CZ2018177A3 - Biodegradation preparation for anaerobic biodegradation BTEX in a rock environment, method of producing this preparation and its use - Google Patents

Abstract

The biodegradation preparation for anaerobic biodegradation of BTEX in the rock environment is prepared by adding an aqueous leach of oxyhumolite at a concentration of 5 to 15 wt. of natural origin containing a mixture of humic acids, and a suspension of nanoparticles of natural origin ferrihydrite at a concentration of 2 to 10 wt. An aqueous oxyhumolite extract containing humic acids is used to stabilize ferihydrite nanoparticles in the biodegradable formulation.

Description

The invention relates to the field of decontamination, in particular to a biodegradable composition for anaerobic biodegradation of BTEX in a rock environment, to a process for the manufacture of the composition and to its use.

BACKGROUND OF THE INVENTION

As part of the remediation of a polluted rock environment by petroleum hydrocarbons such as benzene, toluene, ethylbenzene and xylenes, collectively referred to as BTEX, a subsequent final solution to remove contamination residues must be used in the area after primary treatment. BTEX substances are well biodegradable under oxic or aerobic conditions, even in groundwater. A major problem is the supply of groundwater with oxygen, especially in view of its low solubility. Groundwater aeration is costly, especially given the necessary density of the injection well network and the inhomogeneity of the environment. Anoxic nitrate biodegradation is an alternative for medium to low permeability rocks. The nitrate retardation is practically zero and therefore the ratio between the mean residence time in the contaminated collector and the rate of their consumption, ie the rate of BTEX biodegradation, is crucial. Incomplete denitrification is also problematic, accompanied by the accumulation of toxic nitrites, which occurs regularly during anoxic biodegradation of non-readily degradable substrates such as BTEX. Biodegradation of benzene under anoxic conditions is minimal.

In recent years, several studies have focused on the possibility of solving this problem by nanomaterials, namely iron oxides and hydroxides, which serve to support anoxic biodegradation of BTEX. The most suitable natural materials for this purpose appear to be ferihydrite in the form of colloidal solutions, goethite in the form of a shell around a quartz sand core, akaganeite and possibly hematite as electron recipients. These oxides either seep in through the wells at the contamination site or they can also be used as reactive barriers.

One method to increase the bioavailability of iron oxides, most commonly ferihydrite, is the form of colloidal solutions using eg citrate. The rate of nanoparticle reduction increases by up to two orders of magnitude compared to non-colloidal iron particle aggregates. The size of the individual colloidal particles is between 1 nm and 1 µm. A relatively high catalytic effect on microbial reduction is also due to the addition of a smaller amount of colloidal oxide solution to the natural environment with macroaggregates.

The second option is to use the so-called “electron pendulum”, which serves to transfer electron between microorganisms and iron. At the same time, these organic ligands stabilize the colloidal solution electrostatically, thereby protecting it from aggregation, which dissolves the resulting aggregates, thereby increasing mobility in the rock environment. This stabilization has a major effect on reactivity as it maintains a high specific surface of the nanosilver. It also extends shelf life, increases solubility and crystallization, and last but not least, such stabilized solutions exhibit much lower toxicity to living organisms.

The ionic strength of the aquatic environment and the rate of injection of the suspension into the well have a major influence on the resulting transport mechanisms of electron transfer between microorganisms and iron. With a common ion content, between 2 and 5 mM, and with natural groundwater flow, nanoparticles can reach up to fifty meters. If the ionic strength is higher, about 10 mM, the distance to which the oxides travel is reduced to a few meters. Knowledge of these parameters enables the mobility control of the infiltrated iron oxides.

- 1 GB 2018 - 177 A3

The origin of the iron oxide particles also has an influence. One study shows that ferrihydrite obtained from the rock environment and treated has several times higher reactivity than synthetically produced, presumably because it contains internally bound organic compounds bound during natural precipitation.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide such a biodegradation composition for anaerobic biodegradation of BTEX in a rock environment which removes the above-mentioned deficiencies, which are created from natural resources, thereby reducing the cost of the biodegradation process. .

SUMMARY OF THE INVENTION

This object is achieved by a biodegradation agent for anaerobic biodegradation of BTEX in a rock environment containing ferihydrite with a stabilizer according to the invention. SUMMARY OF THE INVENTION The biodegradation composition comprises from 2 to 10% by weight, a suspension of nanoparticles of naturally occurring ferrihydrite, i.e. iron (III) as the final electron acceptor, from 5 to 15% by weight of a naturally occurring oxyhumolite leachate of perhydrate in suspension and up to 100% by weight, water. Stabilization of ferihydrite nanoparticles maintains a high specific surface area of nanosilver, increases solubility and crystallization, and the biodegradation composition of the present invention exhibits much lower toxicity to living organisms. The use of natural sources of ferrihydrite and humic acids significantly reduces the cost of producing a biodegradation agent for efficient anaerobic biodegradation of BTEX in the rock environment.

Humic substances are natural organic substances resulting from the decomposition of mostly plant residues. Humic substances are hardly subject to further decomposition and are present in large quantities in soil, peat, coal and some waters. According to their solubility, they are divided into humic acids, humic acids and fructonic acids. The starting material for the production of sodium and potassium salts of humic and phonic acids is oxyhumolite. It is a type of granular incoherent charcoal of dark brown to brown-gray color with low degree of coalification and high content of humic acids as a component of humus. Oxyhumolite, popularly called capuchin, has been used in the past and is still used to increase soil fertility due to its high organic content and excellent sorption properties.

The concentration of the individual components of the biodegradation product, ie the suspension of nanoparticles of ferihydrite, aqueous leach of oxyhumolite and water is determined by the permeability of the rock environment, ie according to the particle size in the rock environment, which must be measured before application of the biodegradation product. The more permeable the rock environment, the denser the biodegradable preparation can be. In a preferred embodiment, the biodegradation composition comprises from 2 to 4 wt%, a suspension of nanoparticles of ferihydrite, from 10 to 15 wt%, an aqueous leach of oxyhumolite and up to 100 wt%. water for biodegradation in a rock environment with a particle size greater than 0,25 mm. In another preferred embodiment, the biodegradation composition comprises from 4 to 6 wt. % suspension of nanoparticles of ferrihydrite, from 8 to 10 wt. % aqueous leach of oxyhumolite and up to 100 wt. water for biodegradation in a rock environment with a particle size in the range of 0.01 mm to 0.25 mm. In another further preferred embodiment, the biodegradation composition comprises from 6 to 10 wt. % suspension of nanoparticles of ferrihydrite, from 5 to 8 wt. % aqueous leach of oxyhumolite and up to 100 wt. water for biodegradation in a rock environment with a particle size of less than 0,01 mm.

The present invention also provides a process for the preparation of the above-described biodegradable preparation for anaerobic biodegradation of BTEX, the preparation of which uses a stabilizer ferrihydrite. The biodegradation preparation is prepared as an aqueous solution by adding to the water an aqueous leach of an oxyhumolite of natural origin at a concentration of 5 to 15% by weight. containing a mixture of humic acids, and a suspension of nanoparticles of naturally occurring ferrihydrite at a concentration of 2 to 10 wt. Water leach

-2 O 2018 - 177 A3 oxyhumolite with humic acids is used for stabilization of nanoparticles of ferihydrite in biodegradation preparation.

In the case of anaerobic biodegradation of BTEX by pressure injection of a biodegradation agent into the rock environment, the permeability of the rock environment, respectively. particle size of the rock environment, by which the concentration of the suspension of nanoparticles of ferihydrite is determined, according to which the concentration of the aqueous leach of oxyhumolite is determined so that BTEX is effectively biodegraded in the rock environment.

The suspension of nanoparticles of ferihydrite may be metered into the aqueous solution in two different formulations, either as a dry powder or as a wet sludge. The dry powder, from which a suspension of nanoparticles of ferrihydrite is subsequently formed in a preferred embodiment, is formed by first extracting the ferrihydrite sludge from the collecting wells in the seepage water stream, which is subsequently dried. In another preferred embodiment, the suspension of nanoparticles of ferihydrite is used in the form of sludge extracted from these collecting wells in a seepage water stream where the sludge is no longer dried and moisture is left therein.

It is also an object of the present invention to use the aforementioned biodegradation preparation produced by the above method for anaerobic biodegradation of BTEX by pressure injection into a rock environment. Pressure grouting is also called direct push and increases the likelihood of migration of the biodegradation agent particles through the rock environment. In this way, an underground reactor, respectively, is formed. bioreactor. Contaminated groundwater flows through this bioreactor and the microorganisms present use trivalent iron from a suspension of nanoparticles of ferihydrite as the final electron acceptor.

The advantages of the biodegradant composition for the anaerobic biodegradation of BTEX in the rock environment according to the present invention are in particular that its active ingredients originate from natural sources, thereby reducing the cost of producing the biodegradable composition while not posing an environmental risk in the rock environment.

DETAILED DESCRIPTION OF THE INVENTION

The suspension of nanoparticles of ferihydrite is applied in a concentration of 2 to 10% by weight, depending on the permeability of the rock environment, which must be measured before application, eg by a field test. The more permeable the rock environment, the denser the seepage suspension. Ferrihydrite is dosed either as a dried powder, optimally as sludge withdrawn from the collection wells installed at the seepage site of the seepage water, from which a suspension of nanoparticles of ferihydrite is subsequently formed. Ferrihydrite has a specific surface area of 234 m ² / g.

An oxyhumolite aqueous extract containing a high humic acid content is prepared by dispensing oxyhumolite into the water available at the site. Surface water with the lowest content of solutes is preferred. 50-100 kg of oxyhumolite per m ^{3 of} water are metered into the IBC container. The mixture is mixed with a submersible pump of 5 to 10 m ³ / h for at least 24 hours. Prior to dosing the aqueous oxyhumolite leachate, the stirring is turned off for 30 minutes to separate the settling suspended solids.

The aqueous leach of oxyhumolite is dosed in an amount of 5 to 15% by weight, into a stirred vessel filled with water available at the site, an IBC container with secured mixing by a submersible pump of 5 to 10 m ³ / h is suitable. Surface water with the lowest content of solutes is preferred. The concentration of oxyhumolite aqueous extract is chosen according to the groundwater composition at the site and must be verified by laboratory tests before application. The aim of the tests is to determine the optimum concentration of aqueous oxyhumolite leachate to stabilize the suspension of nanoparticles of ferihydrite. The sedimentation rate is measured. The powder or sludge formed is then metered

The amount of ferrihydrite so that the final concentration is in the range of 2 to 10% mass, depending on the permeability of the rock environment at the site.

The prepared biodegradation agent for anaerobic biodegradation of BTEX in the rock environment is soaked by pressure injection or direct push technology into pre-selected horizons of contaminated rock environment. The leak pressure is between 2 and 10 bar.

Example 1

The biodegradation preparation is prepared as an aqueous solution containing 2 wt. % suspension of nanoparticles of ferrihydrite and 12 wt. aqueous leach of oxyhumolite and the remainder of the water. The biodegradation product prepared in this way is then applied by the direct push method, ie by pressure injection into a rock environment with a particle size larger than 0.25 mm, ie into a sand environment. Application of the biodegradation agent is suitable for the permeability of the rock environment with a filtration coefficient of less than 10 ^-4 ms- ¹ .

Example 2

The biodegradation preparation is prepared as an aqueous solution containing 5 wt.%, A suspension of nanoparticles of ferihydrite and 8 wt. aqueous leach of oxyhumolite and the remainder of the water. The biodegradation preparation prepared in this way is then applied by the direct push method, ie by pressure injection into the rock environment with a particle size in the range of 0.01 to 0.25 mm, ie into the dust environment. Application of biodegradation is appropriate for permeability rock masses in the range of values of the coefficient filter 10 ^{'4-10' _1 5} ms.

Example 3

The biodegradation preparation is prepared as an aqueous solution containing 10 wt. % suspension of nanoparticles of ferrihydrite and 5 wt. aqueous leach of oxyhumolite and the remainder of the water. The biodegradation product prepared in this way is then applied by the direct push method, ie by pressure injection into a rock environment with a particle size smaller than 0.01 mm, ie into a clay environment. The application of the biodegradation agent is suitable for the permeability of the rock environment in the range of values of the filtration coefficient of 10 ^-5 to 10 ^-6 ms- ¹ . Permeability of less than 10 ^-6 m ^_1 is not recommended biodegradation medicine.

Industrial applicability

The biodegradation agent for anaerobic biodegradation of BTEX in the rock environment of the present invention can also be used in groundwater decontamination.

PATENT CLAIMS

Claims (2)

Biodegradable preparation for anaerobic biodegradation of BTEX in a rock environment comprising ferihydrite with a stabilizer, characterized in that it contains 2 to 10 wt. % suspension of nanoparticles of ferihydrite of natural origin, 5 to 15 wt. a stabilizer consisting of an aqueous leach of oxyhumolite of natural origin containing a mixture of humic acids for stabilizing the nanoparticles of ferihydrite in suspension and up to 100 wt. water. A biodegradable preparation according to claim 1, characterized in that it contains from 2 to 4 wt. % suspension of nanoparticles of ferrihydrite, from 10 to 15 wt. aqueous leach of oxyhumolite;