GB2215326A

GB2215326A - Multilayer porous structure, particularly for the separation of liquid and solid phases

Info

Publication number: GB2215326A
Application number: GB8805472A
Authority: GB
Inventors: Lajos Papp; Istvan Szonyi; Ferenc Miklossy; Jozsef Anyos; Attila Weininger; Jozsef Voelgyesi
Original assignee: KELETMAGYARORSZAGI VIZUEGYI
Current assignee: KELETMAGYARORSZAGI VIZUEGYI
Priority date: 1988-03-08
Filing date: 1988-03-08
Publication date: 1989-09-20
Also published as: FR2628652A1; DD267915A5; GB8805472D0; FR2628652B3; DE3807748A1

Description

222 15326 MILILTILAYEiR POROUS sTRucTuRE, pARTICULA.RLy FO,- -Eiu,

SEPARATIONT OF LIQUID AND SOLID PHASES The invention relates to a multilayer porous filtering and/or dispersing structuret where at least one layer is formed by cemented solid grains. The.Porous layers are joined to one another by using adhesive The porous filtering and/or dispersive structure according to the invention is suitable for the separation of solid and liquid phases, as well as for dispersing gases into liquid, or liquids into other liquids or gases. The structure according to the invention is particularly

applicable to advantage in the field of waste -,rater purification and generally for water treatment.

In the course of water purification - among r> others - filtering and decomposition of biological organic matter are carried out; occasionally aggressive gases are expelled from, or gas is injected into the liquids, furthermore the sludges of waste water are dei- .ratered /desiccated/. The filter structure according to the invention is effectively applicable in above processes: in certain cases liquid containing solid phase is poured over the filter structure to filter out the solid phase; in other cases in the course of oispersion - gas in the form of fine bubbles is injected through the structure into the liquid mass.

Various methods are known for filtering and de-tiatering /sludge/: e.g. sand filtering; filtering C.

with rigid filter plates, cemented gravel, textile and metal sieves, as well as mechanical filtering /centrifugal and vacuum filtering, sludge compression, etc./.

t - 2.- Desiccation is the classic method of dewatering the sludge.

Efficiency of the known mechanical filtering and de-matering methods is favourable, but their field of application is really narrow, and their use in the dbwatering technologies is limited by the specific high cost of investment and operation. Hence, filtering technologies based mainly on the utilization of natural mate rials are used in the waste water purification, among them the sand filtering is the most generally used method.

Grain size of the material in the sand filters is increasing in the flow direction of the liquid. The solid phase passing from the waste water through the sand filter infiltrates the sand-layer, while the liquid phase flows through. Consequently the filter layer be comes clogged, and it w111 be operative only by removing the filtered solid phase with counterflow flushing, or the clogged lyaers are stripped and replaced.

Filter structures consisting of rigid, multilayer filter plates are described in the US patent specification No. 4,452,698 and 4,381,998. These filter structures made of cemented granular material comprise a supporting layer and a filtering layer; the supporting

C) layer is naturally permeable, but its pores are greater than those of the filter plates. Material of the grains is inorganic, e.g. AI 2 0 3' corundum, silicone carbide, boron carbide, etc. grains are used for the preparation of filters. These filters are fairly costly structures.

The US patent specification No. 4,382,863

11 -- 3 - r relates to a similar structure consisting of three layers and it is similarly costly.

According to the Hungarian patent application No. 216/83, homogeneous /singlelayer/ cemented grav-el filter is used for reducing the groundwrater pressuxel e.g. for drainage of cellars.

The sludge desiccation is one of the most problematic phases of the irater treatment. The sludge desicca tion requires large areat its functioning greatly depends C> on the climatic conditions, thus, dewatering of the sludge takes a long time and stripping of the desiccated sludge requires manual work for protection of the drain system. Further utilization of the manually stripped sludge is inhibited by its gravel content.

The gasliquid system in the course of waste water treatment appear partly upon removal of the gases present in the liquid with the aid of other gases injected into the liquid, and partly while using gases during the biological purification. Expulsion of the aggressive CO 2 with air injection is an example for the former case, and dispersion of air or oxygen in the liquid mass for the latter case, to provide the vital conditions for micro -organisms present in the liquid phase. Deep air injec tion. with nozzles in the most effective method among the technologies used for this purpose,.%,here hoi.,ever the gas injection at a steady rate is problematic. Further diffi culty is that intermittent gas injection is - required in most cases, and during standstills it may result in clogg- ing of the nozzles caused by the solid phase present in the liquid.

The aim of the invention is to provide a filtering and/or dispersive structure performing the filtering with maximal efficiency, the operation of which requires only minimal cost and energy, which is not sensitive to clogging and injects the gas into the liquid uniformly distributed at a steady rate.

The invention is based on the recognition that if the filter grains are joined with hydrophobic adhesive to the filter layer, the adhesive film covering the grains on the surface of the filter structure receives electrical charge during the filtering process, the sign of which is identical ifith that of the solid grain in the material to be filtered, whereby the solid grains, particles present in the material to be filtered are repulsed. This way effective electrostatic field will be developed in the range of the external filter grain layer containing hydrophobic adhesive coating, which prevents the grains present in the material to be filtered from adhesion to the surface of the filter structure. Instead, a natural filter cake will develop from the grains above the filter structure, which is not in direct contact with the filter structure. As a result, cleaning of the filter requires only external washing, because no solid impurities can penetrate into the interior of the filter, its pores do not get clogged. The invention is based on the further recognition, that in the course of biological

C w --- 5 purification, or after aeration used for expelling detri mental gases, external synthotic resin coating prevents the solids and/or microorganism from deposition on the surface in contact with the liquid, and from clogging of the pores functioning as nozzles. This way more efficient biological purification and gas injection will be possible. On the basis of these recognitions, the C) problem was solved according to the invention with a multilayer porous structure provided with at least one supporting layer and at least one active layer, the pore size of which latter is smaller than that of the supporting layer, and at least the active layer consists of chemically inactive, inorganic - suitably silicate based - granular material, e.g. basalt, zeolite, Al 2 0 3 grains and binding material/s/9 and its essential feature is that hydrophobic binding material formed by silicone resin and/or bisphenol-A based epoxy resin is present at least on the surface of the grains constituting the active layer.

Thus, subject of the invention is a multylayer, porous structure for the separation of-solid and liquid systems, and for the dispersion of gas and liquid systems, particularly for the treatment and purification of waste waters and sludges, consisting of at least one usually upper thin active layer and one, usually lower thick supporting layer, both of which are porous, but the pores of the active layer are smaller than those of the supporting layer, and at least the active layer consists of chemically inactive, inorganic material, suitably materials of the silicate industry, preferably basalt, 6 -5 1-5 zeolite, Al 2 0 3 etc. grains and binding material/s/, characterized by having intensively hyerophobic binding material, such as silicone resin and/or bisphenol-A based epoxy resin - at least on the surface of the filter grains constituting the active layer. Usually upper and usually lower layers are spoken about, because the filter structure can be built in not only horizontally /e.ig. for gravitation filtering/, but it may be vertical as ifell.

The silicone resins are selected suitably from resin types having siloxane units of functionality 1 to 4 arid/or from products of branched structure produced by the condensation of monometers of 1 to 3 functionality, preferably phenyl methyl polysiloxane and/or phenyl methyl polysolixane polyester arid/or phenyl methyl siloxane /Polymerized with H 2 0 3 / are applicable.

Such bisphenol-A based synthetic resin produced e.g. from 4,4'-dihydroxy diphenyl propane and epichloro-hydrin is used as epoxy resin having groups of 4-17 OH functionality the molecular weight of which is between 380 and 3800, its epoxy equivalent between 175 and 4000, ester equivalent between 80 and 200, molecular viscosity is between 5 and 150 p /at 200C/1 and its specific weight is between 1.14 and 1.2. Its formula:

CH 2-CH -CH 2 9 /-O-R-O-CH 2 -CHCH 2-0R_/n 0 - CH 2_ MCH 2 0 OH 0 The filter structure is suitably formed so as to have the thickness of the active layer between 7 - -5 and 15 mm, and that of the supporting layer 50 and 15 0 mm.

Uhile use of the relatively small pores is expedient on the surface-of the porous filtering and/or dispersive structure in contact with liquid in order to form a more efficient electrostatic field, it is ad visable to reduce the filter resistance in the opposite direction, and thus, to use larger pores on the side opposite to the surface in contact with the liquid, more. over a suitably perforated steel plate or any other metal structure, possibly a plastic structure. e.g. aluminium or plastic screen may be used for the supporting layer.

The resin bringing about the hydrophobic and electrostatic field, cements the filter grains at the same time, thereby providing for a constant pore

CD size.

With regard to the foregoing, according to a further criterion of the invention, the size of grains forming the active layer/s/ is between 0.2 and 1 =, and pore size of the layer/s/ is between 0.1 and 1 mm.

It is preferable when the supporting layer of the porous filter- and/or dispersive structure is formed by a perforated steel plate, or perforated structure made of other metal or synthetic material, e.g. aluminimum screen, or a layer consisting., of inorganic grains and binding material, mrhere the grain size is C:> between 1 and 5 mm, the pore size between 0.8 and 1.2 mm, preferably about 1 mm. Generally, the thickness of the active layer/s/ is betifeen 5 and 15 uLm, that of the supporting layer/s/ between 50 and 150 mm.

The porous structure can be formed 1-.,ith more than two layers e.g. the two upper layers consist of inorganic filter grains and binding material, while C> the lot.7er one is a perforated steel plate, or perforated structure made of other metal or synthytic material, e.g. aluminium or plastic screen. But the filter structure may also be build up with mechanical strengthening, e.g.

reinforcement of the supporting structure.

A further embodiment of the porous structure according to the invention is characterized by being built up with three layers, %There at least one of them is an external active layer, and the intermediate layer consists of inorganic grains and binding material.

Geometry of either the active surface or the supporting layer may differ from the plane, e.g. it may be tubular, conical, semispherical, or candleshape, etc.

2-5 1Then filtering with the structure according to the invention, a thick solid phase /e.g. sludge/ will develop on the surface of the active layer - funo tioning as filter layer - which however does not stick to it. Consequently the sludge can be mechanically removed, whereas the filter is regenerated by external t..-ashins.

Ho.t.;ever, the multilayer porous structure according to the invention is suitable not only for 1 U 9 - 1 filtering, but for dispersion of gas in liquid as well. In this case the required gas is injected from the supporting layer, and the earlier filter surface will function as active dispergator /atomizer/. Especially in such case, it is advisable to provide the surface with a geometry different from the plane. Fine distribution of the injected gas is ensured by the fine pores of the active surface, moreover the hydrophobic binding material on the surface facing the liquid prevents - e.g. in case of intermittent operation - the micro-organism, e.g. phyto- and monoplankton organism /algae/ from deposition and clogging the pores. This way the C> structure is permanently operative.

The invention is described in detail by way of examples, as follows: Exam. Rle 1 Filter structure according to the invention is prepared for the filtering of communal sewage slucige calculated for 1 m 2 surface, as follows:

active layer material: aluminium oxyde /A1 2 0 31 granulometric composition:

size /FL1PA standard/ quantity /kg/ 22 lo.4 36 Mo Mo binding material: epoxy resin adhesive /TIPOX IHS/ 1.22 kg layer thickness 5 mm 1 n Permeability coefficient of the active filter plate: K = 2.1 x 10-3 cm/s. voids volume n = 32 Supporting layer - material: pearl gravel - grain size: 3-7 mm.

- binding material: epoxy resin adhesive /TIPOX IHS/ 2.5 kg - thickness: 45 mm.

- mass: 90.0 kg The initial dry substance content of the comiraunal sewage sludge was 2.0 % /thus its moisture content was 98.0 c%-/. A 4 %o solution of "Zetag 57" was used as conditioning agent. The extract content of dewatered sludge was 38 %. Clean filtrate, free from suspended matter i-ras obtained.

FEPA is an international standard related to grain size,.the equivalent of -which is Hungarian standard No. 6506-64.

One of the components of the 11TIPOX T_HS11 epoxy resin adhesive is bisphenol-A diglycidyl ether epoxy resin, and the other component is an aliphatic polyar-,LLr,e mixture. &ianufacturer: Tiszamenti VegyimUvek, Tiszaszederk6ny, Hungary/.

The "Zetag 57" is a polyacryl amide based polyelectrolyte, the product of the "Allied Colloid GmbH" /Hamburg, GFR/.

Example 2

I-Taste water sludge of a leather factory 1 was filtered with the structure according to the tiony 1 m 2 of which was produced as follows:

active filter layer material: silicone carbide /SIC/ granulometric composition:

size /FEPA standard/ quantity /kg/ 22 lo.4o 36 o.6o o.6o binding material: silicone resin ad- hesive /VP 2261/ 1.35 kg - thickness: 5 mm The active filter plate iras exposed to heat treatment at 150 0 C temperature for 3 hours. Its co efficient of permeability and voids volume are the same as those in example 1. - - supporting layer: same as described in example 1.

The initial dry substance content of the leather factory's waste water sludge was 1-5 /thus its moisture content 98.5 11S/. A 4 %o solution of "Zetag 57" was used as conditioning agent in this case, too. Chromi um content of the waste water was 1000 mg/l. As a result of filtering, dewatered sludge with 30 extract content and filtrate with 0.05 mg/l chromium content was obtained free from suspended matter.

The VP 2261 silicone resin adhesive is a proauct of Wacker Chemie Co. /Miinchen, GFR/.

Example 3

Oily waste water sludge was filtered ifith the structure described in example 1. The initial dry substance content of the sludge ifas 2 %, moisture content 98 %., and a 4 %o solution of "Zetag 57" was used as conditioning agent. As a result of filtering, dewatered sludge containing 33 % dry substance and filtered water suitable for the public sewerage system were obtained.

In all three examples, only washing of the surface was necessary for regenerating the active C> surface of the filter plate.

The filter resistance in 'the layers did not change everi after a long operating time, re.L..-ashing was not necessary. E, xample 4 Mlith the filter structure described in example 2, air was dispressed in water. The rate of air delivery over 1 m 2 surface of the structure was 20 J/h; amount of oxygen 100 g/0 2 /h; power consumption: gross o. 6 k-i..,/iooo g o 2; bubble size: d mean - 2.5 mm.

The main advantage of the invention is that rewashing is unnecessary for regeneration of the structure, only periodical flushing of the surface is needed, the demand of which for power, time and live labour is minimal. Production of the structure is and its applicability is manifold.

-5 1 c simple, a - 13 Naturally, the invention is not limited to.the examples described in the foregoing, but it is realizable in many ways within the protective scope - defined by the claims.

14 -

Claims

1. Multilayer porous structure for the separation of liquid and solid phases and/or dispersing liquid or gas, particularly for the treatment of waste water and sludges, comprising at least one supporting layer and at least one active layer the pore size of -;jbich is smaller than that of the supporting layer, at least the active layer consisting of chemically inactive, inorganic - suitably silicate based - granular material, e.g. basalt, zeolite, Al 2 0 3 grains and binding material/s/, c h a r a c t e r i z e d by having hydrophobic binding material formed by silicone resin and/or bisphenol-A based epoxy resin, at least on the surface of the grains constituting said active layer.

2. Structure according to claim 1, c h a r a a t e r i z e d in that said binding materials are resin types having siloxane units of 1 to 4 functionality and/or resin types of branched structure produced by the condensation of monomers of I to 3 functionality expediently phenyl methyl polysiloxane and/or phenyl methyl polysiloxame polyester and/or phenyl methyl vinylsiloxane polymerized suitably with H 2 0 2.

3. Structure according to claim 1, c h a r e c t e r i z, e d in that said hydrophobic binding material consists of an epoxy resin, being a bisphenol-A based synthetic resin produced from 4,41-dihydroxy diphenyl propane and eDichlorohydrin, having h a molecular weight between 380 and 3SOO, epoxy equivalent between 175 and 4000, ester equivalent between 80 and 200; comprising groups of 4 to 17 OH functionality having the molecular viscosity between 5 and 150 /at 20 OC/; and specific weight between 1.14 and 1.2.

4. Structure according to any of claims 1-3, c h a r a c t e r i z e d in that size of the grains forming said active layer/s/ is between 0.2 and 1 nun; and pore size of the layer/s/ is between 0.1 and 1 mm.

5. Structure according to any of claims 14, c h a r a c t e r i z e d in that its supporting layer is formed by perforated steel plate, or layer consisting of inorganic grains and binding ma terial, wherein the grain size is between 1 and 5 mm., pore size between 0.8 and 1.2 mm, preferably about 1 mm.

6. Structure according, to any of claims 1-5t c h a r a c t e r i z e d by the thickness of the active layer/s/ being between 5 and 15 mm, and that of the supporting layer/s/ between 50 and 150

7. Structure according to any of claims 1-61 c h a r a c t e r i z e d in that the supporting layer contains a structure, preferably reinforcing steel linings to increase the mechanical strength.

8. Structure according to any of claims 1-7 p c h a r a c t e r i z e d by being built up with three layers, wherein at least one external active layer and one intermediate layer consist of inorganic grains and binding material.

9. Structure according to any of claims 1-61 chara c ter ize d inthat surface of the active layer and/or supporting layer differs from the plane, it is suitably tubular, conical, semispherical, or candle-shape.

10.. Multilayer porous structure for the separation of liquid and solid phases and/or dispersing liquid or gas, substantialJN7 as described herRin.

Published 1989 atThe Patent Mae, State House,68.171 High Holborn, LondonWClR4TP. Purther copies maybe obtained from The Patent Office. Sales Branch, St Mw7 Cray, Orpington, Kent BRS 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent, Con. 1187 n;