WO2015181576A1

WO2015181576A1 - Biofilm carrier made of yarns

Info

Publication number: WO2015181576A1
Application number: PCT/HU2015/000052
Authority: WO
Inventors: István KENYERES; Márton KENYERES
Original assignee: Biopolus Technológiák Zrt.
Priority date: 2014-05-30
Filing date: 2015-05-29
Publication date: 2015-12-03
Also published as: HU4460U; CN205087986U; WO2015181576A4

Abstract

This invention relates to a biofilm carrier (B) made of yarns comprising a central yarn (1) made of elementary fibres (4), where the individual elementary fibres (4) constituting the central yarn (1) constitute a continuous fibre running over the entire length of the yarn (1), and a loop (2) made of further yarns (1) is fixed to the central yarn (1) at least at two anchor points (3a, 3b) and, moreover, the arc length of the loop (2) between two adjacent anchor points (3a, 3b) is bigger than the length of the central yarn (1) between two adjacent anchor points (3a, 3b).

Description

BIOFILM CARRIER MADE OF YARNS

The invention relates to a biofilm carrier made of yarns.

Operations based on micro-biological transformation and microbiologically produced materials are used to a significant and growing extent by modern economy. The operations based on microbiological transformation include, but are not limited to, e.g., biological sewage treatment, anaerobic digestion of organic materials to biogas, several pharmaceutical and food industrial fermentations, and even biological air cleaning. Suffice it to quote a few examples of the biologically producible substances, such as bio-ethanol, bio-polymers (such as e.g., polylactic acid or polyhydroxyalkonates), enzymes, organic acids, antibiotics and numberless other important products.

The microbiological transformations concerned are carried out decisively in liquid-phase and less frequently in gas-phase reactors, so-called bioreactors. Bioreactors provide adequate conditions for the operation of the micro-organisms responsible for the transformation, the necessary nutrients and environmental conditions. Where adequate conditions exist, the performance of the bioreactor is defined basically by the quantity (concentration) and state of the micro-organisms introduced there.

The micro-organisms responsible for biological transformation are present in the bioreactor basically in two forms, free-floating, so-called planktonic, form or attached to a surface, as so- called biofilm phenotype. Under natural conditions and if possible, the micro-organisms prefer the biofilm form. Micro-organism colonising on biofilm can attain very high cell concentration and thanks to the complex structure created and the binding materials used for it, they can function substantially more efficiently than their freely floating congeners.

The above realisation has led to the increasing use globally of biofilm-based bioreactors, i.e., so-called biofilm reactors, for the various biological transformations. Industrial-size biofilm reactors have first appeared in biological sewage treatment, but today they are used in a growing number of industrial fermentation technologies.

In the biofilm reactors, the micro-organisms colonise and form a biofilm on carriers having an adequate surface for that purpose. One of the most important requirements is that the biofilm carriers must be able to bond the largest possible biomass quantity while making the resulting biofilm permeable for the nutrients in the liquid phase and for the metabolites produced by the micro-organisms. Depending on the design of the carriers, the thickness of the biofilm that is permeable and hence suitable for technological purposes ranges from tenth of millimetres to as many as a few centimetres.

Two main groups of biofilm carriers are known, namely the floating carriers (floating in the fluid space of the bioreactor) and carriers of a fixed design. Fixed carriers have moved to the foreground in recent years due to their much more favourable properties than those of the floating carriers (no energy demand for movement, floating, no need for special filtering steps, no mechanical wearing problem due to friction etc.).

Moreover, among the biofilm carriers of fixed design the previously experienced rigid structures have been replaced by flexible structures and in particular - due to their favourable surface and cost characteristics - the fibrous and filamentary, essentially textile-based, carriers are the most widespread. One of the most preferred designs of biofilm carriers made of woven synthetic textiles is disclosed in Hungarian patent specification HU 227 984, whereas examples of looped synthetic textile carriers are disclosed in US 5,771 ,716 and US 7,862,890. It can be said that, of the flexible, textile-based biofilm carriers, the looped arrangements have proved to be more favourable due to the fact that the loops provide some kind of protection to the micro-organisms adhering to the surface of the textile yarns against the shear effect of the liquid flow, and thus a bigger volume of biomass can adhere to the surface.

However, even though the textile-based and in particular looped textile biofilm carriers constitute the most favourable binding surface for the micro-organisms in the biofilm reactors today, the currently well-known and widespread solutions have serious drawbacks.

The main drawback of the known solutions is that, due to their design, the specific textile material quantity used for bonding a unit of biomass (1 kg of dry matter) is rather significant (around 0.2 to 0.5 kg).

The quantity and adequate operation of the biofilm developing on the surface of the carrier is limited, moreover, by the speed and depth of entry of the nutrients required for the metabolism of the micro-organisms in the biofilm and the way the resulting metabolites can be released from it. These imply limits for the volumetric efficiency and utilisation of the bioreactors.

Moreover, the known biofilm carriers are typically made of homogenous material and as compared to the surfaces of the diverse materials and properties existing side by side in nature, which reduces the biodiversity and thus the efficiency of the resulting biofilm.

Therefore, the objective of the invention is to create a biofilm carrier suitable for eliminating the drawbacks of the prior art carriers, that is, where the specific textile material quantity required for bonding a unit of biomass is substantially smaller, and the depth of the entry of the nutrients necessary for the metabolism of the micro-organisms and the speed of the release of the resulting metabolites and the efficiency of the biofilm are enhanced.

The specified objective has been realised by designing a biofilm carrier made of yarns and possessing a central yarn made of elementary fibres, where the individual elementary fibres constituting the central yarn constitute a continuous fibre running over the entire length of the yarn, and a loop made of further yarns is fixed to the central yarn at least at two anchor points and, moreover, the arc length of the loop between two adjacent anchor points is bigger than the length of the central yarn between two adjacent anchor points.

The distance of the two adjacent anchor points fixing the elementary fibres of the yarn to each other is 5 to 50 mm.

The distance of the two adjacent anchor points fixing the yarn and the loop to each other is 15 to 150 mm.

The elementary fibres are fixed to each other at the anchor points by gluing, mechanical bonding or welding.

A biofilm-generating surface unit is fixed on the yarn and/or the loop.

The biofilm-generating surface unit is fixed near the anchor points.

The biofilm-generating surface unit is arranged on a carrier ring.

The carrier ring is fixed on the yarn and/or the loops by gluing.

In the following, the invention will be discussed in detail with reference to the enclosed drawing. In the drawing,

Figures la - Id show a preferred embodiment of the biofilm carrier, Figure 2 shown the structure of the yarn of the biofilm carrier in magnification,

Figure 3 shows biofilm carriers B suspended in the circular cylinder-shaped module,

Figure 4 shows biofilm carriers B suspended in a star-shaped frame module,

Figure 5 shows biofilm carriers suspended in a module with a square design,

Figure 6 shows biofilm carriers suspended in a square-shaped module similar to that in Figure 5,

Figure 7 shows a surface unit formed on a biofilm carrier, and

Figure 8 shows the carrier ring.

In a preferred embodiment of a biofilm carrier B shown in Figures la to Id, loops 2 made of yarn 1 similar to yarn 1 (Figure lb) are formed around a central stretched yarn 1 made of elementary fibres 4 (Figure la), to be fixed in the reactor space not shown in the Figures. Elementary fibres 4 of central yarn 1 shown n Figure la, made of elementary fibres 4, run along the entire length of yarn 1 between ends V 1 , V2 of yarn 1.

Loops 2 shown in Figure lb are fixed to central yarn 1 at least at two anchor points 3a, 3b, preferably by gluing, welding or mechanical bonding, e.g. knotting, netting etc. As can be seen in the Figures, the arc length of loop 2 between two adjacent anchor points 3a, 3b is bigger than the length of the central yarn 1 between two adjacent anchor points 3a, 3b. The distance of two adjacent anchor points 3a, 3b fixing yarn 1 and loop 2 to each other is preferably 15 to 150 mm.

Figures lc and Id show preferred embodiments of the biofilm carrier in a plan view. Whereas in Figure lc there are four, in Figure Id six yarns forming loops 2 are fixed to central yarn 1. Of course, it is conceivable to use a single or even more than six yarns forming the loop 2.

Figure 2 shows the structure of yarn 1 in magnification. As can be seen in Figure 2, elementary fibres 4 of yarn 1 are fixed to each other at anchor points 5a, 5b preferably by gluing welding or mechanical bonding, e.g. knotting, netting etc. The distance of two adjacent anchor points 5a, 5b fixing the elementary fibres of yarn 1 to each other is 5 to 50 mm.

The material of yarn 1 and thus of elementary fibres 4 of loop 2 may be polyethylene, polyester, polypropylene, polyamide etc. Elementary fibres 4 constituting yarn 1 constitute a continuous elementary fibre 4 over the entire length of the biofilm carrier. With this design, the specific biofilm carrier B quantity required for a unit biomass quantity bondable in biofilm form can be reduced by as many as 50-70% relative to the prior art solutions.

Figures 3 - 6 show the placement of some preferred embodiments of biofilm carrier B ain modules M arranged in the bioreactor. Schematic representations are shown of biofilm carriers B suspended in cylindrically-shaped module M in Figure 3, in star-shaped module M in Figure 4, and in square-shaped modules M in Figures 5 and 6, respectively. Central yarn 1 of biofilm carriers B can be fixed in the modules M by fixing the ends V 1 and V2 of yarn 1 shown in Figure la.

Figure 7 presents a biofilm carrier B where the basically inorganic-based biofilm-creating surface unit 6 shown in Figure 8 is applied on yarn 1 and/or loops 2, preferably close to e.g. anchor points 3a, 3b. Surface unit 6 is preferably made of carrier ring 7 and biofilm-creating material fixed to the external surface of carrier ring 7. Surface unit 6 is preferably fixed by gluing R. Besides the plastic fibre surface of yarn 1 and loops 2, surface unit 6 with inorganic- based micro-particulates and preferably made with open macro pores provides efficient assistance to the colonising of such micro-organisms and the colonisation of the biofilm carrier that could not or could hardly colonise on the surface of the synthetic fibres. The material of supplementary surface unit 6 with different physical/chemical properties may be perlite, zeolite, other clay minerals or e.g. charcoal of decisively calcium phosphate composition. This design makes the simple and economical use in the same system of different biofilm-generating surfaces complementing each other's characteristics.

By using biofilm carrier B according to the invention it is possible to eliminate the drawbacks of the prior art carriers, that is, the specific quantity of the textile material used for bonding a unit biomass is substantially smaller, the depth of the entry of the nutrients required for the metabolism of the micro-organisms and the speed of the release of the resulting metabolites as well as the efficiency of the biofilm increase.

Claims

1. A biofilm carrier (B) made of yarns characterized by comprising a central yarn (1) made of elementary fibres (4), where the individual elementary fibres (4) constituting the central yarn (1) constitute a continuous fibre running over the entire length of the yarn (1), and a loop (2) made of further yarns (1) is fixed to the central yarn (1) at least at two anchor points (3 a, 3b) and the arc length of the loop (2) between two adjacent anchor points (3a, 3b) is bigger than the length of the central yarn (1) between two adjacent anchor points (3a, 3b).

2. The biofilm carrier according to claim 1 characterized in that the distance of the two adjacent anchor points (5a, 5b) fixing the elementary fibres (4) of the yarn (1) to each other is 5 to 50 mm.

3. The biofilm carrier according to claims 1-2 characterized in that the distance of the two adjacent anchor points (3a, 3b) fixing the yarn (1 ) and the loop (2) to each other is 15 to 150 mm.

4. The biofilm carrier according to claims 1 to 3 characterized in that the elementary fibres (4) are fixed to each other at the anchor points by gluing, mechanical bonding or welding.

5. The biofilm carrier according to claims 1 to 4 characterized in that a biofilm-generating surface unit (6) is fixed on the yarn (1) and/or the loop (2).

6. The biofilm carrier according to claim 5 characterized in that the biofilm-generating surface unit (6) is fixed near the anchor points (3a, 3b).

7. The biofilm carrier according to claims 5-6 characterized in that the biofilm-generating surface unit (6) is arranged on a carrier ring (7).

8. The biofilm carrier according to claims 5-7 characterized in that the carrier ring (7) is fixed on the yarn (1) and/or the loops (2) by gluing (R).