WO2016094959A1

WO2016094959A1 - A filtration system for removing suspended and colloidal material from wastewater

Info

Publication number: WO2016094959A1
Application number: PCT/AU2015/050810
Authority: WO
Inventors: Brian DORIAN
Original assignee: Dorian Brian
Priority date: 2014-12-20
Filing date: 2015-12-18
Publication date: 2016-06-23

Abstract

There is provided a filtration system for removing suspended and colloidal material from wastewater wherein the suspended and colloidal material has a suspended and colloidal material particle size and wherein the filtration system has a self-cleaning filter comprising a screen having a screen size greater than the suspended and colloidal material particle size. In use, a chemical doser is used to introduce the coagulation chemicals to coagulate the suspended and collodial material to form coagulated material having a particle size greater than that of the screen size for collection by the screen.

Description

A filtration system for removing suspended and colloidal material from wastewater

Field of the Invention

[1] The present invention relates to filtration systems and in particular, but not necessarily entirely, to a filtration system for removing suspended and colloidal material from wastewater, especially for suspended and colloidal material having a particle size of substantially 10 μιη.

[2] The invention has been developed for use in/with the screw type self-cleaning filter as substantially shown in figure 1 and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use and may be equally applicable to other filter types including those having blade type self-cleaning filters.

[3] Furthermore, while in preferred embodiments, there will be described the self-cleaning filter comprising a screen having a screen size of between 30 μιη and 300 μιη the addition of coagulation chemical (which may comprise at least one of a pH adjuster, 30 μιη to 300 μιη coagulant and flocculant) so as to increase the size of suspended and colloidal material from substantially 10 μιη to greater than substantially 50 μιη for collection by the screen, it should be noted that these particle sizes and screen sizes are exemplary only and that other particle and screen sizes may be equally applicable within the purposive scope of the embodiments described here and of increasing the particle size of the suspended and colloidal material to a size greater than a screen size of the filter.

Background

[4] Waste water from food processing plants such as dairies, abattoirs or other industrial process can contain significant levels of suspended solids or colloidal material.

[5] The amount of colloidal material or suspended solids can relate to the biochemical oxygen demand (BOD) or chemical oxygen (COD) of the waste water.

[6] Discharging water high in BOD/COD and or suspended solids is very expesive.

[7] Existing wastewater treatment methods may comprise a primary treatment stage prior to discharge or further processing.

[8] The primary stage may comprise basic screening with a 1mm to 6mm screen to collect larger particles. These collected large particles are then shed under gravity or removed via washing and a collected for disposal.

[9] During further treatment stages (if any), the wastewater may further be stored for periods prior to being processed through a clarifier, DAF or IAF device and subjected to chemical treatment which can include pH adjustment, coagulation and flocculent addition to concentrate the suspended solids or colloidal material to a sludge. A sludge of between 1-6% solids may be realised from wastewater comprising about 5000-10000 ppm suspended solids or colloidal material. Up to 90-98% of suspended solids and colloidal material can be removed if chemicals are used.

[10] The capital and operational expenditure of the above wastewater treatment methods is justified given the expense of disposing of waste water being high in BOD/COD and/or suspended solids to sewer.

[11] Furthermore, the resulting sludge is still liquid in nature and is classified as a prescribed waste. As such, disposing of this sludge also has a high associated costs.

[12] As such, additional processing can be used to dewater the resulting sludge to reduce the volume of the sludge and therefore the disposal cost. Dewatering may be performed using centrifuges, belt presses or inclined screw presses and the like. Dewatering may be further enhanced using chemicals, such as by the addition of high levels of flocculant dosage (in the order of 100- 200ppm).

[13] As such, a need therefore exists for a filtration system that is able to sufficiently remove suspended and colloidal material and produce a sufficiently dewatered sludge in a more efficient and cost-effective manner than the above treatment processes.

[14] The present invention seeks to provide a filtration system, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[15] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Disclosure

[16] According to one aspect, there is provided a filtration system for removing suspended and colloidal material from wastewater, the suspended and colloidal material having a suspended and colloidal material particle size, the filtration system comprising a pressurised chamber for receiving the wastewater therein; a chemical doser fluidly connected to the pressurised chamber for the addition of a coagulation chemical to the pressurised chamber; and a self-cleaning filter fluidly connected to the pressurised chamber for filtering the wastewater, the self-cleaning filter comprising a screen having a screen size greater than the suspended and colloidal material particle size, wherein, in use the chemical doser may be adapted to introduce the coagulation chemicals to coagulate the suspended and collodial material to form coagulated material having a particle size greater than that of the screen size; and the self-cleaning filter may be adapted to collect the coagulated material.

[17] The screen may be cylindrical and the system may further comprise a screw adapted to rotate within the screen to cause peripherally facing screw wipers of the screw to clean the inner surface of the screen to cause the coagulated material to fall to collection bin.

[18] The chemical doser may further be adapted to introduce a pH change agent.

[19] The collection bin may comprise a purge valve adapted to discharge the coagulated material.

[20] The purge valve may be a differential pressure purge valve adapted to allow the release of the coagulated material under the pressure of the wastewater within the pressurised chamber.

[21]

[22] The purge valve may be opened at periodic intervals.

[23] The suspended and colloidal material particle size may be substantially 10 μιη.

[24] The coagulated material particles size may be substantially 50 μιη.

[25] The screen size may be greater than substantially 50 μιη.

[26] The screen size may be less then substantially 300 μιη.

[27] The coagulation chemical may comprise at least one of a coagulant and flocculant.

[28] At least one of the coagulant and flocculant may comprise polyacrylamide.

[29] The coagulation chemical may comprise a pH changer.

[30] In use, the chemical doser may be adapted to introduce the chemicals at a continuous flow rate.

[31] The flow rate may be determined in accordance with a flow rate of the wastewater through the filtration system.

[32] The flowrate of the wastewater may be substantially 15 m³ per day.

[33] The flowrate of the wastewater may be substantially 60 m³ per day.

[34] The pressurised chamber may be pressurised to less than 5 bar.

[35] Other aspects of the invention are also disclosed.

Brief Description of the Drawings

[36] Notwithstanding any other forms which may fall within the scope of the present invention, a preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[37] Figure 1 shows a filtration system in accordance with an embodiment of the present disclosure; and [38] Figure 2 shows an exemplary filtration circuit in accordance with an embodiment of the present disclosure.

Description of Embodiments

[39] For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure.

[40] Before the structures, systems and associated methods relating to the filtration system are disclosed and described, it is to be understood that this disclosure is not limited to the particular configurations, process steps, and chemicals disclosed herein as such may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the disclosure will be limited only by the claims and equivalents thereof.

[41] In describing and claiming the subject matter of the disclosure, the following terminology will be used in accordance with the definitions set out below.

[42] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[43] As used herein, the terms "comprising," "including," "containing," "characterised by," and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps.

[44] It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

[45] Turning now to figure 1, there is shown a filtration system 100 for removing suspended and colloidal material 135 of substantially 10 μιη from wastewater 110.

[46] The filtration system 100 comprises a pressurised chamber 150 for receiving the wastewater 110 therein. It should be noted that the pressurised chamber 150 need not be substantially pressurised but may be pressurised under the force of the introduced wastewater 110 alone. As will be described in further detail below, the pressurisation of the pressurised chamber 150 assists in the dewatering of the coagulated material/sludge. [47] The system 100 further comprises a chemical doser 120 fluidly connected to the pressurised chamber 150 for the addition of coagulation chemicals 115 to the pressurised chamber 150. As will be described in further detail below, the chemicals are adapted to cause the suspended and colloidal material 135 to coagulate to form coagulated material 140 for filtration.

[48] In embodiments, as opposed to the chemical dozer been fluidly coupled with the pressurised chamber 150 itself, the coagulation chemicals may be added by the chemical dozer upstream prior to the wastewater entering the pressurised chamber hundred and 50. Doing so will increase the mixing of the wastewater and the coagulation chemicals. Furthermore, a static mixer may be employed to further enhance the mixing and/or reaction time of the coagulation chemical.

[49] As such, the filtration system 100 further comprises a self-cleaning filter. In the embodiment shown, the self-cleaning filter comprises a screen 180 having a screen size of greater than 50 μιη.

[50] In the embodiment shown, the screen 180 is a drum type screen and therefore is substantially cylindrical. In this regard, the screen 180 divides the pressurised chamber 150 into an unfiltered section 185 and a filtered section 180.

[51] Furthermore, the self-cleaning filter is a screw type self-cleaning filter having a screw 125 adapted to rotate within the screen 180 to cause the peripherally facing screw wipers 130 clean the inner surface of the screen 180 to cause the coagulated material 140 to fall to collection bin 145.

[52] Other types of mechanisms may be employed to clean or wipe the screen 180, such as by utilising blades and the like.

[53] Now, as can be appreciated, on account of the suspended and colloidal material having particles of substantially 10 μιη, the screen 180, having a screen size of greater than substantially 50 μιη, wouldn't effectively be able to collect the suspended and colloidal material.

[54] As such, in use, the chemical doser is adapted to introduce at least one of a coagulant, flocculant and pH change to coagulate the suspended and colloidal material 135 to form the coagulated material 140.

[55] As can be seen from the figure, the coagulated material 140, on account of the flow of the wastewater, collects on the inside surface of the screen 180. Thereafter the wipers 130 of the rotating scree 125 collect the coagulated material for collection within the collection bin 145.

[56] The material collected on the screen 180 surface may also be removed (depending on the particular nature of the deposit via) a black flushing mechanisms. Back flushing is conducted by forcing clean water, filtered water or air back through the filter 100.

[57] Backflushing can be triggered automatically at periodic intervals using a timer, pressure reading setpoint or manually. [58] The collection bin 145 may comprise a purge valve 170 adapted to discharge the coagulated material. The purge valve 170 may be a differential pressure purge valve adapted to allow the release of the coagulated material 170 under the pressure of the wastewater 110 within the pressurised chamber 170. In alternative embodiments, the purge valve 170 may be opened at periodic intervals, such as at set intervals or on demand.

[59] Specifically, the opening of the purge valve 170 can be triggered manually, via a pressure gauge or by timer. These functions are automated via a PLC controller.

[60] During the abovementioned backflushing, the purge valve 170 is opened.

[61] In embodiments, the chemical doser 120 is adapted to introduce the coagulation chemicals continuously. In this regard, the flow rate of the coagulation chemicals is usually determined in accordance with the flow rate of the filtration system 100 which may range typically from 15-200 m³ per day.

[62] It should be noted that while the suspended and colloidal material is described herein as having particle sizes of substantially 10 μιη, in practice, suspended and colloidal material may have sizes of less than this including as high as 20 μιη for example.

Pilot pla nt test results

[63] The present inventor constructed a mobile (trailer mounted) pilot plant which was brought onto various sites for trailing. The pilot plant needed only coupling to a fresh water and 3 phase power source for operation.

[64] The pilot plant allowed for flexibility in controlling the filtration processes described herein wherein valve opening and closing can be controlled to pressure set points (either via a timer or manually).

[65] The pilot plant is further configurable to allow the selection of either the blade or screw 125 to optimise sludge rejects can be achieved with optimum water content of reject sludge. The screw 125 or blade assembly is controlled by a motor which can also be set on a duty cycle. The motor can come on or off at a predetermined interval so as water quality and sludge rejects are at optimum.

[66] Results showed that the pilot plant, when applied to processing dairy waste water attained solids rejects of 30%w/v.

Exempla ry ci rcuit

[67] Turning now to figure 2, there is shown an exemplary circuit 200 comprising the filter 100.

[68] The circuit 100 comprises a wastewater tank 225 for storing wastewater for filtration. In other embodiment, as opposed to storing the wastewater in the tank 225, the wastewater may be drawn directly from a source. [69] In this embodiment, the wastewater tank 225 comprises a level sensor 220 to control the addition of further wastewater.

[70] The coagulation chemicals 115 are introduced into the tank 225 for mixing using a mixer 215. In embodiments, a pH adjuster may also be introduced.

[71] Wastewater comprising the coagulant is then pumped via pump 210 fire a static mixer 205 to the filter 110.

[72] Filtered wastewater 160 flows from the filter 100 to the sewer 160.

[73] In embodiments, a liquid emulsion polymer 230 may be added to the wastewater prior to introduction to the filter 100.

[74] Coagulated material collects within the sludge bin 145. In embodiments, the sludge bin 145 may comprise a .5 cm mesh such that liquid may be filtered for return to the tank 225.

Advantages

[75] As can be appreciated from the above, the filtration system 100 comprises a number of advantages as compared to existing arrangements.

[76] Firstly, the filtration system 100 has less capital equipment cost when compared to the above-mentioned prior art multiple state processing arrangements. Specifically, whereas the prior art may comprise a primary treatment phase comprising basic screening and subsequent treatment phases having clarification, coagulation and a dewatering stages, the filtration system 100 is able to provide filtration at the 10 μιη level and dewatering in a single stage.

[77] In this regard, it is noted that the filtration system 100 is able to produce filtered wastewater 160 being the same or of greater filtration then the above-mentioned existing arrangements and coagulated material/sludge 140 having the same or less water than that produced by the above- mentioned existing arrangements.

[78] As such, the filtration system 170 has benefits of: waste water treatment plant capital investment reductions in the order of 80%; return on investment time frames reduce by 50% and possibility of waste sludge recycling or reuse by third parties.

[79] Furthermore, the utilisation of the self-cleaning filter removes the requirement for the addition of water during the filter cleaning process. For example, conventional filters require additional water to clean the filter screen. However, the addition of water would disadvantageously increase the water content of the coagulated material/sludge 140 and therefore increased disposal costs.

[80] Furthermore, the utilisation of flocculant, over and above providing the coagulation advantages, further enhances the water reduction of the coagulated material 140. [81] Furthermore, the utilisation of a screen 180 having a screen size of greater than 50 μιη advantageously increases the throughput capacity of the filtration system 100 and furthermore reduces the pressurisation required to force the wastewater through the screen 180. Rather, the filtration system 100 advantageously utilises the above-mentioned chemical dosage to increase the particle size of the suspended and colloidal material to greater than 50 μιη such that the higher throughput screen size of 50 μιη may still be employed to achieve the superior throughput characteristics while yet being able to effectively collect the suspended and colloidal material 135.

[82] Furthermore, the pressurisation of the pressurised chamber not only forces the wastewater through the screen 180 but further enhances the reduction of the water content of the final coagulated material 140.

[83] Furthermore, it is the pressurisation of the chamber 150 that allows effective dewatering of resulting sludge. Field pilot plant studies have shown that, for example, diary water can be filtered and the resulting sludge has solids content of 30%w/v. Dairy sludge from waste water treatment is practically difficult to dewater via other technologies.

[84] Furthermore, the utilisation of a 10 μιη screen to capture the suspended and colloidal material would become blocked quickly and wouldn't be cleanable using a self-cleaning filter. The blockage of the screen would result in a considerable reduction of the flow of the wastewater. Conversely, the utilisation of a 50 - 300 μιη screen and commendation with a self-cleaning filter provides advantages in high flow rate while still being able to capture suspended and colloidal material.

Interpretation

Embodiments:

[85] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[86] Similarly it should be appreciated that in the above description of example embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description of Specific Embodiments are hereby expressly incorporated into this Detailed Description of Specific Embodiments, with each claim standing on its own as a separate embodiment of this invention.

[87] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Different Instances of Objects

[88] As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

Specific Details

[89] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. Terminology

[90] In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "forward", "rearward", "radially", "peripherally", "upwardly", "downwardly", and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

Comprising and Including

[91] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

[92] Any one of the terms: including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising.

Scope of Invention

[93] Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

[94] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Industrial Applicability

[95] It is apparent from the above, that the arrangements described are applicable to the filter industries.

Claims

1. A filtration system for removing suspended and colloidal material from wastewater, the suspended and colloidal material having a suspended and colloidal material particle size, the filtration system comprising:

a pressurised chamber for receiving the wastewater therein;

a chemical doser fluidly connected to the pressurised chamber for the addition of a coagulation chemical to the pressurised chamber; and

a self-cleaning filter fluidly connected to the pressurised chamber for filtering the wastewater, the self-cleaning filter comprising a screen having a screen size greater than the suspended and colloidal material particle size, wherein, in use:

the chemical doser is adapted to introduce the coagulation chemicals to coagulate the suspended and collodial material to form coagulated material having a particle size greater than that of the screen size; and

the self-cleaning filter is adapted to collect the coagulated material.

2. A filtration system as claimed in claim 1, wherein the screen is cylindrical and wherein the system further comprises a screw adapted to rotate within the screen to cause peripherally facing screw wipers of the screw to clean the inner surface of the screen to cause the coagulated material to fall to collection bin.

3. A filtration system as claimed in claim 1, wherein the chemical doser is further adapted to introduce a pH change agent.

4. A filtration system as claimed in claim 1, wherein the collection bin comprises a purge valve adapted to discharge the coagulated material.

5. A filtration system as claimed in claim 1, wherein the purge valve is a differential pressure purge valve adapted to allow the release of the coagulated material under the pressure of the wastewater within the pressurised chamber.

6. A filtration system as claimed in claim 1, wherein the purge valve is opened at periodic intervals.

7. A filtration system as claimed in claim 1, wherein the suspended and colloidal material particle size is substantially 10 μιη.

8. A filtration system as claimed in claim 1, wherein the coagulated material particles size is substantially 50 μ.

9. A filtration system as claimed in claim 1, wherein the screen size is greater than substantially 50 μη-ι.

10. A filtration system as claimed in claim 9, wherein the screen size is less then substantially 300 μη-ι.

11. A filtration system as claimed in claim 1, wherein the coagulation chemical comprises at least one of a coagulant and flocculant.

12. A filtration system as claimed in claim 11, wherein at least one of the coagulant and flocculant comprises polyacrylamide.

13. A filtration system as claimed in claim 1, wherein the coagulation chemical comprises a pH changer.

14. A filtration system as claimed in claim 1, wherein, in use, the chemical doser is adapted to introduce the chemicals at a continuous flow rate.

15. A filtration system as claimed in claim 14, wherein the flow rate is determined in accordance with a flow rate of the wastewater through the filtration system.

16. A filtration system as claimed in claim 15, wherein the flowrate of the wastewater is substantially 15 m³ per day.

17. A filtration system as claimed in claim 15, wherein the flowrate of the wastewater is substantially 60 m³ per day.

18. A filtration system as claimed in claim 1, wherein the pressurised chamber is pressurised to less than 5 bar.