GB1568264A

GB1568264A - Filler for waste water treatment and process for production of same

Info

Publication number: GB1568264A
Application number: GB2471/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-01-21
Filing date: 1977-01-21
Publication date: 1980-05-29
Also published as: JPS5289239A; DE2702043A1; DE2702043B2; JPS5615317B2

Description

(54) FILLER FOR WASTE WATER TREATMENT AND PROCESS FOR PRODUCTION OF SAME (71) I, TADAKI MORIMURA, a citizen of Japan, of No. 4-25, Segawa 5chome, Minoo-shi, Osaka, Japan, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a filler for waste water treatment and a method for the prF duction of the filler.

The treatment of different kinds of industrial and domestic waste water and sewage has hitherto involved biological processes, cspecially the activated sludge process. With the latter process, however, there has been difficulty in controlling and maintaining sludge of high activity and good precipitability, and great care has been exercised in the control and maintenance of these properties of the sludge in most equipment of this type.

In spite of this, the phenomena of bulking and dispersion have frequently occurred leading to the effluence of the activated sludge with the treated water with attendant deterioration of the treated water.

With a view to overcoming the aforementioned difficulty in the activated sludge process, attempts have been made to endeavour to hold the sludge in suspension in the waste water to be treated. In an attempt to effect the holding of the sludge in suspension, small branches of bamboo or trees or plastic nets have been used. Also the rotary disc process has been proposed in which a disc is rotated to achieve better contact with the oxygen in the air.

In addition, earthen ware and concrete pipes and porous pipes of synthetic resin and other porous materials have been employed as drainpipes for underdraining. These, however, have limited water-permeable area. Thus, even with porous pipes of synthetic resin, which show the largest water-permeable area, it is impossible, for reasons of pressuretighmess, to attain more than 50% waterpermeability to total surface area.

It is an object of the present invention to provide an improved device for holding bacteria in an activated sludge in suspension which is more advantageous in many respects than prior proposals to fix or hold a suspension.

Another object of the present invention is to provide a method for the production of a filler for waste water treatment which is suitable for use as the said holding device or fixer.

A further object of the present invention is to provide a filler in the form of a pipe also suitable for use as an improved drainpipe for underdraining and which is more advantageous than conventional drainpipes in many respects.

According to the present invention, a waste water treatment filler comprises a threedimensional reticular assembly of curled synthetic resin filaments melt-adhered to one another at their contact points and defining voids between adjacent filaments, the assembly defining one or more channels extending lengthwise of the filler, the filler or a number of said fillers arranged adjacent each other being fitted, in use, within a waste water treatment tank, whereby impurities in waste water to be treated and contained in the tank and passing through the voids and the or each channel are held in suspension by the voids and accumulate therein to form an activated sludge to purify waste water in contact therewith.

The invention also includes a method for the production of the filler as set out in the immediately preceding paragraph, the method comprising drawing synthetic resin filaments extruded from nozzles, before they become solidified, at a speed lower than the speed at which the filaments are extruded from the nozzles, thereby to curl each filament into a coil, to melt-adhere the filaments to one another at their contact points to form a three-dimensional recticular assembly, and followed, immediately thereafter, by cooling the assembly to solidify the same.

Preferably, the diameter of the filaments extruded from the nozzles is so determined as to be in the range of 1-2 mm.

The specific gravity of the synthetic resin used for manufacturing the filaments may be approximately 0.93. The reticular assembly may have a void/total volume in the range of 80 to 98%.

Any suitable synthetic resin may be used for the manufacture of the reticular assembly.

It has been found, however, that polypropylene resins are particularly suitable for this purpose, since they are light in weight, mechanically strong, and resistant to deterioration in water and do not release noxious or organic materials in water due to the fact that they contain no plasticisers.

The filler may take any suitable form and be of any size appropriate for the use to which it is to be put. The filler may be in the form of a pipe or a mat.

The filler in accordance with the present invention is used in the activated sludge process and exhibits an excellent micro-organism or bacteria-fixing effect. More particularly, the filler has the following advantages: (a) It has voids of different sizes, both large and small, and has a large void volume.

Accordingly; (b) it is able to fix or hold large amounts of microorganisms or bacteria in suspension; (c) when used in an aerator, it does not reduce the available volume of the aerator too much; and (d) the growth of the micro-organisms or bacteria does not cause clogging to occur; (e) Its voids and shapes can be varied as desired, dependent on the quality of the waste water, the B.O.D. (Biochemical Oxygen Demand) loading, the amount of sludge, and other factors; (f) It is light in weight and tough and resistant to deterioration over a long period of time; (g) If a porous filler is made by bonding filaments by using an adhesive, the adhe sive is subject to destruction by bacteria, whereas in the filler according to the present invention, the adhesion is not destroyed by bacteria and is semi permanently stable since the filaments are bonded together through melt-adhesion.

The filler in accordance with the present invention can therefore be used not only in general water clarifiers but also in equipment for the treatment of different kinds of industrial waste water. Furthermore it can be used not only for the reduction of B.O.D. or C.O.D.

(Chemical Oxygen Demand) but also for the removal of the nitrogen content or other tertiary treatment. Thus, at B.O.D. volume loads in the range of 0.15 to 1.7 kg-B.O.D./ m." day, the use of the filler in 40 to 50% by apparent volume based on the aerator volume gives treated water of good stable quality and of low S.S. (Suspended Solid) content. When the filler is used, the microflora in the clarifier is occupied predominantly by filamentous bacteria and it becomes possible to retain sludge (filamentous bacteria) of high density and activity, i.e., the filler is of high capacity for S.S. retension. Furthermore, by use of the filler, it becomes possible to effect stable nitrification of ammonia nitrogen.

Two embodiments of a filler capable of use as a suspension holding device or fixer or as a drainpipe in accordance with the invention are now described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective and schematic view of the first embodiment of filler; Figure 2 is a schematic plan view of the filler illustrated in Figure 1 and which has been fitted in a water treatment tank; Figure 3 is a partial, sectional and schematic illustration of apparatus for producing the second embodiment of filler; Figure 4 is a partial, sectional and schematic illustration of the same apparatus, as shown in Figure 3 except that the filler is manufactured by a different process, and Figure 5 is a transverse sectional view through the filler as produced by the apparatus shown in Figure 3 or 4.

Reference is now made to Figures 1 and 2, wherein one embodiment of the filler of the present invention is shown. The filler 3 comprises a three-dimensional reticular assembly of synthetic resin filaments defining voids between adjacent filaments and a multiplicity of channels 2 extending lengthwise of the filler.

The filler is produced by drawing polypropylene resin filaments 1 extruded downwards from nozzles (not shown), before they become solidified, at a speed lower than the speed at which they are extruded from the nozzles, thereby to curl each filament 1 into a coil. The filaments 1 are melt-adhered to one another at their contact points, and are, immediately thereafter, cooled to solidify the melt-adhered filaments. The filler is fitted within a waste water treatment tank 4 to form an insert therein which in use is immersed in the water being treated and thus acts to hold suspended solids in the water being treated. This embodiment of the filler in accordance with the invention has the advantages that it is extremely easy to produce and that a number of such fillers arranged adjacent each other can be easily arranged in the waste water treatment tank 4 as shown in Figure 2.

Waste water to be treated and contained in the tank 4 passes through the voids and the channels 2 of the or each filler 3, whereby impurities in the form of suspended solids, e.g. bacteria or micro-organisms, in the waste water are held in suspension by the voids and accumulate in the voids to form an activated sludge. The waste water as it continues to pass through the voids and the channels comes into contact with the activated sludge and is thereby purified. When the voids contain an over-accumulation of activated sludge, the over-accumulation of sludge is precipitated at the bottom of the channels 2 and avoids the or each filler becoming clogged even when used for a long period of time.

Using the embodiment of the filler of the invention illustrated above, a test of waste water treatment was made, the experimental conditions and the results obtained being described in the following table: Conditions for treatment: B.O.D. of effluent water 100 ppm Residence time 12 hours B.O.D. volume load 0.2 kg-B.O.D./m3.day B.O.D. S.S. load 0.1 kg/B.O.D./kg.S;S.day Results of treatment:

D Water treated by Activated Standard sludge process activated employing the filler sludge of the present Effluent Water process invention pH 6.62 6.71 6.56 (6.55-6.77) (6.00-6.76) (6.18-6.84) C.O.D. 75.0 20.8 9.8 Mn (72.0-80.0) (13.0-39.0) (6.0-14. 0) (ppm)3 B.O.D. 103 -21.8 6.8 (ppm) (99.0-110.0) (9.0-51.0) (6.0-9.0) S.S. . 0 20.3 2.8 (ppm) (16.9s31.0) (2.0--5 .0) MLSS 2020 3 (ppm)4 Remarks: 1. The numerical values are mean values during the operation time.

2. The numerical values in the parentheses are minimum and maximum values.

3. C.O.D., is Chemical Oxygen Demand Manganate.

4. M.L.S.S. is Mixed Liquor Suspended Solids.

These results show that the activated sludge process employing the filler of the invention has excellent capacity for waste water treatment in comparison with the conventional activated sludge process.

Reference is now made to Figures 3 to 5, where another form of the filler in accordance with the present invention and the apparatus for making it is shown. In Figure 3, a downwardly-directed die 5 of an extruder is provided with a plurality of nozzles of small diameter arranged in a ring. Filaments 6 of synthetic resin (e.g. polypropylene) are extruded through the nozzles to form a pipe.

Below the die 5 there is a jacketted annular coolant injector 7 having in its inner wall a plurality of nozzles 8. The filaments 6, after being extruded from the nozzles in the die 5, pass through the annular coolant injector 7 and the filaments 6 are cooled and solidified by the action of water or other liquid coolant jets issuing from the nozzles 8. Below the coolant injector 7 there are rolls 9, 9' which pull the filaments through the coolant injector 7. In operation, the filaments 6 are drawn by the rolls 9, 9', at a speed lower than the speed at which the filaments 6 are extruded from the nozzles in the die 5. Thus the softer parts of the filaments above the water- or other liquid-cooled and solidified parts of the filaments 6 curl to form coils and are meltadhered to one another at their contact points to produce a filler comprising a threedimensional reticular assembly in the form of a pipe 10 defining voids between adjacent filaments and one channel extending lengthwise of the pipe 10. The resulting endless pipe may be cut to any desired length.

Figure 4 shows a similar embodiment to that shown in Figure 3 except that a rod 11, extending from the centre of the undersurface of the die 5 into the jacketted annular coolant injector 7, is provided to define the inner diameter of the pipe 10.

In each of the embodiments illustrated in Figures 3 and 4, the upper portion of the inner wall of the jacketted annular coolant injector 7 is tapered toward the bottom to define a funnel-shaped hollow in the upper cavity of the coolant injector. Furthermore, the inwardly-projecting upper edge 12 of the coolant injector 7 is provided at its lower end with a nozzle 8', from which nozzle 8' a coolant (water) jet issues so as to prevent the extruded filaments 6 from adhering to the inner wall of the coolant injector 7.

The resultant pipe is annular in crosssection, as shown in Figure 5. It is to be understood, however, that the pipe may be of any desired tubular shape in cross-section, e.g., it may be loofah-shaped.

The pipe thus produced is fitted within a waste water treatment tank in an appropriate position and immersed in the water being treated and forms a filler or insert to hold or fix suspended solids in the water being treated.

However, such pipe is also suitable for use as a drainpipe for underdraining. The waterpermeable area of the pipe is greater than those of the conventional porous synthetic resin pipes by 20 to 30%. Furthermore, the pipe exhibits excellent pressure-tightness and therefore, when buried in the ground, is resistant to failure due to earth pressure. Moreover, in the drainpipe, water-permeable pores are densely distributed all over the surface, so that the clogging of the pores is reduced. In addition, the density, i.e., the water-permeable area proportion, of the pipe can be easily adapted to the soil quality of the ground in which the pipe is to be buried by appropriately adjusting conditions for manufacture, such as the temperature or viscosity of the melted synthetic resin filaments extruded from the nozzles, or the speed at which the filaments are extruded, are drawn or are cooled and solidified.

The filler may alternatively be in the form of a mat.

WHAT I CLAIM IS: 1. A waste water treatment filler comprises a three-dimensional reticular assembly of curled synthetic resin filaments melt-adhered to one another at their contact points and defining voids between adjacent filaments, the assembly defining one or more channels extending lengthwise of the filler, the filler or a number of said fillers arranged adjacent each other being fitted, in use, within a waste water treatment tank, whereby impurities in waste water to be treated and contained in the tank and passing through the voids and the or each channel are held in suspension by the voids and accumulate therein to form an activated sludge to purify waste water in contact therewith.

2. A filler as claimed in Claim 1 wherein said synthetic resin is polypropylene.

3. A filler as claimed in Claim 1 or 2 wherein the diameter of said filaments is in the range of 1 to 2 mm.

4. A filler as claimed in any preceding claim wherein the void/total volume of the reticular assembly is in the range of 80 to 98%.

5. A filler as claimed in any one of Claims 1 to 4 wherein said filler is in the form of a pipe or a mat.

6. A method for the production of the filler as claimed in Claim 1, comprising: drawing synthetic resin filaments extruded from nozzles, before they become solidified, at a speed lower than the speed at which the filaments are extruded from the nozzles, thereby to curl each filament into a coil, to melt-adhere the filaments ta one another at their contact points to form a three-dimen sional reticular assembly, and followed, immediately thereafter, by cooling the assembly to solidify the same.

7. A waste water treatment filler constructed substantially as described herein with reference to Figures 1 and 2 of the accompanying drawings.

8. A pipe-shaped waste water treatment filler or drainpipe constructed substantially as described herein with reference to Figures 3 and 5 or Figures 4 and 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. coolant injector 7 there are rolls 9, 9' which pull the filaments through the coolant injector 7. In operation, the filaments 6 are drawn by the rolls 9, 9', at a speed lower than the speed at which the filaments 6 are extruded from the nozzles in the die 5. Thus the softer parts of the filaments above the water- or other liquid-cooled and solidified parts of the filaments 6 curl to form coils and are meltadhered to one another at their contact points to produce a filler comprising a threedimensional reticular assembly in the form of a pipe 10 defining voids between adjacent filaments and one channel extending lengthwise of the pipe 10. The resulting endless pipe may be cut to any desired length. Figure 4 shows a similar embodiment to that shown in Figure 3 except that a rod 11, extending from the centre of the undersurface of the die 5 into the jacketted annular coolant injector 7, is provided to define the inner diameter of the pipe 10. In each of the embodiments illustrated in Figures 3 and 4, the upper portion of the inner wall of the jacketted annular coolant injector 7 is tapered toward the bottom to define a funnel-shaped hollow in the upper cavity of the coolant injector. Furthermore, the inwardly-projecting upper edge 12 of the coolant injector 7 is provided at its lower end with a nozzle 8', from which nozzle 8' a coolant (water) jet issues so as to prevent the extruded filaments 6 from adhering to the inner wall of the coolant injector 7. The resultant pipe is annular in crosssection, as shown in Figure 5. It is to be understood, however, that the pipe may be of any desired tubular shape in cross-section, e.g., it may be loofah-shaped. The pipe thus produced is fitted within a waste water treatment tank in an appropriate position and immersed in the water being treated and forms a filler or insert to hold or fix suspended solids in the water being treated. However, such pipe is also suitable for use as a drainpipe for underdraining. The waterpermeable area of the pipe is greater than those of the conventional porous synthetic resin pipes by 20 to 30%. Furthermore, the pipe exhibits excellent pressure-tightness and therefore, when buried in the ground, is resistant to failure due to earth pressure. Moreover, in the drainpipe, water-permeable pores are densely distributed all over the surface, so that the clogging of the pores is reduced. In addition, the density, i.e., the water-permeable area proportion, of the pipe can be easily adapted to the soil quality of the ground in which the pipe is to be buried by appropriately adjusting conditions for manufacture, such as the temperature or viscosity of the melted synthetic resin filaments extruded from the nozzles, or the speed at which the filaments are extruded, are drawn or are cooled and solidified. The filler may alternatively be in the form of a mat. WHAT I CLAIM IS:

1. A waste water treatment filler comprises a three-dimensional reticular assembly of curled synthetic resin filaments melt-adhered to one another at their contact points and defining voids between adjacent filaments, the assembly defining one or more channels extending lengthwise of the filler, the filler or a number of said fillers arranged adjacent each other being fitted, in use, within a waste water treatment tank, whereby impurities in waste water to be treated and contained in the tank and passing through the voids and the or each channel are held in suspension by the voids and accumulate therein to form an activated sludge to purify waste water in contact therewith.