Treating industrial process water

Abstract

Provided herein is a method for treating industrial process water to reduce or prevent proliferation of contaminating microorganisms, such as contaminating bacteria, in apparatus using the industrial process water; which method comprises administering to the water an amount of a phosphorus-scavenging microorganism so as to reduce the level of bioavailable phosphorus in the water. Also provided herein is use of a phosphorus-scavenging microorganism for the reduction or prevention of proliferation of contaminating microorganisms, such as contaminating bacteria, in apparatus using industrial process water by reducing the level of bioavailable phosphorus in the water.

Description

[0001] TREATING INDUSTRIAL PROCESS WATER

[0002] The present invention relates to a method for treating industrial process water for reducing or preventing proliferation of microorganisms such as bacteria, and the use of microorganisms therefor.

[0003] Background to the Invention

[0004] Contaminating microorganisms such as bacteria can present a problem when apparatus or machinery, used for example in industrial processes, comes into contact with aqueous systems. Bacteria in water can exist in a free-floating form (sometimes known as planktonic) or can be in the form of a biofilm associated with surfaces. Biofilms in particular can be difficult to remove because they contain not only bacterial mass but also a protective sheath or film formed by the bacteria.

[0005] High levels of bacterial proliferation can be very problematic in industrial processes. Industrial process water used for example in the manufacture of pulp, paper and board is particularly susceptible to bacterial proliferation problems. These processes involve water containing microbial nutrients such as cellulose fibres and starch and are operated at temperatures enabling microorganisms to flourish. It is also common to recirculate the same process water several times in the manufacturing process. If left untreated, paper and board products may become defective and regular downtime for cleaning is required. It is therefore desirable to control microbe problems and this has been achieved by adding biocidal materials to the process waters.

[0006] Biocidal materials can be expensive and can cause their own problems such as corrosion damage in the case of some chlorinated biocides. Even where biocides are successfully used on immersed areas, splash areas which are not exposed to a constant flow of process water, such as machine frames, can develop biofilm slimes which do not respond to standard biocide treatment. It is frequently necessary to use very high levels of biocides in order to remove biofilm and control biofilm formation.

[0007] WO2020 / 173963 addresses a problem of reducing organic deposits in water bearing systems such as paper machines. It is proposed to use bacterial spores or bacteria derived from bacterial spores which cannot digest cellulose but can digest saccharides forming the organic deposits. Certain species of Bacillus are described. Use of bacteria to treat biofilms is also mentioned in a Master’ s thesis by Heidi Toivonen published in May 2021 from Turku University. However, none of the bacteria were characterised or made available to the public.

[0008] There is therefore a need to provide improved control of contaminating microorganisms in industrial circulated water systems such as those used in the manufacture of paper and board.

[0009] Summary of the Invention

[0010] In a first aspect, the present invention provides a method for treating industrial process water to reduce or prevent proliferation of contaminating microorganisms, such as contaminating bacteria, in apparatus using the industrial process water; which method comprises administering to the water an amount of a phosphorus-scavenging microorganism so as to reduce the level of bioavailable phosphorus in the water.

[0011] In a second aspect, the present invention provides use of a phosphorus-scavenging microorganism for the reduction or prevention of proliferation of contaminating microorganisms, such as contaminating bacteria, in apparatus using industrial process water by reducing the level of bioavailable phosphorus in the water.

[0012] In accordance with the method for treating industrial process water, proliferation of microorganisms such as bacteria may be reduced or prevented. Such proliferation may be proliferation of free, planktonic microorganisms or those present in a structure such as a biofilm. Such biofilms are typically present on the surface of the apparatus using the industrial process water. Reduction or prevention of proliferation may arise by killing pre-existing microorganisms or stopping proliferation of new microorganisms. In this way, biofilm formation may also be reduced or prevented and pre-existing, formed biofilm may be reduced or removed, for example by dissolution of biofilm so that the microorganisms become planktonic and are subsequently killed.

[0013] It has surprisingly been found that proliferation of contaminating microorganisms such as in biofilms is associated with elevated levels of bioavailable phosphorus in the industrial process water. It has been surprisingly found that the higher the level of bioavailable phosphorus, the greater the biofilm problem becomes. This means that, by treating the water with microorganisms that remove the phosphorus - phosphorus-scavenging microorganisms - a reduction or prevention in the proliferation of the contaminating microorganisms can be achieved. Bioavailable phosphorus is typically phosphorus available for microbial proliferation or metabolism. Bioavailable phosphorus is water soluble and not bound to cellular biomass. Orthophosphate is a typical form of bioavailable phosphorus.

[0014] The use of the phosphorus-scavenging microorganisms to treat the industrial process water enables a reduction in the use of conventional biocides which is beneficial in terms of cost, environmental impact and the health and safety of those working with the apparatus. A biocide may be used in combination with the phosphorus-scavenging microorganism to treat the industrial process water. Where the phosphorus-scavenging microorganism reduces or removes pre-existing biofilm, for example by dissolution of the biofilm, the contaminating microorganisms from the biofilm may become planktonic. Treatment of industrial process water containing these planktonic bacteria by a suitable biocide will kill the planktonic bacteria. Conventional biocides need not to be used in such high quantities as hitherto used to treat biofilm because of the action of the phosphorus-scavenging microorganism in releasing planktonic bacteria from the biofilm. The biocide may be used as a unitary composition with the phosphorus-scavenging microorganism or may be administered sequentially or simultaneously with phosphorus-scavenging microorganism. The biocide may be administered at the same location as the phosphorus-scavenging microorganism or at a different location.

[0015] A phosphorus-scavenging microorganism according to the present invention must be effective in removing phosphorus from the industrial process water, typically under the conditions under which the industrial process water is used in the apparatus. Those conditions will vary, depending on the industrial process water in question. Cooling water may reach elevated temperatures of at least 35° C, such as at least 40° C or at least 50° C. Water used in industrial manufacturing processes such as process water used in paper, board, pulp and tissue mills may reach similar temperatures. However, cooling water is far less likely to contain contaminating materials such as cellulosic fibre material, fines and fibre fragments as well as chemicals used in the industrial manufacturing process such as retention chemicals. The phosphorus- scavenging microorganism according to the present invention must be able to remove phosphorus under the conditions specific to the industrial process water, typically by intracellular accumulation of the phosphorus. Various types of industrial processes are discussed in further detail below.

[0016] Phosphorus-scavenging microorganisms are well-known in this technical field. They have been used for many years in enhanced biological phosphorus removal to address the environmental impact of excess phosphorus present in municipal wastewater discharges. A review of this subject may be found in Diaz et al in Chemosphere 309 (2022), 136518. It is thought that some phosphorus-scavenging microorganisms actively accumulate phosphorus and may do so by storing it in intracellular storage organelles.

[0017] Such phosphorus-scavenging microorganisms include species of Acinetobacter sp., Candidatus Accumulibacter phosphatis (Accumulibacter), Dechloromonas sp., Tetrasphaera sp., Aeromonas, Bacteroidetes, Flavobacterium, Sphaerotilus_f_uc, Paracoccus, Azospira, Propioni vibrio, Rhodocyclaceae_uc, AB186832_g, AB552905_g, Sterolibacterium_f_uc, AM167962_g, Thiobacillus_f_uc, Proteobacteria, Thauera, Zoogloea, Zoogloea_f_uc, and Pseudomonas. Illustrative Dechloromonas species include Dechloromonas aromatica strain RCP, Candidatus Dechloromonas phosphatis, and Candidatus Dechloromonas phosphorous. Illustrative Tetrasphaera species include T. australiensis (strains Ben 109 and Ben 110), T. japonica (strain T1-X7), T. elongata (strain Lp2), (strain ASP12), T. jenkinsii, T. veronensis, T. vanveenii and Candidatus Nostocoida limicola. Also included are the Archaea: Halobacterium salinarium and Halorubrum distributum', Alcaligenes, Streptococcus and Brevibacteria; and yeasts such as Kuraishia capsulata.

[0018] Preferred phosphorus-scavenging microorganisms include Candidatus Accumulibacter phosphatis (Accumulibacter), Dechloromonas sp. and Tetrasphaera sp..

[0019] The method of the invention is applicable to a variety of industrial processes. Many of these processes use process water which contains components which provide nutrition to contaminating microorganisms. In addition, many industrial processes operate at elevated temperature. The temperature of the process water may reach at least 35° C, such as at least 40° C or at least 50° C. Such elevated temperatures can also promote the proliferation of contaminating microorganisms. The microorganisms present in the water may proliferate in biofilms and cause biofouling and biocorrosion, also known as microbiologically influenced corrosion (MIC). Microbial biofilms may reduce conductive heat transfer across surfaces and may clog hydraulic systems with consequent energy losses and possible production cutbacks and shutdowns.

[0020] The industrial process water to be treated relates to water from any apparatus or equipment used in any industry and includes industrial circulating water wherein the industrial process water is recirculated in the apparatus as well as water stored for industrial use. Included is water used in industrial manufacturing processes such as process water used in paper, board, pulp and tissue mills, process water used in moulded fibre production, process water used in textile production, or process water used in man-made cellulosic fiber (MMCF) production, treatment, or recycling; water used as cooling water which may be circulated through pipework, and water used in the oil and gas industry. Examples of waters in oil and gas industry requiring control of microorganisms are injection waters, fracturing fluids, tankage, pipelines and hydrostatic test waters.

[0021] Industrial manufacturing processes comprising fibre material, such as manufacture of paper, board, pulp, tissue, moulded pulp, non-woven, MMCF, viscose or the like are particularly suitable for treatment according to the invention. The industrial process water optionally further comprises cellulosic fibre material, fines and / or fibre fragments of natural origin. The process water may also comprise starch. The cellulosic fibre material typically originates from softwood, hardwood or non-wood sources, such as bamboo, straw or kenaf, or any mixtures thereof. Preferably the cellulosic fibre material originates from lignocellulosic fibre material. More preferably the cellulosic fibre material is lignocellulosic fibres. The cellulosic fibre material may originate from any suitable mechanical, chemi-mechanical or chemical pulping process or any of their combinations or any other suitable pulping process known as such. The cellulosic fibre material may also comprise fibre material which originates from recycled board, paper or pulp. For example, the cellulosic fibre material may comprise cellulosic fibres that originate from hardwood and have a length of 0.5 - 1 .5 mm and / or from softwood and have a length of 2.5 - 7.5 mm. The process water may also comprise inorganic mineral particles, such as fillers and / or coating minerals; hemicelluloses; lignin; and / or dissolved and colloidal substances. The process water may also comprise papermaking additives, such as starch, sizing agents, inorganic or organic coagulation or flocculation agents, natural or synthetic polymers of different length and / or charge, dyes, optical brighteners or any combination thereof. The cellulosic fibre material may also be cellulosic fibres for textiles, including virgin fibre and recycled textiles as the fibre source material.

[0022] Accordingly, the apparatus using the industrial process water may comprise apparatus for manufacturing paper, board, pulp, tissue, moulded fibre, or textiles, or apparatus for MMCF production, treatment or recycling, and preferably apparatus for manufacturing paper, board, pulp or tissue.

[0023] In one arrangement, the industrial manufacturing process uses process water optionally comprising cellulosic fibre material of natural origin and is a pulp and / or paper and / or board manufacturing process, where the process water shows high temperature and / or high flow rate. The phosphorus-scavenging microorganism according to the invention is thus added or dosed to a pulp and / or paper and / or board manufacturing system. The water in these processes often shows high flow and high shear rates, which may induce the formation of biofilm on the process surfaces due to the stress of microorganisms. For example, in paper and board making environments the flow rates may typically be higher than 1 m / s, even over 10 m / s, typically from 1 to 20 m / s or from 1 to 10 m / s.

[0024] The industrial manufacturing process comprising cellulosic fibre material of natural origin may be a pulp and / or paper and / or board manufacturing process, where the pH of the aqueous environment is in the range 5 - 9, preferably 7 - 8.5.

[0025] In one arrangement of the present invention the phosphorus-scavenging microorganism may be administered to the industrial manufacturing process having process water optionally comprising cellulosic fibre material, which is a paper, tissue and / or board manufacturing process, especially in a short loop of the paper or board making process. In a typical paper and board making process, pulp stock is passed into a headbox, which distributes the pulp stock onto a moving wire in a forming section, on which the continuous paper web is formed. The short loop or short circulation section of a paper / board machine is here understood, as customary in the art, the part of the manufacturing system that re-circulates and recycles at least a part of excess water from the pulp stock, collected in a wire pit in the forming section, back to the headbox for re-use.

[0026] Alternatively, or in addition, the phosphorus-scavenging microorganism may be administered to the pulp and / or paper and / or board manufacturing process, to process water in any location of the process, such as circulating water tank, circulating water tower, filtrate water towers; to clear or cloudy filtrate storage tanks; pulpers; aqueous streams upstream / downstream of the pulpers; broke system and aqueous process streams upstream / downstream of vessels therein; wire pit process streams upstream / downstream of the pit; paper machine blend chest process streams upstream / downstream of the chest; fresh water tank; warm water tank and / or shower water tank.

[0027] Alternatively, or in addition, the phosphorus-scavenging microorganism may be administered to the pulp and / or paper and / or board manufacturing process to any location in a long loop of the paper or board making process. The long loop or long circulation section of a paper / board machine is here understood, as customary in the art, the part of the manufacturing system that handles excess water and broke. A major part of the recovered water exits the short loop and is pumped to the long loop, which includes: save-all for capturing useful fibres from the recovered water for reuse, storage tanks for filtrate water used for example in machine showers, and storage tanks for recirculated water used for example as dilution water for importing pulp from pulp mill to paper / board machine. A part of the long loop is the broke system for handling of wet and dry paper rejects from the machine. This material is repulped and reused as a part of the pulp stock.

[0028] Advantageously, the phosphorus-scavenging microorganism is administered to the industrial process water via a fresh water tank or tower; broke filtrate tank or tower; white water tank or tower; circulating water tank or tower; or shower water tank or tower.

[0029] Advantageously, the phosphorus-scavenging microorganism may be administered to the pulp and / or paper and / or board manufacturing process so as to treat splash areas which are particularly prone to accommodating contaminating biofilms. Splash areas include equipment surfaces above the surface of the industrial process water such as any surfaces of equipment which are not immersed or exposed to constant flow of the process water. Examples of such surfaces are those areas of wire section, vacuum boxes, wire water collecting system, wire channel and wire pit that are not exposed to continuous flow of process water but are exposed to splashes and mist. Other examples of such surfaces are machine frames, surfaces of support structures above, under or next to or alongside the moving wire or press felt, surfaces of shower bars, surfaces for controlling splashing of water, and surfaces of ventilation system. Treatment of the splash areas may be accomplished by a general reduction in the levels of bioavailable phosphorus because of the removal of phosphorus by the phosphorus-scavenging microorganisms. Alternatively, or in addition, treatment of the splash areas may be accomplished by the phosphorus-scavenging microorganisms reaching those areas and reducing the levels of bioavailable phosphorus in situ.

[0030] Typical bacteria found in industrial process water include the following:

[0031] Acidovorax A. delafieldii

[0032] Acinetobacter A. Iwoffii, A. radioresistens, A. baumannii

[0033] Bacillus B. amyloliquefaciens, B. atrophaeus, B. cereus, B. circulans, B. coagulans, B. firmus, B. fusiformis, B. halodurans, B. jeotgali, B. licheniformis, B. megaterium, B. mycoides, B. pumilus, B. simplex, B. smithii, B. sphaericus, B. subtilis, B. thuringiensisBrevibacillus B. agri, B. brevis, B. laterosporus

[0034] Brevundimonas B. vesicularis, B. diminuta

[0035] Burkholderia B. caryophylli, B. cepacia, B. kururiensis, B. multi vorans

[0036] Cloacibacterium C. normanense

[0037] Clostridium C. intestinale, C. magnum

[0038] Deinococcus D. geothermalis, D. grandis

[0039] Enterobacter E. amnigenus, E. cloacae, E. hormaechei, E. kobei, E. radicincitans, E. sakazakii Enterococcus E. durans, E. Casseliflavus

[0040] Exiguobacterium E. acetylicum, E. aestuarii, E. marinum, E. mexicanum

[0041] Hydrogenophaga H. palleronii

[0042] Klebsiella K. pneumoniae, K. oxytoca, K. variicola

[0043] Meiothermus M. silvanus

[0044] Methylobacterium M. mesophilicum, M. zatmanii, M. extorquens

[0045] Microbacterium M. esteraromaticum, M. testaceum, M. maritypicum, M. paraoxydans, M. phyllo sphaerae

[0046] Nocardiopsis N. alba, N. dassonvillei, N. umidischolae, N. composta, N. prasina Pantoea P. agglomerans

[0047] Pseudomonas P. aeruginosa, P. fluorescens, P. putida, P. stutzeri, P. monteilii, P. plecoglossicida

[0048] Pseudoxanthomonas P. taiwanensis

[0049] Rhizobium

[0050] Rubellimicrobium

[0051] Sphaerotilus S. natans

[0052] Sphingomonas S. capsulata, S. paucimobilis, subclades S. trueperi and S. aquatilis Staphylococcus S. epidermidis, S. haemolyticus, S. warneri

[0053] Xanthobacter X. Agilis

[0054] Typical fungi found in industrial process water include:

[0055] Aspergillus

[0056] Candida

[0057] Penicillium

[0058] Saccharomyces

[0059] Bacteria found in industrial process water indicative of microbial contamination include Meiothermus, Deinococcus and / or Pseudoxanthomonas. These bacteria are commonly found in papermaking processes and frequently form biofilms which are problematic to the apparatus used in papermaking. Other bacteria known to cause biofilm formation in papermaking processes include Rubellimicrobium, Roseomonas, Thermus and Tepidimonas.

[0060] Alternatively, or in addition, the phosphorus-scavenging microorganisms of the invention may be administered to cooling water systems which may be in a separate circuit from the industrial manufacturing process. Typically, such cooling water systems comprise circulating water which contacts with a heat exchanger that is in contact with process water or apparatus from the industrial manufacturing process. Cooling water systems can operate at a wide range of temperatures depending on the temperature of the water supply and the temperature at which the industrial process or apparatus to be cooled. Temperatures in the range 5° C to 50° C or more are found. Many such systems operate at elevated temperature, such as at least 30° C. The phosphorus-scavenging microorganism may be administered to the cooling water via a water basin, evaporation tower, pipelines, heat exchanger or source water.

[0061] Proteobacteria are the dominant microbial group found from cooling water biofilms.

[0062] The phosphorus-scavenging microorganism may be added to the process water as dried bacteria or as a wet slurry / solution. In practice, this could be prepared on-site or remotely and brought to site as needed. For example, a solution could be prepared on site a few hours before dosing to the apparatus.

[0063] Generally, in the apparatus for industrial manufacturing or cooling water processes, the site at which the phosphorus-scavenging microorganism is administered is not necessarily the site at which the problem of contaminating microorganisms needs to be addressed. It will be understood that administration to the process water via a storage tank, for example, may be intended to treat the contaminating microorganisms downstream of the storage tank, possibly after a period of circulation in the apparatus, during which the phosphorus-scavenging microorganisms may multiply and / or scavenge phosphorus.

[0064] The phosphorus-scavenging microorganism may be administered batchwise or continuously to the process. Preferably it is dosed batchwise, in one to three dosing points in the process, in a manner so that the phosphorus-scavenging microorganism reaches all parts of the process which are prone to biofilm formation.

[0065] In general, the phosphorus-scavenging microorganism may be added to the process water in biostatic or biocidal amounts. Biostatic amount refers to an amount sufficient to at least prevent and / or inhibit the activity and / or proliferation of the microorganisms or the biofilm. Biocidal amount refers to more effective activity, such as to an amount capable of reducing the activity and / or proliferation of the microorganisms or the biofilm and / or killing most or all of the microorganisms present in the process water.

[0066] Detailed description of the invention This invention will now be described in more detail, by way of example only, with reference to the accompanying Figures, in which:

[0067] Figures 1 and 2 are bar charts comparing decrease in biofilm levels with bioavailable phosphorus levels in the presence of varying ratios of phosphorus-scavenging bacteria to Meiothermus bacteria; and

[0068] Figures 3 and 4 are bar charts comparing decrease in biofilm levels with bioavailable phosphorus levels in the presence of varying ratios of phosphorus-scavenging bacteria to P seudoxanthomonas bacteria.

[0069] The term “comprises” as used throughout the description and claims herein means “includes or consists of’. The term denotes the inclusion of at least the features following the term and does not exclude the inclusion of other features which have not been explicitly mentioned. The term may also denote an entity which consists only of the features following the term.

[0070] Example 1

[0071] Correlation between bioavailable phosphorus levels and biofilm levels in paper machines

[0072] Bioavailable phosphorus was determined from a sample of industrial circulating process water after filtration using an ashless filter paper and then filtration with a 0.45 pm (or smaller) sterile filter. After that the amount of phosphorus was determined by methods known in the art.

[0073] To the inventors’ knowledge, the quantity of bioavailable phosphorus has not hitherto been correlated with levels of contaminating microorganisms such as observed in biofilm. The inventors have now analyzed process water from eight paper machines in China and Europe. At the same time formation of biofilm in these machines was assessed visually.

[0074] Based on the experimental data it was surprisingly found that the quantity of bioavailable phosphorus in tested process water correlates with cleanliness of splash areas (Table 1). Table 1, Quantity of bioavailable phosphorus in process water of different paper machines. Data is presented as average of results from two different sampling days (Mills A, B, C and G), three sampling days (Mill H) and four sampling days (Mills D, E and F). Surfaces cleanliness of the machines was evaluated for the whole research period.

[0075] * Based on visual observations. 1 = The cleanest surfaces, 4 = The highest amount of slime.

[0076] Machines with low bioavailable phosphorus content had the cleanest splash areas. Without being bound by theory the amount of phosphorus bioavailable to microorganisms on the splash areas appears to control the rate of biofilm proliferation on these areas.

[0077] Example 2 Reduction of biofilm levels using phosphonis-scavcnging bacteria.

[0078] Experimental procedures

[0079] Materials and Methods

[0080] Pure cultures of Meiothermus silvanus, a microbe species commonly found in paper machine biofilms (Ekman J, Journal of Industrial Microbiology & Biotechnology 34:203-211) and Pseudoxanthomonas taiwanensis, another species commonly found in paper machine environments (Desjardins, E & Beaulieu, C, Journal of Industrial Microbiology & Biotechnology 30:141-145) were used to study the efficacy of various chemicals to reduce or prevent biofilm formation.

[0081] Biofilm tests were done in fibre-containing synthetic paper machine water, SPW (prepared according to Peltola, et al., J. Ind. Microbiol. Biotechnol. 38: 1719-1727) using 96-microwell plate wells with peg lids (Thermo Fischer Scientific Inc., USA). Plates were incubated at 45 °C with a rotary shaking (150 rpm) providing high flow in each well.

[0082] A phosphorus-scavenging bacterium designated strain SR72 was isolated from a board machine and it has been identified by sequencing as Ralstonia sp. The strain has been deposited at VTTCC (VTT Culture Collection, Tietotie 2, 02044 Espoo, Finland) on Nov 7th, 2023 and accorded accession number VTT E-233624.

[0083] Biofilm tests

[0084] At the beginning of the cultivations biofilm-forming bacterial pre-cultures were diluted to the same Optical Density (OD595) value with either Meiothermus or Pseudoxanthomonas precultures. From there Strain SR72 was added in different proportions compared to either Meiothermus or Pseudoxanthomonas. E.g. 1 / 99 refers to 1 part of Strain SR72 and 99-parts of Meiothermus or Pseudoxanthomonas. The initial amounts of bacteria were also determined by platings on agar plates and the ratios were calculated from the results.

[0085] Wells of 96-microwell plates with peg-lids were filled with SPW and inoculated with the above bacterial cultures. Biofilm was grown at 45 °C with a rotary shaking (150 rpm) for 24 hours in the presence or absence of Strain SR72 as indicated in Figures 1 to 4. After 24 hours from starting the test, the wells were emptied and the biofilm amount on the pegs was quantified.

[0086] Quantification of Formed Biofilm

[0087] The amount of biofilm formed on the peg surfaces was quantified with a staining solution by adding 200 pl of 1 % Crystal Violet (Merck Millipore KGaA, Germany) in methanol to each well in a clean 96-well plate and placing the biofilm-containing peg-lid on it. After 3 minutes the wells were emptied and the wells and pegs were rinsed 3 times with tap water. Finally the peg-lid was placed in a clean 96-well plate, the attached Crystal Violet was dissolved into ethanol and the absorbance at 595 nm was measured.

[0088] Results and conclusions

[0089] Figure 1 shows that at a starting orthophosphate level of 3.25mg / l (NO sample - only growth medium; Ml 00 all bacteria are Meiothermus), the presence of Strain SR72 scavenges orthophosphate and reduces biofilm levels by up to nearly 80% in the 24-hour experiment. A high level of biofilm reduction is observed even at the lowest ratio of SR72:Meiothermus, suggesting that this ratio is sufficient to scavenge substantially all bioavailable phosphorus.

[0090] Figure 2 shows that at a higher starting orthophosphate level of 5.44mg / l (NO sample - only growth medium; M100 all bacteria are Meiothermus), the presence of Strain SR72 also scavenges orthophosphate and reduces bio film levels by up to nearly 95% in the 24-hour experiment. At this higher starting orthophosphate level not all bioavailable phosphate is scavenged, suggesting that the quantity of SR72 cells reaches a maximum within the 24-hour period.

[0091] Figure 3 shows that at a starting orthophosphate level of 3.12mg / l (Ref sample - only growth medium; P100 all bacteria are Pseudoxanthomonas), the presence of Strain SR72 scavenges orthophosphate and reduces biofilm levels by up to around 70% in the 24-hour experiment. Figure 4 shows that at a higher starting orthophosphate level of 5.36mg / l (Ref sample - only growth medium; Pl 00 all bacteria are Pseudoxanthomonas), the presence of Strain SR72 also scavenges orthophosphate and reduces biofilm levels by up to around 80% in the 24-hour experiment.

[0092] Pseudoxanthomonas grows much more quickly than Meiothermus. Therefore, over the 24- hour period of the experiments, the level of biofilm reduction is much more sensitive to the SR72:Pseudoxanthomonas ratio than the corresponding ratio for Meiothermus. This is evident from Figures 3 and 4 which show the need for higher ratios of SR72:Pseudoxanthomonas to achieve higher levels of biofilm reduction.

[0093] Taken together, the results show that a phosphorus-scavenging microorganism reduces levels of bioavailable phosphorus in a model medium for paper machine process water and simultaneously reduces levels of biofilm from two common biofilm-forming microbial contaminants.

Claims

Claims:

1. A method for treating industrial process water to reduce or prevent proliferation of contaminating microorganisms, such as contaminating bacteria, in apparatus using the industrial process water; which method comprises administering to the water an amount of a phosphorus-scavenging microorganism so as to reduce the level of bioavailable phosphorus in the water.

2. A method according to claim 1, which comprises reducing or preventing biofilm formation and / or reducing or removing formed biofilm, optionally wherein the biofilm is present on the surface of the apparatus using the industrial process water.

3. A method according to claim 1 or claim 2, wherein the industrial process water is recirculated in the apparatus.

4. A method according to any preceding claim, wherein the industrial process water comprises cooling water; process water used in paper, board, pulp and tissue mills; process water used in moulded fibre production; process water used in textile production; or process water used in man-made cellulosic fiber (MMCF) production, treatment, or recycling.

5. A method according to claim 4, wherein the apparatus comprises apparatus for manufacturing paper, board, pulp, tissue, moulded fibre, or textiles, or apparatus for producing, treating or recycling MMCF, preferably apparatus for manufacturing paper, board, pulp or tissue.

6. A method according to claim 5, wherein the industrial process water comprises cellulosic fibre material.

7. A method according to claim 5 or claim 6, wherein the phosphorus-scavenging microorganism is administered to the industrial process water via a fresh water tank or tower; broke filtrate tank or tower; white water tank or tower; circulating water tank or tower; or shower water tank or tower.

8. A method according to any of claims 5 to 7, wherein the contaminating microorganisms comprise bacteria belonging to a genus of Meiothermus, Deinococcus Pseudoxanthomonas, Rubellimicrobium, Roseomonas, Thermus and / or Tepidimonas.

9. A method according to claim 4, wherein the industrial process water is cooling water and the phosphorus-scavenging microorganism is administered to the cooling water via a water basin, evaporation tower, pipelines, heat exchanger or source water.

10. A method according to claim 9, wherein the contaminating microorganisms comprise bacteria belonging to an order selected from Sphingomonadales, Pseudomonadales, Rhizobiales, and Burkholderiale.

11. A method according to any preceding claim, wherein the temperature of the water reaches at least 35°C, optionally at least 40°C, preferably at least 50°C.

12. Use of a phosphorus-scavenging microorganism for the reduction or prevention of proliferation of contaminating microorganisms, such as contaminating bacteria, in apparatus using industrial process water by reducing the level of bioavailable phosphorus in the water.

13. Use according to claim 12, which comprises reducing or preventing biofilm formation and / or reducing or removing formed biofilm, optionally wherein the biofilm is present on the surface of the apparatus using the industrial process water.

14. Use according to claim 12 or claim 13, wherein the industrial process water is recirculated in the apparatus.

15. Use according to any of claims 12 to 14, wherein the industrial process water comprises cellulosic fibre material.

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