Systems and processes for early detection of biological ammonia oxidation in water using fluorometry
Inventors
FAIREY, JULIAN • DO, THIEN DUC • PIFER, ASHLEY • WAHMAN, DAVID
Assignees
United States, US Environmental Protection, Administrator of • University of Arkansas at Little Rock • US Environmental Protection Agency
Publication Number
US-11255783-B2
Publication Date
2022-02-22
Expiration Date
2039-08-30
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Abstract
This invention relates generally to a system and process for early detection of biological ammonia oxidation in water utilizing a fluorescence-based sensor and process. Various embodiments are configured to read increases in a fluorescence excitation-emission wavelength pair that is responsive to a period of time (days to weeks or even longer) prior to the onset of biological ammonia oxidation, which is considered to be a nitrification event. Fluorescence excitation/emission pairs that have proven to be reliable include a fluorescence excitation wavelength of about 230 nm and an emission wavelength of about 345 nm and an excitation wavelength of 325 and an emission wavelength of 470. The system and process enable drinking water utilities to improve management of its distribution systems and facilitate earlier corrective actions, resulting is less loss of treated water through flushing and other tangible benefits.
Core Innovation
This invention relates to a system and process for early detection of biological ammonia oxidation in water utilizing a fluorescence-based sensor and process. The invention is configured to read increases in fluorescence excitation-emission wavelength pairs that are responsive during a period of time (days to weeks or longer) prior to the onset of biological ammonia oxidation, considered a nitrification event. Reliable fluorescence pairs include excitation at about 230 nm with emission at about 345 nm, and excitation at about 325 nm with emission at about 470 nm.
The problem being solved is the difficulty in detecting biological ammonia oxidation early in drinking water distribution systems. Biological ammonia oxidation degrades drinking water quality by depleting disinfectants, forming nitrite/nitrate, reducing dissolved oxygen, lowering pH and alkalinity, and increasing microbial presence. Traditional detection methods rely on measuring inorganic nitrogen species when oxidation is already occurring, requiring remedial actions such as flushing that result in significant treated water loss.
The invention provides early warning detection of biological ammonia oxidation without requiring chemicals or sample preparation, allowing water utilities to implement corrective actions before water quality deteriorates. Fluorescence measurements at selected excitation-emission wavelength pairs can indicate microbial activity or dissolved organic carbon levels prior to measurable ammonia oxidation. This enables improved management of distribution systems, earlier remedial actions, and reduced water loss through flushing.
Claims Coverage
The patent includes two independent claims describing methods for early detection and remediation of biological ammonia oxidation based on fluorescence measurements.
Method of early detection and treatment of biological ammonia oxidation in water
A method involving selecting fluorescence excitation and emission wavelengths responsive to components in water before measurable ammonia oxidation onset; determining a baseline fluorescence value; selecting a corrective action threshold based on the baseline; collecting water samples; exciting the sample at the selected wavelength; measuring fluorescence emission; comparing measured fluorescence to baseline; determining entry into a pre-oxidation stage when fluorescence exceeds the threshold; initiating remediation efforts upon detection; and repeating the process if not exceeded.
Method of determining the need for remedial action to prevent biological ammonia oxidation
A method comprising selecting a fluorescence excitation-emission wavelength pair with signal changes preceding biological ammonia oxidation; establishing a baseline fluorescence value over a period of acceptable ammonia oxidation levels; selecting a corrective action threshold relative to this baseline; collecting water samples; exciting and measuring fluorescence; comparing measured values to baseline; determining remediation necessity if fluorescence exceeds threshold; otherwise repeating measurements; and initiating remedial action until fluorescence returns below the threshold.
The claims cover methods that utilize fluorescence excitation-emission wavelength pairs to detect impending biological ammonia oxidation early, define corrective action thresholds based on baseline fluorescence, and guide remediation efforts to prevent water quality degradation.
Stated Advantages
Enables early warning of biological ammonia oxidation before traditional methods detect it.
Allows earlier corrective actions in water distribution systems, reducing treated water loss from flushing.
Improves management of drinking water utilities' distribution systems.
Operates without use of chemicals or complex sample preparation steps.
Facilitates real-time or continuous monitoring using fluorescence-based instruments combined with analytical software to reduce measurement noise and interference.
Documented Applications
Use by drinking water utilities to detect impending biological ammonia oxidation in chloraminated distribution systems.
Monitoring microbial activity at various locations in water distribution systems to facilitate targeted maintenance.
Evaluating the effectiveness and duration of remedial actions such as free chlorine conversion or flushing.
Identifying undesirable flow patterns, blending zones, and water age within distribution systems.
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