US 5,853,589 A · Advanced biological phosphorus removal using a series of sequencing batch reactors

Abstract

The biological process is for treating wastewater in order to remove the phosphorus therefrom and thus obtain clarified water. The process is using two sequencing batch reactors (SBR) in series filled with a sludge-mixed liquor. The process consists of: continuously feeding wastewater into the first (SBR) operating under anaerobic conditions for equalization and anaerobic treatment by controlling in-time any fermentation reaction occurring therein in order to produce an acidogenesis fermenting phase of organic materials and prevent the methanogenesis phase. Then, the fermented wastewater from the first SBR is rapidly transferred by batch into the second SBR. In the second SBR, the wastewater is first anaerobically treated to store a maximum amount of volatile fatty acids (VFAs) in the phosphorus removal biomass. Then, the fermented wastewater is mixed and aerated for causing the phosphorus removal biomass to rapidly consume the volatile fatty acids stored therein and to absorb the phosphorus in solution in the wastewater, thereby producing a phosphorus-rich sludge-mixed liquor. Then, the phosphorus-rich sludge-mixed liquor is removed under oxygenated conditions to avoid resolubilization of the phosphorus in the water. The sludge remaining in the second SBR is allowed to settle, thereby causing formation of an upper layer of clarified water. Finally, the upper layer of clarified water is decanted. The clarified water obtained contains a low concentration of phosphorus, preferably less than 0,5 mg/l of phosphorus in solution.

Claims12

Dependent claims

A biological process for treating wastewater having a ratio of biodegradable BOD loads to phosphorus in solution at least equal to 25/1, in order to remove said phosphorus and thus obtain clarified water, said process using at least two sequencing batch reactors (SBR) filled with a sludge-mixed liquor and comprising the steps of:

a) continuously feeding said wastewater into a first (SBR) operating under anaerobic conditions;
b) in said first SBR,
i) equalizing and anaerobically mixing the wastewater;
ii) controlling in-time any fermentation reaction occurring therein in order to produce and maximize an acidogenesis fermenting phase of organic materials and prevent a methanogenesis fermenting phase thereof;
c) rapidly transferring the wastewater from the first SBR to a second SBR;
d) in said second SBR,
i) anaerobically treating the waste water from the first SBR in order to store a maximum amount of volatile fatty acids (VFAs) within a phosphorus removal biomass;
ii) mixing and aerating the wastewater, such aerating causing the phosphorus removal biomass to rapidly consume the volatile fatty acids stored therein and to absorb the phosphorus in solution in the wastewater, thereby producing a phosphorus-rich sludge-mixed liquor;
iii) removing a given amount of the phosphorus-rich sludge-mixed liquor from the second SBR under oxygenated conditions to avoid resolubilization of the phosphorus in the water;
iv) allowing the sludge remaining in the second SBR to settle, thereby causing formation of an upper layer of clarified water;
and
v) decanting the upper layer of clarified water formed above the liquor after the settling period (iv), said clarified water containing a low concentration of phosphorus.

9 more elements

A biological process for treating wastewater having a ratio of biodegradable BOD loads to phosphorus in solution at least equal to 25/1, in order to remove said phosphorus and thus obtain clarified water, said process using two sequencing batch reactor (SBR) filled with a sludge-mixed liquor and comprising the steps of:

a) continuously feeding said wastewater into a first (SBR) sized to provide 2 to 24 hours of hydraulic retention time and operating under anaerobic conditions;
b) in said first SBR,
i) equalizing and anaerobically mixing the wastewater;
ii) controlling in-time any fermentation reaction occurring therein in order to produce an acidogenesis fermenting phase of organic materials and prevent a methanogenesis fermenting phase thereof;
iii) allowing the sludge to settle in the first SBR;
iv) controlling odors by intermittently introducing oxygen or air in the first SBR for less than five minutes per day;
c) rapidly transferring the wastewater from the first SBR to a second SBR;
d) in said second SBR,
i) anaerobically treating the waste water from the first SBR in order to store a maximum amount of volatile fatty acids within a phosphorus removal biomass;
ii) mixing and aerating the wastewater, such aerating causing the phosphorus removal biomass to rapidly consume the volatile fatty acids stored therein and to absorb the phosphorus in solution in the wastewater, thereby producing a phosphorus-rich sludge-mixed liquor;
iii) removing the phosphorus-rich sludge-mixed liquor from the second SBR under oxygenated conditions to avoid resolubilization of the phosphorus in the water;
iv) allowing the sludge remaining in the liquor to settle, thereby causing formation of an upper layer of clarified water;
and
v) decanting the upper layer of clarified water formed above the liquor after the settling period (iv);
e) filtering the removed sludge-mixed liquor by using a micronic filtration process to obtain a filtrate and a thickened sludge;
f) adding said filtrate to the first SBR;
g) treating the thickened sludge in an aerated sludge holding tank;
h) removing water from said treated sludge;
and
i) transferring said water obtain in step (h) into the first SBR.

17 more elements

Dependencies are inferred from the claim text.

Advanced biological phosphorus removal using a series of sequencing batch reactors

Life of this patent

Advanced biological phosphorus removal using a series of sequencing batch reactors

Life of this patent

Abstract

Claims12