The present invention relates to controlling organic fouling of pipes and heat exchangers in large industrial cooling systems.

Fouling of industrial pipe work systems including heat exchanger is a well known problem. At present, fouling of heat recovery and transfer equipment costs industries up to billions of pounds per year. Despite technological progress being made in the prevention, mitigation and removal techniques for industrial fouling, this problem remains one of the major unresolved problems in thermal science.

Many industries use water from natural sources to remove heat from factory processes. An inherent problem of such systems is the ingress of flora and fauna which grow in pipes, forming a bio-film and thereby blocking the pipework. Although screens and filters are often used to block intake positions in the systems, such filters only eliminate the larger organisms. The biofilm is actually created by the smaller organisms, bacteria, followed by other forms including microscopic plants, algae, larvae and single cell organisms. As a result, heat exchangers become clogged by organic growth and have to be opened periodically in order to be cleaned.

The various processes currently used for cleaning these systems are labour intensive and expensive. As much as 8% of the maintenance cost in a typical industrial plant can be due to fouling mitigation in heat exchangers. In many cases, aggressive chemicals are required for offline mitigation of fouling. This results in problems including increased safety hazards for personnel and additional operating costs. Furthermore, the fouling process starts again immediately after the cleaning process is completed and the rapid accumulation of bio-film deposits reduces system performance until the next cleaning treatment is initiated. Thus, industrial processes which involve regular offline cleaning of heat exchangers are expensive, cumbersome and inefficient.

To address these problems, several solutions have been proposed. Existing methods of moderating the impact of the organic growth of microorganisms involve the use of oxidizing chemical biocides for killing the microorganisms. Sodium hypochlorite, for example, is often used as a biocide.

A problem with using such chemical solutions is that they can damage the environment when used excessively. The creation of disinfection byproducts (DBP) such as trihalomethane (THM) is a known danger of using sodium hypochlorite. DBP/THM are undesirable because they are known to be toxic or carcinogenic. For this reason, the use of biocide products is strictly regulated by laws in force such as Directive 98/8/EC of the European Parliament and of the Council.

The problem of cleaning heat exchangers by use of chemicals is enhanced by the fact that some of the organisms in the water use sticky polysaccharides, calcium and other minerals to form bio-film which they can protect themselves in. The introduction of chemicals which kill the free floating/swimming species prevents them from competing with those in the bio-film for space or nutrients so that contamination can be relatively quickly reestablished. The growth is exponential therefore the biomass can double several times a day, depending on species, temperature and nutrition.

Traditionally, the change in efficiency of the system to transfer heat, ΔΤ, has been used as an indication for the need to treat heat exchangers. By measuring how much temperature the system is able to transfer between two liquids, one can establish when efficiency of the system has fallen and cleaning is required. In other words one waits until the organic growth results in the highest degree of contamination before any action is being undertaken.

A widespread method of treatment is "shock dosing" or "pulsed injection" with sodium hypochlorite. One of the many known drawbacks with using this chemical is the creation of DBP/THM. The DBP/THM are created by the chemical reaction of the chlorine in the sodium hypochlorite and the organic material. By delaying the treatment until the organic growth is at a peak results in the highest degree of contamination, an increased amount of DBP/THM is thereby created. The present invention provides a solution for treating industrial pipe work systems and heat exchangers which addresses the above mentioned problems. According to an aspect of the present invention there is provided a method of controlling bio-film growth in an industrial pipe work system as claimed in claim 1.

According to a further aspect of the present invention there is provided a system for controlling bio-film growth on an industrial pipe work system as claimed in claim 16.

The industrial pipe work system may be a heat exchanger system. Fouling of systems including pipe work and heat exchangers is a biological phenomenon. Accordingly, the present inventors have recognised that if fouling is to be dealt with effectively from an engineering point of view, it is important that the biological principles which determine its development be understood. Advantageously, the presently claimed method uses intelligent monitoring and understanding of the fouling process by commencing treatment when the amount of bio-film has not developed to a stage which is difficult to treat nor would treatment create harmful side effects so that relatively less effort and lower levels of active ingredients are required and there and there is less impact on the environment. The present method therefore eliminates microorganisms which are part of the first phase of formation of the biofllm which can still be reversed.

As a result, the growth of bio-film over time can be halted or reversed. Furthermore, the need for heat exchanger teardown and cleaning is reduced or eliminated. Further advantageous features are set out in the appended dependent claims.

Figure 1 is a graph illustrating the temporal evolution of various species which usually cause system fouling; Figure 2 shows stages of colony formation according to S0ren Molin BioCentrum DTU;

Figure 3 schematically represents a method of controlling bio-film growth in accordance with present invention;

Figure 4 represents the evolution of two streams in a method according to the present invention;

Figure 5 is a table listing standard redox potentials of 'disinfecting substances' created in water; and

Figure 6 represents the water flow through three banks of heat exchangers in a system in accordance with the present invention.

Embodiments of the present invention will now be described with reference to the figures. A bio-film usually forms in water systems where the flora and fauna create a symbiotic relationship in order to survive and colonize the system. Figure 1 shows the temporal evolution of bacteria, algae, diatoms, ciliates and flagellates, as published in "Marine Fouling and Its Prevention Contribution No. 580 from the Woods Hole Oceanographic Institute Copyright 1952 by U.S. Naval Institute, Annapolis, Maryland George Banta Publishing Co., Menasha, Wi, USA. As illustrated in Figure 1 , bacteria are typically the first individuals to enter the system. Bacteria arrive quickly, while the remaining species only arrive when enough sticky material is formed to accommodate them. There are many species of bacteria which are known to create polysaccharide slime on the system surfaces.

The individual bacteria communicate well between each other, placing their colonies at optimum distances from each other in order to most efficiently share the nutrients of the effluent. When the biomass of a given area has too much demand to be supported by the available nutrients, portions of colonies are instructed to break free and form new locations downstream. The bacteria are able to "glue" precipitated calcium and other minerals together to give structure to the bio-film. In case of periodic attacks by chemicals, the bacteria communicate with each other giving orders or warnings to create more sticky coating for protection.

Once the sticky material is in place, it can be populated by other species such as protozoa, diatoms, etc. The diatoms, which tend to give a characteristic brown colour to the water body, secrete a more gelatinous material. Unlike bacteria, the diatoms and other organisms have mechanisms for attaching themselves to the surfaces they live on. Regardless of the complexity of the bio-film created there are colonies breaking away and flowing downstream from the remaining population to form new colonies. The first phase of colony formation starts with the arrival of a few individuals attaching to the surface. The colonies become increasingly established until late in the first phase of formation when it is said the colonisation process is irreversible. According to S0ren Molin BioCentrum DTU, the stages of colony formation for Pseudomonas aeruginosa are as shown in Figure 2: reversible attachment (1 ), followed by irreversible attachment (2), cell proliferation (3), biofilm formation (4) and, finally, disintegration (5).

As shown in Figure 3, the method includes the step of monitoring (SO), for example by bio-indicators, a part of the system, such as a liquid stream. A relevant threshold for the bacteria on the system surface forming a new bio-film or colony forming units (CFUs) is then determined (S1 ). If the detected CFUs are above the relevant threshold (S2), a "shock" treatment or treatment dosage is applied to the stream and therefore CFUs within the stream (S5). By creating a "shock" treatment of a system based on analysis of the formation rate of the slime from the bacteria, the formation of the bio-film is reversed and the system remains clean over time. Accordingly, the present invention prevents the formation of new bio-film by disrupting the colonization of the first individuals colonizing the system, i.e. stopping its first stage of establishment in the system.

Preferably, in a method of controlling bio-film growth in accordance with present invention, the intensity of the required shock is evaluated (S3) and/or adjusted (S4). These steps (S3 and S4) may be applied in sequence the individual heat exchangers and pipe constructions. In a preferred embodiment, the evaluation the intensity of the required shock (S3) takes into account any levels of natural THM which may be present in the system. The naturally occurring THM is taken into consideration when deciding and measuring treatment (shock) parameters in order to constantly control the actual level of THM generation from the system. In other words, the method considers how much THM was already present in the system and how much THM was added following treatment.

Adjusting the treatment dosage (S4) may comprise adjusting the treatment dosage (shock) applied to the detected biofilm to correspond to the limited need of treatment due to early detection of biofilm.

The usual guidelines for the use of existing systems are provided in the Reference Document (BREF) issued by the European Integrated Pollution Prevention and Control (IPPC) on the application of Best Available Techniques to Industrial Cooling Systems (published at http://eippcb.jrc.es/reference/). This document specifies acceptable levels of oxidants which can be applied to the system, measured by the concentration being released into nature usually over a 24 hour period. In an intelligent system, the levels of treatment to the individual components can be adjusted so that the known total being generated and applied to the entire system does not exceed the permitted levels. An objective of this invention is not to only comply with the suggested guidelines but to optimise the system to the lowest level possible according to the operating conditions that may change depending on season and growth cycles of the organic species in question.

In order to adjust the level of treatment (S4), the total amounts of species in and out of the overall system as well as at individual heat exchanger and nodes may be measured respectively. The heat exchangers are often arranged in branches or groups/nodes. Water is usually pumped in bulk and spread through the system. As long as the measured quantity of microorganisms coming out of the system or at the node is greatly reduced, the level of treatment can be adjusted (S4) to lower the level of treatment being used. If, however, seasonal changes in population, temperature, anabolic or catabolic phases of life of the flora and fauna affect available nutrient levels, the relevant threshold and/or shock intensity (i.e. the level of treatment) can be adjusted to control their effect.

The method may be repeated on each point of intervention. Eventual adjustments of effect applied to each point of intervention in the system are staggered, i.e. spread over a period of time, so that the total application will never exceed the targeted allowable levels of 'end-of-pipe' emissions. 'End-of- pipe' emissions form the output from the overall system as it leaves the factory. Looking at Figure 6 described below, one can see that a "shock" dosage for the largest heat exchanger flow would only be equivalent to less than half of allowable dosing if the other streams are temporarily not receiving treatment.

Accordingly, the treatment may be in sequence or rotation so that the system emission totals are not exceeded. For example, if a heat exchanger has 100 water passages to be treated and one may not exceed a certain amount at 'end- of-pipe', then there could be a sequential application of heavy treatment for the individual passages while none to the others. The total flow would dilute the oxidation agents and the system would be in compliance. From the temporal development of the biofilm shown in Figure 1 , the present inventors have estimated that it would be sufficient for each water passage to be treated briefly once every other day. The same applies to the rotating or sequential treatment of the heat exchangers in a much larger assembly.

In addition to measuring the formation rate of bacteria CFUs, determining the relevant threshold (S1 ) may use the communication between the individuals in the bio-film to establish (S2) when an early stage "shock" should be initiated. This may involve, for example, isolating a heat exchanger and recirculation of a good mixture of electrochemically produced oxidants in the system. At that point the intelligent system stops production of oxidants in other parts of the system and spreads the concentration from the 'shock' throughout the entire system in order to maintain an acceptable low level of treatment.

A further option is to allow the effluent from the recirculation or the continual flow to be neutralised if the dilution of the total flow does not reduce the free chlorine to acceptable levels. This can be accomplished for example by adding sodium theosulphate to the system as is commonly done with fish aquariums and in treatment of effluents from waste water treatment systems where active ingredients are undesired

Studies of the individual distances between micro-colonies have shown that the colony pattern is non-random. There is competition between the colonies for at least one of the essential nutrients, production of antagonists from the colonies, or controlled development. Such studies include research by DTU Technical University of Denmark and have been further discussed in "Complex adaptive systems ecology by Molin, Jan Copenhagen Business School, Molin, S0ren (Cwisno: 1652) in journal: Adv. Micro. Ecol., vol: 15, pages: 27-79, 1997 and Mar Biol (2010) 157: 1 105-1 1 1 1 DOI 10.1007/s00227-010-1392-x 123: "Immunocytochemical evidence that symbiotic algae secrete potential recognition signal molecules in hospite" by Douglas A. Markell and Elisha M. Wood-Charlson.

Essentially, by measuring the placement of bacteria colonies on a surface by means of nano conductivity, optical analysis or other means, one determines the threshold and finds out (S1 , S2) when the initial, critical step of bio-film formation is taking place. An initial, controlled "shock" can then be scheduled at that time instead of waiting until there is enough load to create too much DBP. This is before the mineral deposits by other individuals such as diatoms take place. A "shock" may be initiated following analysis of the signals from the individual species such as bacteria algae or the probably chemotropic/chemotaxic response to the signals. The analysis does not have to necessarily be done by capturing the signals but can also be done using the organisms themselves as reagents and following their chemotropic/chemotaxic response to the signals. An additional way of determining the relevant threshold (S1 ) or evaluating the intensity or effect of the required "shock" (S3) involves the knowledge of life cycles of the various microorganisms entering the system. If the individuals are in a catabolic life phase for example, a "shock" having a lesser effect on the system would be required. If the individuals are in an anabolic cycle on the other hand, a stronger "shock" is necessary.

In summary, methods for adjusting the amount of "shock" effect used in the electrochemical process in order to minimize the creation of DBP include early intervention triggered by the first stage of bio-film formation measured by bio- indicators and adjustment according to the anabolic or diabolic growth cycle of the microorganisms. Advantageously, intervention when organic load is low results into minimal formation of DBP due to lack of material to react with.

Advantageously, calculating the effect of the electrochemical process in order to document that the level of effect being used is always at minimum and theoretically possible, ensures that the release of DBP is always minimised. It is also possible to neutralise the active ingredients in the treatment to comply with regulations such as directive regulations, if necessary.

The BREF issued by the European Integrated Pollution Prevention and Control (IPPC) covering this sector specifies that the release of chemicals is to be measured at "end-of-pipe" and is usually based on treatment over a 24 hour period. "End-of-pipe" represents the output from the overall system as it leaves the factory. This means that if a very effective method such as that according to the present invention is employed quite early on in the flow there will be a lot of time for the material to be dispersed. This also means that the "shock" can be applied during night-time when electricity costs are reduced.

The present invention provides for minimising "shock" effects (and therefore the creation of DBP) by treating each stream according to its own characteristic for generating bio-film instead of the blind "one-size-fits-aH" approach currently practiced and by rotating the 'shock' when higher levels of treatment are used so that the total effect is always kept at a minimum.

The following describes a case study carried out by the present inventor. The creation of toxic byproducts including THM is a known danger of using sodium hypochlorite as a biocide which is present accepted as "Best Available Technology" (BAT). In the present case study THM is not formed in great amounts because of the lack of ammonia, which is a product of metabolism in animals and other organics. A site assessment has been planned to predict the quantity of THM in other locations and what could be designed to study the difference between the present approach and state-of-the-art. If only the natural flora and fauna are treated in quantities that have not produced much ammonia, not much THM can be produced. A system according to the invention may typically comprise several heat exchangers, although it will be appreciated that the method may be applied to a single heat exchanger. The overall characteristic of the system is the collection of cool water from areas as free from contaminants and organics as possible which is pumped into the factory to various points to cool the respective processes.

According to the invention, some many streams in the system may be treated. A stream is defined as a subdivision of the bulk flow that is pumped through ever smaller pipes and heat exchangers in the system. Each one these streams has its own characteristics. The speed of the flow, surface inside the pipe, temperature of the water, amount of heat to be picked up from the various processes and the size of the pipe all contribute to considerations of treatment.

The size of the pipes, the amount of heat exchanged, the periods of use (constantly or intermittent), the history of maintenance and direct measurement of microorganisms in and out of the system, for example, give a profile defining the treatment cycle that is indicated.

According to the executive summary of the IPPC BREF document mentioned above, ""Emissions of oxidizing biocides in open once-through systems, measured as free oxidant at the outlet, vary between 0.1 [mg FO/I] and 0.5 [mg FO/I] depending on the pattern and frequency of dosage." -see page vii of the executive summary." On page xi, it is further mentioned that "For seawater, BAT- levels of free residual oxidant (FRO) in the discharge, associated with these practices, vary with applied dosage regime (continuous and discontinuous) and dosage concentration level and with the cooling system configuration. They range from <0.1 [mg/l] to 0.5 [mg/l], with a value of 0.2 [mg/l] as 24h-average." As stated above, an objective of the present invention is to provide low dosage levels using the optimization methodology. The present inventors have recognised that this will vary from site to site thereby providing a method in accordance with the invention. More specifically, the following parameters may be used to determine when the "shock" is applied to treat the system:

1. The operation of a heat exchanger being constant or periodical. The present inventors have developed two procedures that can be evaluated according to the time when the heat exchanger is being treated. The two procedures are referred to as a 'shock' level treatment (corresponding to the operation of the heat exchanger being 'constant') and a ('background level' corresponding to the operation of the heat exchanger being 'periodical'). If the level of biofilm is in the late stage of the first phase of biofilm establishment at a particular location of on the system, a 'shock' level of treatment (i.e. high level of treatment mode) can be initiated for a few minutes to reverse the fouling process. At the same time, the level of treatment of other locations would not be in the same high level of treatment mode so that the level of treatment combined for the whole system does not exceed targeted limits. After the initial 'shock' is applied, one can be revert to using only background levels of treatment to control organic growth.

2. If the operation is periodical, the factors determining its time of use. For example, continual flow can help keep biofilm growth at lower levels while water standing still allows for more biofilm growth. The treatment prescribed may include for example a short 'shock' before operation starts after a still period, in order to prevent the early stages of biofilm growth. Knowledge of these factors may help schedule the treatment automatically, according to the treatment indicated by other parameters. 3. The rates of bio-film production according to their size and location. These rates vary throughout the year and according to temperature and nutrition available to the microorganisms. 4. The position of the treatment location on a particular node or branch of the system Since biofilm establishment is realized by the movement of individuals along the flow of a system branch or node it can be understood that the furthest location downstream in the system receives feeds from all the colonies upstream of it. The branch or node will often be smaller downstream and this gives more surface area per amount of flora and fauna wishing to colonize. For example 100 litres in a very large pipe will only have a small amount of surface which is exposed to, while 100 litres in smaller pipes will have many times the surface to form biofilm on. 5. The maintenance profile on a particular type of system. This can be indicative of historic rates of infection of a given position and size of a heat exchanger. For example, if it can be observed that a particular heat exchanger has had to be opened and cleaned often, it can be established that this system would have to have more prevention planned.

6. Other sizes of other heat exchangers operating at the same time. These may indicate the quantity of oxidants that can be generated without exceeding the permitted average level of oxidants. 7. The organism settlement rate for a given period. This relates to larvae and protozoa which "settle" into the bio-film created by the bacteria where they are protected from chemical treatment if the bio-film is too well established. Larvae have difficulty settling if there is no bio-film to settle in. 8. The projected effluent level if treatment on a particular system unit, heat exchanger begins at a given time. This relates to the total production taking place on several heat exchangers at any time and checks that starting a new treatment will not cause excess. All production is based on Faraday's constant and this can be calculated. The rate of disbursement of the oxidation material in the system depends on organic load, temperature and nature of the oxidant being produced. Only sodium hypochlorite is controlled by the biocide directive. The free radicals which are produced according to the invention last only for about half of a nanosecond.

9. The microorganisms most likely to enter in the system at a given time of the year. This is information may be included in a computer program for optimising the system. The different microorganisms have different settlings and growth characteristics. This can range from single cell protozoa to larvae of clams barnacles and other crustaceans as well as algae and diatoms. All of these represent variables which may be included in the computer program.

10. The life cycle of the individual microorganisms being anabolic or catabolic. In other words, the criteria is whether the individual microorganisms are maturing or dying.

1 1. The probable rate of multiplication of the microorganisms at a given temperature and nutrition. This parameter is part of the site characteristics where specifically the life cycle of those microorganisms identified are considered in the overall strategy of biofilm control.

12. Water temperature

13. Nutritional load. This parameter is important because, together with temperature, the amount of food available to the individuals is one of the determining factors of growth rate.

14. The placement of the colonies being sporadic or forming patterns. This is indicative of the state of establishment of the bio-film which the bacteria try to establish. The placement of the colonies within the system is an important parameter for establishing the time of treatment in order to apply a 'shock' at the optimum time and thereby stop the symbiotic process of the colonies. According to S0ren Molin BioCentrum DTU the adaptive positioning of colonies is an indication of the maturity of the development shown in Figure 2. 15. The relative economy of shock (i.e. low dosage of shock) and neutralisation within the heat exchanger. This applies to cases where a heat exchanger can be taken off line and high levels of oxidants may therefore be used. If the total quantity would cause the permitted level of emissions from the system to be exceeded, a known process such as the addition of sodium theosulphate may be used for example.

16. The environmental implications of the treatment options described above.

Figure 4 is a graph which represents the evolution of two streams as a function of time in a system according to the present invention. The entire system comprised eight streams (i.e. eight nodes). This system was monitored and the two "worse case" stream examples were selected for trials. The y axis of the graph of Figure 4 shows the number of colony forming units (CFU) of bacteria coming out of the system. This number was used to represent the status of the biofilm in the branches and pipes within the unit. Indicated on the x axis of the graph of Figure 4 are incidents where samples of the two streams were taken and the bacteria cultivated on selected agar plate.

Most of the peaks which may be observed in the graph of Figure 4 represent days where the system had been inactive for a period of time, usually a weekend. Occasionally, peaks are caused by biofilm tearing loose from the inner surfaces of the system. In this trial a "shock" level of treatment was used to flush the system then the system was rinsed and treatment level adjusted so that the water would comply with European drinking water quality directive for operation during the day. As can be seen from the graph of Figure 4, the number of bacteria colonies decreased over time, indicating a control of the biofilm. As can be seen from the graph of Figure 4, the growth in one of the streams was greater than in the other. The streams were handled with the same oxidant load. One can see that if the dosing had been adjusted to the flow and organic load, the total growth would have been lower. In this specific case the higher organic load was in the stream with the least flow, so by giving the total volume a specific level of oxidants the inventors were using too much dosing on the higher flow.

Mapping of the organic load/bio-film growth in the respective lines is provided to indicate where the greatest problem is. The mapping of the CFUs of bacteria shows progressive decrease in the level of contamination. In the case represented by Figure 4, the bacteria were incubated for 3 days to determine which species could be a problem and the treatment adjusted to that. Other methods can be used to determine which bacteria are present and what their rate of multiplication is in order to determine treatment. Since measurement of free chlorine is at end-of-pipe there is freedom in the combination of better technology and better targeting. In a similar manner to chemotherapy for treatment of cancer, this approach allows to target the treatment of identified problems very precisely without undue harm to the environment. The objective in both treatment strategies is to only apply the necessary level of active ingredients.

A rotating shock can be used to create heavy loads of oxidation agents in the lines one at a time. A rotating shock means that the pipes and heat exchangers are never all treated with heavy loads of oxidants at the same time. This means that if, for example, a "shock" is applied with only the appropriate effect for a system which is three times more efficient than dosing with sodium hypochlorite, the amount of free chlorine at end-of-pipe can be minimized. Advantageously, rotation of treatment cycles minimises DBP in order to always keep end-of-pipe measurements of free chlorine below permitted levels.

Figure 5 is a table listing exemplary standard redox potentials and reactions which may be used in the process according to the invention, as published by Millazo, G. and Caroli, S. 1978, Tables of standard electrode potentials, John Wiley and Sons, Chichester. It will be understood that results are dependent on many factors such as contents of the water, active surfaces of the reactors, and current densities amongst others. Destruction of molecules in the water being treated by free radicals created by the process, including those in the bodies of bacteria and other organisms is much faster than the addition of sodium hypochlorite, and therefore can result in a process which is three times more efficient than dosing with sodium hypochlorite. The reaction of the free radicals is typically around half of a nano second. As can be seen from the table in Figure 5 listing the standard redox potential of many of the "disinfecting substances" created in the water by the example studied, many are stronger than chlorine (Cl ₂ ).

Using one or more of the oxidants listed in the table of Figure 5 results in a treatment mixture which is much stronger and effective than common treatment chemicals which include sodium hypoclorite for example. This enabled effective treatment of the system with traditional "shock" dosage levels of 50 ppm to be reduced to 16 ppm or lower, both levels resulted in residual levels at "end-of- pipe" of approximately 2 ppm. Figure 6 indicates percentages of the overall water flow through three banks of heat exchangers (represented by columns) in a system in accordance with the present invention. The top arrow indicates the flow of cold water from the environment (sea) which is spread through the points of use (heat exchangers in each of the three banks) represented along the three columns. The bottom arrow indicates the warmed water which is being returned to the environment. As may be seen from Figure 6, the largest percentage of water flow in the system takes place in the middle heat exchanger bank represented in the central column.

Using the method according to the invention, the generation of oxidants only needs to be dimensioned for a 45.85% (19 km ³ /h) flow. If that requires, for example, applying a treatment solution of 2 parts per million for 15 minutes at intervals arrived at on, the method (as shown on Figure 3) and all production to the other flows is stopped. The overall system remains within the indicated level for approximately 50 km ³ /h. Additionally, individual stream flows in the system have individual characteristics and growth rates. When the system is properly configured, it delivers a treatment shock to an individual stream only. Once the 45% unit flow has been treated, the system could then treat the entire third bank of heat exchangers using a treatment shock which is has a smaller effect. Once the largest flow is treated, the method can be rotated to the smaller flows and the modules for the system periodically be taken out of service for maintenance.

The present invention represents a much more effective solution compared to the traditional solution taking into account the levels of oxidation substances, free radicals and sodium hypochlorite produced. By using the many variables to optimize the system, the organic growth is effectively controlled resulting in the lowest level of undesirable products in the effluent.