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BR-112021008727-B1 - METHOD FOR MONITORING AND CONTROLLING THE TREATMENT OF A MUNICIPAL WASTEWATER STREAM OR AN INDUSTRIAL WASTEWATER STREAM AND APPARATUS FOR MONITORING AND CONTROLLING A MUNICIPAL OR INDUSTRIAL WASTEWATER STREAM

BR112021008727B1BR 112021008727 B1BR112021008727 B1BR 112021008727B1BR-112021008727-B1

Abstract

MEASURING AND CONTROLLING ORGANIC MATTER IN WASTEWATER STREAM. The present invention relates to a method for monitoring and controlling the treatment of a wastewater stream. The method comprises measuring the UV absorption of a wastewater influent and/or wastewater effluent, measuring the turbidity of the wastewater influent and/or wastewater effluent, and determining the concentration of dissolved organics in the wastewater influent and/or wastewater effluent based on the measured UV absorption. The method further comprises controlling the dosage of at least one coagulant to the wastewater influent based on the measured UV absorption and/or the determined concentration of dissolved organics, and optionally based on the measured turbidity, and optionally controlling the dosage of at least one flocculant to the wastewater influent based on the measured turbidity.

Inventors

  • Marjatta Piironen
  • Sakari Halttunen
  • Iiris Joensuu
  • ANNE MÄKI

Assignees

  • KEMIRA OYJ

Dates

Publication Date
20260310
Application Date
20191114
Priority Date
20181114

Claims (20)

  1. 1. Method for monitoring and controlling the treatment of a municipal wastewater stream, or an industrial wastewater stream, wherein said treatment comprises subjecting the wastewater stream to both: - at least one biological treatment step in a bioreactor, followed by a solids separation unit (604), and - at least one chemical treatment step, characterized in that the method comprises: measuring the UV absorption of the biologically treated wastewater influent or wastewater effluent from the solids separation unit (604) after the biological treatment step; optionally measuring the turbidity of the wastewater influent or wastewater effluent; determining the concentration of dissolved organics in the wastewater influent or wastewater effluent based on the measured UV absorption; controlling the dosage of at least one coagulant to the wastewater influent based on the measured UV absorption and the determined concentration of dissolved organics.
  2. 2. Method according to claim 1, characterized in that: the method comprises measuring the turbidity of the wastewater influent or wastewater effluent and controlling the dosage of at least one coagulant to the wastewater influent based on the measured turbidity; or the method comprises controlling the dosage of at least one flocculant to the wastewater influent based on the measured turbidity; or the measurement of UV absorption and turbidity occurs from the wastewater effluent obtained from a tertiary treatment in a separation unit (604) of a biologically and chemically treated wastewater influent; wherein the dosage of at least one coagulant and optionally the dosage of at least one flocculant occurs downstream of the secondary treatment in a sedimentation unit (603) of a biologically treated wastewater influent and upstream of the tertiary treatment.
  3. 3. Method, according to claim 1 or 2, characterized in that: the measurement of UV absorption and turbidity occurs from the wastewater influent obtained from a secondary treatment in a sedimentation unit (603) of a biologically treated wastewater influent; wherein the dosing of at least one coagulant and optionally the dosing of at least one flocculant occurs downstream of the secondary treatment and upstream of a tertiary treatment in a separation unit (604) of a biologically and chemically treated wastewater influent.
  4. 4. A method, according to any one of claims 1 to 3, characterized in that the method comprises: conducting a sample of a biologically and chemically treated wastewater influent into a settling vessel; measuring the 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 the UV absorption and the settled turbidity of a clarified portion of the sample; determining the concentration of dissolved organics in the clarified portion of the sample based on the measured UV absorption; controlling the dosage of at least one coagulant to the wastewater influent based on the measured UV absorption and the determined concentration of dissolved organics, and optionally based on the settled turbidity; Optionally control the dosage of at least one flocculant to the wastewater influent based on the settled turbidity, a separation efficiency in the settling vessel, or a settling velocity in the settling vessel.
  5. 5. Method according to claim 4, characterized in that: the sample is conducted from a point located downstream of a secondary treatment in a sedimentation unit (603) of a biologically treated wastewater influent, and upstream of a tertiary treatment in a separation unit (604) of the biologically and chemically treated wastewater influent; wherein the dosing of at least one coagulant and optionally the dosing of at least one flocculant occurs downstream of the secondary treatment and upstream of the point from where the sample is conducted to the settling vessel.
  6. 6. Method according to claim 1, characterized in that: the measurement of UV absorption and turbidity occurs from the wastewater effluent obtained from a secondary treatment in a sedimentation unit (603) of a biologically and chemically treated wastewater influent; wherein the dosing of at least one coagulant and optionally the dosing of at least one flocculant occurs upstream of a secondary treatment.
  7. 7. Method, according to claim 1 or 6, characterized in that: the measurement of UV absorption and turbidity occurs from the biologically treated wastewater influent upstream of a secondary treatment in a sedimentation unit (603) from a biologically treated wastewater influent and upstream of the coagulant and flocculant dosing; wherein the dosing of at least one coagulant and optionally the dosing of at least one flocculant occurs downstream of the secondary treatment.
  8. 8. Method according to claim 1, 6 or 7, characterized in that the method comprises: conducting a sample of a biologically and chemically treated wastewater influent into a settling vessel; measuring the 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 the UV absorption and the settled turbidity of a clarified portion of the sample; determining the concentration of dissolved organics in the clarified portion of the sample based on the measured UV absorption; controlling the dosage of at least one coagulant to the wastewater influent based on the measured UV absorption and the determined concentration of dissolved organics, and optionally based on the settled turbidity; optionally control the dosage of at least one flocculant to the wastewater influent based on the settled turbidity, a separation efficiency in the settling vessel, or a settling velocity in the settling vessel, wherein the sample is conducted from a point located upstream of a secondary treatment in a sedimentation unit (603) of a biologically treated wastewater influent, and downstream of the coagulant and flocculant dosage; wherein the dosage of at least one coagulant and optionally the dosage of at least one flocculant occurs upstream of the secondary treatment and upstream of the point from which the sample is conducted to the settling vessel.
  9. 9. Method, according to claim 4, 5 or 8, characterized in that the method comprises: calculating the separation efficiency in the settling vessel based on a difference between the initial turbidity and the settled turbidity; calculating the settling velocity in the settling vessel by dividing the difference between the initial turbidity and the settled turbidity by the settling time; controlling the dosage of at least one coagulant and flocculant to the wastewater influent based on the calculated separation efficiency or the calculated settling velocity.
  10. 10. Method according to claim 9, characterized in that the method comprises: estimating a separation efficiency of the separation unit (604) based on the separation efficiency calculated in the settling vessel or the settling velocity calculated in the settling vessel.
  11. 11. A method, according to any one of claims 4 to 10, characterized in that the method comprises: predetermining a correlation factor or function between the turbidity settled in the settling vessel and the turbidity of the wastewater effluent; and predicting the turbidity of the wastewater effluent based on the turbidity measured from the settling vessel, using the predetermined correlation factor or function.
  12. 12. A method according to any one of claims 4 to 11, characterized in that the particles in the sample are allowed to settle in the settling vessel so that the turbidity of the sample no longer changes markedly after the selected settling time.
  13. 13. A method according to any one of claims 1 to 12, characterized in that the method comprises: predetermining a calibration equation or calibration curve between UV absorption and the concentration of dissolved organics, and determining the concentration of dissolved organics, based on the measured UV absorption, using the predetermined calibration equation or by comparing the measured UV absorption to the predetermined calibration curve.
  14. 14. A method according to any one of claims 1 to 13, characterized in that UV absorption is measured at a single wavelength or in a narrow wavelength range.
  15. 15. A method according to any one of claims 2 to 14, characterized in that the method comprises: measuring a pH value of biologically treated wastewater influent obtained from secondary treatment; measuring a pH value of biologically or chemically treated wastewater influent downstream of secondary treatment and upstream of tertiary treatment; measuring a pH value of wastewater effluent obtained from tertiary treatment; measuring a pH value of wastewater effluent obtained from secondary treatment; or measuring a pH value of a clarified portion of a wastewater sample settled in a settling vessel; wherein, if required, the method comprises controlling the dosage of at least one pH adjusting chemical or coagulant to the wastewater influent or wastewater effluent based on a measured pH value.
  16. 16. Method, according to any one of claims 1 to 15, characterized in that the method comprises: determining the concentration of total organic matter in the influent or effluent of wastewater based on measured UV absorption, the determined concentration of dissolved organics or the turbidity of the influent or effluent of wastewater.
  17. 17. A method, according to any one of claims 1 to 16, characterized in that it is a continuous method, an automated method, or a computerized method.
  18. 18. A method, according to any one of claims 1 to 17, characterized in that it comprises: determining a value of at least one key variable selected from: solids generation in coagulation, sedimentation efficiency (NTU), sedimentation rate (NTU/min), comparison of separation efficiency in a sedimentation tank and separation efficiency on a full scale, effect of coagulant dosage on pH, coagulation of hard COD, confirmation of hard COD removal, confirmation of hard COD coagulation, coagulation of hard COD divided by the turbidity generated, or coagulation of hard COD divided by the total COD value of the lignin-like material removed, wherein the method comprises controlling the dosage of at least one coagulant, flocculant to the effluent or wastewater influent based on the determined value of at least one key variable.
  19. 19. A method according to any one of claims 1 to 18, characterized in that the method further comprises: measuring the concentration of dissolved phosphorus in a wastewater influent or wastewater effluent; controlling the dosage of at least one coagulant to the wastewater influent based on the measured concentration of dissolved phosphorus.
  20. 20. A method according to any one of claims 1 to 19, characterized in that the method further comprises: measuring the total phosphorus concentration in a wastewater influent or wastewater effluent; controlling the dosage of at least one coagulant to the wastewater influent based on the measured total phosphorus concentration.

Description

FIELD OF THE INVENTION [0001] The present invention relates to monitoring a wastewater flow, and more particularly to a method and apparatus for controlling the treatment of wastewater originating from a pulp production process. BACKGROUND OF THE TECHNIQUE [0002] The following background description technique may include insights, discoveries, understandings, or descriptions, or association with descriptions not known of the relevant technique prior to the present invention, but provided by the present invention. Some of such contributions covered by the present description of the invention will be evident from its context. [0003] Chemical oxygen demand (COD) indicates the amount of oxygen that can be consumed by reactions in a solution and can be expressed as the mass of oxygen consumed over a volume of solution (mg/L). COD can be used to quantify the amount of oxidizable or organic pollutants (organic matter) in water. [0004] In wastewater treatment, regulations for chemical oxygen demand (COD) are becoming more stringent globally. While readily degradable organics can be removed from wastewater by biological wastewater treatment, the amount of recalcitrant organics ("hard COD") in wastewater effluent still frequently exceeds environmental limits. Currently, COD is typically monitored by manual measurements. This is not sufficient for economical dosing of chemicals into wastewater. Chemicals can be fed into the wastewater stream as a constant dosage (mg/L), or as a constant flow (L/s). This does not ensure that COD is below the release limit in the wastewater effluent. SUMMARY [0005] The following is a simplified summary of features described herein to provide a basic understanding of some exemplary aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts described herein in a simplified form as a prelude to a more detailed description. [0006] In one aspect, the subject matter of the independent claims is provided. The modalities are defined in the dependent claims. [0007] One or more examples of implementations are presented in more detail in the attached drawings and in the description below. Other features will be evident from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS [0008] The invention will now be described in more detail by means of preferred embodiments with reference to the accompanying drawings in which: Figures 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b and 5 illustrate exemplary embodiments; Figure 6 illustrates an exemplary system; Figure 7 illustrates exemplary monitoring and control of COD content. DETAILED DESCRIPTION OF MODALITIES [0009] The following modalities are exemplary. Although the report may refer to "a," "one," or several modalities in various locations, this does not necessarily mean that each such reference is to the same modality(ies), or that the characteristic applies only to a single modality. Unique characteristics of different modalities may also be combined to provide other modalities. Furthermore, the words "comprising," "containing," and "including" should be understood as not limiting the modalities described, as consisting only of those characteristics that have been mentioned, and such modalities may also contain characteristics/structures that have not been specifically mentioned. [0010] An embodiment describes a method and apparatus for monitoring and controlling the treatment of a wastewater stream originating from a pulp production process. The wastewater stream is subjected to at least one biological and/or chemical treatment step. The method comprises measuring the UV absorption of a wastewater influent and/or wastewater effluent, and measuring the turbidity of the wastewater influent and/or wastewater effluent. The method further comprises determining the concentration of dissolved organics (i.e., dissolved organic matter) in the wastewater influent and/or wastewater effluent based on the measured UV absorption, controlling the dosage of at least one coagulant to the wastewater influent based on the measured UV absorption and/or the determined concentration of dissolved organics, and optionally based on the measured turbidity, and optionally controlling the dosage of at least one flocculant to the wastewater influent based on the measured turbidity. [0011] In one embodiment, the measurement of UV absorption and turbidity occurs from wastewater effluent obtained from tertiary treatment in a separation unit of biologically and chemically treated wastewater influent, and the dosing of at least one coagulant and optionally the dosing of at least one flocculant occurs downstream of secondary treatment in a sedimentation unit of biologically treated wastewater influent and upstream of tertiary treatment. [0012] In one embodiment, the measurement of