WO2011117235A1

WO2011117235A1 - Method for the infiltration of reactive substances for in-situ groundwater treatment

Info

Publication number: WO2011117235A1
Application number: PCT/EP2011/054340
Authority: WO
Inventors: Claus Nitsche; habil Jochen GROßMANN
Original assignee: GICON GROßMANN INGENIEUR CONSULT GMBH; Bgd Boden- Und Grundwasserlabor Gmbh
Priority date: 2010-03-22
Filing date: 2011-03-22
Publication date: 2011-09-29
Also published as: DE102011005904A1; DE102011005904B4

Abstract

The invention relates to a method for the infiltration of reactive substances for in‑situ groundwater treatment within a reaction zone of a porous aquifer, the porosity of which is composed of hydraulically active porosity and hydraulically low active porosity. The infiltration by the reactive substances occurs in at least one conditioning phase and then at least one operating phase. The amount of the substances to be infiltrated in the conditioning phase is determined in consideration of the diffusive and flow-determined substance-exchange processes in the groundwater between hydraulically active porosity and hydraulically low active porosity, the consumption of the reactive substances during the groundwater treatment and the consumption of the reactive substances in side reactions in the groundwater. The amount of the substances to be infiltrated in the operating phase is determined in consideration of the diffusive and flow-determined substance-exchange processes in the groundwater between hydraulically active porosity and hydraulically low active porosity and the consumption of the reactive substances during the treatment of groundwater flowed after. During infiltration, in the conditioning phase, at least the amount of reactive substances determined for the conditioning phase is infiltrated. In the operating phase, infiltration is at first suspended so that untreated groundwater flows into the reaction zone. Reactive substances are then infiltrated in at least the amount determined for the operating phase.

Description

Process for infiltrating reactive substances for in situ groundwater treatment

The invention relates to a process for the infiltration of reactive substances for in situ groundwater treatment. The method is suitable for use in the treatment of groundwater with substances contained therein, e.g. dissolved iron and thus for in situ treatment of groundwater and for use in the treatment of groundwater with contaminants contained therein, and thus for in situ remediation of groundwater.

If groundwater is contaminated or contains geogenic elevated concentrations of substances, there is the possibility of in situ groundwater treatment via the infiltration of reactive substances into groundwater. The aim of such a treatment is the reduction of the concentration of substances or pollutants in the groundwater and thus the in situ groundwater treatment or the in situ groundwater remediation. Therefore, for the purposes of the invention, the term "groundwater treatment" is understood to mean the treatment of groundwater as well as the groundwater remediation.The infiltration of the reactive substances initiates groundwater treatment.

For the purposes of the invention, infiltration means the introduction of substances, in particular reactive substances, into the groundwater. The purpose of the reactive substances is to initiate and maintain physicochemical and / or biochemical processes in which the substances to be treated are reduced to a predetermined target value (target concentration).

The determination of the physicochemical or biochemical process parameters in a groundwater area is carried out in a known manner in laboratory experiments. This makes it possible to determine what amount of reactive substances is consumed for in situ groundwater treatment. DE 10 2009 038 017.5 discloses a method for determining the microbial degradation rate of the first order in a laboratory experiment designed in close proximity to nature. In it, the natural degradation processes are simulated in several different series-connected reactors containing a soil sample. The method makes it possible to obtain a reliable prognosis of the natural substance degradation processes in groundwater. It is also possible with this method to predict which amount of reactive substances must be supplied for a desired substance degradation.

DE 3938844 AI describes a process for the distribution of reactive substances in a groundwater stream for the purification of groundwater. The aim of the method disclosed therein is pulsed to enter one or more substances in the groundwater area and to mix this with the natural groundwater quickly and evenly using the hydrodynamic dispersion so that after a flow of 100 m already homogeneous mixture is visible. The amount of reactive substances, such as ethanol, is calculated before infiltration. The calculation is carried out solely taking into account the physicochemical and / or biochemical processes in the groundwater with reference to the usable porosity, which is also referred to as hydraulically effective porosity or mobile porosity. In this case, any side reactions are not taken into account.

EP 1169271 B1 discloses a process for the in situ treatment of tert-butyl methyl ether (MTBE) or tert-butyl alcohol-containing (TBA) groundwater. In the process, a microbial culture growing under aerobic conditions is infiltrated into the groundwater, which is capable of decomposing MTBE and / or TBA. Furthermore, an oxygen-containing gas is introduced in pulsed injections into the groundwater to ensure the growth of microorganisms. The amount of oxygen to be infiltrated is controlled on the basis of in situ oxygen measurements, whereby the calculation of a respective minimum volume of oxygen per injection takes place solely on the basis of the total volume consideration of the substrate to be treated.

The processes known from DE 3938844 A1 and EP 1169271 B1, as well as other known processes, have the following disadvantages:

The amount of reactive substances required for in situ groundwater treatment is underestimated during planning. In practice, significantly larger amounts of reactive substances must be infiltrated than have been reported in the planning. Often, this increased consumption of reactive substances is due to side reactions, such as pyrite oxidation.

Reliable planning of the amount of reactive substances to be infiltrated is not possible.

A spatial limitation of a reaction zone of the in situ groundwater treatment, in which the substance conversions are completed, is not possible.

Thus, the final concentration of the infiltrated reactive substances in the treated groundwater is unpredictable. The observance of a limit concentration of the reactive substances in the treated groundwater is an essential aspect of groundwater treatment. It is therefore not possible to exclude groundwater contamination by reactive substances used for in situ treatment in previous methods.

Furthermore, it is advantageous not only for cost reasons, to keep the amount of reactive substances supplied as low as possible and to implement this during the groundwater treatment to the largest possible extent. It is the object of the invention to provide a method for in situ groundwater treatment which can be better planned with regard to the use of reactive substances. It is a further object of the invention to provide a method in which an in situ groundwater treatment takes place within a closed reaction space and in which contamination of the groundwater outside the reaction space with reactive substances is avoided.

The object is achieved by a method for infiltration of reactive substances for in situ groundwater treatment within a reaction zone of a porous aquifer whose pore volume from a pore volume fraction (mobile porosity or usable porosity, also referred to herein as "hydraulically effective porosity") and a no or only slightly traversed pore volume fraction (immobile porosity, also referred to herein as "hydraulically low effective porosity") composed.

According to the invention, the infiltration of the reactive substances takes place via infiltration devices, as known from the prior art. According to the method of the invention, the infiltration is carried out in a regime of at least one conditioning phase and then at least one management phase. The conditioning phase for the initial enrichment of the reactive substances within the entire pore volume of the aquifer to a previously defined final concentration and for the initial reduction of substances to be treated groundwater to a previously defined target concentration. The management phase serves to maintain the final state of the conditioning phase.

In accordance with the invention, the calculation of the amount of reactive substance to be infiltrated within the conditioning phase takes place under consideration

the diffusive and flow-related mass transfer processes in the groundwater between the hydraulically active and hydraulically low porosity of the aquifer, the consumption of reactive substances in groundwater treatment and the consumption of reactive substances in side reactions in groundwater.

According to the invention, the calculation of the amount of reactive substances to be infiltrated in the management phase takes place taking into account: the diffusive and flow-related mass transfer processes in the groundwater between the hydraulically active and hydraulically low porosity of the aquifer and the consumption of the reactive substances in the groundwater treatment of the inflowing groundwater.

When calculating the amount of reactive substances to be infiltrated in the management phase Side reactions are not considered.

The determination of the parameters necessary for the calculation takes place for the groundwater area to be treated in a known manner by means of tracer tests (in particular for the following parameters: hydraulically effective and hydraulically low effective porosity and dispersivity) and / or (preferably near-natural) laboratory scale experiments (physicochemical or / and biochemical parameters).

According to the invention, the infiltration of the reactive substances takes place in the following steps:

a) conditioning phase: infiltration of the reactive substances in at least the calculated amount of substance for the conditioning phase, b) management phase:

Suspend the infiltration of the reactive substances so that untreated groundwater flows into the reaction zone,

Infiltration of reactive substances in at least the calculated amount of substance for the treatment phase.

The invention is based on the observation of the inventors that the previously observed excess consumption of reactive substances in the infiltration compared to the planning not only from the consumption in side reactions, such as pyrite oxidation, resulted. The additional consumption is mainly due to the accumulation of reactive substances in the areas of the aquifer that are not or only slightly flowed through. Thus, the infiltrated reactive substances diffuse from the pore fraction of the aquifer flowing through into the pore fraction which is not or only slightly perfused and are therefore initially no longer available for physicochemical or biochemical processes in the hydraulically effective pore volume. In previous planning, the actual reaction space was therefore not in line with the planned one.

Therefore, the calculation of the amount of material to be infiltrated takes place according to the invention, taking into account the diffusive mass transfer within the groundwater in the hydraulically effective and low effective portion of the pore volume. The aim of the method according to the invention is to consider the diffusive mass transfer processes on the one hand during the planning and at the same time to use for an improvement of the in situ groundwater treatment (especially with regard to an improved mixture of the infiltrated reactive substances with the substances to be treated present in the groundwater).

In addition, it should be avoided that pollution of the groundwater with the infiltrated reactive substances occurs outside the previously defined reaction zone within which the groundwater treatment takes place. It is known that not all pores of a groundwater area are flowed through by the groundwater. A flow-related mass transfer takes place only in the flow-through pore fraction, which is therefore also referred to as hydraulically effective pore fraction n ₀ (or hydraulically effective pore volume fraction, porosity, mobile porosity). The hydraulically low effective porosity n _st (or hydraulically low effective pore fraction, hydraulically low effective pore volume fraction, immobile porosity) refers to the proportion of the pore volume of the aquifer, which is filled with water, which does not or only with a very small share in the groundwater flow participates. In the proportion of hydraulically low effective porosity, the mass transfer takes place almost exclusively due to the diffusion, the flow-related mass transfer is negligible in it.

The total pore content (s) of an aquifer is therefore composed of the hydraulically effective (n ₀ ) and the hydraulically low effective pore fraction (n _st ) in the case of an existing groundwater flow (n = no + n _st ). The hydraulically effective porosity is a basic parameter for the calculation of the pore water velocity. In average aquifers with low nonuniformities, the hydraulically effective porosity is at least 80% of the total pore volume. In aquifers with increased non-uniformity, the hydraulically effective porosity is less than 80% of the total pore volume. The hydraulically effective porosity is not like the overall porosity a soil-typical parameter (depending on soil type and storage density), but is additionally dependent on the acting hydraulic conditions, especially the groundwater flow velocity. With increased groundwater flow velocity, the proportion of hydraulically effective porosity decreases.

The hydraulically low effective porosity is strongly dependent on the composition of the aquifer. In the case of aquifers with low nonuniformity (homogeneous composition), it could be demonstrated that the hydraulically low effective porosity (n _st ) is 10% -20% of the total porosity (0.1 n <n _st <0.2 n). In aquifers with an increased to large non-uniformity (increased inhomogeneous to highly inhomogeneous composition), the hydraulically low effective porosity is higher, so that n _st > 0.2 n.

The composition of the porosity of the groundwater region to be treated, and thus the hydraulically effective and hydraulically low effective porosity, is determined prior to carrying out the groundwater treatment process according to the invention in a known manner. At the beginning of the process according to the invention, these parameters are thus known. Preferably, the proportion of the hydraulically low effective pore fraction is determined by Tracerversuche. A method for determining the hydraulically low effective pore fraction is disclosed in DD 218 681 AI.

The consideration of the aforementioned mass transfer and material conversion processes in the Calculation of the amount of substance of the reactive substances to be infiltrated has the advantage that the method can be planned with regard to the use of reactive substances. Furthermore, the method according to the invention avoids contamination of the groundwater with the infiltrated reactive substances occurring outside of a previously defined reaction zone within which the groundwater treatment takes place.

The method according to the invention is based on the approach that the reactive substances are first distributed within a so-called conditioning phase (also referred to herein as conditioning) in the total pore volume, ie both in the hydraulically effective and the hydraulically low effective pore volume. The distribution of the reactive substances within a delimited area of the aquifer, the so-called reaction zone (or reaction space), is considered. The distribution of reactive substances in the hydraulically low effective pore volume fraction is also referred to herein as enrichment of the reactive substances in the hydraulically low effective pore volume.

The reaction space comprises the porous aquifer, the pore volume of which is composed of a hydraulically effective (n ₀ ) and a hydraulically low porosity fraction (n _st ). The pore volume of an aquifer is the total volume of the aquifer minus the volume of the rock body. The pore volume is thus that volume which is filled within the aquifer with groundwater.

In the process according to the invention, the materials of reactive substances to be infiltrated are calculated before the actual groundwater treatment. The amount of reactive substances to be infiltrated results for the conditioning phase from the following requirements:

1. The amount of substance necessary to enrich the entire pore volume, which at the beginning of the groundwater treatment is free of reactive substances, with reactive substances.

2. The amount of substance consumed during infiltration for side reactions in groundwater, in particular the conversion of other substances in the reaction space (for example the reaction of pyrite or organic matter).

3. The amount of substance that is consumed for the conversion of the reactive substances by the substance conversion processes of the groundwater treatment (target reactions) to a previously defined target concentration. Preferably, the target concentration of the substances to be treated is the permissible limit for the respective substance.

In the process according to the invention, for determining the amount of substance mentioned under point 1, which is necessary for the enrichment of the pore volume, both the convective and the diffusive mass transport within the groundwater are considered in the hydraulically effective and hydraulically low effective pore volume. The amount of substance required for the processes named under items 2 and 3 is determined prior to the start of the process according to the invention in a known manner by determining the physicochemical and / or biochemical parameters. Preferably, a method and a device according to DE 10 2009 038 017.5 are used to determine the amount of substance for consumption in the groundwater treatment and in further side reactions.

During conditioning, the reactive substances are distributed both in the hydraulically active and in the hydraulically low effective pore volume fraction of the reaction space and react there with the substances to be treated as well as with the other substances contained, such as pyrite.

The aim of the conditioning phase is to achieve a previously defined final concentration of the reactive substances within the groundwater in the reaction zone. At the same time, this means that at the end of the conditioning phase side reactions in which reactive substances are consumed are almost complete and thus negligible. At the conclusion of the conditioning phase, the reactive substances are therefore present at the end of the reaction zone of length L _R at most in the previously defined final concentration. It is obvious to the person skilled in the art that in the infiltration of reactive substances in liquid form, the previously defined final concentration is less than the concentration of the reactive substances in the infiltrate.

During the conditioning phase, the following mass transfer processes take place in a process according to the invention:

At the beginning of the conditioning phase, there is a thermodynamic equilibrium in the groundwater area to be treated between the hydraulically effective pore volume fraction n ₀ and the hydraulically low effective pore volume fraction n _st . In both pore volume fractions, therefore, the substances to be treated are contained in the same concentration (see FIG. 1A).

The infiltration of the reactive substances into the groundwater takes place exclusively via the hydraulically effective pore volume fraction n ₀ . Due to the concentration gradient of the reactive substances in the hydraulically active and hydraulically low effective pore volume, the following diffusive mass transfer processes take place:

Diffusion of the reactive substances from the hydraulically effective pore volume fraction into the hydraulically low effective pore volume fraction,

Diffusion of the substances to be treated from the hydraulically low effective pore volume fraction in the hydraulically effective pore volume fraction (see Fig. 1B).

Upon completion of the conditioning, the following conditions prevail within the reaction space (see FIG. 1C): At the end of the reaction space L _R , the reactive substances are present at a maximum of the previously defined final concentration. At the end of the reaction space L _R , the substances to be treated are present at a maximum of the previously defined target concentration. Within the reaction space of length L _R , the substances to be treated are present hydraulically effective pore volume in maximum of the previously defined target concentration before, reactive substances are present in both the hydraulically effective and in the hydraulically low effective pore volume fraction of the reaction chamber in a maximum of the previously defined final concentration.

According to the method of the invention, the groundwater treatment takes place within a longitudinally limited reaction zone in an aquifer. The reaction zone (or reaction space) is understood to mean the volume of the aquifer, which, taking into account the pore water velocity and the reaction time from the infiltration site, is necessary in order to treat the groundwater until a target concentration of substances to be treated is reached. Before the start of the process according to the invention, the kinetics of the mass transfer and conversion processes taking place in the groundwater (enrichment, consumption by groundwater treatment, consumption in side reactions) are determined. The width and thickness of the reaction space depend on the groundwater area to be treated. At the end of the reaction zone of length L _R , the substances to be treated are present in a maximum of the previously defined target concentration (preferably the permissible limit value for the particular substance to be treated).

The length of the reaction space L _R is the horizontal distance from the location of infiltration to the end of the reaction space. It is defined by the relationship shown in equation (1):

L _R = v _a * t _R (1)

v _a pore water velocity (identical to the separation rate) t _R Reaction time until the target concentration of the substances to be treated is reached at the end of the reaction space.

Both the pore water velocity and the necessary reaction time are environmental fixed parameters, which result from the nature of the aquifer and the concentration of substances to be treated in the groundwater. The determination of the pore water velocity and of the mass transfer and conversion processes in the groundwater area to be treated are carried out before the beginning of the process according to the invention in a known manner, preferably by in situ Tracer or ex situ investigations taken soil and groundwater samples on a laboratory scale, determined.

At the end of the reaction space with the length L _R , the concentration of the reactive substances is at most the previously defined final concentration. Preferably, a substance concentration which is lower than the maximum permissible concentration for the reactive substances is selected as the final concentration.

The need for the mass of reactive substances to be infiltrated during conditioning (K) is preferably derived from the following relationship:

SRS, K ⁼ SPV, K + SZ, K + SB, K (2)

S _RS , _K total mass of the reactive substances to be infiltrated in the conditioning phase,

S _PV , _K mass of reactive substances for the enrichment of the reactive substances in the entire pore volume,

S _ZR , _K Mass of reactive substances for the reaction in side reactions in the total pore volume, S _B , _K mass of reactive substances for groundwater treatment.

The concentration of the reactive substances at the end of the reaction space of length L _R can advantageously be influenced by the selection of the material mass of the infiltrate (Sp _V ) necessary for the enrichment of the pore water and preferably results from the following equation (3):

Co, i, K ⁼ (SRS, K-SZR, K-SB, K) / PVR (3)

are there

Co _, i, _K concentration Co _, i, _{K of} the reactive substances in the groundwater at the end of the reaction zone (final concentration),

PV _R pore volume of the aquifer throughout the reaction space.

The concentration of reactive species to be infiltrated into the reaction space is preferably calculated using equations (2), (3) and (4) from equation (5). It is taken into account that the infiltration of the added substances can only take place via the hydraulically effective pore volume fraction no:

under the use of

(C ₀ , i, _K * PV _R + S _Z R _{, K} + S _B , K) (C _0A K * PV _R + S _Z R, K + S _B , K) / (V _R * n ₀ ) (5)

no hydraulically effective porosity of the reaction zone,

V _R total volume of the reaction zone,

Cy _{; K} Concentration of the reactive substances in the infiltrate.

Equation (5) applies to the case that at the beginning of the conditioning phase no reactive substances to be infiltrated are contained in the reaction space. However, if reactive substances are already present in the groundwater and their concentration has to be taken into account, the concentration of the reactive substances in the groundwater shall be calculated accordingly in equation (5).

With the concentration of the reactive substances (i) flowing into the reaction space during the conditioning phase (Cy _{; K} ), a high concentration gradient is generated between the hydraulically effective and the hydraulically low effective pore volume, which accelerates the mass transfer between the two pore volume fractions.

Preferably, the conditioning phase is repeated in a method according to the invention. This is carried out in particular in the case where the enrichment of the hydraulically low effective pore volume with reactive substances and / or the side reactions within the reaction zone are not completed at the end of a conditioning phase. This is the case, in particular, when the kinetics of the side reactions taking place in the reaction space do not permit completion of the side reactions in the context of a conditioning phase. A repetition of the conditioning is preferably carried out in the case when the final concentration of the reactive substances at the end of the reaction space of length L _R , which is actually present after the infiltration of the previously calculated amount of substance, is more than 20% less than the previously defined final concentration.

After the reactive substances have been distributed as part of the conditioning in both the hydraulically effective and the hydraulically low effective pore volume fraction, during the management phase in the conversion processes that take place in the context of in situ groundwater treatment according to the invention, the reactive substances used in the conditioning phase were enriched in the hydraulically low effective pore volume fraction.

The management phase covers two phases of operation: the suspension of the infiltration of the reactive substances followed by a re-infiltration of reactive substances (intermittent infiltration of reactive substances). The management phase is preferably repeated at least once.

By suspending the infiltration of reactive substances, untreated groundwater initially flows into the reaction space. In the process, the substances contained in the inflowing groundwater become too treated substances with the reactive substances in situ, which were enriched as part of the conditioning within the reaction zone.

The suspension of the infiltration of the reactive substances takes place only so long that no untreated groundwater emerges from the reaction space and that preferably not all of the amount of reactive substances contained in the hydraulically effective and hydraulically low effective pore volume is consumed by the groundwater treatment.

The concentration of the substances to be treated at the end of the reaction zone of length L _R does not exceed a previously defined target concentration for the management phase. The concentration of reactive substances at the end of the reaction zone of length L _R does not exceed a previously defined final concentration for the management phase. This is preferably identical to the final concentration for the conditioning phase.

In the case of re-infiltration of reactive substances during the management phase, the amount of infiltrated material is preferably as high as is necessary in order to convert the substances to be treated contained in the after-flowed groundwater. The reactive substances contained in the hydraulically low effective pore volume should also be used for the implementation of the substances to be treated (herein also "managed").

In the first phase of the management phase, untreated groundwater flows into the reaction space. The untreated groundwater can be introduced into the reaction space exclusively via the hydraulically effective pore volume fraction. The following mass transfer processes are triggered by the subsequent flow of the untreated groundwater:

Diffusion of pollutants from the hydraulically effective pore volume fraction in the hydraulically low effective pore volume fraction,

Diffusion of the reactive substances from the hydraulically low effective pore volume fraction in the hydraulically effective pore volume fraction.

The mass transfers in the first phase of the management phase are therefore exactly the reverse of the mass transfer processes of the conditioning.

As a result of the afterflow of the untreated groundwater, part of the reaction space is filled with the substances to be treated. These are converted by the reactive substances that are present within the reaction space. The inflow of untreated groundwater is interrupted in the second phase of the management phase with the re-infiltration of reactive substances. As a result, reactive substances are re-enriched in the groundwater of the reaction space.

The time for which the infiltration of the reactive substances is suspended (herein also: post-flow time) preferably calculated before the beginning of the method according to the invention. Since in the first operating phase of the management phase not the complete reaction space is filled up with untreated groundwater, the length fraction at which the untreated groundwater flows into the reaction space is described by a reduction factor r _B. This is determined before the beginning of the method according to the invention. Preferably, the reduction factor r _{B is} 0.5 maximum. This means that in the first phase of the management phase, only untreated groundwater enters the reaction space until, based on the hydraulically active pore content, a maximum of 50% of the reaction space length is filled with untreated groundwater.

In determining the reduction factor, the concentration of the substances to be treated contained in the inflowing groundwater and the material conversion processes with the reactive substances are particularly preferably taken into account. The reduction factor is preferably determined in such a way that a lower amount of substance to be treated is contained in the groundwater which has flowed through the length fraction than can be reacted with the entire amount of reactive substance contained in the hydraulically low effective pore volume. For this purpose, the stoichiometry of the material conversion processes as well as the minimum concentration of the reactive substances contained in the hydraulically low pore volume have to be taken into account, at which the groundwater treatment can take place.

Preferably, the reduction factor is to be set so that the reactive amount of substance is always so large that the material conversion processes can still take place.

The post-flow time is preferably calculated with the following equation (6): = r _B * L _R / v _i a (6)

t _IB time for the afterflow of the untreated groundwater during the management phase (post-flow time, corresponds to the time of exposure of the infiltration),

L _R length of the reaction zone,

V; a pore water velocity,

Reduction factor for the management phase (<1).

The reduction factor r _B is preferably calculated from the following relationship:

/ (Cy * no) (8) where f _{s is the} factor for the stoichiometric conversion (indicates the ratio of the amount of substance to be treated to the amount of substance of reactive substances)

C0, concentration of reactive substances in groundwater at the end of the reaction zone at the end of the conditioning phase or the previous management phase,

Cy, concentration of reactive substances in untreated groundwater,

C "-" Minimum reactive substance level at which groundwater treatment can take place.

The need for the mass of reactive substances to be infiltrated during the management phase is preferably derived from the following relationship:

are there

SRS, B total mass of reactive substances to be infiltrated in the management phase,

SPV, B mass of reactive substances for the enrichment of the reactive substances in the downstream groundwater,

S _B , B Mass of reactive substances for groundwater treatment of the downstream groundwater.

The concentration of reactive substances at the end of the reaction space of length L _R can be regulated by the method according to the invention. Thus, with the method according to the invention, it is advantageously possible to reduce the final concentration in the case of repeated repetition of the management phase by infiltrating or increasing a correspondingly smaller amount of reactive substances by infiltrating a correspondingly larger amount of reactive substances.

The process according to the invention is preferably carried out in such a way that the final concentration of the reactive substances is kept constant during the management phase. Particularly preferably, the final concentration of the reactive substances in the management phase corresponds to that of the conditioning phase (Co, i, B = Co, i, i).

The concentration of the reactive substances at the end of the reaction space of length L _R in the management phase is preferably calculated by the following balance which applies when the final concentration of the reactive substances in the management phase corresponds to the conditioning phase (C ₀ , i, _B = C ₀ , i, _K ):

QB = SPV, B / PV _R , B (3a) are there

Co, i, B Concentration of reactive substances in groundwater at the end of the reaction zone, PV _{R; B} Volume of post-flow untreated groundwater (see equation (7)).

The amount of groundwater which has flowed during the first part of the management phase is calculable and is preferably calculated using the following equation:

PV _{R; B} = A _R * v _f * V (7)

A _R Area of the reaction space perpendicular to the flow direction in m ² , Vf Filtering speed according to Darcy, t _IB Postflow time in h.

The filter velocity according to Darcy (Vf) is to be determined before carrying out the method according to the invention.

Deviating from the conditioning phase, the concentration Co, i, B of the reactive substances flowing out of the reaction space during the management phase is not calculated taking into account the total pore volume of the reaction space, but only taking into account the pore volume of the reaction space exchanged within the first operating phase of the respective management phase ,

The concentration of reactive substances to be infiltrated during the management phase is calculated using equations (2a), (3a) and (4a) from equation (5a). It is taken into account that the infiltration of the reactive substances can only take place via the hydraulically effective pore volume, which was exchanged during the inflow of the groundwater to be treated into the reaction space, PV _{R, B} :

The calculation of the amount of reactive substances infiltrated during the management phase is preferably carried out according to equation (5a):

using (2a) ^■ => Cy _{; B} * PV _{R; B} = S _PV , B + S _B , B using (3 a) ^■ => Cy _{; B} = Co, i, B + S _B , B / PV _{R; B} (5 a) with

PV _{R; B} volume of post-flow untreated groundwater, Cy _{; B} concentration of reactive substances to be infiltrated during the management phase.

In the process according to the invention, reactive substances are infiltrated into a groundwater area. The infiltration of the reactive substances is carried out using known infiltration devices, in particular wells or groundwater measuring points. In the method according to the invention both infiltration devices, which allow a horizontal infiltration, as well as infiltration devices for vertical infiltration are used. Infiltration wells for vertical infiltration are particularly preferably used in a method according to the invention.

According to the method of the invention, substances present in the groundwater (herein "substances to be treated") are treated by the infiltration of reactive substances which are suitable for the conversion or decomposition of these substances The reactive substances are then subjected to physicochemical and / or biochemical processes involved in the conversion or decomposition of the substances to be treated contained in the groundwater The result of groundwater treatment with a method according to the invention is:

the reduction of the concentration of the substances to be treated to a target concentration which is preferably equal to or less than the maximum permissible limit for the substance concerned and

- The prevention of contamination of the reaction space following groundwater area with reactive substances.

Within the meaning of the invention, substances to be treated in groundwater include both substances of geogenic origin (in particular iron and / or manganese) and pollutants (in particular organic pollutants).

The choice of reactive substances depends on the type and nature of the substances to be treated in the groundwater. Preferred reactive substances are nutrients, electron acceptors and / or trace elements. The person skilled in the art knows which reactive substances promote the desired substance conversion processes, which lead to the reduction of the substances to be treated contained in the groundwater. Therefore, those skilled in the art will be able to make a selection of suitable reactive substances for groundwater treatment. In a preferred embodiment of the method according to the invention nitrate is infiltrated as a reactive substance for the treatment of BTEX-containing groundwater.

Preferably, preliminary tests are carried out for the identification of suitable reactive substances, which simulate the treatment of the intended groundwater area on a laboratory scale. Appropriate experimental facilities are known from the prior art. For the in situ remediation of groundwater contaminated with organic matter is used for identification suitable reactive substances preferably a method and a device according to DE 10 2009 038 017.5 used.

Preferably, several different reactive substances are infiltrated for in situ groundwater treatment in a process according to the invention. In this case, the infiltration of the different reactive substances takes place simultaneously or at different times.

If several different substances are treated by the in situ groundwater treatment in a process according to the invention, the conversion of the individual substances necessarily takes place at different reaction rates. The length of the reaction space with the length L _R is calculated in this case with the reaction time t _R of the substance which reacts slowest (ie for the substance in which the time to reach the target concentration of the substances to be treated at the end of the reaction chamber highest is). As a result, individual reaction zones are contained within the entire reaction space for the faster-reacting substances, which are each characterized by the location of the beginning of the material transformation of the respective substance and its end.

In the event that several substances that require different reaction conditions are treated in the context of a method according to the invention (in particular the change from aerobic to anaerobic conditions), the reaction space consists of several reaction zones and it will be the beginning of a new reaction zone preferably further reactive substances infiltrated. This is preferably done with a time delay with the infiltration of the reactive substances at the beginning of the (entire) reaction space.

The infiltration of the amount of reactive substances required for the groundwater treatment is carried out either by a solids addition (ie as a mass flow) and / or by infiltration of an aqueous solution of the reactive substances (ie in a volume flow impressed on the groundwater flow).

With the method according to the invention, it is desirable to achieve a high concentration gradient in the groundwater between the two aforementioned pore volume fractions to achieve an intensive diffusive mass transfer between hydraulically effective and hydraulically low effective pore volume. For this purpose, as part of the conditioning phase reactive substances are infiltrated with the aim of enrichment in hydraulically effective and also in the hydraulically low effective pore volume. The amount of infiltrated reactive substances during the conditioning phase is therefore higher, at least by the amount of substance compared to the management phase, which is consumed for the reaction of the reactive substances in side reactions.

For the calculation of the amount of substance to be infiltrated in the conditioning phase and Management phase in a method according to the invention, the knowledge of location-related parameters is necessary. These include the Darcy filter speed, the porosity of the aquifer, the proportion of hydraulically effective and low effective pore volume, the pore water velocity, the concentration of the substances to be treated, the degradation or reaction rates of the substances to be treated by reactive substances, the consumption more reactive Substances in side reactions and others. These parameters are location-dependent and are determined prior to carrying out a method according to the invention in a known manner. Pore water velocity and hydraulically effective and hydraulically low effective pore volume fraction are preferably determined from the results of tracer experiments in the groundwater area to be treated. Total pore volume fraction and the reaction time, which is required for the treatment of groundwater to below the permissible value, are preferably determined in ex situ preliminary experiments, particularly preferably on a laboratory scale.

It is characteristic of the method according to the invention that both diffusive as well as convection-dependent mass transport processes as well as the consumption of reactive substances in (not counting the groundwater treatment) side reactions are taken into account. Only the consideration of the totality of these mass transfer and conversion processes enables an improved calculation of the reactive substances to be used, the delimitation of the reaction space and the avoidance of contamination of the groundwater area following the reaction space with reactive substances.

In a preferred embodiment of the invention, the method according to the invention is carried out in combination with a hydraulically active measure. A particularly preferred hydraulic measure is the pump-and-treat method. In this case, a forced, almost constant alignment of the groundwater flow, which is thus largely independent of the groundwater recharge occurs. As a result, the spatial effect and balancing of the method according to the invention is improved. In the process according to the invention, the dosage of the reactive substances can be effected both via the withdrawn and subsequently infiltrated groundwater and via additional infiltration wells.

Compared with the prior art, the method according to the invention enables a reliable calculation of the reactive substances to be used, the delimitation or definition of the reaction space and thus the balancing ability of an in situ groundwater treatment and the avoidance of contamination of the groundwater area following the reaction space with reactive substances.

By considering the enrichment of the reactive substances in the hydraulically low effective pore volume and the conversion of other (not to be treated) substances in side reactions, in which the reactive substances are consumed, which is in the context of the conditioning phase to infiltrating amount of reactive substances calculable. By knowing the reaction kinetics, the reaction space can be delimited and, in connection with the calculation result of the consumption of reactive substances, the groundwater treatment can be balanced.

With the completion of the conditioning phase, the side reactions are completed so far that they no longer have to be taken into account. Furthermore, the reactive substances are distributed in the hydraulically effective and hydraulically low effective pore volume and enriched in it, so that in the management phase only the substances contained in the inflowing groundwater need to be treated. This makes it possible to optimize the amount of reactive substance to be used during groundwater treatment.

A further advantage of the method according to the invention is that, by taking into account all mass transfer and conversion processes, the final concentration of the reactive substances at the end of the reaction space of length L _R can be reliably calculated beforehand, thus avoiding contamination of the groundwater outside the reaction zone with reactive substances becomes. The controlled, calculated addition of the reactive substances makes it possible to ensure that a predefined maximum permissible concentration of reactive substances leaving the reaction space is not exceeded.

Reference to the following figures and embodiments, the invention will be explained in more detail, without limiting the invention to these.

Fig. 1 Schematic representation of the mass transfer processes in conditioning and management. Shown in each case is the reaction space for the groundwater treatment, which is divided into the hydraulically effective pore volume fraction (n ₀ ) and the hydraulically effective pore volume fraction (n _st ). (AC) mass transfer in the conditioning phase. At the beginning of groundwater treatment, the concentration of substances to be treated (ZBS, marked black) in n _st and no is the same (A). The infiltration of reactive substances (RS, marked white) takes place via the hydraulically effective pore volume fraction no, resulting in diffusion-related mass transfer into the hydraulically low effective pore volume (B). Upon completion of the conditioning, reactive substances are distributed in the hydraulically effective and in the hydraulically low effective pore volume (C). (EN) mass transfer during a management phase. As a result of untreated, untreated groundwater in the first part of the management phase, untreated ZBS enter the reaction space (D). In the second part of the management phase, reactive substances are infiltrated (E). During the management phase, no untreated ZBS leave the reaction space. Fig. 2 Schematic representation of a reaction space of an in situ remediation of a contaminated with BTEX groundwater area by infiltration of nitrate in vertical section. IE ... infiltration level, KE ... control level, RZ ... reaction zone, t _R ... reaction time for natural groundwater flow, BTEX ... benzene, toluene, ethylbenzene and xylene.

Exemplary Embodiment 1: Mass transfer processes within the reaction space of a process according to the invention

The starting point is the thermodynamic equilibrium existing between n ₀ and n _st before the conditioning phase in the groundwater area to be treated, with the result that in both porosity fractions the same concentration of the substances to be treated is present in the groundwater (FIG. 1A).

After the infiltration of the reactive substances into the groundwater area, which takes place exclusively via the hydraulically effective porosity fraction no, the mass transfer shown in FIG. 1B results due to the existing gradients between no and n _st :

Diffusion of the substances to be treated from the hydraulically low effective pore volume fraction in the hydraulically effective pore volume fraction.

Due to the mass transfer, mixing of the substances to be treated with the reactive substances within the reaction space is advantageously ensured at the same time, thereby providing optimal conditions for the material conversion processes.

As a result of the initiated material conversion processes, reactive substances are consumed in both the hydraulically active and the hydraulically low effective pore volume fraction, thereby converting and degrading the substances contained in the groundwater. The processes between n ₀ and n _st shown in FIG. 1B simultaneously achieve optimum mixing of the reactive substances (RS) and the substances (ZBS) to be treated within the reaction space.

The conditioning phase is ended when approximately the practically achievable state in n ₀ and n _st shown in FIG. 1 C has been reached:

at the end of the reaction space, the substance concentration of the reactive substances is the previously defined target value, At the end of the reaction space, the substance or pollutant concentration is equal to or less than the target value permissible for the respective substance to be treated; in the total hydraulically effective pore volume, the concentration of substances to be treated is equal to or less than the target value permitted for the particular substance to be treated , Reactive substances are distributed in both the hydraulically effective and in the hydraulically low effective pore volume fraction of the reaction space, ie that an enrichment of the reactive substances in the hydraulically low effective pore volume was carried out. It is practically not possible to distribute the reactive substances completely homogeneously in the hydraulically low effective pore volume fraction.

Following the conditioning phase (or conditioning phases when repeating it), at least one management phase follows. With the occurring afterflow of the groundwater within the first operating phase of the management and the associated subsequent flow of the substances contained in the groundwater to be treated, the mass transfer between no and n _st shown in FIG. 1D begins:

Due to the diffusion-related mass transfer at the same time a good mixing of RS and ZBS is achieved within the reaction space.

In the first operational phase of the management, only part of the reaction space is filled up with the substances or contaminants to be treated. This avoids that the reactive substances enriched in the reaction space are completely consumed and that unreacted substances to be treated leave the reaction space (FIG. 1D).

The afterflow of the untreated groundwater is interrupted in the second operating phase of the management with the re-infiltration of reactive substances (Fig. IE). With the method according to the invention, it is advantageous to infiltrate into the reaction space only as much reactive amount of substance as is actually required for the groundwater treatment. It is avoided that untreated ZBS leave the reaction space (FIG. IE).

Exemplary embodiment 2: In situ remediation of a groundwater area contaminated with BTEX by infiltration of nitrate (calculation of the amount of material to be infiltrated) In a groundwater area contaminated with BTEX an in-situ groundwater remediation should take place. In order to determine the process parameters required for carrying out the in situ remediation process according to the invention, the following preliminary tests were carried out:

Laboratory tests by means of a method according to the German patent application DE 10 2009 038 017.5 "Method and device for determining microbial degradation rates of the first order in porous media of the soil and groundwater area" and

a tracer test with uranine to determine v _a , n ₀ , n _st; Dispersivity and the real groundwater flow path.

This identified the following results and parameters:

The BTEX is being reduced to the remediation target of 30% of the groundwater contamination with the addition of nitrate (NO ₃ ) over a period of about 15 days. During this reaction time, especially o-xylene, m, p-xylene and ethylbenzene are microbially degraded.

tR, N03 = 15 d

Vf = 0.023 m / d (Darcy filter speed) v _a = 0.178 m / d no = 0.13 n _st = 0.25

n = 0.38

According to the decomposition function of the 1st order determined from the results of the laboratory experiments, the dimensioning of the length of the reaction space, which is limited by so-called control planes, was carried out using equation (1) (see FIG. 2). The abbreviations used are analogous to those used in FIG.

The distances result according to equation (1):

IE - 1. KE: L _R = v _a * t _R : L _R = 0.178 m / d * 15 d = 2.7 m

In order to allow an intermediate control according to the first-order degradation function determined in the laboratory, another control plane (2.KE) was arranged.

The nitrate addition is calculated only for the reaction zone (RZ). The total volume of the RZ is 2.7 m ³ , resulting in the following parameters or characteristic values:

PV _R = V _R * n PV _R = 2700 L * 0.38 PV _R = 1026 L

For the pyrite oxidation taking place in the RZ, the conditioning phase was used Nitrate consumption determined by:

5Z, K ^" 400

For the microbial degradation of BTEX occurring in the ICC, a nitrate consumption was determined for the conditioning phase of:

S _{B, K} = 238 g

A nitrate output concentration from the 1st RZ of approx. 200 mg / L was specified. Using equation (5), the nitrate input concentration is as follows: (C ₀ , i * PV _R + S _Z R, K + S _B , K) / (V _R * n ₀ ) (5) C _K = (0 , 2 g / L * 1026 L + 400 g + 238 g) / (2700 L * 0.13) C _K = 2.4 g / L

Thus, during the conditioning phase, 351 L of water with a nitrate concentration of 2.4 g / L are to be infiltrated into the 1RZ. The infiltration volume corresponds to the hydraulically effective pore volume (V _R * no), wherein the infiltration volume flow is preferably calculated with a geohydraulic model so that the predetermined area of the reaction space is detected. Preferably, the determination of the infiltration-effective area is directly related to the application of equation (1).

In the subsequent management phase to be used reduction factor r _B was in equation (6) is calculated as follows: r _B = f _s * (C _0, rC _min) * n _st / (C _{I; i} * n ₀₎ r _B = 0, 2 * (200 mg / L-150 mg / L) * 0.25 / (46 mg / L * 0.13) r _B = 0.4

This results in the time for the subsequent flow of the substances or contaminants to be treated, based on the first reaction zone (1st RZ) with the naturally acting pore water viscosity according to equation (6) to: = r _B * L _R / v _a (6) t _{I; B} = 0.4 * 2.7 m / 0.178 m / d = 6 d

At an area of 0.74 m ² , a groundwater _volume V _BTEX contaminated with BTEX flows into the RZ during this time _; i): V _BTEX , _I ⁼ Area of l .RZ * Filtering speed according to Darcy (Vf) * Postflow time (ti) V _BTEX , _I = 0.74 m ² * 0.023 m / d * 6 d V _B TEX, I = 0, lm ³ = 100 l

Subsequently, the nitrate is infiltrated into the RZ, whereby the nitrate level set in the RZ during the conditioning phase should continue to apply.

Based on the laboratory tests it was determined:

S _{B; B} : 133 g N0 ₃

S _{RS; B} = 0.2 g / L * 100 L + 133 g S _{RS; B} : 153 g N0 ₃

Equation (5a) gives the nitrate concentration to be infiltrated, which must be supplied during a management phase:

Cy, _B = CO, I, B + (SB, B / PV _{R, B} ) (5a)

C _B = 0.2 g / L + (133 g / 100 L)

C _B = 1, 53 g / L

Thus, during the first management phase, 100 L of water with a nitrate concentration of 1.53 g / L are to be infiltrated into the RZ. The infiltration volume preferably corresponds to the pore volume in the reaction space, which was exchanged during the management phase by the substances in the reaction space located in the groundwater inflow of the reaction space (PV _{R, B} ), the infiltration volume flow preferably being calculated with a geohydraulic model such that the predetermined area the reaction space is detected. Preferably, the determination of the infiltration-effective area is directly related to the application of equation (1).

Subsequently, the management phase is repeated. List of abbreviations

Area of the reaction space perpendicular to the flow direction in m benzene and toluene

Benzene, toluene, ethylbenzene and xylene

Concentration of the reactive substances in the infiltrate (conditioning)

Concentration Co, i, K of the reactive substances in the groundwater at the end of the reaction zone (final concentration)

Concentration of the reactive substances in the infiltrate (management)

Concentration of reactive substances in groundwater at the end of the reaction zone (management phase)

Minimum concentration of reactive substances at which the

Groundwater treatment can take place

infiltration level

control plane

Length of the reaction space

Total porosity of the reaction zone

hydraulically effective porosity

hydraulically low effective porosity

Volume of post-flow untreated groundwater

Pore volume of the aquifer in the entire reaction space reactive substances

reaction zone

Total mass of reactive substances to be infiltrated in the conditioning phase

Mass of reactive substances for the enrichment of the reactive substances in the total pore volume (conditioning)

Mass of reactive substances for the reaction in side reactions in the total pore volume (conditioning)

Mass of reactive substances for groundwater treatment (= reaction of substances to be treated with reactive substances)

Total mass of reactive substances to be infiltrated in the management phase

Mass of reactive substances for the accumulation of reactive substances in the downstream groundwater

Mass of reactive substances for groundwater treatment of the after-stream Grand water

Rehabilitation target value (final concentration of BTEX to be achieved)

flow time

Reaction time needed for treatment of the Grand Water to below the permissible value for natural Grand Water Flow

Pore water velocity

Total volume of the reaction zone

substances or contaminants to be treated

Claims

claims

1. A process for the infiltration of reactive substances for in situ groundwater treatment within a reaction zone of a porous aquifer, whose porosity is composed of a hydraulically active and a hydraulically low effective porosity, in which the infiltration of the reactive substances via infiltration devices, wherein the infiltration in one Regime from at least one conditioning phase and then at least one management phase takes place, initially the amount of substances to be infiltrated in the conditioning phase substances taking into account the diffusive and flow-related mass transfer processes in the groundwater between the hydraulically active and hydraulically low porosity of the aquifer, the consumption of reactive substances the groundwater treatment and consumption of reactive substances in side reactions in groundwater and the quantity of substances infi during the management phase Taking into account the diffusive and flow-induced mass transfer processes in the groundwater between the hydraulically active and hydraulically weak porosity of the aquifer and

the consumption of reactive substances in the groundwater treatment of the post-streamed groundwater and the infiltration of the reactive substances in the following steps: a) conditioning phase: infiltration of the reactive substances in at least the determined amount of substance for the conditioning phase, b) management phase:

Infiltration of reactive substances in at least the determined amount of substance for the management phase.

2. The method of claim 1, wherein the total mass of the reactive substances to be infiltrated in the conditioning phase from the sum of the respective masses for the consumption of the reactive substances for enrichment of the reactive substances within the reaction zone by diffusion and flow mass transfer, the consumption of reactive substances for the treatment of groundwater within the reaction zone and the consumption of reactive substances for side reactions within the groundwater of the reaction zone, the total mass of reactive substances to be infiltrated in the management phase from the sum of the respective sub-masses for the consumption of the reactive substances to enrich the reactive substances within the groundwater that has flowed into the reaction zone by diffusion and flow-related mass transfer, and the consumption of the reactive substances to treat the groundwater that has flowed into the reaction zone, and the time to suspend infiltration in the management phase e from the ratio of the product of the horizontal extent of the reaction zone and a predetermined length fraction, which indicates to what proportion of the horizontal extent the inflowing groundwater is to penetrate into the reaction zone, with the pore water velocity within the reaction zone.

3. The method according to any one of the preceding claims, wherein the conditioning phase is repeated.

4. The method according to any one of the preceding claims, wherein the management phase is repeated at least once.

5. The method according to any one of the preceding claims, wherein a plurality of different reactive substances are infiltrated simultaneously or at different times.

6. The method according to any one of the preceding claims, wherein the reactive substances are infiltrated in the form of an aqueous solution.

7. The method of claim 1 to 5, wherein the reactive substances are infiltrated as a solid.

8. The method according to any one of the preceding claims, characterized in that the calculation of the volume and the concentration of the reactive substances to be infiltrated in the conditioning phase is carried out with the following equations:

Total mass S _RS , _{K of} the reactive substances to be infiltrated in the conditioning phase:

SRS, K ⁼ SPV, K + SZR, K + SB, K (2) with Sp _V , _K · · · mass fraction for the enrichment of the reactive substances in the total pore volume, S _ZR , _K · · · mass fraction for the reaction in side reactions all in one Pore volume, S _B , K · · · mass fraction for groundwater treatment, using equations (3) and (4)

Concentration Co, i, K of the reactive substances in the groundwater at the end of the reaction zone Co, i, K ⁼ (SS, K-SZ, K-SB, K) / PR (3) with PV _R ... Pore volume of the aquifer in the entire reaction space, to be infiltrated concentration Cy _{; K of} the reactive substances

C _UK = S _RS , _K / (V _R * no) (4) with n ₀ ... hydraulically effective pore volume fraction of the total volume of the reaction zone, V _R ... Total volume of the reaction zone.

9. The method according to any one of the preceding claims, characterized in that the calculation of the volume and the concentration of the reactive substances to be infiltrated in the management phase is carried out with the following equations:

Total mass SRS, B of the reactive substances to be infiltrated in the management phase:

with Sp _V , B · · · mass fraction for the enrichment of the reactive substances in the downstream groundwater, S _B , B · · · mass fraction for the groundwater treatment of the after-flowed groundwater,

Concentration Co, i, B of the reactive substances in the groundwater at the end of the reaction zone

with PVR, B · · · Volume of post-flow untreated groundwater, concentration to be infiltrated Cy _{; B} of reactive substances

10. The method of claim 8 or 9, wherein Co, i, B = Co, i, K is.

1 1. The method according to any one of the preceding claims, characterized in that the time t _{IB of} the exposure of the infiltration of reactive substances in the management phase is calculated using the following equation (6): = r _B * L _R / v _a (6) L _R ... Length of the reaction zone, v _a ... Pore water velocity, r _B ... Reduction factor for the management phase, with r _B <1, wherein the reduction factor r _{B is} calculated using the following equation:

with f _s ... factor for the stoichiometric conversion, Co, i ... Concentration of the reactive substances in the groundwater at the end of the reaction zone at the end of the conditioning phase or the previous management phase in mg / L, Cy ... Concentration of the reactive substances in the untreated groundwater, C _m ; _n. ... minimum concentration of reactive substances at which groundwater treatment can take place.

12. The method according to any one of the preceding claims, wherein the conditioning phase and management phase in combination with a hydraulically active measure, in particular pump and treat, takes place.