GB2489036A - Attached growth media element for water treatment - Google Patents

Abstract

An attached growth media element 1 for use in the treatment of contaminated water comprises a plurality of attached growth media members 5 that extend radially from an elongate core member 3. The attached growth media members are arranged helically along a longitudinal axis of the elongate core. The growth media members may comprise filaments, leaves or feathered strips. In a preferable arrangement, the growth media members are arranged in a first helical arrangement, comprising growth media leaves (205b, Fig. 4), and a second helical arrangement comprising growth media filaments (205a, Fig. 4). Suitably, the growth media members are flexible and/or resilient and may have a textured surface. Inoculants can be embedded in, or fused to, the growth media elements. The attached growth media may have alternating sections or dark coloured and light coloured attached growth media. An attached growth media system comprises a plurality of such attached growth media elements. A method of treating a body of water is also claimed.

Description

I Attached Growth Media Element 3 The present invention relates to the field of water treatment. More specifically, the present 4 invention relates to attached growth media, and in particular provides an improved attached growth media element, and filters employing such attached growth media 6 elements, suitable for use in the treatment of contaminated water, wastewater, potable 7 water, industrial water as well as polluted water bodies.

9 Background to the invention

11 Attached growth processes are well known in the field of water treatment. Attached 12 growth refers to the presence of waste-consuming bacteria and/or other organisms that (in 13 contrast to activated sludge processes where the waste-consuming bacteria grow in 14 suspension) are attached to a natural or artificial surface; the medium.

16 Attached growth processes can include breakdown and metabolism of organic matter, 17 transformation, stabilisation, and removal of nutrients and chemicals as well as reduction 18 of pathogens among other treatment processes. As the bacteria and/or attached 19 organisms break down the organic matter a biologically active film is formed on the media.

1 Eventually, as the biological film grows, portions of it slough off of the supporting surface to 2 be replaced with a new film. This sloughing is a necessary part of the process in order to 3 maintain aerobic conditions and allow water to flow through. If the media is allowed to clog 4 then anaerobic conditions may develop.

6 One advantage of attached growth media systems is that the beneficial biological 7 organisms remain relatively stable and are less subject to washing out, as can happen in 8 suspended growth treatment processes.

Typical attached growth media may comprise natural elements such as gravel, sand, 11 rocks, peat or plant roots, or artificial elements such as textiles (woven or non-woven 12 sheets or strips), engineered plastic balls, beads, chips, wafers, foam pieces etc. 13 However, known attached growth media and systems employing such known attached 14 growth media suffer from a number of disadvantages that limit their effectiveness.

16 It is therefore an object of embodiments of the present invention to obviate or mitigate one

17 or more of the disadvantages of the prior art.

19 For example, it is an object of at least one embodiment of the present invention to provide an attached growth media element that may provide high media surface area densities. It 21 is an additional object of such embodiments to achieve same while reducing instances of 22 clogging.

24 It is also an object of at least one embodiment of the present invention to provide an attached growth media element that attracts a diverse range of attached growth 26 organisms.

28 It is another object of at least one embodiment of the present invention to provide an 29 attached growth media system that is suitable for deployment in challenging applications such as high flow, suspended trash and solids, shock loads and complex pollution 31 constituents.

33 It is another object of at least one embodiment of the present invention to provide an 34 attached growth media system that may be added to an existing treatment works, without the requirement for additional apparatus.

2 Finally, it is a yet further object of at least one embodiment of the present invention to 3 provide a filter capable of operating with varying attached growth media densities.

1 Summary of the invention

3 According to a first aspect of the invention, there is provided an attached growth media 4 element for use in the treatment of contaminated water and the like, the attached growth media element comprising; 6 a plurality of attached growth media members; and 7 an elongate core member; 8 wherein the attached growth media members extend radially from the elongate 9 core member; and wherein the attached growth media members are arranged helically along a 11 longitudinal axis of the elongate core member.

13 The helical arrangement of the attached growth media members provides a number of 14 advantages. Such a configuration prevents bunching of groups of neighbouring members, which can occur if arranged in a linear fashion and be of detriment to the effective porosity 16 of the system. This also results in an improved water throughput and avoids the "warp and 17 weave" effect experienced in some conventional media elements (such as woven media) 18 which can constrict fluid flow and reduce the effective contact area between attached 19 growth and the water to be treated.

21 Furthermore, that the attached growth media members extend radially from the elongate 22 member provides additional advantages in that small suspended detritus, dead biomass or 23 waste material may freely slide or slough off of the ends of the attached growth media 24 members thus preventing entanglement or fouling by rubbish or other detritus materials that are known to pose a significant challenge in known attached growth media systems.

26 In addition, there is also provided thereby a range of densities; as will be understood the 27 density of media members is greater proximal to the elongate core member than distal 28 therefrom. Accordingly, a diversity of biological growth environments (for example, 29 denser, less dense, anaerobic, anoxic, aerobic, high flow, low flow, sheltered, exposed, etc.) are provided by which a corresponding diversity of attached growth organisms 31 (providing different treatments and/or advantages) can be accommodated in close 32 proximity to one another.

34 Optionally, the attached growth media members are arranged in a plurality of helical arrangements along a longitudinal axis of the elongate core member.

2 Providing a plurality of helical arrangements provides for multiple sets of attached growth 3 media to be disposed on a single elongate core member, further increasing the interaction 4 area between attached growth and the water to be treated, without increasing the risk of bunching.

7 Preferably, the attached growth media members comprise attached growth media leaves.

8 Alternatively, the attached growth media members comprise attached growth media 9 filaments. Yet further alternatively, the attached growth media members comprise attached growth media leaves and attached growth media filaments. Alternatively, or 11 additionally, the attached growth members comprise feathered strips.

13 Attached growth media leaves particularly lend themselves to establishing a continuous 14 helical fluid path along the length of the attached growth media element by virtue of neighbouring leaves overlapping. This is particularly advantageous for providing aerobic 16 bacteria with air, which can, for example, travel upwards through the media, tending 17 towards a helical fluid path, and substantially continually interacting with the growth media 18 surface. Of course, attached growth media filaments of suitable rigidity or resilience may 19 also provide the same effect.

21 Optionally, the attached growth media members are arranged in a first helical arrangement 22 substantially comprising attached growth media leaves and a second helical arrangement 23 comprising attached growth media filaments.

Most preferably, the attached growth media members are flexible. Flexibility allows the 26 members to move, aiding filtration and sloughing; in effect providing a self-cleaning 27 function. The members may also brush against neighbouring members of the same 28 attached growth media element or a neighbouring attached growth media element to 29 provide or enhance the self-cleaning function. Optionally, or alternatively, the attached growth media members are resilient.

32 Preferably, the attached growth media members comprise a material of substantially 33 neutral buoyancy. Optionally, the material is selected from the group comprising 34 polypropylene, polyethylene, nylon or polyester.

1 Optionally, the attached growth media members comprise a textured surface. The 2 textured surface promotes growth and aids adhesion of attached growth organisms.

4 Optionally, the attached growth media members are inoculated. Inoculation improves performance characteristics and may be effected by a mixture of one or more of bacterial, 6 mycological and enzyme, nutrient and mineral constituents. The mixture may be adjusted 7 for the particular water treatment characteristics required. Optionally, the attached growth 8 media members are infused with inoculant by spray application or submersion in an 9 inoculation tank. Alternatively, or additionally, dried inoculants are fused to the attached growth media members. Further alternatively, or additionally, inoculants are embedded in 11 the attached growth media.

13 Optionally, the attached growth media members comprise materials having a variety of 14 magnetic properties. Optionally, the attached growth media members comprise materials having a variety of ionic properties. For example, the helical arrangement of attached 16 growth media members may be arranged to provide alternating sections of anionic and 17 cationic attached growth media. A variety of material properties provides a variety of 18 conditions which will attract a corresponding variety of bacterial and biological organisms, 19 thus increasing the potential range of contaminants that can be treated.

21 Optionally, the attached growth media members comprise a plurality of different coloured 22 attached growth media. Preferably, the helical arrangement of attached growth media 23 members are arranged to provide alternating sections of dark coloured and light coloured 24 attached growth media. Variety of colour and/or contrasting light and dark sections also contribute to the desired effect of attracting a diverse range of bacterial and biological 26 organisms.

28 Most preferably, the elongate core member is flexible. Optionally, or alternatively, the 29 elongate core member is resilient.

31 A flexible and/or resilient core member provides similar benefits to those provided by 32 flexible and/or resilient attached growth media members in that the risk of clogging or 33 fouling is thereby reduced, and that the associated movement provides variable and 34 dynamic filtering conditions. It will also aid in the sloughing of detritus and the like, and 1 allow neighbouring attached growth media elements to interact. Resilience prevents 2 neighbouring elements from becoming entangled.

4 Optionally, the elongate core member exhibits a perpendicular flexibility ratio under design flow velocities of between 15% and 50% of its overall length.

7 The elongate core member may comprise a metallic material, polymer, acrylic, glass 8 reinforced plastic or other non-soluble durable material. The elongate core member may 9 comprise a plurality of materials. The composition of the elongate core member can be selected to provide a desired or predetermined flexibility and/or resilience.

12 Optionally, the elongate core member further comprises a hollow bore adapted to receive 13 an air supply, and one or more air outlets disposed on or in the elongate core member to 14 communicate air from the air supply to the attached growth media members. Air bubbles can also rise up through the media elements in a spiral fashion effected by the helical 16 arrangement of the attached growth media members. This lengthens contact time and 17 improves oxygen transfer rates, resulting in increased biological oxygen demand (BOD) 18 and chemical oxygen demand (COD) reduction and nutrient removal.

Preferably, the attached growth media element further comprises an attachment means 21 located at an end of the elongate core member. Most preferably, the attachment means is 22 adapted to allow the attached growth media element to rotate and or pivot. Examples of a 23 suitable attachment means may comprise a swivelling attachment and an articulated 24 attachment.

26 The provision of such an attachment means not only provides a means by which the 27 attached growth media element may be attached, for example to a framework from which 28 an array of same or like attached growth media elements are suspended, but provides a 29 means for said attached growth media element to move as a whole within a contaminated water body. For example, such an attachment as described herein may allow a 31 hemispherical zone of possible positions.

33 Such freedom of movement has additional benefit in open water or high throughput 34 applications in which large volumes and faster currents can be experienced, for example during seasonal storm events. The attached growth media elements (at one extreme) can 1 pivot to align substantially parallel with the current or flow which reduces the risk of surge 2 flows causing tearing, tangling, media dispersion and other detrimental effects which the

3 prior art is known to suffer from.

Optionally, the attached growth media element further comprises a weighted portion 6 located at an opposite end of the elongate core member. The weighted portion assists in 7 maintaining a vertical orientation of the attached growth media element when suspended.

9 Optionally the attachment means and/or the weighted portion is integrally formed with the elongate core member.

12 According to a second aspect of the invention, there is provided an attached growth media 13 system comprising a plurality of attached growth media elements according to the first 14 aspect.

16 Such a system may be added to an existing treatment works, without the requirement for 17 an additional containing vessel as is typically required with bead or wafer media, or a 18 bottom and top supporting structure rack as is typically required with woven or sheet 19 media. The ability to easily add attached growth media to an existing water treatment works, with minimal modification, is advantageous. Furthermore, such a system presents 21 a solution to a problem in treatment sites where loss of autotrophic nitrifiers indicates 22 necessity of more stable attached growth media.

24 Preferably, the system comprises a first configuration in which at least two of the plurality of attached growth media elements are spaced apart from one another. Such a 26 configuration may correspond to a "cleaning mode" in which the cleaning and/or aeration 27 of the attached growth media elements is made easier by said spacing.

29 Preferably, the system comprises a second configuration in which at least two of the plurality of attached growth media elements are proximal to one another. Such a 31 configuration may correspond to a "filtering mode" in which the attached growth media 32 elements form an effective curtain for filtering purposes. Optionally, in the second 33 configuration the at least two attached growth media elements are aligned such that 34 respective helical arrangements of media members are interleaved.

1 In a filtering application, preferably the attached growth media members of neighbouring 2 elements overlap by between 10% and 70% of their length.

4 Optionally, the system further comprises an aeration device to provide an air supply to one or more of the attached growth media elements. Air bubbles can rise up through the 6 media elements in a spiral fashion effected by the helical arrangement of the attached 7 growth media members. This lengthens contact time and improves oxygen transfer rates, 8 resulting in increased BOD and COD reduction and nutrient removal.

Optionally, the system further comprises an outflow tanks to receive processed water.

12 Preferably, the elements are removeably attached within the system. This allows 13 individual elements to be removed, inspected and (if necessary) replaced. The 14 removeable attachment may comprise a swivelling attachment, articulated attachment, or a cylindrical mounting plate having an eyelet.

17 Embodiments of the second aspect of the invention may include one or more features of 18 the first aspect of the invention or its embodiments, or vice versa.

According to a third aspect of the present invention, there is provided a method of treating 21 a body of water comprising the step of installing an attached growth media system of the 22 second aspect within, or in fluid communication with, the body of water.

24 Optionally, the method comprises the step of flowing water to be treated through the attached growth media system.

27 Optionally, the method comprises the step of varying an effective density of attached 28 growth media by varying the position (and hence the separation/overlap) of the attached 29 growth media elements.

31 Optionally, the method comprises the step of performing a first treatment cycle in which 32 the attached growth media elements are closely packed. This provides a small pore or 33 dense bio-filtration stage.

1 Optionally, the method comprises the step of performing a second treatment cycle in which 2 the attached growth media elements are spaced apart. This allows a flushing and 3 cleaning process in which filtered material may slough off the ends of the media members.

Optionally, the method further comprises the step of aerating the attached growth media.

7 Embodiments of the third aspect of the invention may include one or more features 8 corresponding to features of the first and second aspects of the invention or its 9 embodiments, or vice versa.

1 Brief description of the drawings

3 There will now be described, by way of example only, various embodiments of the 4 invention with reference to the drawings, of which: 6 Figure 1 provides a side view of an attached growth media element in accordance with an 7 embodiment of the present invention; 9 Figure 2 provides a top-down view of the attached growth media element shown in Figure 1; 12 Figure 3 provides a side view of two attached growth media elements in accordance with 13 an alternative embodiment of the present invention; Figure 4 provides a side view of an attached growth media element in accordance with a 16 further alternative embodiment of the present invention; 18 Figure 5 provides a side view of a plurality of attached growth media elements within a 19 flowing body of water; 21 Figure 6 provides a side view of a closely spaced arrangement of attached growth media 22 elements providing a filter curtain; and 24 Figure 7 provides a cross-sectional schematic side view of an attached growth media system in accordance with a yet further alternative embodiment of the present invention, 26 shown in (a) a first configuration in which the elements are spaced and (b) a second 27 configuration in which the elements are compressed.

1 Detailed description of preferred embodiments

3 Figure 1 provides a side view of an attached growth media element 1 which can be seen 4 to comprise an elongate central member or core 3 upon which are disposed a number of filaments 5. These filaments 5 comprise the attached growth media and are arranged, in 6 this embodiment, in a pair of helical arrangements 7,9 that extend along the length of the 7 elongate central member 3.

9 (It will be readily understood that a single helical arrangement or indeed three or more helical arrangements may be employed without deviating from the scope of protection 11 defined by the appended claims).

13 The filaments 5 are fixed to the elongate central member 3 at a first end 11, and are free at 14 the opposite end 13 (more clearly visible in the top-down view of Figure 2). This allows small suspended detritus, dead biomass or waste material to freely slide off the loose end, 16 a.k.a. sloughing, preventing entanglement or fouling by rubbish or filamentarous detritus 17 materials which is a particular problem with attached growth media systems of the prior 18 art. Thus the attached growth media element 1 is provided with a self-cleaning 19 mechanism. In addition, the filamentary nature of the attached growth media 5, being for example non-woven and non-branching, allows for high attached growth media densities 21 without risk of clogging with solids.

23 The filaments 5 can be affixed to the elongate central member 3 by a variety of suitable 24 means. For example, they may be affixed by means of direct binding or winding within two or more twisted core elements or by waterproof adhesives. The filaments 5 may be made 26 of long lasting materials of substantially neutral buoyancy, such as polypropylene, 27 polyethylene, nylon or polyester for example.

29 As evident in Figure 2, the filaments 5 are denser proximal 11 to the elongate central member 3, and less dense at their distal ends 13. This provides a range of media density 31 that in turn provides an important diversity of biological growth environments. For 32 example, more robust and aerobic organisms may favour the distal 13 (i.e. less dense) 33 ends of the filaments 5 and more delicate organisms may favour the inner 11 more 34 protected and more densely packed ends of the filaments 5. This feature presents the opportunity for autotrophic and heterotrophic organisms and dependent water treatment 1 process to occur and take place simultaneously in close proximity within each media 2 element 1 and any system in which such elements are employed.

4 The helical arrangement prevents the attached growth media filaments 5 from forming bunches that would reduce the flow through and porosity of the media, and allows a high 6 flow throughput of water. Similarly, the helical arrangement avoids the undesirable warp & 7 weft effect of woven media which can also constrict the flow of water reducing the amount 8 of contact surface area between attached growth organisms and the water being treated.

It is envisaged that the helical arrangements may also include sections or strips of 11 impermeable membrane, geotextile, or plastic mesh to enhance the form, structure and 12 surface area of the media, and/or complement the helical arrangement.

14 Individual filaments 5 may be comprised of single strands (as illustrated) or crimped lengths of continuous filament (not shown). Advantageously, the filaments 5 are provided 16 with a textured surface area to assist in the adhesion and growth of attached growth 17 organisms. As stated above, the filaments 5 are affixed to the core in a helical 18 arrangement, conducive to even distribution of attached growth and at all sides, and a 19 consistent friction and self-cleaning effect (see below) throughout the element 1. This configuration allows very high surface areas to be possible (for example, ranging from 21 100 m2/m3 up to over 1000 m2/m3).

23 The elongate central member 3 of this embodiment is semi-rigid, i.e. flexible and/or 24 resilient, and thus provides a predetermined range of mobility without causing entanglement of filaments 5. The elongate central member 3 advantageously has a 26 lateral/horizontal flexibility ratio under design flow velocities of 15% to 50% of its overall 27 length. It is envisaged that elements I according to the invention may have an effective 28 length ranging from a fraction of a meter up to and greater than five meters.

As the length of the element increases the diameter of the central member 3 generally 31 increases to maintain a desired flexibility ratio. Central member 3 materials may typically 32 be metallic, poly, or acrylic, or glass re-enforced plastic or other non-soluble durable 33 material. The central member 3 may be constructed of a single or multiple core materials, 34 to achieve the desired flexibility and/or resilience.

1 When disposed in an array, individual media elements I in the array will come in to contact 2 with neighbouring elements in which case they may bend; however the resilience of the 3 central member 3 prevents the elements from wrapping around each other. In this way a 4 continuous movement in the media may be accommodated without the risk of entanglement.

7 The flexibility of the central member 3 may allow the element to be both strong and light, 8 and able to cope with high flow velocities, such as may be found in an open water system 9 or variable flow water treatment facilities. Thus, problems associated with prior art attached growth media elements (such as those incorporating sheets or strips of textiles or 11 curtains which can become entangled or tear; or plastic pellets, wafers or balls, which are 12 prone to media loss) are overcome.

14 The attached growth media element I is also provided with a connection means 15 by which it can be suspended from a structure to which it is connected (for example an 16 attached growth media system as shown in Figure 7 and described below). In this case, 17 the connection means 15 comprises a swivelling top piece which allows the media element 18 1 to rotate and pivot within a hemispherical zone of possible movement (a 2rr solid angle) 19 with respect to the connection point.

21 That the element 1 is thereby provided with freedom to move presents an additional 22 benefit where faster currents can be experienced, for example in open water 23 bioremediation applications and/or in seasonal storm events. High flows rates have posed 24 significant problems for attached growth media systems of the prior art which may experience tearing, tangling and dispersion of media and system and media components.

27 To overcome these problems, the flexibility and freedom of movement provided by the 28 fixing method of this embodiment of the present invention allows increased velocity flows 29 (for example > 3m/second) to displace the elements I (see Figure 5 for example in which fluid flow A displaces a plurality of like elements 1). If the current is sufficiently strong, the 31 elements I may become substantially parallel to the flow, effectively folding them upwards 32 and out of the way. This for example would allow surge flows to pass smoothly under the 33 array of folded up elements I with limited drag resistance and minimal risk of damage to 34 the elements I and the media comprised therein. Similarly in high flow instances, the 1 flexible attached media members 5 are swept in to a stream lined configuration, allowing 2 currents to pass by and detritus to brush off easily 4 The combination of a flexible/resilient central member 3, movement of the element I as a whole and flexibility of individual growth media filaments 5 provide variable and dynamic 6 conditions which resemble natural filtration forms. These features prevent the system from 7 clogging or fouling. It is known that sloughed solids can present a considerable challenge 8 for attached growth media systems, however the flexibility and movement possible in this 9 embodiment of the present invention allows a continuous gentle self-cleaning process as the media filaments 5 and elements I themselves may sway in a current and brush 11 against each other (filaments against neighbouring filaments and elements against 12 neighbouring elements) by which action accumulated solids are loosened and dead 13 attached growth organisms can be brushed free in a continual process of gentle cleaning 14 and renewal of the attached growth media.

16 As each media element I may be affixed solely at the top (or solely at the bottom), as the 17 element I swivels, rotates or otherwise moves about the connection means 15, any large 18 suspended detritus or waste materials that might otherwise become lodged in the element 19 1 can freely brush off of the end of the media element I as it moves in the water.

21 A weighted end piece 17 helps maintain a vertical orientation of the media element I when 22 suspended, and provides a degree of resistance to displacement of the media element I 23 when situated in a moving body of water.

An alternative embodiment of the present invention is illustrated in Figure 3 (like reference 26 numerals indicating like features). There is provided an attached growth media element 27 101 which can be seen to comprise an elongate central member or core 103 upon which 28 are disposed a number of leaves 105. These leaves 105 comprise the attached growth 29 media and as per the previous embodiment are arranged in a pair of helical arrangements 107,109 that extend along the length of the elongate central member 103.

32 The leaves 105 are in contrast to the filaments 5 of the previously described embodiment.

33 The provision of leaves 105, being flattened and having a larger surface area per 34 individual element, than the corresponding filaments 5, lend themselves particularly to providing continuous helical flow paths (indicated generally by arrows B) along the length 1 of the element 101 (although it will be understood that such flow paths are possible with 2 the previously described embodiment).

4 The flow paths B provide a means by which air can be communicated from the bottom of the element 101 to the top, thereby providing an air supply to substantially all of the 6 attached growth provided upon the element 101. In use, air bubbles may rise up through 7 the attached growth media in a corresponding helical motion, providing extensive contact 8 time and thereby increased oxygen transfer rates, resulting in increased biological oxygen 9 demand, chemical oxygen demand reduction, and nutrient removal.

11 Figure 4 illustrates a further alternative embodiment of the present invention, in which the 12 attached growth media element 201 is provided with attached growth media members in 13 the form of both filaments 205a and leaves 205b. Such an embodiment of the present 14 invention allows the advantages of both the filamentary element I and the leaved element 101 within a single element 201, as well as providing increased attached growth diversity.

17 Figure 6 illustrates a closely spaced array of attached growth media elements I arranged 18 to providing a filter for the treatment of water. The individual helical arrangements 19 (examples 7 and 9 indicated) can be seen to overlap to provide a dense filter. It will also be apparent that by varying the overlap or separation of neighbouring elements 1, such an 21 array also provides options for variable density filtering.

23 Where a dense filter is required, the array may be arranged so the individual elements 24 overlap by, say 10% to 75%, providing a dense biological matrix of filaments (alternatively leaves, or leaves and filaments). Where a less dense filter is required, the array may be 26 arranged to provide a greater separation between neighbouring elements 1.

28 Figure 7 shows a cross-sectional schematic side view of an attached growth media system 29 300 for the treatment of wastewater flow within a water treatment facility or within a body of water. Several elements 301 (which may correspond to elements 1, 101, 201 or other 31 element within the scope of the present invention) are disposed within the system, 32 suspended within a vessel of water. Figure 7a shows a first configuration in which the 33 elements 301 are spaced apart, while Figure 7b shows a second configuration in which the 34 elements 301 are closely packed. An overflow tank 304 is provided to receive filtered water.

2 In use the system may be installed in a new or existing water treatment facility or in a 3 body of water, and may be provided with a lateral flow to effect bio-filtration of solids and 4 particulate contaminants within the water body. In the configuration of Figure 7(b) the array of elements 301 provides a filter comparable to a vertically oriented horizontal flow 6 biofilter with an overlapping filter matrix, achieving a attached growth version of a 7 membrane bio-reactor, where the water to be cleaned is to be passed through overlapping 8 attached growth media rather than a membrane. An array support structure is arranged so 9 as to allow variation of the density of the elements (and hence attached growth media).

Accordingly, during an active treatment cycle the array of elements 301 may be packed 11 tightly together providing a small pore or dense bio-filtration stage (as per Figure 7(b)) and 12 during a cleaning cycle the elements 301 may be separated (as shown in Figure 7(a)) 13 allowing a flushing and cleaning process, allowing filtered material to slough of the ends of 14 the media strands and settle to the bottom of the reactor where they may be digested, or removed.

17 Aeration systems may be integrated with the media system 300, either through a aeration 18 device in close proximity to the elements 301 or through an air supply line extending 19 through individual core members (e.g. by a combination of conduits or throughbores and one or more outlets). Alternatively a compressed water flow draft tube and Venturi jet may 21 be integrated with the core members, for the supply of air. In use, bubbles rise up through 22 the media (illustrated figuratively by arrows 306) providing the various effects and 23 advantages previously described. Aeration may form part of the flushing and cleaning 24 process.

26 Performance characteristics of the media elements of the present invention may be 27 increased by inoculation -for example with a pre-treatment of the media members in a 28 blend of bacterial, mycological and enzyme, nutrient and mineral constituents which may 29 be adjusted for the water treatment characteristics of each application site. The filaments (or leaves, or feathered leaves) may be infused by spray application or submersion in an 31 inoculation tank. Dried inoculants may be fused to the attached growth media by passing 32 the filaments or leaves through a closed chamber filled with a turbulent heated cloud of 33 dried inoculants, by which process the heated inoculants stick to the media and form a 34 long lasting bond. Inoculants may alternatively be blended with the raw material of the attached growth media effectively embedding the inoculants within the filaments or leaves.

2 The growth media may be composed of materials having a plurality of magnetic and/or 3 ionic properties. This diversity of material properties establishes conditions attractive to 4 different bacterial and biological groups. Alternating sections of anionic and cationic media members increases the biological diversity of attached growth organisms attaching 6 themselves to the media and enhances the range of contaminants which may effectively 7 be treated.

9 Similarly, the growth media may also provide colour contrasts, which further contribute to the diversity of bacteria and biological organisms, further enhancing treatment efficacy. For 11 example, alternating sections of dark and light coloured media may be provided.

12 Embodiments of the present invention may include sections of dark brown or black 13 filaments or leaves alternating with sections of white or light brown filaments or leaves.

14 Use of contrasting colours within the media provides for a diversity of attached growth organisms. In another example, alternating red and green or purple and yellow 16 arrangements of media establish preferable growth sections for different bacteria.

18 Both colour contrast and ionic contrast are advantageously included in sections of media 19 or alternatively along individual filaments or leaves. Particular embodiments alternate both contrasting colour as well as opposing ionic properties so as to attract the greatest 21 diversity of attached growth treatment bacteria and achieve the greatest range of 22 treatment capability.

24 The invention provides an improved attached growth media element suitable for use in the treatment of contaminated water, wastewater, potable water, industrial water as well as 26 polluted water bodies. The attached growth media element comprises a plurality of 27 attached growth media members that are arranged helically on an elongate core member 28 and extend radially therefrom. Benefits include reduced bunching of members, improved 29 water throughput, increased effective contact area between attached growth and water to be treated, and reduced risk of fouling. In addition, the elements provide a diversity of 31 biological growth environments by which a corresponding diversity of attached growth 32 organisms can be accommodated. An attached growth media system comprising a 33 plurality of such attached growth media elements provides varying filtering densities and 34 may be added to an existing treatment works without the requirement for additional apparatus. Corresponding methods are also provided.

2 The nature of the elements disclosed herein overcomes the many and varied challenges of 3 providing hardy and efficient attached growth media and greatly expands the range of 4 applications in which attached growth media can be effectively employed.

6 The foregoing description of the invention has been presented for the purposes of 7 illustration and description and is not intended to be exhaustive or to limit the invention to 8 the precise form disclosed. The described embodiments were chosen and described in 9 order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and 11 with various modifications as are suited to the particular use contemplated. Therefore, 12 further modifications or improvements may be incorporated without departing from the 13 scope of the invention herein intended.