SI22584A - Process of treatment of textile dyeing waste waters with combination of natural biomass carriers in biofilter - Google Patents

Abstract

The invention is based on a problem of how to design a biological process of treatment of highly colourised textile waste waters with a fixed biomass in a bio-filter in which there is such a combination of natural materials that the latter have high specific surface, excellent ability to enhance growth and development of various microorganism populations, and high filtration, adsorption and ion exchange ability. Zeolitic tuff, turf and sand are actively included into biochemical impurity degradation processes so that they bind physico- chemically or remove structurally various dyes and textile auxiliary agents, which is an advantage against systems with plastic biomass carriers that are chemically inert. After a longer period of retention on the surface of natural materials, various microorganisms (biomass) develop and significantly affect mechanisms of removal of organic compounds from textile waste water. By this, colourisation, pH and organic load of waste water are reduced. The system is designed in such a manner that the materials remain wetted and in contact with waste water for all the time of operation, which still improves the effect of treatment. The process and preparation are flexible, because in the case of potential change of quantity or composition of waste water, the treatment can be adapted to new conditions. Advantages of the process against systems with active carbon (which are often applied for treatment of textile waste waters) and conventional systems with active sludge are in its simplicity, low investment and operating costs and environmental friendliness.

Description

PROCEDURE FOR TREATMENT OF TEXTILE DYEWATER WASTE WITH THE COMBINATION OF NATURAL BIOMASS CARRIERS IN THE BIOFILTER

FIELD OF THE INVENTION

The present invention relates to the field of environmental protection, and more specifically includes the biological treatment of textile dye wastewater in a biofilter with attached biomass in which such a combination of natural materials having a large specific surface area, excellent growth and development ability of various microorganisms populations, high adsorption and ionic capacity all necessary for the effective removal / decomposition of dyes and textile auxiliaries from waste water, as well as for the reduction of high pH values. The process and preparation are flexible, since any changes in the amount or composition of the wastewater can be adapted to the new conditions.

TECHNICAL PROBLEM

A technical improvement of this invention is the use of a combination of zeolite tuff, peat and sand as biomass carriers in a biofilter with attached biomass for the treatment of textile dye waste water instead of expensive activated charcoal, which must be replaced or replaced after a certain time. regenerate, which is a huge expense, since dye desorption is very problematic.

Dyestuff wastewater contains structurally different colorants in combination with textile auxiliaries, such as: wetting agents, equalizing agents, sequestering agents, detergents and chemicals such as various salts and bases. The presence of all these substances influences the increase of organic and inorganic pollution parameters such as pH, BOD, COD, TOC, coloration, sulfides, anionic surfactants, toxicity, etc. It is therefore an object of the invention to design such a natural purification system whose purification capacity (reduction of pollution parameters) will be adaptable to changes in the amount, concentration and chemical composition of the colored wastewater intended for treatment at a low investment and operating cost.

Natural materials used for wastewater treatment are actively involved in the processes of biochemical degradation of impurities, so that they chemically bind certain substances from the process or emit them into the process, which is an advantage over chemically inert biomass carriers. The resulting reactions are filtration, adsorption, ion exchange, complex formation, chemical oxidation and reduction, sedimentation, biological conversion and degradation, etc.

Natural zeolites belong to a group of rock-forming minerals found in pyroclassic sedimentary rocks, which are chemically sodium, calcium or potassium alumosilicates with a porous three-dimensional skeletal structure consisting of interconnected channels and cavities filled with water, along which the processes alternate adsorption. Peat is a very inexpensive and easily accessible partially fossilized plant material with a high affinity for water, poor chemical stability and a tendency to shrink and / or swell The main components of peat are lignin, cellulose, fulvic and humic acids. All of these ingredients contain polar functional groups such as alcohol, methoxy, carboxyl, keto, phenolic and ether, which are involved in the chemical bonding of dyes and organic molecules from wastewater. Due to the polar nature of the peat, the adsorption of dissolved particles such as metal ions and polar organic molecules is possible. The sand in the system serves as a filter for larger particles of impurities, ensures rapid infiltration and prevents water retention and algae development.

On the surface of natural materials, various microorganisms (biomass) develop after a long retention time, which significantly affect the mechanisms of removal of impurities (organic compounds) from wastewater. In the first phase of the system, aerobic microorganisms develop in the upper layers, where most of the suspended and colloidal particles are removed, and after a certain period of operation, anaerobic microorganisms begin to develop and grow in the lower layers. The cell wall of microorganisms is composed of various organic compounds such as chitin, lipids, amino acids, etc. that can react with dyes through mechanisms of surface adsorption, ion exchange, complex formation and micro-sedimentation. The degree of discoloration by biomass depends on the structure of the dye, the size and charge of the dye molecule, the toxicity of the individual substances, the pH of the wastewater and the salt content, and on the parameters of the system (residence time, type and amount of carrier, flow rate, etc.). The compacted biofilter develops biomass with a very high level of activity, so their purification efficiency is very high in terms of volume. Due to the formation of biomass in the system and the biodegradation of organic matter in textile wastewater, natural materials are not saturated even after prolonged operation of the system (as in the case of activated carbon), so they do not need to be replaced (lower costs), but regular loosening and biofilter backwash.

Known state of the art

In numerous patents and other publications, the authors cite methods for treating textile wastewater in biological reactors, but little is known about biofilters with attached biomass that use natural materials to purify colored wastewater from the textile industry.

Patents describing the biological treatment of textile wastewater are as follows:

Patent CN1874964 / 06 describes a reactor and a method for anaerobically treating wastewater. Patent KR20050043401 describes the treatment of textile wastewater containing dispersed dyes with mixed populations of Bacillus Cereus KVVLC1 and Bacillus Cereus KVVLC2 and a method for the biological treatment of textile wastewater. Patent ES2127703 / 1999 also describes the degradation of textile dyes by the use of bacteria.

There are various designs of biofilters for the treatment of various wastewater; according to the inlet of wastewater, they are divided into biofilters with inflow at the top and biofilters with inflow at the bottom, according to the flow of wastewater and air are divided into confluent and countercurrent (M. Roš, Biological wastewater treatment, 2nd edition, Ljubljana 2001: GV Publishing House).

Patents describing processes for the treatment of industrial wastewater in various biofilters or. combined cleaning with the other methods are as follows: KR200449138B, KR20040054359, KR20050012876, KR20010002276, KR0109663Y, KR20030055513, KR20030055477, ΜΧΡΑ05003086, US2006283795, but none containing biofilter and natural waste materials, natural waste materials, natural materials.

The use of various natural materials for the removal of dyes from wastewater from the textile industry is known from the literature. Authors A. Bousher, X. Shen, R.G.J. Edyvean, Water Research, 31 (8) 2084-2092, describe the removal of colored organic compounds by adsorption on inexpensive waste materials; authors M. Alkan, S. Qelikgapa, O. Demirba§, M. Dogan, Dyes and Pigments 65 (2005) 251-259, describe the kinetics of the removal of blue reactive and blue acid dye from aqueous solution by adsorption on sepiolite (natural zeolite) in dependence on different pH, temperature and addition of salt; by Y.S. Ho, G. McKay, Chemical Engineering Journal 70 (1998) 115-124, describe the kinetics of sorption of acidic and basic dye from aqueous solution to peat depending on different pH, initial dye concentration and temperature; authors S.B. Bukallah, M.A. Rauf and S.S. AlAli, Dyes and Pigments 74 (2007) 85-87, describe the kinetics of adsorption of methylene blue dye from aqueous solution to sand, in the presence of anions and cations, and depending on the initial dye concentration and the amount of sand; authors Υ.Ε. Бенкли, М.Ф. Can, M. Turan and M.S. Qelik, Water Research 39 (2005) 487-493, describe a process for removing three reactive azo dyes in a biofilter filled with modified natural zeolite.

DESCRIPTION OF THE INVENTION

A process for the treatment of textile dye waste water carried out in a system (Figure 1) comprising a waste water tank (1), a biofilter (2) filled with a combination of biomass carriers up to 85% by volume and above the supports a water tower (10) , comprising 10-15% biofilter, outlet pipe with flow control valve (3), plastic hose driven up to the height of the carrier backfill (4), allowing the carriers to be constantly wetted. The wastewater inlet is at the top, the outlet at the bottom of the biofilter, the flow is vertical and the flow rate is adjusted so that the residence time in the biofilter is 8-10 hours. The biofilter combines three systems, namely anaerobic, anoxic and aerobic systems, to enable the efficient treatment of textile wastewater containing structurally different dyes, textile auxiliaries and chemicals.

At the bottom of the biofilter (Figure 1) is a 0.2 mm diameter polypropylene mesh (5) which prevents the rinsing of the supports and clogging of the effluent. The biofilter is filled with a combination of natural materials (Figure 2), with a porosity of 0.51, in layers from the bottom up:

- (10% by volume) washed coarse sand 2-12 mm in diameter (6), which prevents the brackets from escaping from the system;

- (45% by volume) zeolite tuff 4-12 mm in diameter (7), with a chemical composition of 62.95% SiO ₂ , 15.92% AI ₂ O ₃ , 3.10% Fe ₂ O ₃ , 3.81% CaO , 1.31% MgO, 4.67% Na ₂ O, 4.67% K ₂ O, 0.03% SO ₃ . Na ⁺ is the dominant cation; other minerals in the rock are quartz, plagioclase and muscovite; Zeolite tuff has a great ability to adsorb, ion exchange and develop the various microorganisms required for the degradation of dyes and textile auxiliaries;

- (20% by volume) peat (8), which is a very effective adsorbent and at the same time lowers the high pH of wastewater;

- (10% by volume) washed coarse sand 2-12 mm in diameter (9) providing coarse filtration;

Natural materials are selected to have a large specific surface area, an excellent ability to grow and develop different populations of microorganisms, a high capacity for adsorption and ion exchange, which is the object of the invention. Larger diameter beams than fine grained materials have the advantage that the system is not clogged, but beams should not be too large because the cleaning effect may also be reduced.

The cleaning process in the biofilter is carried out in several successive phases: Phase 1 is the filtration and surface adsorption of dyes and textile auxiliaries; Phase 2 is aerobic biodegradation of textile auxiliaries; Phase 3 is the anaerobic digestion of dyes, which mainly occurs in the lower part of the biofilter, where anaerobic microorganisms begin to develop and grow after a certain period of system operation, because there is sufficient food in the wastewater; Phase 4 enables the completion of dye mineralization under aerobic conditions; It is necessary to maintain the temperature in the range of 12 to 25 ° C and to rinse or rinse. loosening biomass carriers after prolonged operation time;

The discoloration of four heavily colored textile wastewater was monitored spectrophotometrically by measuring the absorbance in the initial and treated wastewater by day, at the wavelength of maximum absorption. The purification effect in the biofilter was evaluated by measuring the pollution parameters such as pH and total organic carbon (TOC) by day. In order to monitor changes occurring in the system, oxidation reduction potential (ORP) measurements were also taken in the samples taken.

The invention is illustrated by the accompanying figures 1-6.

Figure 1: Purification system with a combination of biomass carriers in a biofilter

Figure 2: SEM images of biomass carriers: zeolite tuff (top left), sand (top right), peat (bottom)

Figures 3-6 show the purification effect of four different textile dye waste water containing structurally different dyes, chemicals and textile auxiliaries, at constant flow through a combination of natural biomass carriers in the biofilter, with a residence time of 8-10 hours. Samples were taken 2x daily, 19 days in a row, except Saturdays and Sundays and analyzed directly. The Z code on the graphs indicates: initial waste water before treatment in the biofilter.

Figure 3: Absorbance at wavelength of absorption maximum by days Figure 4: pH by days Figure 5: TOC by days

Figure 6: Oxidation reduction potential (ORP) by day

Figure 3 shows that the initial absorbances in the four textile wastewaters are between 0.95 and 1.5, which means that they are strongly colored. After absorption of the wastewater through the biofilter with the attached biomass, the absorbance decreases by days to a final value of 0.0291, 0.1094, 0.1783 and 0.244 (day 19), the color decreases by about 97%, 91%, 81% and 84% for individual waste water. With a longer holding time of wastewater in the system (5 days and more), without flow, complete (visible) discoloration was observed.

Figure 4 shows that the initial pH in the four textile wastewaters is very high

9.6 and 10.2 because cellulose fibers are colored in a strongly alkaline medium (pH 12). After treatment in a biofilm with fixed biomass, they are reduced to values between 7 and 8.5, which is within the permitted limit values for discharge into watercourses; pH 6,5-9 (Official Gazette RS 35/96 and Official Gazette RS 47/07). Peat, which has a pH between 3 and 4 and, in a small amount of 20% of the volume of the biofilter, successfully lowers the pH, has the greatest effect on reducing the wastewater pH.

Figure 5 shows that the initial TOC values are very high between 137 and 165 mg / L, which means that textile wastewater is heavily contaminated with organic compounds, which is mainly influenced by the addition of textile auxiliaries such as sequestering, equalizing, wetting, washing, etc. agents, less the addition of dyes. After passage of the wastewater through the biofilter with a combination of natural biomass carriers, the TOC is reduced by days to a final value of 29, 32, 51 and 59 mg / L (day 19), which is within the permitted limit values for discharge into watercourses; 60 mg / L (Official Gazette RS 35/96) and represents a reduction of approximately 81%, 80%, 63% and 64% for individual wastewater.

Figure 6 shows the measurements of the oxidation reduction potential (ORP) in four colored textile wastewater. Initial effluents have a high ORP of between 107 and 205 mV, which is still increasing in the first part of the test, which means that oxidants and more oxygen are present in the biofilter. At this stage, adsorption and filtration of dyes and textile auxiliaries, and partly aerobic biodegradation of textile auxiliaries, take place. It then decreases to a final value of 7, 52, 90 and 52 mV (last day) through the duration of the test and the amount of effluent flowed through the combination of ORP carriers. The measurements confirm that during the purification process, conditions in the lower layers of the biofilter changed from aerobic environment to anoxic, free of oxygen and dominated by reduced compounds, allowing anaerobic biodegradation of various dyes that are difficult to decompose under aerobic conditions. The change in the ORP in the wastewater after passing through a combination of carriers is significantly influenced by the initial ORP of the colored wastewater, the ORP of the carriers, the duration of the individual treatment, the amount of wastewater expired and the residence time. In addition, ORP is highly dependent on external factors such as: temperature, reactions in wastewater, measurement time, oxygen content in wastewater, etc.

Claims (5)

A process for the treatment of textile dye waste water by a combination of natural biomass carriers in a biofilter, characterized in that a biofilter with attached biomass is used for cleaning. Method according to claim 1, characterized in that as a carrier of biomass in the biofilter we use a combination of natural materials in layers and bottom-up order: 10% by volume washed coarse sand 2-12 mm in diameter, 45% by volume zeolite tuff 4- 12 mm, 20% by volume peat, 10% by volume washed rough sand 2-12 mm in diameter. Method according to the preceding claims, characterized in that the flow of wastewater through the column is constant so that the wastewater retention time in the system is 8 to 10 hours. Method according to the preceding claims, characterized in that the wastewater flow is vertical with the inlet at the top of the biofilter and the outlet at the bottom. Method according to the preceding claims, characterized in that the materials in the biofilter are wetted throughout the system.