WO2016204649A1

WO2016204649A1 - Biocomposite material for purification of sewage waters from nitrite, nitrate and phosphate ions

Info

Publication number: WO2016204649A1
Application number: PCT/RU2015/000864
Authority: WO
Inventors: Aleksei Georgievich DEDOV; Ekaterina Aleksandrovna IVANOVA; Elena Evgenyevna BELOUSOVA; Galina Aleksandrovna DOLNIKOVA; Aleksandr Gavrilovich ISHKOV; Rafet Kutuzovich Idiatulov; Mikhail Petroich KIRPICHNIKOV; Elena Sergeevna LOBAKOVA; Delgir Andreevna SANDZHIEVA; Anna Dmitrievna PONOMARENKO; Anastasia Nikolaevna SHARONOVA
Original assignee: Publichnoe Aktsionernoe Obschestvo "Gazprom"
Priority date: 2015-06-17
Filing date: 2015-12-09
Publication date: 2016-12-22
Also published as: CA2957653C; RU2608527C2; CN107074597B; CA2957653A1; CN107074597A; RU2015123301A

Abstract

Application: the invention relates to biocomposite material containing non-woven polymer and immobilized organism aggregation, and it may be used for purification of household and industrial sewage waters from contamination with nitrites, nitrates and phosphates. Biocomposite material is non-woven polymer based on acrylonitrile and methyl methacrylate copolymer derived by aerodynamic formation; filler which is active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds (Lemnaceae) family incorporated into polymer during its aerodynamic formation totaling 10-50% of polymer weight; and immobilized microorganism aggregation that reduces concentration of nitrate, nitrite and phosphate ions. The technical result involves improvement of operational characteristics and intensification of biological purification process due to increase in the material specific surface for immobilization of microorganisms. 2 examples.

Description

BIOCOMPOSITE MATERIAL FOR PURIFICATION OF SEWAGE WATERS FROM

NITRITE, NITRATE AND PHOSPHATE IONS

The invention relates to biocomposite material containing non-woven polymer and immobilized organisms and may be used for purification of household and industrial sewage waters from contamination with nitrites, nitrates and phosphates.

Apart from physical and physicochemical methods of sewage waters purification, biological cleaning methods are widely used at the present time. These methods are based on capability of microorganisms to use contaminants as a food source during their life activity. Biological purification of sewage waters can be performed both in natural conditions (sewage farms, absorption fields, maturation ponds) and special structures (aerotanks, biofilters) with help of various materials. Artificial cultivation of microorganisms in favorable environment specially created therefore (breeding ground composition, abundance of dissolved oxygen, temperature) enhances biological purification of sewage waters significantly.

In addition to that, materials used for biological purification of sewage waters have a variety of disadvantages which determines relevance of development of new highly efficient materials.

There are known materials for purification of sewage waters such as, for instance, active sludge (No. RU 2185338, 2002; No. RU 22961 10, 2005; No. RU 2012103445, 2010; No. RU 2422380, 2010; No. RU 2322399, 2006), load layers whereon active sludge is applied (No. RU 2099293, 1995; No. RU 2259962, 2004; No. RU 2472719, 2011 ; No. RU 2280622, 2006), active sludge immobilized on polymer floating load (No. RU 2448056, 2010), inert loading material with further fouling by biofoil, with which metal is engaged in direct contact (No. RU 2075202, 1995).

There is a known material for biological purification of sewage waters described in No. RU 2050336, 1995, which is a carcass (in the form of brushes of lavsan or nylon) or porous (expanded clay) carrier for microorganisms in combination with an additional carrier in the form of clay-containing and chemically active porous lime-containing sedimentary rocks, and porous minerals based on potassium aluminum silicates used at stages of anaerobic primary sludging and second stage aerobic treatment; and there is a porous carrier, such as expanded clay, in combination with an additional carrier in the form of clay-containing and chemically active porous lime-containing sedimentary rocks, and porous minerals based on potassium aluminum silicates at the first stage of aerobic treatment, however, carcass or porous carrier of the second stage aerobic treatment is modified with microalgae (chlorella and/or scenedesmus), and the additional carrier in the form of clay-containing and chemically active porous lime-containing sedimentary rocks and porous minerals based on potassium aluminum silicates is also used at the stage of clarified water removal.

Disadvantages of this material are: complex composition, necessity to use it in multistage sewage water purification procedures based on combination of anaerobic and aerobic processes.

The closest analog is material for biological cleaning of sewage waters described in No. RU 49525, 2005, which is a biofilter containing a polymer netted load with fiber bundles characterized in that a biofilter load is fixed on a carcass block of rectangular plastic frames fixed together in the form of a parallelepiped. In this case the polymer net is fixed on fringes and along the parallelepiped height in diametral planes that are perpendicular to its longitudinal axis. As a result of contact with sewage water, biofoil of immobilized microorganisms forms on the netted load with fiber bundles. Treated liquid flows freely around net threads and fiber bundles fixed thereon, whereby (due to developed interaction surface) necessary mass exchange between sewage water and microorganisms fixed on the net-like load surface is reached.

Application of this material allows reaching over 60% purity of sewage water according to nitrates and phosphates.

Disadvantages of this material are insufficient purification of sewage waters from nitrates and phosphates due to formation of biofoil of immobilized microorganisms only on the surface of the netted load which determines relatively small specific working area and applicability of material described only in agriculture and public services when purifying household sewage waters.

The object of the present invention is to create more efficient biocomposite material with improved purification capability designed to clean household and industrial sewage waters from nitrite, nitrate, and phosphate ions to the level which complies with requirements of current regulatory standards.

The set task is accomplished through described biocomposite material for purification of sewage waters from nitrite, nitrate and phosphate ions that contain non-woven polymer which is based on acrylonitrile and methyl methacrylate copolymer derived by means of aerodynamic formation method; filler which is active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds (Lemnaceae) family incorporated into polymer during its aerodynamic formation totaling 10-50% of polymer weight; and immobilized microorganism aggregation that reduces concentration of nitrate, nitrite, and phosphate ions.

The achieved technical result involves improvement of operational characteristics and intensification of biological purification process due to increase in the material specific surface for immobilization of microorganisms. High efficiency of this material results from microorganisms being fixed both on polymer fibers surface and in structures of introduced fillers: active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds {Lemnaceae) family.

Described biocomposite material is derived with help of the following method.

Derivation of non-woven polymer on the basis of acrylonitrile and methyl methacrylate copolymer that contains active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds {Lemnaceae) family as filler is performed by aerodynamic formation method. The aerodynamic formation method is described, for instance, in B. V. Zametta, L. V. Agen, N. B. Zaikina, E. G. Moroz. "Derivation of non- woven materials by aerodynamic formation", Moscow: Textile Industry, 1973, No. 1, p. 64-67. Initial polymer raw material in pellets is melted in a melting device (extruder) or dissolved in a solvent, e.g. dimethylformamide, and filtered to remove impurities. Filler, such as active carbon (GOST 6217-74 or GOST 4453-7) and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds {Lemnaceae) family, is added to molten or dissolved polymer, and they are pushed through a bushing block. Streams that come out of the bushing are extracted and directed to a delivery unit surface with help of a muzzle device. A spinning bath is delivered from nozzles to the delivery unit surface at the same time. As a result, separation of fibers takes place, and structure of a fibered polymer sheet with incorporated filler (active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds {Lemnaceae) family) is formed. The formed sheet of non-woven polymer material is taken off of the delivery surface, washed from solvent in a washing device and dried in a dryer at 70-100°C. Polymer non- woven material has volumetric density of 50-220 kg/m³; diameter of fibers is 4-41 μηι.

In this case non-sterile plants of the Sphagnum genus are used, in particular nemorose Sphagnum (Sphagnum nemoreum), compact Sphagnum (Sphagnum compactum). Procedure of preparation of non-sterile plants of the Sphagnum genus involves the following. Firstly, various kinds of non-sterile sphagnum moss of the Sphagnum genus are dried either in natural conditions at room temperature or in a drying box at temperature 50-70°C until constant weight is reached. Then dried sphagnum moss is milled in an electric driven vibration drum mill. Milling is performed in a steel cup with a cover partially filled with balls having diameter 5-6 mm and made of the same material as the cup. Number of balls is 2-3 pieces. Particle fineness of material after milling is 50-60 μιη. Amount of introduced filler can be 10 to 50% of polymer weight.

Cell walls of water plants of the Duckweeds (Lemnaceae) family are used, in particular star duckweed (Lemna trisulca) and Lemna turionifera. The procedure of preparation of the Duckweeds {Lemnaceae) water plant cell walls involves the following. Biomass of water plants of the Duckweeds (Lemnaceae) family is washed in running water, then placed into 40% solvent of ethyl spirit warmed up to 50°C (in 1 :2 proportion) and extracted within 48 hours. Spirit is removed after extraction. Then the procedure is repeated with 70% solvent of ethyl spirit. After that received wall cells of water plants of the Duckweeds (Lemnaceae) family are dried. Nuclei size of derived structures varies from 10 nm to 10 μηι. Amount of derived structures can reach up to 10-50% of polymer weight.

Incorporation of filler (active carbon in the powder form and milled non-sterile plants of the Sphagnum genus or active carbon in the powder form and cell walls of water plants of the Duckweeds (Lemnaceae) family) is performed during the process of polymer fibers derivation from solvents or molten material by aerodynamic formation.

Immobilization of microorganisms is performed by immersing of non-woven polymer on the basis of acrylonitrile and methyl methacrylate copolymer into the cell suspension of microorganism aggregation that reduces concentration of nitrate, nitrite, and phosphate ions that adhere to fiber surface due to adhesion. Cell immobilization can be achieved by continuous oscillation at 100-200 rps, temperature of 18-26°C during 1-2 days. Upon process completion the derived biocomposite material is washed in distillated water to remove microorganism cells that have not attached.

In particular, bacteria of Arthrobacter, Bacillus, and Pseudomonas genera are used as an aggregation of microorganisms that reduces concentration of nitrate, nitrite and phosphate ions, aggregations containing methylotrophic yeast of the Torula genus.

Sewage waters to be purified are run through layers of described biocomposite material in the recirculation mode. Sewage delivered to the plant from above naturally flows from top downward along the entire plant. Sheets of biocomposite material fixed with special fixtures are placed inside the plant. Sewage water goes through the biocomposite material sheets, whereon cleaning from nitrate, nitrite, and phosphate ions takes place due to involvement of these ions in metabolic process of microorganisms with formation of gaseous nitrogen as the final product.

Thereby, introduction of active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds (Lemnaceae) family at the stage of formation of non-woven polymer material by aerodynamic method allows obtaining an additional unexpected effect that involves increase of material porosity (both on the surface and in the inner structure) and, consequently, higher degree of settlement of this material with microorganism aggregations due to increase in affinity of synthetic non-woven polymer material with biological objects. Introduction of fillers (active carbon and milled non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds (Lemnaceae) family) to polymer fibers results in increase of the microorganism immobilization surface and creation of favorable environment, reducing sensitivity of microorganisms to environmental changes.

Examples that illustrate but do not limit the invention are given below.

Example 1.

To purify sewage waters containing nitrite, nitrate, and phosphate ions in concentrations of 16.5 mg/1, 225 mg/1, 17.5 mg/1 respectively, biocomposite material based on acrylonitrile and methyl methacrylate copolymer derived by aerodynamic formation is used. Its thickness is 1.52 mm, volumetric density is 0.09 g/cm³, porosity is 92%. The said material contains 15% of milled active carbon, dried and milled plant of the Sphagnum genus - nemorose Sphagnum (Sphagnum nemoreum) - 15% of said polymer weight; immobilized cells of the microorganism aggregation that reduce concentrations of nitrate, nitrite, and phosphate ions in the function of which an aggregation including methylotrophic yeast of Torula genus, bacteria of Arthrobacter, Bacillas, Pseudomonas genera are used - 50% of polymer weight.

Contaminated sewage waters circulate for 2 days through the plant, inside of which sheets of said biocomposite material are placed. Due to increase of material surface for immobilization of microorganisms degree of sewage water purification on the 2nd day in terms of N0₃ ^" ion is 99%.; in terms of N0₂ ^~ ion - 92%; in terms of P0₄ ^3" ion - 81%, which exceeds the purification degree of known material by approximately 20%. Residual concentration of nitrite, nitrate, and phosphate ions after purification is considerably lower than the threshold limit value (TLV). Thus, efficiency of sewage water purification with this biocomposite material is significantly higher than that of the known material.

Example 2.

To purify sewage waters containing nitrite, nitrate, and phosphate ions in concentrations of 16.5 mg/1, 225 mg/1, 17.5 mg/1 respectively, biocomposite material based on acrylonitrile and methyl methacrylate copolymer and derived by aerodynamic formation is used. Its thickness is 1.46 mm, volumetric density is 0.1 g/cm³, porosity is 91%.

Said material contains 17% of milled active carbon and structures of water plant cell walls of star duckweed (Lemna trisulca) - 20% of said polymer weight; immobilized cells of the microorganism aggregation that reduce concentrations of nitrate, nitrite, and phosphate ions, in the function of which an aggregation including methylotrophic yeast of Torula genus, bacteria of Arthrobacter, Bacillas, Pseudomonas genera is used - 50% of polymer weight. Contaminated sewage waters circulate for 2 days through the plant inside of which sheets of said biocomposite material are placed. Due to increase of the material surface for immobilization of microorganisms degree of sewage water purification on the 2nd day in terms of NO3^" ion is 99%.; in terms of N0₂ ^" ion - 91%; in terms of P0₄ ^3" ion - 85%, which exceeds the purification degree of known material by approximately 24%. Residual concentration of nitrite, nitrate, and phosphate ions after purification is considerably lower than the threshold limit value (TLV). Thus, efficiency of sewage water purification with this biocomposite material is significantly higher than that of the known material.

Use of different amounts of filler within the agreed interval in described material results in similar consequences.

The provided data implies that described biocomposite material has highly developed specific surface due to incorporation of active carbon and non-sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds (Lemnaceae) family, which increases the amount of immobilized cells both on surface and in the material structure. This material demonstrates high efficiency in cleaning of household and industrial sewage waters from nitrite, nitrate, and phosphate ions to the level that is lower than the TLV for water bodies of drinking and household and agricultural purposes, and allows for decreasing the above- mentioned ions in sewage water by 81 -99% wt.

Claims

Biocomposite material for purification of sewage waters from nitrite, nitrate, and phosphate ions that contains non-woven polymer based on acrylonitrile and methyl methacrylate copolymer derived by aerodynamic formation; filler which is active carbon and milled non- sterile plants of the Sphagnum genus or active carbon and cell walls of water plants of the Duckweeds (Lemnaceae) family incorporated into polymer during its aerodynamic formation totaling 10-50% of polymer weight; and immobilized microorganism aggregation that reduces concentration of nitrate, nitrite and phosphate ions.