
.
There is also a NH
4
detector AD
1
connected to tank T
1
, a NH
4
detector AD
n
connected to tank T
n
, a TSS detector TD
1
connected to tank T
1
, and a TSS detector TD
n
connected to tank T
n
and an air supply connected to at least one of said tanks.
A controller connects to an air supply, inlets I
1
and I
n
, outlets O
1
and O
n
, NH
3
detectors AD
1
and AD
n
, and TSS detectors TD
1
and TD
n
. The controller shifts between operational cycles C
1
and C
2
, wherein in cycle C
1
, I
1
and O
n
are on, I
n
is off and F
1
is in a cleaning mode until AD
1
≧X or TD
1
≦Y, wherein X and Y are selected concentrations of NH
3
and TSS, respectively, and wherein in cycle C
2
, I
n
and O
1
are on, I
1
is off and F
n
is in a cleaning mode until AD
n
≧X or TD
n
≦Y.
In another aspect, the invention relates to a system for removing nutrients from wastewater including a first wastewater treatment tank T
1
having a first tank inlet I
1
and a first tank O
1
with a first tank membranous filter F
1
, an Nth wastewater treatment tank T
n
having an Nth tank inlet I
n
and an Nth tank O
n
with an Nth tank membranous filter F
n
, a second wastewater treatment tank T
2
operatively connected to tank T
1
to permit wastewater to flow between tanks T
1
and T
2
and having a second tank inlet I
2
connected to inlets I
1
and I
n
, a third wastewater treatment tank T
3
operatively connected to tank T
2
to permit wastewater to flow between t
Bubel, Sr. Mark J.
Goodley James J.
Lee Jaw Fang
Liu Wenjun
McGurney William D.
BioChem Technology, Inc.
Drodge Joseph W.
Piper Rudnick LLP
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