EP4688666A1

EP4688666A1 - Method and arrangement for selecting a flocculating agent for use in a dewatering process for sludge

Info

Publication number: EP4688666A1
Application number: EP24715848.8A
Authority: EP
Inventors: Vesa-Matti TIKKALA; Michael Recktenwald
Original assignee: Kemira Oyj
Current assignee: Kemira Oyj
Priority date: 2023-03-30
Filing date: 2024-03-26
Publication date: 2026-02-11
Also published as: WO2024200913A1; FI20235366A1

Abstract

A method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest is disclosed. The method may comprise obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest, com- paring the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants, each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge, and thereby identifying the most similar sludge sample(s) from the plurality of sludge samples, and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent(s) used in the dewatering process(es) for sludge in the waste water treatment plant(s) with the most similar sludge sample(s).

Description

METHOD AND ARRANGEMENT FOR SELECTING A FLOCCULATING AGENT FOR USE IN A DEWATERING PROCESS FOR SLUDGE

TECHNICAL FIELD

The present disclosure relates to a method and arrangement for selecting a flocculating agent for use in a dewatering process for sludge and to a computer program .

BACKGROUND

During the treatment of waste water in waste water treatment plants (WWTPs ) , residual streams are dewatered or thickened to reduce the volume of liquid waste and to produce a solid-like waste for disposal or possible reuse . Such a residual stream may be referred to as sludge . The sludge may be separated into a liquid-rich stream, often referred to as rej ect water or filtrate , and a solid phase , often referred to as sludge cake . Waste water treatment plants add various flocculating agents to the sludge to promote the aggregation of solids and to improve dewatering and thickening processes for sludge .

Selecting the best performing flocculating agent for use in a dewatering process for sludge is a complex task . The properties of a sludge obtained in a waste water treatment plant may depend on various factors , such as the location of the WWTP, the source of the waste water, and the processes applied in the waste water treatment plant . Typically lengthy trial-and-error experimentation may be required to test a variety of flocculating agents , which may be time consuming, disruptive to the operation of the WWTP, and costly .

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description . This Summary is not intended to identify key features or essential features of the claimed subj ect matter, nor is it intended to be used to limit the scope of the claimed subj ect matter . A method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest is disclosed . The method may comprise obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

An arrangement for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest is disclosed . The arrangement may comprise means for obtaining and/or receiving first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , means for comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and means for selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

A computer program is also disclosed, the computer program comprising instructions which, when executed by an apparatus , cause the apparatus to perform at least the following : obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

A computer-readable medium is also disclosed, the computer-readable medium comprising instructions which, when executed by an apparatus , cause the apparatus to perform at least the following : obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings , which are included to provide a further understanding of the described embodiments and constitute a part of this specification, illustrate various advantageous features and examples of their combinations . In the drawings : Figure 1 illustrates a flow chart representation of a method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest according to an embodiment ;

Figure 2 illustrates a flow chart representation of a method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest according to an embodiment ;

Figure 3 illustrates a block diagram of an arrangement 300 according to an exemplary embodiment ; and

Figure 4 illustrates a block diagram of an arrangement 400 according to an exemplary embodiment .

DETAILED DESCRIPTION

A method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest is disclosed .

The method may comprise obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

An arrangement for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest is also disclosed . The arrangement may comprise means for obtaining and/or receiving first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , means for comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and means for selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

The method may comprise measuring the first values of the plurality of parameters measured from the sludge sample obtained from the waste water treatment plant of interest . However, the waste water treatment plant of interest may have the first values or at least some of the first values of the plurality of parameters already available , if they have e . g . been measured earlier .

The arrangement may further comprise means for measuring the first values of the plurality of parameters measured from the sludge sample obtained from the waste water treatment plant of interest . Such means may comprise e . g . an analysis apparatus for measuring the first values of the plurality of parameters . The means may depend on the exact parameters to be measured . For example , for measuring parameters such as the contents of metals and/or phosphorus ( inorganic parameters ) , the means may comprise an inductively coupled plasma atomic emission spectroscopy ( ICP- AES ) apparatus or an inductively coupled plasma mass spectrometry ( ICP-MS ) apparatus . For measuring CST , the means may comprise a CST instrument or other CST apparatus . For measuring charge , the means may comprise a particle charge detector or other suitable apparatus for measuring the charge . For measuring zeta potential , the means may comprise a laser diffraction instrument . The method and/or arrangement may be used for adj usting the dewatering process for sludge in the waste water treatment plant of interest and/or for determining the operation of the dewatering process .

In the context of this specification, the term "dewatering process for sludge" may be understood as referring to a process in which a liquid phase ( rej ect water) and solid phase are separated from a sludge produced in a waste water treatment plant . Residual water typically remains in the solid phase , which increases the volume of the solid phase ( sludge cake ) that is eventually disposed and thereby increases the costs of the disposal of the solid phase . The dewatering process may include the use of a dewatering unit , such as a centrifuge .

The method and arrangement may allow for selecting an optimal flocculating agent without the need for lengthy trial-and- error experimentation . A well-suited flocculating agent may be selected without disrupting the operation of the WWTP of interest . Costs involved may be reduced significantly .

The method and arrangement may also provide better selection of the flocculating agent as compared e . g . to experts , whose opinion is not always correct or does not always take into account all possible parameters .

The selection of a well-suited or optimal flocculating agent may provide various benefits . I f the sludge cake dry solids obtained from the dewatering process may be increased, a smal ler volume of sludge will go to landfil ling, which may significantly reduce downstream costs . Further, the consumption of the flocculating agent may, at least in some embodiments , be reduced . It may also have an effect on which type of apparatus is required in the dewatering process - if a well-performing flocculating agent may be selected, the need for expensive investments in equipment may be reduced or even obviated .

The method may further comprise providing identification information of the flocculating agent selected .

The arrangement may further comprise means for providing identification information of the flocculating agent selected .

The method may further comprise using the selected flocculating agent in the dewatering process for sludge in the waste water treatment plant of interest. For example, the selected flocculating agent may be added to sludge in the dewatering process for the sludge in the waste water treatment plant of interest.

The arrangement may further comprise means for using the selected flocculating agent in the dewatering process for sludge in the waste water treatment plant of interest. Such means may comprise e.g. a dosing apparatus for dosing the flocculating agent to the dewatering process for sludge in the waste water treatment plant of interest.

The plurality of parameters may be selected from the following parameters:

- conductivity,

- dry solids content,

- volatile solids content,

- total organic carbon (TOC) ,

- chemical oxygen demand (COD) ,

- total nitrogen,

- Al,

- Ca,

- Fe,

- K,

- Mg,

- Na,

- P,

- charge, zeta potential,

- capillary suction time (CST) .

These parameters may be measured according to standard methods used in the art. For example, total nitrogen may be measured according to the Kjeldahl method. Inorganic parameters, such as the content /concentration of metals and phosphorus, may be measured by ICP.

The method or arrangement is not particularly limited as to how many parameters the plurality of parameters may include. The plurality of parameters may comprise e.g. at least 10, or at least 11, or at least 12, or at least 13, or at least 14, or at least 15, or all of the following parameters:

- conductivity, - dry solids content,

- volatile solids content,

- total organic carbon (TOC) ,

- chemical oxygen demand (COD) ,

- total nitrogen,

- Al,

- Ca,

- Fe,

- K,

- Mg,

- Na,

- P,

- charge, zeta potential,

- capillary suction time (CST) .

The plurality of parameters may comprise at least a plurality of the following parameters, or at least all of the following parameters:

- Al,

- Ca,

- Fe,

- K,

- Mg,

- Na,

- P.

These parameters including the contents or concentrations of various inorganic components unexpectedly appear to have an effect on the selection of the flocculating agent, considering that most of the sludge is organic material. Not to be bound by theory, they seem to have an effect on the similarities of the sludge samples and/or may e.g. interact with the flocculating agent and thereby affect he selection of the flocculating agent.

The plurality of parameters may comprise at least a plurality of the following parameters, or at least the following parameters : charge, zeta potential, capillary suction time (CST) . These parameters relate to the capability of particles in the sludge to flocculate and to the rate at which water is released from a sludge matrix. They thereby seem to have a significant effect on the selection of the flocculating agent. These parameters also typically require specific equipment for determining them. Charge is a parameter characterising particles in the sludge. If particles in the sludge have a high negative charge, a flocculating agent, such as a polymer, with a high positive charge for charge neutralisation may be preferred to improve flocculation. Thus the charge may affect at least the charge and/or the charge density of the flocculating agent to be selected. Zeta potential is a parameter related to charge, but in addition to particles in the sludge, the entire composition of the sludge may affect the zeta potential. CST is a parameter related e.g. to the capability of the sludge to release water. If a sludge has a high CST, it tends to release water slowly, and a flocculating agent suitable for improving the water release may be selected and/or the dosage of the flocculating agent may be adjusted. A low CST corresponds to fast water release, which is desired. In other words, a flocculating agent that is capable of lowering the CST may be selected.

The plurality of parameters may comprise at least a plurality of the following parameters, or at least the following parameters :

- conductivity,

- dry solids content,

- volatile solids content,

- total organic carbon (TOC) ,

- chemical oxygen demand (COD) ,

- total nitrogen.

These parameters are commonly available and e.g. often measured by WWTPs.

The flocculating agent may be e.g. any chemical agent suitable for causing suspended solids to form a floc during the dewatering process of the sludge. Different WWTPs may use different flocculating agents, or some WWTPs may use the same flocculating agents. Various properties of the flocculating agent (s) may have an effect on the dewatering performance. Further, as the flocculating agent interacts with the sludge in the dewatering process, the properties of the sludge will naturally have an effect on the dewatering performance when using a particular flocculating agent.

The flocculating agent (s) may comprise or be e.g. a polymer, such as a cationic polymer. The polymer may comprise or be e.g. a polyacrylamide, polyamine, polydiallyldimethylammoniumchloride (polyDADMAC) , melamine formaldehyde, natural polymer, natural polysaccharide, or any mixture or combination thereof. The flocculating agent may, additionally or alternatively, comprise or be an inorganic flocculating agent, such as a salt of aluminium, iron, magnesium, calcium, zirconium, or zinc, or any mixture or combination thereof.

When the most similar sludge sample (s) from the plurality of sludge samples has/have been identified, the flocculating agent may be selected e.g. on the basis of the flocculating agent used in the other WWTP(s) with the most similar sludge sample (s) . Alternatively or additionally, information available from the flocculating agent (s) used in the other WWTP(s) with the most similar sludge sample (s) may further be utilized to select a flocculating agent or properties thereof that may provide better dewatering process performance.

The method may further comprise obtaining a first value of a dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest, comparing the first value of the dewatering process performance parameter from the waste water treatment plant of interest to second values of the dewatering process performance parameter from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants, thereby identifying the most similar sludge sample (s) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance, and using the properties of the flocculating agent (s) used in the other waste water treatment plant (s) with the most similar sludge sample (s) having the higher or lower value of the dewatering process performance parameter to select and/or to adjust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest .

The selecting and/or adj usting the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest may include e . g . selecting a flocculating agent having properties more similar to the flocculating agent ( s ) used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , or selecting a flocculating agent used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having the higher or lower value of the dewatering process performance parameter .

In this manner, it may be possible to achieve a better sludge dewatering performance by selecting and/or adj usting the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest . Various properties of the flocculating agent may be balanced .

The arrangement may further comprise means for obtaining and/or receiving a first value of a dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest , means for comparing the first value of the dewatering process performance parameter from the waste water treatment plant of interest to second values of the dewatering process performance parameter from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants , thereby identifying the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , and means for using the properties of the flocculating agent ( s ) used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having the higher or lower value of the dewatering process performance parameter to select and/or to adj ust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest .

The dewatering process performance parameter may comprise or be at least sludge cake dry solids . The sludge cake dry solids is a parameter strongly related to the costs involved in sludge disposal . A higher value of sludge cake dry solids is indicative of improved dewatering process performance . I f the sludge cake dry solids obtained from the dewatering process may be increased, a smaller volume of the solid phase ( sludge cake ) will go to land- filling, which may significantly reduce downstream costs . Therefore it is typically an important parameter of the dewatering process performance .

The dewatering process performance parameter may further comprise at least one of suspended matter ( suspended solids ) in rej ect water, turbidity of rej ect water, release of P, Cl , NH₄ , and/or Ca to rej ect water, or power consumption in the dewatering unit used in the dewatering process . A lower value of these dewatering process performance parameters is indicative of improved dewatering process performance . The rej ect water may be understood as referring to water obtained from the dewatering process for the sludge , for example in a dewatering unit , such as a centrifuge .

In embodiments in which more than one dewatering process performance parameter is obtained, the method may comprise obtaining first values of dewatering process performance parameters from the sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the dewatering process performance parameters from the waste water treatment plant of interest to second values of the dewatering process performance parameters from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants , thereby identifying the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , and using the properties of the flocculating agent (s) used in the other waste water treatment plant (s) with the most similar sludge sample (s) having the higher or lower value of the dewatering process performance parameter to select and/or to adjust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest.

In embodiments in which more than one dewatering process performance parameter is obtained, the arrangement may comprise means for obtaining first values of dewatering process performance parameters from the sludge sample obtained from the waste water treatment plant of interest, means for comparing the first values of the dewatering process performance parameters from the waste water treatment plant of interest to second values of the dewatering process performance parameters from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants, thereby identifying the most similar sludge sample (s) having higher or lower first values of the dewatering process performance parameters, wherein the higher or lower values of the dewatering process performance parameters are indicative of improved dewatering process performance, and means for using the properties of the flocculating agent (s) used in the other waste water treatment plant (s) with the most similar sludge sample (s) having the higher or lower values of the dewatering process performance parameters to select and/or to adjust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest.

The properties of the flocculating agent (s) are not particularly limited. The properties of the flocculating agent (s) may comprise e.g. at least one of standard viscosity (SV) , charge density, or dosage. However, other properties could also be contemplated. For example, the properties of the flocculating agent (s) may comprise e.g. at least one of standard viscosity (SV) , charge density, dosage, molecular weight, structure (e.g. linear, branched) , charge (anionic, cationic, neutral, amphoteric) , or appearance (e.g. dry, emulsion) . The method may further comprise scaling and/or normali zing the first values of the plurality of parameters prior to comparing the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants .

Scaling may be understood, as commonly in the field, as referring to transforming the first values of the plurality of parameters such that they fit within a specific scale , for example within the range of 0 - 100 or 0 - 1 .

Normali zing may be understood, as commonly in the field, as referring to transforming the first values of the plurality of parameters such that they may be described as a normal ( or roughly normal ) distribution .

The arrangement may further comprise means for scaling and/or normali zing the first values of the plurality of parameters prior to comparing the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants .

The comparing of the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples may be done using various different methods , for example by clustering, by machine learning, or by various other suitable methods .

The comparing of the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples may be done by calculating the similarity of the first values of the plurality of parameters from the sludge sample ( or the scaled and/or normali zed values thereof ) to the second values from the plurality of sludge samples obtained from the other waste water treatment plants ( or the scaled and/or normali zed values thereof ) using a distance met- ric . The distance metric may quantify the distance ( s ) between the sludge sample from the WWTP of interest and the plurality of sludge samples obtained from the other waste water treatment plants . The distance metric may be , for example , Euclidian distance or any other appropriate distance metric . The distance metric may be e . g . an LI norm ( such as Manhattan distance ) , an L2 norm ( such as Euclidean distance ) , cosine similarity, fractional norm, or other distance metric . It should be appreciated that since the distance metric is measured based on the values of the plurality of parameters , the term "distance" should not be interpreted as corresponding to any physical distance or any other strictly physical quantity .

Thus , the arrangement may comprise means for comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples obtained from the other waste water treatment plants using a distance metric, such as an LI norm, e . g . Manhattan distance ; an L2 norm, e . g . Euclidean distance ; cosine similarity; fractional norm; or other distance metric .

The plurality of sludge samples obtained from the other waste water treatment plants may comprise at least 30 , or at least 50 , or at least 100 sludge samples obtained from other waste water treatment plants , and/or sludge samples from at least 30 , or at least 50 , or at least 100 other waste water treatment plants . Each of the plurality of sludge samples obtained from the other waste water treatment plants may be obtained from a different waste water treatment plant . In some embodiments , the plurality of sludge samples obtained from the other waste water treatment plants may include two or more samples obtained from the same waste water treatment plant , for example when they are obtained from different stages of the waste water treatment plant (e . g . from biological or chemical treatment stage ) .

The other waste water treatment plants may include e . g . waste water treatment plants that are located in different geographical locations , such as in different countries . For example , the other waste water treatment plants may include e . g . waste water treatment plants that are located in countries in Northern Europe , Southern Europe , Eastern Europe , and/or Western Europe . In other examples , the other waste water treatment plants may include e . g . waste water treatment plants that are located in different continents .

The other waste water treatment plants may include e . g . waste water treatment plants with a person equivalent ( PE ) of at least 100 000 , or only waste water treatment plants with a person equivalent ( PE ) of at least 100 000 .

The waste water treatment plant of interest may comprise a biological and/or a chemical treatment stage . The sludge sample obtained from the waste water treatment plant of interest may be obtainable or obtained from any stage of the WWTP of interest in which sludge is produced . The sludge sample obtained from the waste water treatment plant of interest may be obtainable or obtained from biological and/or chemical treatment of waste water . The sludge sample obtained from the waste water treatment plant of interest may be obtainable or obtained from primary treatment and/or from secondary treatment of waste water .

The plurality of the sludge samples obtained from the other waste water treatment plants may include sludge samples obtainable or obtained from biological and/or chemical treatment of waste water . The other waste water treatment plants may include waste water treatment plants comprising a biological and/or waste water treatment plants comprising a chemical treatment stage . The plurality of the sludge samples obtained from the other waste water treatment plants may include sludge samples obtainable or obtained from primary treatment and/or from secondary treatment of waste water .

In the context of this specification, the term "primary treatment" may be understood as referring to a treatment intended to remove coarse , suspended and floating solids from raw waste water . It may include screening to trap solid obj ects and sedimentation to remove suspended solids .

In the context of this specification, the term "secondary treatment" may be understood as referring to a treatment including a biological treatment and intended to remove dissolved organic matter, phosphorus and nitrogen remaining after the primary treatment .

The other waste water treatment plants may include e . g . waste water treatment plants with different feed flow properties ( for example , waste water treatment plants in which feed flows are obtainable or obtained from households , from industry, or any mixture or combination thereof ) .

The various means described in this specification may comprise or be the same or different means , for example the same apparatus , computing unit or processor, or different apparatuses , computing units or processors , which may arranged at one or more locations .

The means may comprise at least one processor and at least one memory including computer program code . The at least one memory and the computer program code may be configured to , with the at least one processor, cause the arrangement to perform the method according to one or more embodiments described in this specification .

The arrangement may comprise at least one processor and at least one memory including computer program code , the at least one memory and the computer program code configured to , with the at least one processor, cause the arrangement to perform the method according to one or more embodiments described in this specification, e . g . : obtain and/or receive first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , compare the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and select a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : measure the first values of the plurality of parameters from the sludge sample obtained from the waste water treatment plant of interest .

The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : scale and/or normali ze the first values of the plurality of parameters prior to comparing the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants .

The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : compare the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples by calculating the similarity of the first values of the plurality of parameters from the sludge sample ( or the scaled and/or normali zed values thereof ) to the second values from the plurality of sludge samples obtained from the other waste water treatment plants ( or the scaled and/or normali zed values thereof ) using a distance metric .

The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain and/or receive a first value of a dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest , compare the first value of the dewatering process performance parameter from the waste water treatment plant of interest to second values of the dewatering process performance parameter from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants , thereby identifying the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , and use the properties of the flocculating agent ( s ) used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having the higher or lower value of the dewatering process performance parameter to select and/or to adj ust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest .

There is provided a computer program comprising instructions which, when executed by an apparatus , cause the apparatus to perform the method according to one or more embodiments described in this specification .

There is further provided a computer-readable medium comprising instructions which, when executed by an apparatus , cause the apparatus to perform the method according to one or more embodiments described in this specification .

EXAMPLES

Reference will now be made in detail to various embodiments , an example of which is illustrated in the accompanying drawings .

The description below discloses some embodiments in such a detail that a person s ki lled in the art is able to uti li ze the embodiments based on the disclosure . Not all steps or features of the embodiments are discussed in detai l , as many of the steps or features will be obvious for the person skilled in the art based on this specification .

Figure 1 illustrates a flow chart representation of a method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest according to an embodiment .

A sludge sample is obtained from a waste water treatment plant (WWTP) of interest 101 .

At 102 , first values of a plurality of parameters measured from a sludge sample from the waste water treatment plant of interest are obtained and/or received . The first values of the plurality of parameters measured from a sludge sample from the waste water treatment plant of interest may be obtained or received in various ways . For example , the WWTP of interest may have already measured them or some of them earlier, and so they or some of them may be obtained from the WWTP of interest . In some embodiments , the method may comprise at 102 measuring the first values of the plurality of parameters , or at least some of them, from the sludge sample from the waste water treatment plant of interest at 101 . As a further example , in arrangements comprising at least one processor and at least one memory including computer program code , the first values of the plurality of parameters measured from a sludge sample from the waste water treatment plant of interest may be obtained from the at least one memory of the arrangement , where it may have been stored ( for example , in a database ) .

At 103 , the first values of the plurality of parameters may be scaled and/or normali zed prior to comparing the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants . The second values from the plurality of sludge samples obtained from the other waste water treatment plants may also be scaled and/or normali zed .

The second values of the plurality of parameters from the plurality of sludge samples may have been obtained from the other waste water treatment plants earl ier, for example during a longterm data collection period, and e . g . stored in a database . The database may also include information concerning the flocculating agent used in each of the other waste water treatment plants in their dewatering process for sludge , and optionally properties of the flocculating agent used . Such properties may include e . g . standard viscosity ( SV) , charge density, and/or dosage , and/or e . g . other properties described in this specification .

At 104 , the first values of the plurality of parameters from the sludge sample are compared to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples . The comparison may be done e . g . by machine learning, by clustering, or by using a suitable distance metric . Examples of suitable distance metrics may include e . g . an LI norm, such as Manhattan distance , an L2 norm, such as Euclidean distance , cosine similarity, and fractional norm . However, the distance metric or other methods of comparing the first and second values are not particularly limited, and various other methods may be contemplated . The distance between the sludge sample obtained from the WWTP of interest and the plurality of the sludge samples obtained from the other waste water treatment plants may be calculated using the suitable distance metric . Thus the other WWTP ( s ) with the most similar sludge samples ( sludge neighbours ) may be identif ied . For example , 1 -5 closest sludge neighbours may be identified .

At 105 , a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest is selected based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

For example , when the closest sludge neighbours have been selected at 104 , subsequently, at 105 , the flocculating agent ( s ) used in these closest sludge neighbours and the information available from them may be used so as to select a suitable flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest . The flocculating agent used in the WWTP from which the closest sludge neighbour is obtained may be selected, or the information from two or more closest neighbours may be used for selecting a suitable flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest . For example , a flocculating agent with properties similar to the flocculating agent ( s ) used in the WWTPs with the closest sludge neighbours may be selected, or the properties of the flocculating agent may be adj usted such that they are more similar to the flocculating agent ( s ) used in the WWTPs with the closest sludge neighbours . I f a suitable flocculating agent is already available , it may be selected directly . Or, a database, for example a polymer database , may be used to find a flocculating agent with desired properties . It may also be possible to select two or more flocculating agents , or any combination or mixture thereof .

Additional information may be utili zed as well when selecting the flocculating agent . For example , if cost or dosage of the flocculating agent is an important factor for the WWTP of interest , then a flocculating agent that is perhaps less costly or that may be used at a lower dosage may be selected .

The flocculating agent selected at 105 may then be used in the sludge dewatering process at the WWTP of interest 101 .

Figure 2 illustrates a flow chart representation of a method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest according to an embodiment .

This exemplary embodiment is simi lar to the method depicted in Fig . 1 , except that the WWTP of interest is not shown for clarity - thus steps 201 , 202 and 203 are similar to steps 102 , 104 and 105 shown in Fig . 1 , respectively . Although the scaling/normali zing shown at 103 in Fig . 1 is not shown in Fig . 2 , it may be performed as desired between 201 and 202 .

Further criteria may be utilized to select the flocculating agent or adj ust the selection after 203 .

At 204 , a first value of a dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest is obtained or received .

The first value of the dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest may be obtained or received in various ways . For example , the method may comprise measuring the first value of the dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest at 204 . In some embodiments , the WWTP of interest may have already measured the first value of the dewatering process performance parameter, and so it may be obtained from the WWTP of interest . As a further example , in arrangements comprising at least one processor and at least one memory including computer program code , the first value of the dewatering process performance parameter may be obtained from the at least one memory of the arrangement , where it may have been stored, e . g . in a database . First values of more than one dewatering process performance parameter may be obtained . For example , the dewatering process performance parameters may further comprise at least one of suspended matter in rej ect water, turbidity of rej ect water, release of P, Cl , NH₄ , and/or Ca to rej ect water, or power consumption in the dewatering unit used in the dewatering process .

At 205 , the first value of the dewatering process performance parameter from the waste water treatment plant of interest is compared to second values of the dewatering process performance parameter from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants , thereby identifying the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance . For example , when the dewatering process performance parameter comprises or is sludge cake dry solids , the most similar sludge sample ( s ) having a higher value of sludge cake dry solids may thus be identified . The higher value of the sludge cake dry solids suggests that the flocculation agent used in said other WWTP is likely to perform well for similar sludges , such as for the sludge obtained from the WWTP of interest .

At 206 , the properties of the flocculating agent ( s ) used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , are used to select and/or to adj ust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest . For example , when the dewatering proces s performance parameter comprises or is sludge cake dry solids , the flocculating agent used in the most similar sludge sample ( s ) having a higher value of sludge cake dry solids may be selected . Or, the properties of the flocculating agent may be adj usted such that they are more similar to the flocculating agent ( s ) used in the WWTPs with the closest sludge neighbours having a higher value of sludge cake dry solids . Properties of the flocculating agent that may be adj usted may include e . g . at least one of standard viscosity ( SV) , charge density, or dosage . In some embodiments , the properties of the flocculating agent that are adj usted include standard viscosity ( SV) , charge density, and dosage .

As a skilled person will understand, the steps described at 204 , 205 and 206 are optional , and are not necessarily performed in the context of steps 201 -203 .

Figure 3 illustrates a block diagram of an arrangement 300 according to an exemplary embodiment . The arrangement 300 comprises one or more processors 301 , and one or more memories 302 that comprise computer program code 303 . The arrangement 300 may also include an input/output module (not shown in Fig . 3 ) , and/or a communication interface 304 for wired and/or wireless communication . Although the arrangement 300 is depicted to include only one processor 301 , the arrangement 300 may include more than one processor . In an exemplary embodiment , the memory 302 is capable of storing instructions , such as an operating system and/or various applications . The memory 302 may additionally be capable of storing the first values of the plurality of parameters from the sludge sample and/or the second values of the plurality of parameters from the plurality of sludge samples obtained from the other waste water treatment plants . For example , the arrangement

300 may comprise a database for storing or configured to store the second values of the plurality of parameters from the plurality of sludge samples obtained from the other waste water treatment plants .

Furthermore , the processor 301 is capable of executing the stored instructions . In an exemplary embodiment , the processor

301 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core proces sors and one or more single core processors . For example , the processor 301 may be embodied as one or more of various processing devices , such as a coprocessor, a microprocessor, a controller, a digital signal processor ( DSP) , a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as , for example , an application specific integrated circuit (AS IC) , a field programmable gate array ( FPGA) , a microcontroller unit (MCU) , a hardware accelerator, a specialpurpose computer chip, or the like . In an exemplary embodiment , the processor 301 may be configured to execute hard-coded functionality . In an exemplary embodiment , the processor 301 may be embodied as an executor of software instructions , wherein the instructions may specifically configure the processor 301 to perform the algorithms and/or operations described herein when the instructions are executed, for example , the steps discussed with respect to Fig . 1 and Fig . 2 .

The memory 302 may be embodied as one or more volatile memory devices , one or more non-volatile memory devices , and/or a combination of one or more volatile memory devices and non-volatile memory devices . For example , the memory 302 may be embodied as semiconductor memories ( such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM ( random access memory) , etc . ) .

In an embodiment , the at least one memory 302 may store program instructions 303 that , when executed by the at least one processor 301 , cause the arrangement 300 to perform the functionality of the various embodiments discussed herein . Further, in an embodiment , at least one of the processor 301 and the memory 302 may constitute means for implementing the discussed functionality . Further, the arrangement 300 may be configured to perform at least some of the examples and embodiments discussed above .

Exemplary embodiments may be implemented in software , hardware , application logic or a combination of software , hardware and application logic . The exemplary embodiments can store information relating to various methods described herein . This information can be stored in one or more memories , such as a hard disk, a solid state drive ( SSD) , an optical disk, a magneto-optical disk, an RAM, and the like . One or more databases can store the information used to implement the exemplary embodiments ( for example , the first values of the plurality of parameters from the sludge sample and/or the second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants ) . The databases can be organi zed using data structures (e . g . , records , tables , arrays , fields , graphs , trees , lists , and the like ) included in one or more memories or storage devices listed herein . The methods described with respect to the exemplary embodiments can include appropriate data structures for storing data collected and/or generated by the methods of the devices and subsystems of the exemplary embodiments in one or more databases .

The components of the exemplary embodiments may include computer readable medium or memories for holding instructions programmed according to the teachings and for holding data structures , tables , records , and/or other data described herein . In an exemplary embodiment , the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media . In the context of this document , a "computer-readable medium" may be any media or means that can contain, store , communicate , propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus , or device , such as a computer . A computer-readable medium may include a computer-readable storage medium that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus , or device , such as a computer . A computer readable medium can include any suitable medium that participates in providing instructions to a processor for execution . Such a medium can take many forms , including but not limited to , non-volatile media, volatile media, transmission media, and the like .

The functionality of the arrangement 300 may be implemented using a cloud computing system or other type of distributed computing system .

Figure 4 illustrates a block diagram of an arrangement 400 according to an exemplary embodiment . The arrangement 400 is similar to the arrangement 300 described in Fig . 3 . In this exemplary embodiment , the arrangement 400 further comprises an analysis apparatus 405 . The analysis apparatus 405 may be configured to measure the first values of the plurality of parameters measured from the sludge sample obtained from the waste water treatment plant of interest . The analysis apparatus 405 may provide the first values of the plurality of the parameters measured from the sludge sample obtained from the waste water treatment plant of interest e.g. via the communication interface 404.

The analysis apparatus 405 and its components may depend on the parameters to be measured. The analysis apparatus 405 may comprise e.g. an inductively coupled plasma atomic emission spectroscopy (ICP-AES) apparatus or an inductively coupled plasma mass spectrometry (ICP-MS) apparatus; a CST instrument or other CST apparatus; a particle charge detector or other suitable apparatus for measuring charge; a laser diffraction instrument; and/or other laboratory equipment.

EXAMPLE 1

A sludge sample from a WWTP in the Netherlands (sludge sample Netherlands A) was provided. Table 1 lists the parameters measured from the sludge sample.

Table 1. Sludge properties of the WWTP of interest (Netherlands A) The sample was compared to previously analysed samples from 30 other WWTPs which were stored in a database . The sites with similar sludge ( sludge neighbours ) were identified by calculating the distance to the current sample and by selecting the 5 closest neighbours . The distance calculation was based on scaled parameter values to level out different ranges of measured values . Euclidean distance was used as the distance measure in this example .

The closest sludge neighbours to the WWTP of interest are listed in Table 2 with the distance calculated based on sludge properties and with the corresponding sludge cake dry solids measurement (proxy for dewatering performance ) and the properties of the polymers used in each of the other waste water treatment plants in the database .

Table 2 . Sludge neighbours of WWTP of interest (Netherlands A) with distance , polymer properties and sludge cake dry solids

The results show that better performance could be achieved in the WWTP of interest (Netherlands A) by selecting a polymer with lower SV and higher charge , as in the WWTP of Netherlands B, which had a significantly higher value of sludge cake dry solids . However, the dosage could be higher in that case .

While there have been shown and described and pointed out fundamental novel features as applied to preferred embodiments thereof , it will be understood that various omissions and substitutions and changes in the form and details of the devices and methods described may be made by those skilled in the art without departing from the spirit of the disclosure . For example , it is expressly intended that al l combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the disclosure . Moreover, it should be recogni zed that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiments may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice . Furthermore , in the claims means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents , but also equivalent structures .

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features , to the extent that such features or combinations are capable of being carried out based on the present specification as a whole , in the light of the common general knowledge of a person skilled in the art , irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims . The applicant indicates that the disclosed aspects /embodiments may consist of any such individual feature or combination of features . In view of the foregoing description it will be evident to a person skil led in the art that various modifications may be made within the scope of the disclosure .

It is obvious to a person skil led in the art that with the advancement of technology, the basic idea may be implemented in various ways . The embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims .

The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A method, a product , an arrangement , or a use , disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages . It will further be understood that reference to ' an ' item refers to one or more of those items . The term "comprising" or "including" is used in this specification to mean including the feature ( s ) or act ( s ) followed thereafter, without excluding the presence of one or more additional features or acts .

Claims

1 . A method for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest , wherein the method comprises obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

2 . The method according to claim 1 , wherein the plurality of parameters are selected from the following parameters :

- conductivity,

- dry solids content ,

- volatile solids content ,

- total organic carbon ( TOC) ,

- chemical oxygen demand (COD) ,

- total nitrogen,

- Al ,

- Ca,

- Fe ,

- K,

- Mg,

- Na,

- P,

- charge , zeta potential ,

- capillary suction time (CST ) .

3. The method according to claim 1 or 2, wherein the plurality of parameters comprises at least 10, or at least 11, or at least 12, or at least 13, or at least 14, or at least 15, or all of the following parameters:

- conductivity,

- dry solids content,

- volatile solids content,

- total organic carbon (TOC) ,

- chemical oxygen demand (COD) ,

- total nitrogen,

- Al,

- Ca,

- Fe,

- K,

- Mg,

- Na,

- P,

- charge, zeta potential,

- capillary suction time (CST) .

4. The method according to any one of claims 1 - 3, wherein the plurality of parameters comprise at least a plurality of the following parameters, or at least all of the following parameters :

- Al,

- Ca,

- Fe,

- K,

- Mg,

- Na,

- P; and/or wherein the plurality of parameters comprise at least a plurality of the following parameters, or at least the following parameters : charge, zeta potential, capillary suction time (CST) ; and/or wherein the plurality of parameters comprise at least a plurality of the following parameters , or at least the following parameters :

- conductivity,

- dry solids content ,

- volatile solids content ,

- total organic carbon ( TOC) ,

- chemical oxygen demand (COD) ,

- total nitrogen .

5 . The method according to any one of claims 1 - 4 , wherein the method further comprises obtaining a first value of a dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest , comparing the first value of the dewatering process performance parameter from the waste water treatment plant of interest to second values of the dewatering process performance parameter from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants , thereby identifying the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , using the properties of the flocculating agent ( s ) used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having the higher or lower value of the dewatering process performance parameter to select and/or to adj ust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest .

6 . The method according to claim 5 , wherein the dewatering process performance parameter comprises or is at least sludge cake dry solids and optionally at least one of suspended matter in rej ect water, turbidity of rej ect water, release of P, Cl , NH₄ , and/or Ca to rej ect water, or power consumption in the dewatering unit used in the dewatering process .

7 . The method according to claim 5 or 6 , wherein the properties of the flocculating agent ( s ) comprise at least one of standard viscosity ( SV) , charge density, or dosage .

8 . The method according to any one of claims 1 - 7 , wherein the method comprises scaling and/or normali zing the first values of the plurality of parameters prior to comparing the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants .

9 . The method according to any one of claims 1 - 8 , wherein the comparing of the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples is done by calculating the similarity of the first values of the plurality of parameters from the sludge sample to the second values from the plurality of sludge samples obtained from the other waste water treatment plants using a distance metric, such as an LI norm, e . g . Manhattan distance ; an L2 norm, e . g . Euclidean distance ; cosine similarity; fractional norm; or other distance metric .

10 . The method according to any one of claims 1 - 9 , wherein the plurality of sludge samples obtained from the other waste water treatment plants comprises at least 30 , or at least 50 , or at least 100 sludge samples obtained from other waste water treatment plants .

11 . The method according to any one of claims 1 - 10 , wherein the other waste water treatment plants include waste water treatment plants that are located in different geographical locations , such as in different countries ; and/or waste water treatment plants with a person equivalent ( PE ) of at least 100 000 .

12 . An arrangement for selecting a flocculating agent for use in a dewatering process for sludge in a waste water treatment plant of interest , wherein the arrangement comprises means for obtaining and/or receiving first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , means for comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and means for selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .

13 . The arrangement according to claim 12 , wherein the arrangement further comprises means for obtaining and/or receiving a first value of a dewatering process performance parameter from the sludge sample obtained from the waste water treatment plant of interest , means for comparing the first value of the dewatering process performance parameter from the waste water treatment plant of interest to second values of the dewatering process performance parameter from the most similar sludge samples from the plurality of sludge samples obtained from the other waste water treatment plants , thereby identifying the most similar sludge sample ( s ) having a higher or lower value of the dewatering process performance parameter, wherein the higher or lower value of the dewatering process performance parameter is indicative of improved dewatering process performance , and means for using the properties of the flocculating agent ( s ) used in the other waste water treatment plant ( s ) with the most similar sludge sample ( s ) having the higher or lower value of the dewatering process performance parameter to select and/or to adj ust the properties of the flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest .

14 . A computer program compri sing instructions which, when executed by an apparatus , cause the apparatus to perform at least the following : obtaining first values of a plurality of parameters measured from a sludge sample obtained from the waste water treatment plant of interest , comparing the first values of the plurality of parameters from the sludge sample to second values of the plurality of parameters from a plurality of sludge samples obtained from other waste water treatment plants , each of the other waste water treatment plants using a flocculating agent in a dewatering process for sludge , and thereby identifying the most similar sludge sample ( s ) from the plurality of sludge samples , and selecting a flocculating agent to be used in the dewatering process for sludge in the waste water treatment plant of interest based on at least information available from the flocculating agent ( s ) used in the dewatering process (es ) for sludge in the waste water treatment plant ( s ) with the most similar sludge sample ( s ) .