Measuring and controlling organic matter in waste water stream

1 . A method for monitoring and controlling treatment of a municipal waste water stream, or an industrial waste water stream, wherein the treatment involves subjecting the waste water stream to both

at least one biological treatment step in a bioreactor followed by a solids separation unit, and

at least one chemical treatment step, the method comprising:

conducting a sample of waste water biologically treated in the bioreactor online as a side stream to a settling vessel;

allowing particles in the sample to settle in the settling vessel for a selected settling time;

measuring UV absorbance from the biologically treated waste water influent or waste water effluent of the solids separation unit after the biological treatment step, wherein the UV absorbance is measured after the selected settling time for the settled sample in a clarified portion of the sample;

determining a concentration of dissolved organics and a concentration of hard COD in the waste water influent or waste water effluent based on measured UV absorbance;

controlling dosing of at least one coagulant and/or other control chemical to the waste water influent based on the measured UV absorbance, the determined concentration of the dissolved organics and the determined concentration of hard COD.

2 . A method as claimed in claim 1 , comprising

measuring turbidity of the waste water influent and/or waste water effluent,

controlling dosing of at least one coagulant and/or other control chemical to the waste water influent based on the measured turbidity; and

controlling dosing of at least one flocculant to the waste water influent based on the measured turbidity.

3 . A method as claimed in claim 2 ,

wherein the measuring of the UV absorbance and turbidity takes place from waste water effluent obtained from a tertiary treatment in a separation unit of a biologically and chemically treated waste water influent; and

wherein the dosing of the at least one coagulant and optionally the dosing of the at least one flocculant takes place downstream from a secondary treatment in a sedimentation unit of a biologically treated waste water influent and upstream from the tertiary treatment.

4 . A method as claimed in claim 3 , wherein the method comprises:

measuring a pH value of the biologically treated waste water influent obtained from the secondary treatment;

measuring a pH value of a biologically and chemically treated waste water influent downstream from the secondary treatment and upstream from the tertiary treatment;

measuring a pH value of the waste water effluent obtained from the tertiary treatment;

measuring a pH value of the waste water effluent obtained from the secondary treatment; and/or

measuring a pH value of a clarified portion of a settled waste water sample in a settling vessel; and

controlling the dosing of at least one pH adjustment chemical and/or coagulant to the waste water influent and/or waste water effluent based on a measured pH value.

5 . A method as claimed in claim 2 ,

wherein the measuring of the UV absorbance and turbidity takes place from waste water influent obtained from a secondary treatment in a sedimentation unit of a biologically treated waste water influent; and

wherein the dosing of the at least one coagulant and optionally the dosing of the at least one flocculant takes place downstream from the secondary treatment and upstream from a tertiary treatment in a separation unit of a biologically and chemically treated waste water influent.

6 . A method as claimed in claim 2 ,

wherein the measuring of the UV absorbance and turbidity takes place from waste water effluent obtained from a secondary treatment in a sedimentation unit of a biologically and chemically treated waste water influent;

wherein the dosing of the at least one coagulant and optionally the dosing of the at least one flocculant takes place upstream from the secondary treatment.

7 . A method as claimed in claim 1 , wherein the sample is biologically and chemically treated waste water influent, and the method comprises:

measuring turbidity of the sample to obtain an initial turbidity value prior to allowing particles in the sample to settle in the settling vessel for the selected settling time;

after the selected settling time, measuring UV absorbance and settled turbidity from a clarified portion of the sample;

determining a concentration of dissolved organics in the clarified portion of the sample based on the measured UV absorbance;

controlling dosing of at least one coagulant to the waste water influent based on the measured UV absorbance and/or the determined concentration of the dissolved organics, and optionally based on the settled turbidity; and

optionally controlling dosing of at least one flocculant to the waste water influent based on the settled turbidity, a separation efficiency in the settling vessel, and/or a settling velocity in the settling vessel.

8 . A method as claimed in claim 7 ,

wherein the sample is conducted from a point located downstream from a secondary treatment in a sedimentation unit of a biologically treated waste water influent, and upstream from a tertiary treatment in a separation unit of the biologically and chemically treated waste water influent;

wherein the dosing of the at least one coagulant and optionally the dosing of the at least one flocculant takes place downstream from the secondary treatment and upstream from the point from where the sample is conducted to the settling vessel.

9 . A method as claimed in claim 7 , wherein the method comprises:

calculating a separation efficiency in the settling vessel based on a difference between the initial turbidity and the settled turbidity;

calculating a settling velocity in the settling vessel by dividing the difference between the initial turbidity and the settled turbidity with the settling time; and

controlling the dosing of the at least one coagulant and/or flocculant to the waste water influent based on the calculated separation efficiency and/or the calculated settling velocity.

10 . A method as claimed in claim 9 , wherein the method comprises:

estimating a separation efficiency of the separation unit based on the calculated separation efficiency in the settling vessel and/or the calculated settling velocity in the settling vessel.

11 . A method as claimed in claim 7 , wherein the method comprises:

predetermining a correlation factor or function between the settled turbidity in the settling vessel and the turbidity of the waste water effluent; and

predicting the turbidity of the waste water effluent based on the settled turbidity measured from the settling vessel, by using the predetermined correlation factor or function.

12 . A method as claimed in claim 7 , wherein the particles in the sample are allowed to settle in the settling vessel such that the turbidity of the sample does not change markedly any more after the selected settling time.

13 . A method as claimed in claim 1 ,

wherein the measuring of the UV absorbance takes place from biologically treated waste water influent upstream from a secondary treatment in a sedimentation unit of a biologically treated waste water influent and upstream from the dosing of the coagulant and flocculant,

wherein the dosing of the at least one coagulant and optionally the dosing of the at least one flocculant takes place upstream from the secondary treatment.

14 . A method as claimed in claim 1 , wherein the method comprises:

conducting a sample of a biologically and chemically treated waste water influent to a settling vessel;

measuring turbidity of the sample to obtain an initial turbidity value;

allowing particles in the sample to settle in the settling vessel for a selected settling time;

after the selected settling time, measuring UV absorbance and settled turbidity from a clarified portion of the sample;

determining the concentration of dissolved organics in the clarified portion of the sample based on the measured UV absorbance;

controlling the dosing of at least one coagulant to the waste water influent based on the measured UV absorbance and/or the determined concentration of the dissolved organics, and optionally based on the settled turbidity; and

optionally controlling the dosing of at least one flocculant to the waste water influent based on the settled turbidity, a separation efficiency in the settling vessel, and/or a settling velocity in the settling vessel,

wherein the sample is conducted from a point located upstream from a secondary treatment in a sedimentation unit of a biologically treated waste water influent, and downstream from the dosing of the coagulant and flocculant; and

wherein the dosing of the at least one coagulant and optionally the dosing of the at least one flocculant takes place upstream from the secondary treatment and upstream from the point from where the sample is conducted to the settling vessel.

15 . A method as claimed in claim 1 , wherein the method comprises:

predetermining a calibration equation or calibration curve between UV absorbance and the concentration of dissolved organics; and

determining a concentration of the dissolved organics, based on the measured UV absorbance, by using the predetermined calibration equation or by comparing the measured UV absorbance to the predetermined calibration curve.

16 . A method as claimed in claim 1 , wherein the UV absorbance is measured at a single wave length or at a narrow wave length range.

17 . A method as claimed in claim 1 , wherein the method comprises:

determining a total organic matter concentration in the waste water influent and/or effluent based on the measured UV absorbance, the determined concentration of the dissolved organics and/or the turbidity of the waste water influent and/or effluent.

18 . A method as claimed in claim 1 , wherein it is a continuous method, an automated method and/or a computerized method.

19 . A method as claimed in claim 1 , wherein the method comprises:

monitoring and controlling treatment of the waste water stream with an apparatus having:

a first optical measurer configured to measure UV absorbance of the waste water influent or waste water effluent;

a processor configured to determine the concentration of dissolved organics in the waste water influent or waste water effluent based on the measured UV absorbance; and

a controller configured to control the dosing of at least one coagulant and/or other control chemical to the waste water influent based on the measured UV absorbance and/or the determined concentration of the dissolved organics.

20 . A method as claimed in claim 19 , comprising

monitoring and controlling treatment of the waste water stream with an apparatus having:

a second optical measurer configured to measure turbidity of the waste water influent and/or waste water effluent;

a controller configured to control the dosing of at least one coagulant and/or other control chemical to the waste water influent based on the measured turbidity, and control the dosing of at least one flocculant to the waste water influent based on the measured turbidity.

21 . A method as claimed in claim 1 , wherein the method comprises:

determining a value of at least one key variable selected from:

generation of solids in coagulation, settling efficiency (NTU), settling speed (NTU/min), comparison of separation efficiency in a settling vessel and full scale separation efficiency, effect of coagulant dosing on pH, hard COD coagulation, hard COD removal confirmation, hard COD coagulation confirmation, hard COD coagulation divided by generated turbidity, and/or hard COD coagulation divided by total COD value of removed lignin like material; and

wherein the method comprises controlling the dosing of at least one coagulant, flocculant and/or other waste water treatment chemical to the waste water effluent and/or influent based on the determined value of the at least one key variable.

22 . A method as claimed in claim 1 , wherein the method comprises:

measuring the concentration of dissolved phosphorus in a waste water influent and/or waste water effluent; and

controlling the dosing of at least one coagulant to the waste water influent based on the measured concentration of dissolved phosphorus.

23 . A method as claimed in claim 1 , wherein the method comprises:

measuring a total phosphorus concentration in a waste water influent and/or waste water effluent; and

controlling the dosing of at least one coagulant to the waste water influent based on the measured total phosphorus concentration.

24 . A method as claimed in claim 1 , wherein the method comprises:

optimizing dosages of chemicals; and/or

optimizing COD, phosphorus and/or suspended solids removal efficiency.

25 . A method as claimed in claim 1 , wherein said treatment further comprises a primary treatment step in a primary treatment unit.

26 . A method as claimed in claim 25 , wherein the biological treatment unit follows the primary treatment step.

27 . A method as claimed in claim 25 , wherein the primary treatment unit is for removal of sludge.

28 . A method as claimed in claim 1 , wherein the solids separation unit following the bioreactor is a sedimentation unit.

29 . A method as claimed in claim 1 , wherein the chemical treatment step following the biological treatment step comprises dosing at least one coagulant to a waste water influent of the solids separation unit.

30 . A method as claimed in claim 29 , comprising measuring the UV absorbance and turbidity from the waste influent or waste water effluent of the solids separation unit after the biological treatment step and the dosing of the at least one coagulant.