Liquid purification or separation – Constituent mixture variation responsive
Reexamination Certificate
2000-01-11
2001-12-25
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Constituent mixture variation responsive
C210S139000, C210S143000, C210S195300, C210S221200
Reexamination Certificate
active
06332978
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the treatment of wastewater, namely a method for reducing nitrate concentration in wastewater.
2. Background
Wastewater is treated to remove its bacterial nutrients, principally biochemical oxygen demand (BOD). BOD is degraded by bacteria primarily by consuming dissolved oxygen (DO) to assist in metabolizing the BOD (aerobic metabolism). Oxygen is provided in treatment systems by aeration. In an oxygen depleted environment when DO levels in the wastewater are sufficiently reduced (anoxic environment), bacteria readily metabolize nitrates in the wastewater. Nitrate reduction by bacteria, however, is generally inefficient in the presence of oxygen. Bacteria capable of functioning in oxygen-rich and oxygen-poor environments will preferably metabolize nutrients aerobically.
If an anoxic environment is maintained for a sufficient time period, nitrate levels within the wastewater can be substantially reduced because bacteria will be forced to consume nitrates as a food source resulting in reduced nitrate concentrations in the effluent (outgoing water). This process is referred to as de-nitrification.
New environmental regulations are requiring reduction in nitrate levels in the effluent from wastewater treatment systems. Several methods, such as those disclosed in U.S. Pat. Nos. 5,582,734 and 4,663,044 discuss possible solutions to nitrate removal in large municipal and commercial wastewater treatment plants. These solutions are inapplicable to relatively small, self-contained wastewater treatment systems that are employed throughout the United States for treatment of wastewater. The small self-contained systems serve wastewater sources that include single family dwellings located in areas not served by municipal sewerage systems. Like larger commercial and municipal treatment systems, these smaller systems are becoming subjected to stricter nitrate removal regulations and encounter treatment problems when attempting to reduce nitrate levels in the wastewater. Unfortunately, no practical solution has been provided that will effectively solve the problems encountered by the small, self-contained systems.
ADVANTAGES AND OBJECTS OF THE INVENTION
The methods of the present invention provide a solution for small, self-contained wastewater treatment systems and work without interruption of flow into the systems. The present invention works with existing and new systems without additional substantial expense and effort and provides methods for effective nitrate reduction in the effluent from the small, self-contained systems.
With the aforementioned considerations in mind, it is therefore an object of this invention to provide a method for reducing nitrate levels in wastewater.
It is a further object of this invention to provide a safe and economical method of reducing nitrate concentration in wastewater that can be used with existing wastewater treatment systems.
It is a further object of the present invention to provide a method for reducing nitrate concentration in wastewater that can be implemented during a continuous wastewater flow situation.
It is a further object of the present invention to provide a method of reducing nitrate concentration in wastewater wherein the method is activated during periods of heavy diurnal flow.
It is a further object of the present invention to provide a method of reducing nitrate concentration in wastewater wherein the method is activated by a change in the dissolved oxygen level in the wastewater.
These and other advantages and objects of this invention shall become apparent from the ensuing description of the invention.
SUMMARY OF THE INVENTION
The present invention comprises apparatuses and method for reducing the nitrate concentrations in wastewater.
The present invention comprises a method for reducing nitrate concentration in wastewater in a wastewater treatment apparatus configured to define an aeration zone and a quiescent zone, wherein wastewater may continuously flow into the aeration zone. The wastewater treatment apparatus further comprises at least one gas outlet positioned within the aeration zone to provide gas flow into the aeration zone when wastewater is present in the aeration zone. The method comprises the step of ceasing gas flow into the aeration zone for a predetermined nitrate reduction period.
The present invention is also a method comprising the steps of ceasing gas flow into the aeration zone during periods of heavy flow and intermittently mixing the wastewater within the aeration zone.
The present invention also comprises a method for reducing the nitrate concentration in wastewater wherein the wastewater apparatus further comprises a dissolved oxygen monitor positioned to monitor the dissolved oxygen levels of the wastewater in the aeration zone. The method comprises the steps of: (a) monitoring the dissolved oxygen level in the aeration zone; (b) ceasing gas flow into the aeration zone when a predetermined dissolved oxygen level has been reached; and, (c) resuming gas flow into the aeration zone when a second predetermined threshold has been reached or a certain period of time has elapsed.
The present invention also comprises a method for reducing nitrate concentration in wastewater in a wastewater treatment apparatus wherein the method comprises the steps of: (a) monitoring the dissolved oxygen level in the aeration zone; (b) ceasing gas flow into the aeration zone when a predetermined dissolved oxygen level has been reached; and, (c) mixing the wastewater in the aeration zone.
The present invention also comprises a wastewater treatment apparatus configured to have an aeration zone and a quiescent zone. The apparatus comprises (a) at least one gas outlet positioned in the aeration zone and fluidly connected to a source of gas; (b) a dissolved oxygen probe positioned in the aeration zone; and, (c) a first controller adapted to regulate gas flow from the source of gas wherein the dissolved oxygen probe provides a dissolved oxygen measurement that is input to the first controller. The present invention also comprises a wastewater treatment apparatus configured to define an aeration zone and a quiescent zone. The apparatus comprises (a) one or more gas outlets positioned in the aeration zone; (b) a timer adapted to regulate gas flow from a source of gas to the gas outlets; (c) a repeat cycle timer adapted to regulate gas flow from the source of gas to the gas outlets, whereby when the timer suspends gas flow into the gas outlets, the repeat cycle timer permits gas flow to the gas outlets at predetermined mixing intervals for predetermined mixing periods.
REFERENCES:
patent: 4130481 (1978-12-01), Chase et al.
patent: 4246111 (1981-01-01), Savard et al.
patent: 5266200 (1993-11-01), Reid
patent: 5624562 (1997-04-01), Scroggins
patent: 5714061 (1998-02-01), Guy et al.
Catanzaro Michael David
Cox Christopher Edward
Cox Raleigh Lee
Delta Environmental Products, Inc.
Hruskoci Peter A.
Jones Walker Waechter Poitevent Carrere & Denegre, LLP
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