WO2018184057A1

WO2018184057A1 - Water biotreatment unit

Info

Publication number: WO2018184057A1
Application number: PCT/AU2018/000038
Authority: WO
Inventors: John David West; Mark John Smith; Akheel SULTAN
Original assignee: Biogill Environmental Pty Limited
Priority date: 2017-04-07
Filing date: 2018-03-20
Publication date: 2018-10-11

Abstract

A water biotreatment unit (100) has a housing (110) defining primary and secondary treatment regions (130) and a secondary treatment region (230). Primary and secondary reservoirs (131, 231) are defined by a lower portion of the primary and secondary treatment regions (130, 230) respectively. The secondary reservoir (231) communicates with the primary reservoir (131) such that, in use, water being treated flows from the primary reservoir (131) to the secondary reservoir (231). Primary and secondary arrays (150, 250) of biotreatment membranes (151) are suspended in the primary and secondary treatment regions (130, 230) above the primary and secondary reservoirs (131, 231) respectively. Each of the biotreatment membranes (151) carries a biomass culture and is draped over, and supported by, a hanger (152) to define two opposing membrane walls each extending downwardly from the hanger (152). Primary and secondary recirculation systems are configured to pump water being treated from the respective reservoir (131, 231) into a flow distribution system (180, 280) disposed above the respective array (150, 250) of biotreatment membranes (151) to distribute the water over the respective array (150, 250) of biotreatment membranes (151). An influent inlet supplies water to be treated to the primary treatment region (130) and an effluent outlet (232) removes treated water from the secondary treatment region (230).

Description

WATER BIOTREATMENT UNIT

Field of the Invention

[0001] The present invention relates to the field of biotreatment of water, such as waste water and aquaculture water, and particularly relates to a water biotreatment unit.

Background

[0002] Various forms of bioreactor are known for treating waste water, utilising biomass cultures to absorb waste nutrients from the waste water. Membrane bioreactors generally utilise permeable membranes carrying a biomass culture that is exposed to the waste water to be treated and oxygen, which is required for the biomass culture to treat the waste water to remove waste nutrients from the same. One form of such a membrane bioreactor form of water biotreatment is described in International (PCT) Publication No. WO 2015/161335. The water biotreatment unit of WO 2015/161335 is particularly suited to batch operations, in which waste water to be treated is recycled back through the unit potentially multiple times, until the waste concentration reaches a desirable level.

Object of the Invention

[0003] It is an object of the present invention to provide a water biotreatment unit that is suitable for continuous, as opposed to batch, operation.

Summary of Invention

[0004] The present invention provides a water biotreatment unit comprising:

a housing defining a primary treatment region and a secondary treatment region;

a primary reservoir defined by a lower portion of said primary treatment region;

a secondary reservoir defined by a lower portion of said secondary treatment region, said secondary reservoir communicating with said primary reservoir such that, in use, water being treated flows from said primary reservoir to said secondary reservoir;

a primary array of biotreatment membranes suspended in said primary treatment region above said primary reservoir;

a secondary array of biotreatment membranes suspended in said secondary treatment region above said secondary reservoir;

each of said biotreatment membranes of said primary and secondary arrays carrying a biomass culture and being draped over, and supported by, a hanger to define two opposing membrane walls each extending downwardly from said hanger;

a primary recirculation system configured to pump water being treated from said primary reservoir into a primary flow distribution system disposed above said primary array of biotreatment membranes to distribute the water over said primary array of biotreatment membranes;

a secondary recirculation system configured to pump water being treated from said secondary reservoir into a secondary flow distribution system disposed above said secondary array of biotreatment membranes to distribute the water over said secondary array of biotreatment membranes;

an influent inlet for supply of water to be treated to said primary treatment region; and an effluent outlet for removal of treated water from said secondary treatment region.

[0005] In a preferred form, said housing comprises a floor, longitudinally opposing first and second end walls, laterally opposing first and second side walls and a dividing wall extending upwardly from said floor and extending longitudinally between said first and second end walls, said dividing wall dividing a lower portion of said housing into said primary reservoir and said secondary reservoir.

[0006] In a preferred form, said dividing wall defines a weir communicating said primary reservoir with said secondary reservoir for overflow of water being treated from said primary reservoir to said secondary reservoir.

[0007] In one form, said effluent outlet is located at a level lower than said weir.

[0008] In a preferred form, said floor slopes downwardly towards said second end wall.

[0009] In a preferred form, said housing further comprises a primary sludge outlet extending from said primary reservoir adjacent said floor through said second end wall and a secondary sludge outlet extending from said secondary reservoir adjacent said floor through said second end wall. [0010] In a preferred form, said housing defines a waterproof tank extending from said floor to above said primary and secondary arrays of biotreatment membranes, said unit being configured to flood said tank for cleaning of said biotreatment membranes.

[0011] In a preferred form, said unit further comprises a scour air system located in each of said primary and secondary treatment regions, each said scour air system comprising a perforated scour air line located below said biotreatment membranes, said scour air system being configured to supply air bubbles to said tank when flooded for scour air cleaning of said biotreatment membranes.

[0012] In a preferred form, said housing has a plurality of air vents located above said primary and secondary reservoirs at a level below said biotreatment membranes and each extending through one of said walls of said housing.

[0013] In one form, said unit further comprises a plurality of channels each communicating with one of said air vents and extending to an opening of said channel located at a level above said biotreatment membranes.

[0014] In a preferred form, said influent inlet is located in said primary recirculation system, such that, in use, water to be treated is supplied to said primary treatment region via said primary flow distribution system.

[0015] In a preferred form, said primary recirculation system communicates with said primary reservoir via a primary reservoir outlet, said primary reservoir outlet being located through or adjacent said first end wall.

[0016] In a preferred form, said secondary recirculation system communicates with said secondary reservoir via a secondary reservoir outlet, said secondary reservoir outlet being located through or adjacent said first end wall.

[0017] In a preferred form:

said primary flow distribution system comprises a primary flow distribution manifold coupled to said primary recirculation system and a plurality of primary spray assemblies arranged above said primary array of biotreatment membranes, and

said secondary flow distribution system comprises a secondary flow distribution manifold coupled to said secondary recirculation system and a plurality of secondary spray assemblies arranged above said secondary array of biotreatment membranes.

[0018] In a preferred form, said unit comprises a plurality of cartridges removably mounted in each of said primary and secondary treatment regions, each said cartridge comprising a cartridge frame and a set of said biotreatment membranes suspended from said cartridge frame.

[0019] In one form, each said scour air system comprises a perforated scour air line mounted to each said cartridge frame and a scour air manifold in fluid communication with each said scour air line.

[0020] In a preferred form, said unit further comprises a structural outer frame, said housing being mounted within said structural outer frame, said structural outer frame having a plurality of corner blocks each configured to engage a twist lock for handling of said unit.

Brief Description of Drawings

[0021] Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings wherein:

[0022] Figure 1 is an isometric view of a water biotreatment unit;

[0023] Figure 2 is an isometric view of the water biotreatment unit of Figure 1 with lids removed from the housing;

[0024] Figure 3 is a plan view of the water biotreatment unit Figure 1 with the lids removed from the housing;

[0025] Figure 4 is a cut away isometric view of the water biotreatment unit of Figure 1 with the lids removed from the housing;

[0026] Figure 5 is a first end elevation view of the water biotreatment unit of Figure 1; [0027] Figure 6 is a second end elevation view of the water biotreatment unit of Figure 1; [0028] Figure 7 is a cross-sectional side elevation view of the water biotreatment unit of Figure i ;

[0029] Figure 8 is a cross-sectional end elevation view of the water biotreatment unit of Figure i ;

[0030] Figure 9 is a sectioned end isometric view of the water biotreatment of Figure 1;

[0031] Figure 10 is a sectioned isometric view of the housing and flow distribution systems of the water biotreatment unit of Figure 1;

[0032] Figure 11 is an isometric view of the housing of the water biotreatment unit of Figure 1;

[0033] Figure 12 is a sectional side elevation view of the housing of Figure 11;

[0034] Figure 13 is an isometric view of a cartridge frame of the water biotreatment unit of Figure 1;

[0035] Figure 14 is a detail view of part of a hanger of the cartridge frame of Figure 13.

[0036] Figure 15 is a simplified flow circuit diagram of the biotreatment unit of Figure 1;

[0037] Figure 16 is a detailed flow circuit diagram of the biotreatment unit of Figure 1;

[0038] Figure 17 is an isometric view of a cartridge incorporating an alternate form of scour air system;

[0039] Figure 18 is an isometric view of the cartridge frame of the cartridge of Figure 17 and scour air manifold.

Description of Embodiments

[0040] Figures 1 to 9 depict a water biotreatment unit 100 according to an exemplary embodiment. The water biotreatment unit 100 comprises a housing 110 defining a primary treatment region 130 and a secondary treatment region 230, as best shown in Figures 2, 3, 8 and 9. Referring to Figures 8 and 9, a primary reservoir 131 is defined by a lower portion of the primary treatment region 130. A secondary reservoir 231 is defined by a lower portion of the secondary treatment region 230. The secondary reservoir 231 communicates with the primary reservoir 131, as will be further described below, such that, in use, water being treated flows from the primary reservoir 131 to the secondary reservoir 231. A primary array 150 of biotreatment membranes 151 is suspended in the primary treatment region 130 above the primary reservoir 131. A secondary array 250 of biotreatment membranes 151 is suspended in the secondary treatment region 230 above the secondary reservoir 231. In Figures 2 to 4, only a small number of the biotreatment membranes 151 are shown for clarity purposes. A primary recirculation system (not shown in Figures 1 to 9) is configured to pump water being treated from the primary reservoir 131 into a primary flow distribution system 180 disposed above the primary array 150 of biotreatment membranes 151 to distribute the water over the primary array 150 of biotreatment membranes 151. Similarly, a secondary recirculation system (not shown in Figures 1 to 9) is configured to pump water being treated from the secondary reservoir 231 into a secondary flow distribution system 280 disposed above the secondary array 250 of

biotreatment membranes 151 to distribute the water over the secondary array 250 of

biotreatment membranes 151. An influent inlet (not depicted in Figures 1 to 9) supplies influent water to be treated to the primary treatment region 130, via the primary flow distribution system 180. An effluent outlet 232 removes treated effluent water from the secondary treatment region 230.

[0041] Each of the biotreatment membranes 151 of the primary and secondary arrays 150, 250 carries a biomass culture and is draped over, and supported by, a hanger 152 (best seen in Figure 9) to define two opposing membrane walls each extending downwardly from the hanger 152. Each draped biotreatment membrane 151 defines two opposing membrane walls extending downwardly from the hanger 152. Each biotreatment membrane 151 may be formed into a loop by stitching the opposing ends of a 4 m x 1 m biotreatment membrane together part way along the ends, leaving an opening at the base of the loop for water and excess decaying biomass, in the form of a sludge, to pass through. In the configuration depicted, the biotreatment membranes 151 of both the primary and secondary arrays 150, 250 are arranged in a series of cartridges 160. Each cartridge 160 comprises a cartridge frame 161 (best seen in Figures 10 and 13) and a set of biotreatment membranes 151 suspended in each cartridge frame 161 as will be further discussed below. In various configurations, there will typically be between 40 and 80 biotreatment membranes 151 in each cartridge 160, and in the specific embodiment depicted there are a set of 65 biotreatment membranes 151 in each cartridge 160, one draped over each hanger 152 (although in Figures 2 to 4, several cartridges 160 are depicted without any biotreatment membranes 151 for clarity purposes). A spacer (not depicted) extends between the opposing membrane walls of each biotreatment membrane 151 to thereby space the membrane walls of each biotreatment membrane 151. This provides an air gap between each of the membrane walls of each biotreatment membrane 151 for air flow therebetween. Forming each biotreatment membrane 151 in a loop helps to keep the membrane walls taut, due to the mass of water and biomass caught in the base of the loop before passing out of the opening in the base.

[0042] Each biotreatment membrane 151 carries a biomass culture for treating water to be treated passing downwardly through the primary or secondary treatment region 130, 230 between adjacent biotreatment membranes 151. The outwardly facing surfaces of adjacent membrane walls of adjacent biotreatment membranes 151 will either be closely spaced, or touching, providing for restrained vertical flow of water down the biomass culture laden membrane walls. The biotreatment membrane 151 and biomass culture are typically that described in International (PCT) Publication No. WO 2007/056818, the entire contents of which are expressly incorporated herein by cross-reference. The biotreatment membrane 151 may be in the form of a permeable, porous and flexible nano ceramic terephthalate membrane, allowing diffusion of oxygen and soluble waste nutrients through the membrane. The biomass culture may comprise bacteria and fungi and may be carried by the biotreatment membrane 151 in the form of a biofilm on the outwardly facing surface (the liquid face) of each membrane wall, and a biofilm on the inwardly facing surface (the gas face) of each membrane wall. The biomass culture acts on a liquid/gas interface, growing through the membrane wall to draw oxygen from the gas face and feeding on nutrients in the water to be treated from the liquid face.

[0043] The housing 110 of the water biotreatment unit 100 of the exemplary embodiment is typically formed of steel and is in the general form of a rectangular prism, having longitudinally opposing first and second end walls 111, 112 and laterally opposing first and second side walls 113, 114. Referring to Figure 4, the housing also has a base 115 and a floor 116 that is supported above the base 115 and slopes downwardly toward the second end wall 112. As best shown in Figures 8 to 10, a dividing wall 117 extends upwardly from the floor 116 and extends longitudinally between the first and second end walls 111, 112. In the embodiment depicted, the dividing wall 117 is located centrally between the first and second side walls 113, 114 and divides a lower portion of the housing 110 into the primary reservoir 131 and secondary reservoir 231. The primary reservoir 131 is bounded by the first and second end walls 111, 112, the first side wall 113 and the dividing wall 117. The secondary reservoir 231 is bounded by the first and second end walls 111, 112, the second side wall 114 and the dividing wall 117. As best seen in Figure 8, as well as sloping toward the second end wall 112, the floor 116 slopes from each of the first and second side walls 113, 114 toward the dividing wall 117. As a result, excess biomass / sludge collecting on the floor 116 within the primary and secondary reservoirs 131, 231 tends to migrate toward the second end wall 112 adjacent the dividing wall 117.

Primary and secondary sludge outlets 133, 233 extend from the primary and secondary reservoirs 131, 231 respectively, adjacent the floor 116 and dividing wall 1 17, through the second end wall 112. The primary and secondary sludge outlets 133, 233 are used to remove sludge collected in the primary and secondary reservoirs 131, 231.

[0044] Laterally extending forklift pockets 118, best depicted in Figure 4, are formed between the base 115 and floor 116 and extend through corresponding openings in each of the first and second side walls 113, 114 of the housing 110. The forklift pockets 118 are configured to receive the tynes of a forklift for lifting and maneuvering of the biotreatment unit 100.

[0045] Each of the side walls 113, 114 and end walls 111, 112 is stiffened by an array of upright stiffening channels 119 and horizontal stiffening bars 120. The stiffening channels 119 are each hollow and define a hollow vent with the wall to which they are fixed, communicating the interior of the housing 110 with the exterior of the housing 110 via a vent outlet 121 (best depicted in Figures 11 and 12) extending through the respective wall. The stiffening channels 119 fixed to the first side wall 113 communicate the primary treatment region 130 with the exterior of the housing 110, whilst the stiffening channels 119 fixed to the second side wall 114 communicate the secondary treatment region 230 with the exterior of the housing 1 10. Each of the vents 121 is located above the primary and secondary reservoirs 131, 231 at a level below the biotreatment membranes 151. The top end of each of the stiffening channels 119 defines an opening 122 (as best shown in Figure 2) on the exterior of the housing 110. The stiffening channels 119 and vents 121 thus provide for ventilation of the biotreatment membranes 151 from below during operation, as will be discussed below.

[0046] Referring to Figures 11 and 12, the interior of the housing 110 is divided into several vertically extending compartments 125 by an array of longitudinally spaced uprights 123 extending upwardly from the dividing wall 117, a longitudinally extending divider rail 124 extending from the first end wall 111 to the second end wall 112, between the first and second treatment regions 130, 230 adjacent the upper opening of the housing 110, and a series of cross members 126 extending laterally from the divider rail 124 to the respective first and second side walls 113, 114. In the arrangement depicted, five compartments 125 are defined in each of the primary and secondary treatment regions 130, 230. Each compartment 125 is sized to receive one cartridge 160 having a set of biotreatment membranes 151. As best shown in Figures 8 and 9, a series of cartridge supports 127 are fixed to the first and second walls 113, 114 and the dividing wall 117 to support the cartridges 160 in each compartment 125 above the primary and secondary reservoirs 131, 231, such that the biotreatment membranes 151 are spaced above the primary and secondary reservoirs 131, 231.

[0047] Referring back to Figure 1, the housing 110 further comprises a series of ten separate lids 128, with one lid 128 being provided for each compartment 125. The lids 128 are separately removable for inspection of each compartment 125 and are supported by the walls of the housing 110, the dividing rail 124 and the cross members 126. In the embodiment depicted, two of the lids 128 house reversible fans 129 to increase ventilation airflow through the primary and secondary treatment regions 130, 230 as desired.

[0048] The housing 110 is mounted within a steel structural outer frame 105 sized and configured to generally correspond to a standard ISO shipping container. In the embodiment depicted the outer frame 105 is sized and configured to correspond to a standard ISO 20 foot shipping container, having overall dimensions of 5900 mm length by 2350 mm width by 2390 mm height. The outer frame 105 is provided with standard ISO corner block 106 at each of its corners, for engaging with standard twist lock mechanisms both for lifting the biotreatment unit 100 with standard shipping container handling equipment and for locking the biotreatment unit 100 to a support surface or other biotreatment unit 100 during transportation.

[0049] As best depicted in Figures 9 and 10, the primary reservoir 131 communicates with the secondary reservoir 231 by way of a weir 134 formed in the dividing wall 117 toward the second end wall 112 of the housing 110. The weir 134 is in the form of a cutout with a depth of approximately 50 mm formed in the top edge of the dividing wall 117. In use, as will be discussed below, when the primary reservoir 131 fills to the level of the weir 134, waste water being treated flows from the primary reservoir 131 into the secondary reservoir 231. The effluent outlet 232 extends from the secondary treatment region 230 through the second end wall 112 at a level lower than the bottom edge of the cutout defining the weir 134. Accordingly, during steady state operation, the depth of the primary reservoir 131 is defined by the level of the lower edge of the weir 134, which in the embodiment depicted is located approximately 500 mm above the lowest point of the floor 116. The depth of the secondary reservoir 231 is defined by the level of the effluent outlet 232. The maximum water level in the secondary reservoir 231 therefore remains lower than the maximum water level in the primary reservoir 131, thereby preventing water being treated in the secondary reservoir 231 from flowing back into the primary reservoir 131.

[0050] As will be discussed further below, influent waste water to be treated is typically supplied to the primary treatment region 130 through an influent inlet located in the primary recirculation system, via the primary flow distribution system 180 such that influent waste water being treated is initially processed through the primary array 150 of biotreatment membranes 151 before reaching the primary reservoir 131. Additionally, or alternatively, an influent inlet 135 may be provided to supply water to be treated directly to the primary reservoir 131. In the embodiment depicted, an influent inlet 135 extends through the first end wall 111 of the housing 110 into the primary reservoir 131. Each of the first and second end walls 111, 112 of the housing 110 is also provided with an emergency overflow port 136, adjacent the top of each of the end walls 111, 112, above the level of the biotreatment membranes 151. Instrument ports 138, 238 also extend through the second end wall 112 into the primary and secondary reservoirs 131, 231 respectively for instruments monitoring conditions in the primary and secondary reservoir 131, 231, such as temperature.

[0051] The housing 110 defines a waterproof tank extending from the floor 116 to above the primary and secondary arrays 150, 250 of biotreatment membranes 151. The floor 116, first and second end walls 111, 112 and first and second side walls 113, 114 form the waterproof tank. Whilst the side walls 113, 114 are perforated with vent outlets 121, the stiffening channels 119 with which the vent outlets 121 communicate are sealed to the respective wall up to the level of the opening 122 at the top of each of the stiffening channels 119, which is located above the level of the top of the biotreatment membranes 151. The housing 110 can thus be flooded, with waste water or fresh water via the influent inlet 135 or via the primary flow distribution system 180. To flood the housing 110, the effluent outlet 232 is sealed closed by way of an outlet valve. The biotreatment membranes 151 may thus be fully submerged in this manner for cleaning as will be further discussed below. [0052] For the cleaning process discussed below, the water biotreatment unit 100 has a scour air system 190 in each of the primary and secondary treatment regions 130, 230 for cleaning of the biotreatment membranes 151 by air scouring. As best depicted in Figures 3 and 10, each scour air system 190 comprises a scour air line 191 extending in a loop from a scour air inlet 192 extending through the first end wall 111 along the respective primary or secondary treatment region 130, 230. The scour air lines 191 are located above the respective primary or secondary reservoir 131, 231 and beneath the respective primary or secondary array 150, 250 of biotreatment membranes 151. Each of the scour air lines 191 is perforated, here with an array of 3 mm diameter apertures each spaced 100 mm apart. Each scour air line 191 is supported above the floor 116 by way of a series of supports 193 upstanding from the floor 116.

[0053] Referring to Figure 5, a primary reservoir outlet 137 extends from the primary reservoir 131 through the first end wall 111. Whilst not depicted in Figures 1 to 9, the primary reservoir outlet 137 is in fluid communication with the primary flow distribution system 180 via the primary recirculation system. The primary recirculation system comprises a primary

recirculation line having an inlet end coupled to the primary reservoir outlet 137 and an outlet end coupled to a primary flow distribution manifold inlet 181 of a primary flow distribution manifold 182 of the primary flow distribution system 180. The primary recirculation system further comprises a primary recirculation pump (not depicted in Figures 1 to 9) mounted in line with the primary recirculation line. The primary recirculation pump operates to draw water being treated from the shallow end of the primary reservoir 131 (opposing the deep end of primary reservoir 131 where sludge accumulates) and pumps the water into the primary flow distribution system 180 for distribution across the primary array 150 of biotreatment membranes 151 as will be further discussed below. As discussed above, influent water to be treated is typically supplied to the primary treatment region 130 through an influent inlet in fluid communication with the primary recirculation system 170. In particular, the influent inlet may be formed in the primary recirculation line.

[0054] Still referring to Figure 5, a secondary reservoir outlet 237 extends from the secondary reservoir 231 through the first end wall 111. Whilst not depicted in Figures 1 to 9, the secondary reservoir outlet 237 is in fluid communication with the secondary flow distribution system 280 via the secondary recirculation system. The secondary recirculation system comprises a secondary recirculation line having an inlet end coupled to the secondary reservoir outlet 237 and an outlet end coupled to a secondary flow distribution manifold inlet 281 of a secondary flow distribution manifold 282 of the secondary flow distribution system 280. The secondary recirculation system further comprises a secondary recirculation pump (not depicted in Figures 1 to 9) mounted in line with the secondary recirculation line. The secondary recirculation pump operates to draw water being treated from the shallow end of the secondary reservoir 231 and pumps the water into the secondary flow distribution system 280 for distribution across the secondary array 250 of biotreatment membranes 151 as will be further discussed below.

[0055] The primary flow distribution system 180 comprises the primary flow distribution manifold 182 that extends along the upper edge of the first side wall 113 and a series of primary spray assemblies 183 arranged above the top of the primary array 150 of biotreatment membranes 151. In particular, one primary spray assembly 183 is located above the centre of each cartridge 160 located in the primary treatment region 130. Each of the primary spray assemblies 183 may be in the form of any suitable spray assembly that distributes water to be treated across the top of the biotreatment membranes 151 of the adjacent cartridge 160. In a particularly preferred form, each of the primary spray assemblies 183 may be of the general form disclosed in Australian provisional patent application no. 2016904390, the entire contents of which are explicitly incorporated herein by cross-reference. Each of the primary spray assemblies 183 may generally comprise an arrangement of several, here four, flow chambers 184 in fluid communication with the primary flow distribution manifold 182 via a distribution branch line 185 that also serves to support the primary spray system 183 above the biotreatment membranes 151. The primary spray system 183 further comprises a rotor mounted in proximity to, and beneath, the flow chamber. Each flow chamber 184 generates a generally vortical flow in water passing through the flow chamber 184. Water exiting the flow chamber 184 impacts rotor blades of the rotor to rotationally drive the rotor, which in turn disperses water impacting the rotor blades across the top of the biotreatment membranes 151. This form of primary spray system 183 avoids the use of small spray nozzles which may otherwise be clogged with waste material carried by the water to be treated. The secondary flow distribution system 280 is essentially identical to the primary flow distribution system 180, comprising the secondary flow distribution manifold 282 and a series of secondary spray assemblies 283 of the same form as the primary spray assemblies 183, communicating with the secondary flow distribution manifold 282 by way of secondary distribution branch lines 285. [0056] The cartridge frame 161 of a cartridge 160 is shown in greater detail in Figures 13 and 14. The cartridge frame 161 has four uprights 162 that are each supported by one of the cartridge supports 127 in the housing 110. A pair of opposing hanger supports 163 extend across opposing ends of the top of the cartridge frame 161, supported by the uprights 162. As shown in greater detail in Figure 14, each of the hanger supports 163 has an inwardly directed face defining a plurality of upwardly opening slots 164. Each of the slots 164 is configured to receive the end of a hanger 152 over which a biotreatment membrane 151 is draped. A pair of opposing spacer bar supports 165 extends across the cartridge frame 161 midway between the upper and lower ends of the cartridge frame 161, beneath each of the hanger supports 163. The spacer bar supports 165 also define recesses, for receipt of spacer bars that extend between the spacer bar supports 165. The spacer bars extend between the opposing membrane walls of each biotreatment membrane 151, ensuring an air gap for flow of ventilating air between the opposing membrane walls. The cartridge frame 161 further comprises further frame elements 166 extending between, and secured to, adjacent uprights 162 to maintain the structural rigidity of the cartridge frame 161. A top bar 167 extends between, and is secured to, two opposing frame elements 166 at the upper end of the cartridge frame 161. The top bar 167 is assembled into place after assembly of the hangers 152 and biotreatment membranes 151 into the cartridge frame 161, with downwardly extending recesses of the spacer bar 167 receiving the top edges of the draped biotreatment membranes 151 and associated hanger 152 so as to assist in securing the biotreatment membranes 151 in the correct spacial relationship.

[0057] The water and air flow circuits of the biotreatment unit 100, along with operation thereof, will now be described with particular reference to Figures 15 and 16 which depict simplified and more detailed schematic fluid flow circuits of the biotreatment unit 100 respectively. Raw effluent water 300 to be treated flows through a raw feed line 301 to the influent inlet 132 in the primary recirculation line 171 of the primary recirculation system 170. As discussed above, alternatively or additionally, the raw influent water 300 may be fed directly to the primary reservoir 131 via an alternate raw feed line 302 and the influent inlet 135 in the first end wall 111 of the housing 110. It is preferred, however, that the raw influent water 300 is fed into the primary recirculation system 170, and subsequently through the primary flow distribution system 180 and through the primary array 150 of biotreatment membranes 151 such that every portion of waste water to be treated receives an initial treatment through the biotreatment membranes 101, eliminating potential short circuiting in the primary reservoir 131. This configuration also better ensures relatively constant waste concentration through the primary reservoir 131, and between the water discharged from the primary array 150 of biotreatment membranes 151 and water flowing over the weir 134 into the secondary reservoir 231. The raw influent water 300 is fed continuously, with a throttling valve being utilised to control the feed flow rate. The raw feed line 301 is also provided with an inline strainer, sampling valve, flow meter and pressure transducer. The pressure in the raw feed line 301 is monitored utilising the flow meter to identify any blockage, which raises an alarm and triggers stopping of the external feed pump (which is not depicted).

[0058] The water to be treated flows from the influent inlet 132 through the primary

recirculation line 171 and into the primary flow distribution manifold 182 of the primary flow distribution system 180. A non-return valve in the raw feed line 301 ensures that waste water in the primary recirculation system 170 cannot feed back towards the supply of raw influent water 300. Water to be treated is fed from the primary flow distribution manifold 182 through each of the primary flow branches 185 to each of the primary spray assemblies 183, which distribute water across the top of the biotreatment membranes 151 of the primary array 150. Water to be treated passes under gravity between the biotreatment membranes 151 on the exterior liquid side of the membrane walls.

[0059] The inner gas side of the membrane walls is ventilated by way of atmospheric vent air 310 being drawn through the opening 122 of each of the hollow stiffening channels 119 and through the vents 121 provided in the first side wall 113 of the housing 110. This flow of atmospheric vent air 310 is driven by convection given that the biotreatment process is exothermic and relatively cool atmospheric vent air 310 is thus drawn into the warmer primary biotreatment region 130 as the warmer air in the primary biotreatment region 130 rises. The flow of ventilation air may be enhanced by operation of the fans 129 mounted in the lids 128 of the housing 110. As the water passes between the biotreatment membranes 151 the biomass culture growing through the membrane wall draws oxygen from the gas side and waste nutrients from the water on the liquid side, thereby extracting waste nutrients from the water to be treated. The treated water then drains from between the biotreatment membranes 151 of the primary array 150 into the primary reservoir 131.

[0060] Water in the primary reservoir 131 is fed back into the primary flow distribution system 180 via the primary recirculation system 170, with water being drawn through the primary reservoir outlet 137 through the primary recirculation line 171 via the action of a primary recirculation pump 172. Some of the biomass growth on the biotreatment membranes 151 also falls into the primary reservoir 131, where it will sink to the floor 116 and migrate toward the deeper end of the primary reservoir 131 adjacent the primary sludge outlet 133.

[0061] As the process continues, the water level in the primary reservoir 131 will increase and the recirculation of water through the primary array 150 of biotreatment membranes 151 will provide a relatively constant concentration of waste within the water in the primary reservoir 131.

[0062] When the level of water in the primary reservoir 131 reaches the level of the weir 134, water starts flowing over the weir 134 into the secondary reservoir 231. The level of water in the secondary reservoir 231 is monitored and when a sufficient depth is reached the secondary recirculation pump 272 of the secondary recirculation system 270 is activated to pump water in the secondary reservoir 231 through the secondary reservoir outlet 237 through the secondary recirculation line 271 into the secondary flow distribution manifold 282 of the secondary flow distribution system 280. The water is then fed through the secondary branch lines 285 into the secondary spray assemblies 283 arranged across the top of the biotreatment membranes 151 of the secondary array 250, where the water to be treated falls under gravity between the biotreatment membranes 151 of the secondary array 250, extracting waste nutrients from the water in the same manner as discussed above in relation to the primary array 150 of

biotreatment membranes 151. As with the primary array 150 of biotreatment membranes 151, vent air 310 is drawn upwardly through the secondary treatment region 230 on the air side of the membrane walls of the biotreatment membranes 151 of the secondary array 250, through the hollow stiffening channels 119 fixed to the second side wall 114 and associated vents 121. Again, water treated drains under gravity into the secondary reservoir 231 and portions of biomass growing on the biotreatment membranes 151 of the secondary array 250 will also fall into the secondary reservoir 231 and migrate toward the secondary sludge outlet 233.

[0063] Once the water level in the secondary reservoir 231 reaches the level of the effluent outlet 232, treated effluent water 304 flows out through the effluent outlet 232 under gravity through an outlet line 303. In the steady state, flow of treated effluent water 304 through the effluent outlet 232 is continuous, with the flow rate generally matching the flow rate of the raw influent water 300 into the system (although at a slightly reduced rate given the rate at which waste is removed from the water). The treated effluent water 304 may be further treated if necessary or desired. Further treatment may include feeding the treated effluent water 304 into a further biotreatment unit arranged in series with the biotreatment unit 100. The quality of the treated effluent water 304 may be controlled through control of process variables, particularly the flow rate of the feed of raw influent water 300.

[0064] Excess biomass, in the form of sludge 305, may be removed from the primary and secondary reservoirs 131, 231 via the primary and secondary sludge outlets 133, 233 and associated sludge outlet line 306. Sludge 305 may be removed during the continuous production process, or whilst the production process is stopped during a cleaning cycle.

[0065] Whilst excess biomass will naturally fall under gravity from the biotreatment membranes 151 into the primary and secondary reservoirs 131, 231, the thickness of biofilm will still tend to gradually increase on the biotreatment membranes 151, gradually impairing the efficiency of the biotreatment membranes 151. In previous biotreatment units utilising biotreatment membranes of the kind described, the excess biofilm thickness has typically been removed in a manual cleaning process which has largely involved hosing the biotreatment membranes from above. This cleaning process, being a manual process, is not controlled and does not reliably provide a controlled and desired biofilm thickness at the end of the cleaning process. Nor does it provide adequate cleaning of the gas side of the membranes.

[0066] The biotreatment unit 100 is configured to provide a controlled and largely automated cleaning process. In the cleaning process, the effluent outlet 232 is closed by way of a valve. The waterproof tank defined by the interior of the housing 110 is then flooded, here via the primary flow distribution system 180. The housing 110 may be flooded utilising raw influent water 300 through the raw feed line 301 and recirculation line 171. Alternatively, a source of cleaning water 307 may be utilised, either being fed through the raw feed line 301 or directly into the interior of the housing 110, potentially through the influent inlet 135 in the primary reservoir 131. The housing 110 is flooded until the biotreatment membranes 151 of the primary and secondary arrays 150, 250 are fully submerged. The emergency overflow ports 136 located toward the top of the first and second end walls 111, 112 prevent the water from overflowing out of the top of the housing 110 during flooding (and during normal production). Once the housing 110 has been flooded, the scour air systems 190 are activated, with scour air 311 being pumped through an air supply line 193 by an air blower 194 through each of the scour air inlets 192 and into the scour air lines 191 provided in each of the primary and secondary treatment regions 130, 230. Scour air 311 then exits the perforations formed in each scour air line 193, forming bubbles which rise through the flooded primary and secondary treatment regions 130, 230, effectively scouring the biotreatment membranes 151 and dislodging excess biomass, which sinks into the primary and secondary reservoirs 131, 231, settling towards the primary and secondary sludge outlets 133, 233. The sludge 305 collected is again extracted through the primary and secondary sludge outlets 133, 233. Additional cleaning of the liquid side of the biotreatment membranes 151 from above may be conducted manually by way of an air lance 195 connected to the air blower 194. Air is blasted across the top of the biotreatment membranes 151 with the lids 128 of the housing 110 removed. At the end of the cleaning process, the housing 110 is drained through the primary and secondary sludge outlets 133, 233, back to the steady state water levels in the primary and secondary reservoirs 131, 231.

[0067] The biotreatment unit 100 described provides for a continuous two stage water biotreatment process, which may allow for both high waste removal rates and low waste concentration in the treated effluent water continuously output by the unit. Once the

biotreatment process has reached the steady state, with both the primary and secondary reservoirs 131, 231 filled, the flow rates and waste concentration of water being fed into each of the primary and secondary treatment regions 130, 230 will be relatively constant for each treatment region. The waste concentration of water fed into the primary treatment region 130 will be higher than the waste concentration of the water being fed into the secondary treatment region 230 (given that this water has already been treated in the primary treatment region 130). The biological reactions occurring during the process have a concentration saturation constant known as the Ks value. At waste concentrations below the Ks value, the micro-organisms of the biofilm start to starve. A two stage system as provided with the biotreatment unit 100 described may thus be advantageous, as it is understood that the biotreatment membranes 151 of the first array 150 in the primary treatment region 130 will grow a different set of micro-organisms than those grown on the biotreatment membranes 151 of the secondary array 250 in the secondary treatment region 230. Specifically, it is understood that the micro-organisms developed on the biotreatment membranes 151 of the secondary array 250 will have a lower Ks value and hence better performance than the micro-organisms developed on the biotreatment membranes 151 of the primary array 150. Having relatively constant concentration of waste in the water feeding into each of the primary and secondary treatment regions 130, 230 may thus effectively allow the biotreatment membranes 151 in each treatment region 130, 230 to self optimise. [0068] Provision of the cleaning process in which the biotreatment membranes 151 are submerged and cleaned by air scouring, in a controlled manner, may also effectively control biofilm thickness on the biotreatment membranes 151 in an effort to improve treatment efficiencies. Controlling the biofilm thickness may minimise the anaerobic fraction of the biomass. Anaerobic catabolic reactions and growth rate are at least one order of magnitude less than for anaerobic bacteria. The growth of anaerobic biomass in the biofilm between the waste nutrient source and anaerobic bacteria adds an additional layer of mass transfer resistance.

Eliminating, or at least reducing, this anaerobic layer may thus significantly improve

performance of the biotreatment membranes 151.

[0069] As discussed above, in the biotreatment unit 100, the scour air system 190 for each of the primary and secondary treatment regions 130, 230 utilises a single scour air line 191 extending along the length of the treatment region and supported beneath the cartridges 160. In an alternate configuration, depicted in Figures 17 and 18, a separate scour air line 391 is mounted in each cartridge frame 161 so as to form a modified cartridge 160'. Each scour air line 391 has a perforated section 396 that extends back and forth across the base of the cartridge frame 161 beneath the set of biotreatment membranes 151. Each scour air line 391 is coupled to a scour air manifold 395 of the scour air system 390.

[0070] A person skilled in the art will appreciate other possible modifications to the

biotreatment unit described. For example, whilst the biotreatment unit has been described with a series of two treatment regions located side by side within the housing 110, it is envisaged that the housing may incorporate three or more treatment regions in series. For example, the use of a larger housing with a structural outer frame matching the size and configuration of a 40 foot ISO container is envisaged with an arrangement of four treatment regions arranged in series, side by side and end to end, with dividing walls between each treatment region and a weir in each dividing wall configured to provide flow of waste water from the reservoir of one treatment region to the next in series. Smaller biotreatment units are also envisaged, including a unit having an outer frame matching the size and configuration of a 10 foot ISO container.

Claims

1. A water biotreatment unit comprising:

a housing defining a primary treatment region and a secondary treatment region;

2. The water biotreatment unit of claim 1, wherein said housing comprises a floor, longitudinally opposing first and second end walls, laterally opposing first and second side walls and a dividing wall extending upwardly from said floor and extending longitudinally between said first and second end walls, said dividing wall dividing a lower portion of said housing into said primary reservoir and said secondary reservoir.

3. The water biotreatment unit of claim 2, wherein said dividing wall defines a weir communicating said primary reservoir with said secondary reservoir for overflow of water being treated from said primary reservoir to said secondary reservoir.

4. The water biotreatment unit of claim 3, wherein said effluent outlet is located at a level lower than said weir.

5. The water biotreatment unit of any one of claims 2 to 4, wherein said floor slopes downwardly towards said second end wall.

6. The water biotreatment unit of any one of claims 2 to 5, wherein said housing further comprises a primary sludge outlet extending from said primary reservoir adjacent said floor through said second end wall and a secondary sludge outlet extending from said secondary reservoir adjacent said floor through said second end wall.

7. The water biotreatment unit of any one of claims 2 to 6, wherein said housing defines a waterproof tank extending from said floor to above said primary and secondary arrays of biotreatment membranes, said unit being configured to flood said tank for cleaning of said biotreatment membranes.

8. The water biotreatment unit of any one of claims 1 to 7, wherein said unit further comprises a scour air system located in each of said primary and secondary treatment regions, each said scour air system comprising a perforated scour air line located below said biotreatment membranes, said scour air system being configured to supply air bubbles to said tank when flooded for scour air cleaning of said biotreatment membranes.

9. The water biotreatment unit of any one of claims 1 to 8, wherein said housing has a plurality of air vents located above said primary and secondary reservoirs at a level below said biotreatment membranes and each extending through one of said walls of said housing.

10. The water biotreatment unit of claim 9, wherein said unit further comprises a plurality of channels each communicating with one of said air vents and extending to an opening of said channel located at a level above said biotreatment membranes.

11. The water biotreatment unit of any one of claims 1 to 10, wherein said influent inlet is located in said primary recirculation system, such that, in use, water to be treated is supplied to said primary treatment region via said primary flow distribution system.

12. The water biotreatment unit of any one of claims 2 to 7, wherein said primary recirculation system communicates with said primary reservoir via a primary reservoir outlet, said primary reservoir outlet being located through or adjacent said first end wall.

13. The water biotreatment unit of any one of claims 2 to 7 or 12, wherein said secondary recirculation system communicates with said secondary reservoir via a secondary reservoir outlet, said secondary reservoir outlet being located through or adjacent said first end wall.

14. The water biotreatment unit of any one of claims 1 to 13, wherein said primary flow distribution system comprises a primary flow distribution manifold coupled to said primary recirculation system and a plurality of primary spray assemblies arranged above said primary array of biotreatment membranes, and

15. The water biotreatment unit of any one of claims 1 to 14, wherein said unit comprises a plurality of cartridges removably mounted in each of said primary and secondary treatment regions, each said cartridge comprising a cartridge frame and a set of said biotreatment membranes suspended from said cartridge frame.

16. The water biotreatment unit of claim 15, when appended to claim 8, wherein each said scour air system comprises a perforated scour air line mounted to each said cartridge frame and a scour air manifold in fluid communication with each said scour air line.

17. The water biotreatment unit of any one of claims 1 to 16, wherein said unit further comprises a structural outer frame, said housing being mounted within said structural outer frame, said structural outer frame having a plurality of corner blocks each configured to engage a twist lock for handling of said unit.