US 2022/0259084 A1Published application

Biological phosphorus and nitrogen removal in activated sludge processing

AssigneeDentro-P, LLC

InventorThomas E. Coleman

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Abstract

An activated sludge process for the treatment of municipal wastewater, particularly applicable to oxidation ditch activated sludge treatment systems which utilize a conventional race track or continuous loop reactor basin configuration. The process removes phosphorus and nitrogen from an activated sludge wastewater treatment system, with an anoxic cycle followed by an aerobic cycle, and followed by a surface wasting cycle until a low flow diurnal period is reached in a diurnal or twenty-four hour period. Automated microprocessor control system using “oxidation-reduction potential” (ORP) and “dissolved oxygen” (DO) as process variable inputs automate aerated and anoxic cycles to optimize phosphorus and nitrogen removal using the available carbon in the influent wastewater resulting in an energy efficient dynamic dissolved oxygen control during the aerated periods.

Claims16

Dependent claims

A method for removing phosphorus and nitrogen from an activated sludge wastewater treatment system, said method comprising the steps of:

a) treating phosphorus and nitrogen-containing wastewater in at an activated sludge bed reactor configured for continuous flow, when during at least one interval in each twenty-four hour period all aeration and mixing is stopped to achieve a deeply anaerobic or fermentation condition in the activated sludge bed reactor in a settled state, the deeply anaerobic or fermentation condition indicated by an oxygen-reduction potential value of less than −200 mV for a fermentation period of at least two hours in a 24-hour period;
b) treating phosphorus and nitrogen-containing wastewater immediately following said fermentation period, with resuming a mixing of the activated sludge bed reactor contents without aeration to create anoxic conditions utilizing any nitrate in solution in a clarified liquid in place above a settled mixed liquor of the activated sludge bed reactor during the fermentation period, and with the mixing under anoxic conditions for an anoxic period, said anoxic period continuing until a depletion of nitrate is detected using a control algorithm based on a derivative of a rate of change in oxygen-reduction potential versus time;
c) treating said wastewater in the activated sludge bed reactor following said anoxic period, by resuming a mixing and aeration and maintaining a constant concentration of dissolved oxygen at a selected low-range setpoint during an aerated period by controlling an input of an air volume based on the measured value of dissolved oxygen in the activated sludge bed reactor contents;
d) determining when the derivative of rate of change of the air flow volume into the activated sludge bed reactor needed to maintain said selected low-range setpoint reaches a predetermined value indicating that conversion of the ammonia nitrogen in the influent wastewater to nitrite or nitrate is complete and thereby initiating programmable time delay period prior to ceasing aeration and the beginning of a subsequent anoxic period;
e) alternating the subsequent anoxic periods and a subsequent aerated periods based on a control algorithm, until a time of the ferment period as subsequently scheduled;
f) withdrawing during one or more of said aerated periods, a specific volume of mixed liquor from a surface of the activated sludge bed reactor and the specific volume of mixed liquor wasted from the activated sludge bed reactor;
and
g) maximizing the utilization of the stored organic carbon substrate in phosphate accumulating organisms under anoxic conditions, and thereby the selection of denitrifying phosphate accumulating organisms over non-denitrifying phosphate accumulating organisms is also maximized in order to further maximize the removal of phosphorus and nitrogen in the activated sludge bed reactor.

5 more elements

A method for removing phosphorus and nitrogen from an activated sludge wastewater treatment system, said method comprising the steps of:

a) beginning a ferment cycle of a sludge wastewater during a low diurnal flow period in a settled mixed liquor bed, and with a measurement of a ratio of oxidants to reductants as an electric potential to provide an ORP of the sludge wastewater in the settled mixed liquor bed;
b) terminating the ferment cycle after an ORP setpoint has been maintained for a ferment cycle ORP setpoint time period, said ORP setpoint less than −200 mV, and said ORP setpoint time period greater than approximately two hours;
c) beginning a first anoxic cycle of the sludge wastewater and maintain mixing without aeration, and with a measurement a first anoxic cycle ORP of the sludge wastewater;
d) terminating said first anoxic cycle when a first anoxic second derivative of the ORP versus an elapsed first anoxic cycle time reaches a predetermined first anoxic derivative setpoint;
e) beginning a first aeration cycle with a first aeration of the sludge wastewater and maintaining a first aeration dissolved oxygen setpoint measured in the sludge wastewater and measure a first aeration airflow versus an elapsed first aeration cycle time;
f) terminating said first aeration cycle when a first aeration second derivative of said first aeration airflow versus the elapsed first aeration cycle time reaches a predetermined first aeration setpoint;
g) initiating a first surface wasting cycle with a first withdrawal of the mixed liquor from a surface of the settled mixed liquor bed;
h) terminating said first surface wasting cycle after a first predetermined volume of the mixed liquor has been withdrawn from said surface of the settled mixed liquor bed;
i) beginning an second anoxic cycle of the sludge wastewater and maintain mixing without aeration, and with a measurement a second anoxic cycle ORP of the sludge wastewater;
j) terminating said second anoxic cycle when a second anoxic second derivative of the ORP versus an elapsed second anoxic cycle time reaches a predetermined second anoxic derivative setpoint;
k) beginning a second aeration cycle with a second aeration of the sludge wastewater and maintain a second aeration dissolved oxygen setpoint measured in the sludge wastewater and measuring a second aeration airflow versus an elapsed second aeration cycle;
l) terminating said second aeration cycle when a second aeration second derivative of said second aeration airflow versus the elapsed second aeration cycle time reaches a predetermined second aeration setpoint;
m) initiating a second surface wasting cycle with a second withdrawal of the mixed liquor from a surface of the settled mixed liquor bed;
and
n) terminating said second surface wasting cycle after a second predetermined volume of the mixed liquor has been withdrawn from said surface of the settled mixed liquor bed.

12 more elements

Dependencies are inferred from the claim text.

Facts

Application: 17/674,755Filed 17 Feb 2022
Priority: 17 Feb 2021
Published: 18 Aug 2022
Term ends: Not estimatedThe source records don’t support an estimate.

Classification15 codes

C02F 3/308
Aerobic and anaerobic processes: biological phosphorus removal
C02F 3/006
Biological treatment of water, waste water, or sewage: regulation methods for biological treatment
C02F 3/1215
Particular type of activated sludge processes: combinations of activated sludge treatment with precipitation, flocculation, coagulation and…
C02F 3/1257
Particular type of activated sludge installations: oxidation ditches