Apparatus and method for waste and water treatment

Abstract

An apparatus for recovering the suspended particles from waste water comprising a tank (10) having an upper section (14) for receiving waste water, a lower chamber (16) and a base plate (18) separating the upper section (14) and the lower chamber (18). In one aspect the base plate is a filter screen that has a central opening (20) and a closure 28 therefore. The apparatus has a filter press plate (24) within the upper section (14) and is moveable between a non-filtering position spaced away from the base plate (18) and a filtering position in which the filter member (24) and base plate (18) are pressed together so as to separate water from the particles and compress the particles to form a substantially dewatered product that can then pass through the opening (20) into the lower chamber (16) for collection.

Claims

1. An assembly for settling suspended waste particles from waste water and recovering the waste particles as a substantially dewatered solid product, the assembly comprising; a tank having an upper section for receiving waste water, a lower chamber and a base plate separating the upper section and the lower chamber, the base plate having an opening therein; a closure moveable between a position in which the base plate opening is closed and a position in which the base plate opening is open; a filter member within the upper section, wherein; the filter member and the base plate are moveable with respect to each other between a non-filtering position in which the filter member is spaced away from the base plate and a filtering position in which the filter member and base plate are pressed together with the closure in the closed position such that suspended waste particles are compressed between the filter member and the base plate to form a substantially dewatered solid product; and when the filter member is returned to the non-filtering position, the closure is moveable to the open position such that the substantially dewatered solid product can pass through the opening into the lower chamber for collection.

2. The apparatus of claim 1, wherein the base plate is stationary and the filter member is moveable relative to the base plate.

3. The apparatus of claim 1, wherein the lower chamber is separated into a dry chamber for receiving the substantially dewatered solid product and a wet chamber for receiving filtered water.

4. The apparatus of claim 3, wherein the dry chamber includes a collector for the substantially dewatered solid product.

5. The apparatus of claim 4, wherein the collector is a downwardly inclined chute.

6. The apparatus of claim 1, that further includes a collection unit movable between a collection position within the lower chamber when the closure is in the open position after filtration such that compressed dewatered solid product can pass into the collection unit and a recovery position in which collected product can be recovered.

7. The apparatus of claim 1, wherein the tank has a circular cross section and the opening is circular and coaxial with the base plate.

8. The apparatus of claim 7, wherein the base plate has an inverted frustoconical shape.

9. The apparatus of claim 8, wherein, the closure is in the form of a conical plug.

10. The apparatus of claim 9, wherein the shape of the filter member has an upper inverted frustoconical section complimentary to the base plate and an inner conical section that is complimentary to the upper surface of the closure.

11. The apparatus of claim 1, wherein, the lower surface of the filter member has a plurality of voids that the particles are compressed into so as to form substantially dewatered discrete solid units.

12. The apparatus of claim 1, which further comprises at least one smaller chamber or hopper mounted to the top surface of the filter member and in fluid communication with the lower surface of the filter member with a non-return valve set to a predetermined pressure for receiving excess compressed particles.

13. The apparatus of claim 1, wherein the filter member and closure are operatively connected together such that a single lifting and lowering arrangement can be used to lift and lower the filter member and closure together.

14. The apparatus of claim 1, further comprising a waste collection unit removeably connected to the closure such that in use the filter member, closure and waste collection unit can be raised and lowed together.

15. A method of recovering suspended waste particles from waste water in the form of a substantially dewatered solid product, the method comprising; providing a tank having an upper section for receiving waste water, a lower chamber and a base plate separating the two chambers, the base plate having an opening therein; a closure moveable between a position in which the base plate opening is closed and a position in which the base plate opening is open; a filter member within the upper section, wherein; the base plate and the filter member being moveable with respect to each between a non-filtering position with the filter member away from the base plate and a filtering position in which the filter member and base plate are pressed together; charging the upper section with the waste water with the closure in the closed position and the filter member in the non-filtering position; allowing the suspended particles to settle; moving the filter member and/or base plate into the filtering position such that the waste particles are compressed between the filter member and the base plate so as to provide a substantially dewatered solid product; returning the filter screen and/or base plate to the non-filtering position; and moving the closure into the open position so that the substantially dewatered solid product waste can pass through the opening into the lower chamber.

16. The method of claim 15, wherein a settling agent is introduced into the waste water either before and/or after the waste water is charged to the upper chamber.

17. The method of claim 15, wherein the waste particles have particle sizes of less than 300 μm, and the waste particle comprise red mud, coal fines or fly ash.

18. The method of claim 15, wherein the settling agent comprises 43.7 wt % to 46.2 wt % of a colloidal clay, 24.1 wt % to 25.9 wt % of an inorganic coagulant, 19.2 wt % to 20.8 wt % of a water purifier ceramic powder, 4.8 wt % to 5.2 wt % of a cationic polymeric coagulant aid and 4.8 wt % to 5.2% of an inorganic coagulant aid and between 15 wt % and 25 wt % of an adsorbent silicate.

19. The method of 18, wherein the colloidal clay is bentonite, saponite, attapulgite, kaolinite or a mixture of any two or more thereof; the inorganic coagulant is an inorganic salt of aluminium and/or iron, the adsorbent silicate is magnesium silicate (Mg.sub.3Si.sub.4O.sub.10(OH).sub.2), magnesium aluminum silicate (AlMgO.sub.4Si+), calcium silicate (Ca.sub.2O.sub.4Si), sodium silicates (Na.sub.2(SiO.sub.2).sub.nO), silica gel or a mixture of any two or more thereof; the cationic polymeric coagulant aid is epichlorohydrin dimethylamine, aminomethyl polyacrylamide, polyalkylene, a polyamine, a polyethyleneimine, sodium alginate, starch, chitosan, or a mixture of any two or more thereof, and the inorganic coagulant aid is CaCO.sub.3.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic view of one aspect of the disclosed apparatus in which the filter screen is in the raised position;

(2) FIG. 2 shows the apparatus as shown in FIG. 1 in the mixing position;

(3) FIG. 3 shows the apparatus of FIG. 1 in the filtering position;

(4) FIG. 4 is a schematic view of another aspect of the disclosed apparatus in which the filter screen is in the raised position;

(5) FIG. 5 shows the apparatus as shown in FIG. 4 in the mixing position;

(6) FIG. 6 shows the apparatus of FIG. 4 in the filtering position;

(7) FIG. 7 is schematic cross section of an apparatus according to a further aspect of the disclosure; and

(8) FIG. 8 is a detail of section A in FIG. 7.

DETAILED DESCRIPTION OF THE FIGURES

(9) FIG. 1 shows an apparatus 10 as disclosed. The apparatus 10 has a tank 12 that has an upper section 14 and a lower chamber 16 separated by a circular base plate 18. The base plate 18 tapers downwards towards a central co-axial circular opening 20.

(10) The apparatus 10 is includes a gantry 22. A filter press plate 24 is suspended from the gantry 22 by a chain 26. The filter press plate 24 has an outer frustoconical section 24a that is complimentary to the base plate 18 and an inner conical section 24b.

(11) Suspended below the filter press plate 24 by arm 30 is a conical closure or plug 28. The plug is dimensioned to seal the opening 20. The cone shape of the plug 28 is complimentary to the shape of the inner part 24b of the filter press plate 24.

(12) Three arms 32 extend below plug 28. These arms support a collection bag (not shown).

(13) The chain 26 is fixed to a hoist 34 for raising and lowering the filter press plate, 24, plug 28 and collection bag together.

(14) FIG. 2 shows the apparatus 10 in the mixing configuration in which the filter press plate 24, plug 28 and collection bag have been lowered by the hoist 34 into a position in which the filter press plate 24 seals against the tank 12 and the plug 28 seals the opening 20 in base plate 18. A mixing chamber 13 is defined between the filter press plate 24 and the base plate 18. In this position, the waste water may be charged to the mixing chamber and mixed with a settling agent.

(15) When used to treat a red mud slurry, the red mud is suitably pretreated to reduce the pH. Red mud has a high pH of about 14 and one known method of treating red mud to reduce the pH of to about 8-10 is to mix the red mud with seawater in a neutralizer. In this case, red mud will suitably be pumped from the neutralizer at a rate of about 5000 liters per hour in a pipe line. The slurry will typically contain about 10 vol % to about 20 vol % suspended red mud particles. A settling agent may be introduced into the pipe line so as to facilitate mixing of the agent with the feed stock. The pipeline includes means for interrupting the flow and creating agitation to facilitate mixing.

(16) The settling agent comprises 43.7 wt %-46.2 wt % bentonite, 24.1 wt %-25.9 wt % Al.sub.2(SO.sub.4).sub.3, 19.2 wt %-20.8 wt % ceramic powder, 4.8 wt %-5.2 wt % chitosan and 4.8 wt %-5.2 wt % CaCO.sub.3 as a suspension in water.

(17) Upon entering the mixing chamber 13, the red mud slurry will be further diluted with sea water (about 2000 liters). The pH will be adjusted with hydrochloric acid to a pH of about 7.3. Further settling agent may be added to provide an effective amount and is further mixed with the slurry. Agitation may occur by any suitable mixing method known in the arts. However, high pressure water jets are particularly suitable. Mixing continues for about 5 minutes, after which time, the floc begins to settle very quickly.

(18) After settling, the filter press plate 24 will be lowered to the filtering position shown in FIG. 3. Arm 30 is slidably received within plug 28 so that the filter screen can be lowered whilst the plug 28 maintains the seal against the opening 20.

(19) The lower face of the filter press plate 24 is profiled to define a plurality of voids dimensioned to correspond to standard briquette sizes for material handling. The water will be squeezed through the filter press plate 24 and the floc is compressed into the voids. The filter press plate 24 may be vibrated during pressing so as to ensure maximum floc is pressed into the voids. Water is forced under pressure through mesh lined apertures in the base plate 18.

(20) It may be appreciated that the complimentary configuration of the inner 24b and outer 24a and outer parts of the filter press plate with the plug 28 and base plate 18 allows for optimization of pressure and an increase in surface area when compared with a flat filter press plate cooperating against a flat surface.

(21) The apparatus 10 also includes four small hoppers 32 fluidly connected to the upper surface of the outer 24a part of the filter press plate 24. The hoppers 32 have a pressurized non-return valve. The pressure will be set so that the floc is pressurized to fill the voids. When this pressure is reached excess floc can enter the hoppers.

(22) When the filtering process is over, the filter press plate 24 and plug 28 will be lifted by the hoist 34 to open the opening 20.

(23) The filtered water that has passed through the mesh into the lower chamber 16 may be pumped to a temporary storage tank. Typically the water is quality tested and may be subject to further treatment. The water may then be released to the environment or recycled back to the filtering process.

(24) The recycled water may be added to the settling agent that is in powdered form for introduction to a new batch of slurry. This may be advantageous if there is excess settling agent present in the filtered water as less settling agent will be required for the next cycle.

(25) The pressed briquettes can then fall out of the voids in the filter press plate 24 and be collected in the collection bag. Some vibration of the filter press plate 24 may be introduced to facilitate release of the briquettes.

(26) The entire filter press plate 24, plug 28, collection bag assembly is then lifted out of the tank 12 to the position shown in FIG. 1. The assembly is then moved sideways along the upper beam 36 of gantry 22 and then lowered so that the collection bag may be collected by a forklift 40 or other suitable material handling vehicle.

(27) The entire process may be under automatic control so that the only manual intervention is collection and replacement of the collection bags.

(28) The collected briquettes may be transported to a facility where any valuable mineral or other material may be reclaimed.

(29) FIGS. 4 to 6 show an alternative apparatus as disclosed herein. The general operation of the mixing and filtering carried out in the alternative apparatus is substantially the same as for the apparatus shown in FIGS. 1 to 3, except as otherwise described. The same reference numerals will be used to refer to the same features as shown in FIGS. 1 to 3.

(30) The lower chamber 16 is separated into an outer wet chamber 50 that receives filtered water and a dry chamber 52 for collection of dewatered solid product by a circular inner wall 54. The wall 54 is concentric with the opening 20 in the base plate such that the plug 28 prevents water from entering the dry chamber 52 during filtration.

(31) The dry chamber 52 includes a chute 56 that is angled downwardly towards opening 58 in the side wall of the lower chamber 16.

(32) In use the plug 28 remains in place where it seals the dry chamber until the filtered water has been allowed to flow into the wet chamber. This apparatus may include suitable filtered water flow control devices such as valves or the like (not shown).

(33) When the plug 28 is opened as shown in FIG. 6, the briquettes can pass into the dry chamber 52 and pass via chute 56 to the outside of the chamber 16 for collection.

(34) The apparatus 10 includes a single hopper 60 for receiving any excess waste. The hopper 60 has an internal circular housing 61 that holds a diaphragm that is operable to apply further pressure to solid product to assist in filling the voids in the filter press plate.

(35) In this aspect arm 30 is a shaft with an agitator 62 for mixing or assisting in mixing the waste water and selling agent. The arm 30 may also provide an inlet for waste water or diluent water that can be injected into the mixture under pressure to further facilitate mixing.

(36) The agitator 62 is moveably mounted to arm 30 so that when the apparatus 10 is in the filtering configuration as shown in FIG. 5, the agitator 62 can slide upwards and may be housed within a recess 64 in the lower surface of the filter press plate 24.

(37) FIG. 7 is a cross section schematic view of a further aspect of an apparatus as disclosed herein. The same reference numbers will be used to describe the same features as found in FIGS. 1 to 6.

(38) The filter press plate 24 and base plate 18 are in the mixing position. The bottom surface of the filter press plate 24 has a profile defining a series of voids 108 that when in the filtering position pressed against the base plate 18, the suspended particles are compressed within the voids to produce dewatered product in the form of briquettes 110. The voids 108 are connected by relief grooves to allow for pressure equalization between the voids.

(39) Collected briquettes 110 are schematically shown collected in a collection bag 112 in the dry collection chamber 52.

(40) The base plate 18 has concentric rings of filter openings 102. In use, the openings 102 are covered by a fine mesh (shown in FIG. 8). The conical plug 28 is in the closed position. Immediately below and concentric with the opening 20 is wall 54 that in use separates inner dry chamber 54 from the outer wet chamber as discussed above with respect to FIGS. 4 to 6.

(41) Two outer O rings 104 seal the base plate against the inner walls of the tank. The upper ring is inclined downwards at an angle of 45°. This aligns with a corresponding angle of an outer O ring 105 surrounding the filter press plate. This angle ensures that the briquettes fall centrally into opening 20.

(42) The bottom of the filter press plate 24 has a central recess 64 that in use receives the agitator 62 when the filter press plate is in the filtering position.

(43) The filter press plate 24 has voids 108 for compressing suspended particles together to for dewatered solid product in the form of briquettes.

(44) The apparatus 10 is shown in the mixing configuration in which a mixing chamber 13 is defined between the filter press plate 24 and the base plate 18.

(45) The upper section 14 of the apparatus in FIG. 7 has a further pre-treatment chamber 115 that is above the filtration chamber 13. The pretreatment chamber 15 has an inner chamber 128 through which drive tube 130 passes. The drive tube 130 houses a plug shaft 140. The plug shaft is engaged with the plug 28 at one end. The plug shaft 140 is operatively connected to a motor 150 for raising and lowering the plug shaft 140 and engaged plug 28.

(46) FIG. 7 also shows hydraulic rams 160 that operate to raise and lower the filter press plate 24.

(47) The pre-treatment chamber 15 has an inlet 162 one on side and an agitator 164 on the other side. The floor 166 of the pre-treatment chamber has two outlets 168, 170 that are controlled by valves 172, 174. The outlets 168, 170 fluidly connect the pre-treatment chamber 15 to the filtration chamber 13 via fluid lines 176, 178 to inlet/outlets 180, 182 through the filter press plate 24.

(48) The fluid lines 176, 178 are extendible and retractable so as to accommodate the movement of the filter press plate 24 between the filtering and non-filtering positions.

(49) In use waste water is introduced into pre-treatment chamber 15 through inlet 162. A pretreatment agent such as an acid or alkali to modify pH may be added by any suitable method known in the water processing arts. When the water has reached a desired pre-treatment value such as a desired pH range, the valves 172, 174 are actuated to release water into the filter chamber 13 through inlets 176, 178.

(50) Each fluid line 176, 178 has a T junction 180, 182 that connects to a second fluid line 184, 186. The second fluid lines 184, 186 are controlled by pressure valves 188, 190.

(51) In use, when the filter press plate 24 and base plate 18 are in the filtering position and water is being expelled through the holes 102 in the base plate 18, a considerable amount of pressure may be generated. Excess pressure can actuate the pressure relief valves 188, 190 to allow excess water to enter fluid lines 176, 178 and which is diverted into the second fluid lines 184, 186 through filters 192, 194 into the wet chamber 50 as indicated by arrows B.

(52) It will also be appreciated that by selective operation of the valves, water in the pre-treatment chamber 14a can be diverted to the wet chamber 16 bypassing the filter chamber 14b. This allows water to be released from the pre-treatment chamber in the event of a malfunction. This provides a simple gravity feed solution, rather than relying on pumps and the like.

(53) FIG. 8 shows a detail of the base plate 18. A filter mesh 200 is stretched across the upper surface of the base plate 18. The filter mesh particle size may be any suitable size, depending upon the nature of the particles being separated. A suitable size is about 40 to 100 microns. The mesh 200 is held in place by a retainer clip 202.

(54) A rubber block plate 204 is mounted below the base plate 18. The block plate 204 is moveable between a sealed position against the base plate 28 such that it blocks openings 102 during the charging and mixing of water in the filter chamber 14b. The upper surface of the block plate 204 has a profile with a series of corrugations 206 that align with openings 102 so as to facilitate sealing.

(55) The block plate 204 is biased towards the closed position by springs 208. When in the filtering step, pressure generated by the press action between the filter press plate and the base plate overcomes the bias so as to move the block plate 204 to an open position.

(56) A briquette 110 is shown on the surface of the base plate 18. As the base plate 18 is at an angle of about 45°, the briquettes normally slide towards the opening 20 in the base plate 28. In some instances a briquette 110 may become stuck on the surface. Should this occur, the briquettes may be dislodged with a jet of pressurized air from beneath base plate 18 and through air holes 102. An air inlet 210 is provided for this purpose.

(57) It will be appreciated that with the disclosed assembly, substantially dewatered solid product that is suitably in briquette form may be handled and transported by conventional dry material handling equipment and vehicles. Dry material transport, handling and storage has many advantages over that of liquids such as slurries in terms of efficiency, safety, economy and environment.

(58) The settling agent that is used in the example causes the fines to coagulate and floc together to form flocs that not only rapidly form and settle but also form flocs that are not overly porous as formed using conventional flocculants such that the floc can be quickly and efficiently dewatered by filter pressing. The present inventor is not aware of any other settling agent that has these properties when used with suspended fine particles such as those found in mineral tailings, coal tailings and other such wastes.

(59) The apparatus as disclosed herein is a single unit that can undergo multiple steps of pretreating, mixing, filtering, briquette formation and collection, clarified water collection. Conventional processes utilize multiple piece of machinery that each action a different step. Covenantal processes also require the pumping of liquids between containers and around the treatment plant. The present apparatus allows fluid to be transferred between chambers and processes using gravity flow. This considerably reduces up front plant costs as well as avoiding costly equipment maintenance, maintenance shut downs, part replacement and the like which considerably adds to operating costs.

(60) It is envisioned that the disclosed apparatus and method can provide an alternative to storing waste in tailing dams or ponds in terms of economy, the environment and health and safety. Additional advantages is that isolated product may be used directly such as coal fines recovered from coal tailing as coal briquettes or may be treated further to recover valuable materials contained therein. For example red mud contains aluminum as aluminum oxide, silicon dioxide, sodium oxide, titanium dioxide and iron oxide.

(61) It will be appreciated that various changes and modifications may be made to the invention as disclosed and claimed herein without departing form the spit and scope thereof.