Methods for the degradation of micropollutants

Abstract

A process for the degradation of micropollutants in wastewater, sewage sludge filtrates and the like, generating hydrogen as the energy source of the process, wherein the process comprises the following steps: - Provision of an electrochemical cell, - Provision of a sample containing micropollutants, - Performing electrolysis on the electrochemical cell with the sample to break down the micropollutants to obtain a purified sample, - Separating and, if necessary, storing the hydrogen produced in electrolysis and - Use of the resulting hydrogen as an energy source for carrying out the electrolysis, characterized in that the electrolysis is carried out at a current density of 25 to 35 mA / cm² 2 is carried out.

Description

[0001] The present invention relates to a process for the degradation of micropollutants, in particular pharmaceuticals, in wastewater, sewage sludge filtrates and the like.

[0002] Micropollutants are environmentally relevant pollutants that occur in waters at concentrations of nanograms or micrograms per liter, or even lower. Some of these substances can have adverse effects on aquatic ecosystems even at very low concentrations or negatively impact the extraction of drinking water from raw water. These substances originate, for example, from agriculture and can enter waters via wastewater as pharmaceutical residues or through general environmental pollution as so-called ubiquitous substances.

[0003] According to this invention, micropollutants are understood to mean certain organic substances such as pharmaceuticals, especially antibiotics, painkillers, hormones, but also biocides or pesticides. Micropollutants also include corrosion inhibitors, flame retardants, UV stabilizers, sweeteners, industrial chemicals, and similar substances.

[0004] Micropollutants enter waterways via various pathways and can be found there in measurable concentrations. One entry pathway for these substances is, for example, the municipal wastewater treatment plant.

[0005] Municipal wastewater contains, among other things, pharmaceutical residues from human excreta or as a result of improper disposal of medications. Conventional wastewater treatment plants equipped with mechanical-biological wastewater treatment are not designed to specifically remove such micropollutants from wastewater. In addition to municipal wastewater treatment plants, direct discharges from industrial plants and inputs from diffuse sources, such as inputs from agricultural land management, are important causes of micropollutant contamination in water bodies.

[0006] Since micropollutants from contaminated wastewater are only minimally removed in wastewater treatment plants, these substances accumulate over time in flora and fauna, causing lasting negative effects. Once accumulated, these substances can enter the food chain and thus pose a health risk to humans.

[0007] Pharmaceuticals such as antibiotics are used in both human and veterinary medicine to treat bacterial infections. It is well known that antibiotics are used extensively in veterinary medicine, especially in animal husbandry. The disadvantage is that these substances are excreted unchanged or as transformants. The contaminated excrement thus enters the environment via grazing animals and manure spreading.

[0008] The combination of the massive use of antibiotics and the lack of wastewater degradation measures in sewage treatment plants is leading to increasing bacterial resistance. This, in turn, leads to a loss of effectiveness of the substances.

[0009] The presence of micropollutants such as antibiotic residues in groundwater has been known for some time, so the Federal Environment Agency has now published a so-called watch list (EU Watch List) listing specific micropollutants that are to be monitored at selected measuring points in water bodies. The aim is to gain insights into the effects of these substances on water quality. This watch list includes the following substances / groups of substances: sex hormones (17-α-ethinylestradiol, 17-β-estradiol, and estrone), diclofenac, macrolide antibiotics (erythromycin, clarithromycin, azithromycin), pesticides (oxadiazon, triallate, methiocarb, neonicotinoids), 2,6-ditert-butyl-4-methylphenol, and 2-ethylhexyl-4-methoxycinnamate.

[0010] Although the amount of these substances in the water can be reliably measured using various analytical methods, there is currently no technology available that makes it possible to reduce the unwanted input sustainably and as cost-effectively as possible, other than to avoid the substances mentioned altogether.

[0011] DE 10 2008 004 663 A1 discloses a process for electrochemical sanitization and germ reduction of biologically treated wastewater. Furthermore, DE 10 2011 085 967 A1 discloses a process for neutralizing negatively charged contaminants in aqueous media, DE 10 2016 001 781 A1 discloses a process for combined wastewater treatment and filtration, and DE 20 2009 012 539 U1 discloses a wastewater treatment device.

[0012] In general, various state-of-the-art processes are currently known for degrading pollutant residues, such as membrane filtration, ozonation, AOP (Advanced Oxidation Processes), adsorption on activated carbon, and the irrigating of treated wastewater. In addition, there are options for retaining or degrading old pharmaceuticals using photocatalytic processes, plasma reactors, or unconventional methods such as the use of genetically modified moss.

[0013] AOP processes are chemical treatment methods that degrade organic and inorganic substances in wastewater through oxidation using ozone, hydrogen peroxide, or a combination of these processes with additional UV irradiation. These processes are used in the treatment of industrial wastewater and, to some extent, in drinking water treatment.

[0014] In this process, the micropollutants are largely converted into compounds such as water, carbon, and salts. Therefore, this process is specifically used for substances that are difficult or impossible to biodegrade, such as pesticides, biocides, or various pharmaceuticals. Furthermore, this process enables the elimination of viruses and bacteria. Important factors influencing the efficiency of these processes are the amount of hydroxyl radicals generated, the organic background load of the wastewater, the pH value, and, especially in UV-based processes, the turbidity. UV irradiation for wastewater disinfection alone cannot eliminate a significant amount of micropollutants. Taking economic aspects into account, this process is currently not sufficiently developed to be suitable for use in a wastewater treatment plant.Ozonation is used in drinking water treatment to eliminate trace contaminants, for surface treatment and to reduce odors.

[0015] Disadvantages of the process, however, include the high energy costs for ozone generation, which must be achieved through electrical arc discharge, the procurement of pure oxygen, and the potential formation of metabolites that pollute water bodies. Furthermore, the excess toxic ozone must be destroyed in a deozonation plant after treatment.

[0016] Furthermore, the ozonation process has shown that low-molecular-weight degradation products are formed, which also have toxic potential. Therefore, it is recommended that, in wastewater treatment plants with ozone treatment, an additional activated carbon treatment be added as a fourth treatment stage for safety reasons. However, based on current knowledge, the use of powdered activated carbon also requires post-treatment of the wastewater following the actual micropollutant elimination process.

[0017] Furthermore, UV treatment with larger liquid volumes presents difficulties due to extremely long and energy-intensive treatment times, due to the low penetration depth of the high-energy radiation and the associated poor effectiveness in turbid wastewater. This results in a very low cost-benefit ratio.

[0018] Reverse osmosis and ultrafiltration systems are used to treat so-called raw water (city water, well water) for drinking water or ultrapure water with low conductivity for industrial cleaning purposes. They are unsuitable for the treatment of heavily contaminated wastewater such as manure. Extremely high pressures, special membranes, and a great deal of energy would be required to generate these pressures, with short operating times and high maintenance costs due to secondary contamination. Furthermore, the even more heavily contaminated concentrate would have to be incinerated, which would also result in the loss of valuable phosphorus and nitrogen-containing nutrients, rendering the manure worthless anyway. It might as well be incinerated without a filtration step.

[0019] The adsorption of pollutants onto activated carbon, already used in some wastewater treatment plants, is based on electrostatic interactions between the adsorbate molecules and the porous graphite crystals of the activated carbon. Activated carbon is used primarily in wastewater treatment, but also in exhaust air purification, drinking water treatment, the food industry, and medicine.

[0020] Due to the listed disadvantages of various alternative technologies for wastewater treatment, traditional activated carbon treatment as the fourth treatment stage in wastewater treatment plants is currently the only available method. The disadvantage of activated carbon, however, is its poor adsorption capacity and the fact that it can only be recycled with immense effort. The loaded and contaminated activated carbon can only be incinerated at temperatures above 1200 °C. The poor CO2 footprint of this disposal method, if all wastewater treatment plants are equipped with this treatment stage, does not represent a sustainable solution.

[0021] There is therefore still a great need for alternative processes for the degradation of micropollutants, especially pharmaceuticals, in wastewater, sewage sludge and the like.

[0022] The object of the present invention is therefore to provide a process for the degradation of micropollutants which overcomes the disadvantages mentioned above.

[0023] According to the present invention, this object is achieved by a method for degrading micropollutants, in particular pharmaceuticals, in wastewater, sewage sludge filtrates, and the like according to claim 1 and the developments in the dependent claims. The method comprises, among other steps: - Provision of an electrochemical cell, - Providing a sample containing micropollutants, preferably a wastewater or sewage sludge filtrate sample containing micropollutants; and - Performing electrolysis on the electrochemical cell with the sample to degrade the micropollutants and obtain a purified sample.

[0024] Furthermore, the use of an electrochemical cell for the degradation of micropollutants, in particular pharmaceuticals, in wastewater and sewage sludge filtrates is disclosed.

[0025] The problem underlying the invention is solved in this way.

[0026] According to this invention, micropollutants are understood to be certain organic substances, e.g., pharmaceuticals, especially antibiotics, but also painkillers, hormones, biocides, or pesticides. These substances can occur in the water cycle in concentrations ranging from a few ng / L to several µg / L. Micropollutants within the meaning of this invention can also be transformation products of the aforementioned organic substances.

[0027] Micropollutants within the meaning of this invention include, for example, the following substances / groups of substances: estrogens such as 17-α-ethinylestradiol (EE2) and 17-β-estradiol (E2), the painkiller diclofenac, macrolide antibiotics such as erythromycin, clarithromycin or azithromycin, pesticides such as oxadiazon, triallate, methiocarb, neonicotinoids 2,6-ditert-butyl-4-methylphenol or 2-ethylhexy-4-methoxycinnamate.

[0028] Corrosion inhibitors, flame retardants, UV stabilizers, sweeteners, household and industrial chemicals and similar substances can also be generally considered micropollutants.

[0029] It is particularly advantageous that all of the aforementioned substances can be degraded using the process according to the invention. Another advantage is that no heavy metals are dissolved in the process according to the invention; any heavy metals present are deposited anodically.

[0030] According to this invention, "degradation of micropollutants" is understood to mean any process in which the aforementioned micropollutants are broken down, i.e., converted into smaller molecules or even their elements as a chemical compound. In this case, the aforementioned micropollutants should be broken down or decomposed as completely as possible into non-toxic or at least less toxic secondary molecules. A chemical conversion of the substances into unreactive forms is also considered degradation within the meaning of this invention.

[0031] According to this invention, “degradation by electrolysis” is understood to mean the splitting or decomposition, but also the chemical conversion of a chemical compound, in particular of micropollutants, under the influence of electric current.

[0032] In electrolysis, a direct electric current is passed through two electrodes in a conductive liquid (electrolyte). The application of an electric current forces a redox reaction of the substances contained in the electrolyte. The electrode connected to the positive pole of the voltage source is the anode, and the electrode connected to the negative pole of the voltage source is the cathode. The redox reactions that occur are partially spatially separated from one another, as oxidation occurs at the anode and reduction at the cathode.

[0033] The method according to the invention makes it possible to degrade micropollutants, particularly antibiotics. The electrochemical cell is preferably operated with direct current. The electrochemical cell has at least one anode and at least one cathode as electrodes. It can be advantageous to connect several pairs of anode and cathode electrodes in series to achieve the best possible results in degrading the micropollutants. This ensures that the sample comes into contact with the corresponding electrodes several times, thus ensuring that electrolytic decomposition occurs repeatedly.

[0034] In general, the electrode pairs that together form the electrochemical cell can be arranged in any desired sequence. Preferably, such electrode pairs can also be arranged in the form of so-called arrays, one behind the other and / or next to the other. This allows for a multitude of parallel electrolytic decompositions.

[0035] A particularly advantageous feature of the process according to the invention is that the decomposition of the micropollutants occurs through anodic oxidation, so that decomposition occurs at the electrode connected as the anode with the release of electrons. Unlike perfluorinated surfactants, which are surface-active substances, antibiotics, for example, do not reduce the surface tension of water but remain in solution.

[0036] The anodic oxidation of micropollutants can be carried out using an anode made of any suitable material. However, the anode is preferably made of lead or lead oxide without introducing lead into the solution, or platinized titanium. Other inert anodes are also possible.

[0037] Wastewater, sewage sludge filtrates, and the like are understood to mean all waters that accrue, for example, in the municipal sewage system. This also includes industrial waters, but also all waters accruing in agriculture, such as liquid manure, slurry, silage sap, manure, or other liquid excretions from farm animals such as cattle, pigs, poultry (e.g., chickens and turkeys), etc., especially those kept in large-scale animal farms or factory farms.

[0038] Wastewater is defined as water that has been contaminated through use. A further distinction is made between greywater (European Standard 12056-1) and blackwater (ISO 6107-7:1997). Furthermore, wastewater also includes rainwater runoff from paved surfaces.

[0039] Sewage sludge filtrate is the filtrate that has been separated from the sewage sludge. Sewage sludge filtrate can arise, for example, in sewage treatment plants as excess water or as turbid water, wastewater, or similar.

[0040] According to the invention, the wastewater or sewage sludge filtrates can be a suspension. A suspension is understood to be a heterogeneous mixture of substances consisting of a liquid and finely dispersed solids. In contrast, a solution is a homogeneous mixture consisting of two or more chemical substances. In particular, according to this invention, solutions are systems in which one or more substances are dissolved in a liquid solvent. The dissolved substances are evenly distributed in the solvent, and the system is therefore a single-phase system.

[0041] The liquid of the suspension or the solvent is preferably water.

[0042] The process according to the invention makes it possible to reduce overall environmental pollution caused by micropollutants. The process according to the invention can, for example, be used within sewage treatment plants as a fourth purification stage. This allows for the best possible water treatment. To relieve the burden on municipal sewage treatment plants, the process can also be used directly at the source, where contaminated wastewater is generated in large quantities, such as in agriculture, industry, hospitals, retirement and nursing homes, and ultimately also in private households, or in remote areas far from sewage systems, such as mountain huts, and in waterless urinals or other urine collection points.

[0043] The process according to the invention is particularly suitable for treating agricultural wastewater. This is because comparatively large quantities of micropollutants enter the wastewater, for example, through the administration of large quantities of antibiotics to animals. The same applies to wastewater from hospitals or nursing homes.

[0044] The process according to the invention offers a multitude of advantages. For example, the electrolytic degradation of micropollutants provides a comparatively easy-to-use electrochemical process. In addition to the desired degree of degradation, it is possible to achieve complete degradation of micropollutants within a comparatively short process time. The process parameters, such as the design of the electrodes, the current density, the applied voltage or the time required for electrolysis, are comparatively easy to adjust and also reproducible. In addition, the process can be easily integrated into existing wastewater treatment processes. Furthermore, the process according to the invention does not require the additional introduction of additives. The additives can be, for example,These may be those that increase conductivity or are required to form hydroxide radicals, such as hydrogen peroxide in the well-known AOP process.

[0045] According to a first embodiment of the method according to the invention, the micropollutants are pharmaceuticals, in particular antibiotics or hormone preparations, wherein the antibiotic is preferably selected from the group consisting of sulfonamides, tetracyclines, macrolides and / or derivatives thereof.

[0046] One representative of the sulfonamides is the antibiotic sulfadimidine. This antibiotic is used primarily in veterinary medicine to treat bacterial infections, such as coccidosis or diphtheria.

[0047] Another representative of this class of substances is sulfamethoxazole, a prescription broad-spectrum antibiotic. The antibiotic is excreted almost entirely in the urine—approximately 17 to 20% in its original form, and the remainder in the form of two metabolites, N-4-acetylsulfamethoxazole and a hydroxylamine derivative. These metabolites exhibit toxicity similar to that of the parent substance. In toxicological studies, the antibiotic even demonstrated carcinogenic and mutagenic potential.

[0048] Tetracyclines are antibiotic drugs produced by bacteria of the genus Streptomyces. They form a subgroup of polyketides. Tetracyclines inhibit bacterial protein synthesis on their ribosomes and thus inhibit the growth of gram-positive, gram-negative, and numerous cell-wall-less bacteria. Tetracyclines are generally poorly metabolized and excreted in a bioactive form. Depending on the species, 50 to 80% of the administered tetracycline is excreted. An important example is tetracycline, which is used as a broad-spectrum antibiotic.

[0049] Macrolides are organic, ring-shaped molecules with up to 60 ring members characterized by intramolecular ester groups. The class of macrolide antibiotics includes a wide variety of substances, with the antibiotics erythromycin, clarithromycin, and azithromycin being particularly important.

[0050] Because antibiotics often cannot be broken down, they accumulate in the environment. Azithromycin is primarily present in aquatic systems and exists in wastewater treatment plants and surface waters between 0.1 and 1 µg / L. The PNEC (predicted no-effect concentration) of this antibiotic is 4.8 µg / L.

[0051] The PNEC (predicted no-effect concentration) is the predicted concentration of a substance that is generally hazardous to the environment, up to which no effects on the environment are observed. Therefore, it is important to keep this value below as much as possible.

[0052] The PNEC for clarithromycin is 0.2 µg / L. In comparison, the measured environmental concentration is up to 0.98 µg / L, thus exceeding the critical value by a factor of five. A link between the toxicity of clarithromycin and its main metabolites to aquatic organisms has already been demonstrated.

[0053] Erythromycin is even less biodegradable in the environment and in wastewater treatment plants than clarithromycin, leading to higher environmental concentrations. The maximum environmental concentration measured to date exceeds the PNEC value by a factor of 8.3.

[0054] According to the invention, antibiotics can be degraded that cannot be degraded, or cannot be degraded sufficiently, using conventional methods. In particular, the method according to the invention degrades antibiotics whose PNEC values ​​have already been significantly exceeded in water bodies. Thus, health impairment is prevented or avoided.

[0055] According to a second embodiment of the method according to the invention, the sample is selected from the group consisting of wastewater, in particular hospital, nursing home or agricultural wastewater, and sewage sludge filtrate.

[0056] According to this embodiment, wastewater and sewage sludge filtrates can be treated, which, by their very nature, typically have a significantly higher load of micropollutants, particularly antibiotics. Accordingly, there is a particular need to treat the resulting wastewater using the process according to the invention.

[0057] According to a further embodiment of the method according to the invention, the sample is an agricultural wastewater sample from animal and / or plant breeding and in particular a liquid manure, slurry or silage juice sample.

[0058] Especially in agriculture, the use of micropollutants such as antibiotics, hormones, biocides, or pesticides is increasing. This design treats and purifies these highly contaminated samples. The purified samples can be reused, for example, as higher-quality fertilizer. Negative impacts on groundwater caused by micropollutants can be avoided at this stage.

[0059] According to a further embodiment of the process according to the invention, the degradation of the micropollutants takes place by anodic oxidation.

[0060] According to a further embodiment of the process according to the invention, the electrolysis is carried out on a Pb / PbO2 anode.

[0061] A particular advantage of this design is that lead electrodes are comparatively inexpensive to manufacture. Other electrodes, such as those made of platinized titanium or so-called BDD electrodes (boron-doped diamond electrodes), are significantly more expensive, but are frequently used due to their stability. However, these electrodes have the disadvantage that they are difficult to produce on a large scale.

[0062] For electrochemical decomposition processes, it is also important that the electrode material itself is inert to prevent undesirable reactions. For example, platinized electrodes are inert in 10% sulfuric acid and do not dissolve. Furthermore, these electrodes corrode easily in the presence of quaternary ammonium salts, so dissolved platinum can cause undesirable chemical reactions.

[0063] In contrast, the design of conducting the electrolysis at a Pb / PbO2 anode offers the advantage that no lead dissolves during electrolysis at the Pb / PbO2 anode. Thus, there is no lead contamination of the sample.

[0064] Composite electrodes such as lead dioxide-coated titanium, lead, or graphite anodes also offer the advantage of being particularly inexpensive to manufacture, characterized by high conductivity, and chemically, mechanically, and electrochemically stable. Furthermore, lead dioxide electrodes exhibit a high oxygen overpotential to decompose micropollutants. This oxygen overpotential is even greater than that of platinum. For example, a comparison of lead dioxide with a platinum alloy showed a potential difference of more than 500 mV at a current density of 40 mA / cm 2 measured.

[0065] According to a further embodiment of the process according to the invention, the electrolysis is carried out on a cathode made of steel, in particular stainless steel.

[0066] Another particularly advantageous feature of this design is that the cathode is also comparatively inexpensive to manufacture. Steel is also chemically inert, so unwanted side reactions between the steel and other sample components are unlikely to occur.

[0067] In addition to the electrode material, the electrode shape can also be preferred. Generally, the electrodes can be designed as rod electrodes or plate electrodes. Other shapes are also possible, with a large surface area being preferred.

[0068] Furthermore, the electrodes can also be designed such that the sample can be passed through the electrode. However, it is particularly preferred that the sample has contact with the electrodes over as large an area as possible, so that the degradation or decomposition of the micropollutants, i.e., the redox reactions, can also take place on the corresponding electrode surfaces.

[0069] According to the invention, the electrolysis is carried out at a current density of 25 to 35 mA / cm 2 carried out.

[0070] According to a further embodiment of the process according to the invention, the electrolysis is carried out at a voltage of at least 3 V, preferably of at least 10 V, in particular of approximately 15 V, and in particular in a range of preferably 7 to 10 V, ie of 7, 8, 9 or 10 V.

[0071] According to a further embodiment of the process according to the invention, the electrolysis is carried out over a period of at least 10 minutes, preferably at least 30 minutes, in particular at least 1 hour and preferably between approximately 10 and 60 minutes, i.e. approximately 10, 20, 30, 40, 50 or 60 minutes.

[0072] In general, the duration of electrolysis depends on the desired degree of micropollutant degradation. If complete degradation is desired, the electrolysis should be carried out for a longer period of time than if only a specific degree of degradation is to be achieved. Generally speaking, the longer the electrolysis runs, the more micropollutants can be degraded. The required time therefore also depends on the degree of micropollutant contamination in the sample. The higher the degree of contamination, the longer the degradation of the micropollutants through electrolysis takes.

[0073] However, it was also found that the degradation of micropollutants through electrolysis can reach saturation after a certain period of time. In other words, there is a period during which the micropollutants can no longer be degraded. In this case, almost 100% degradation of the micropollutants in the sample is achieved.

[0074] The time required to achieve a satisfactory degree of degradation of micropollutants also depends on the nature of the electrochemical cell. If the electrodes have a very large surface area, degradation occurs correspondingly faster than if the electrodes have a smaller surface area.

[0075] When selecting the period in which the electrolysis should take place, the cost-benefit ratio should always be taken into account, since electricity costs are incurred to operate the electrochemical cell.

[0076] According to a further embodiment of the method according to the invention, by carrying out the electrolysis, a degree of decomposition of the micropollutants within the purified sample of ≥ 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35% or ≥ 30% is achieved.

[0077] The degree of decomposition of the micropollutants within the purified sample is calculated from the absolute initial content of the micropollutants before electrolysis and the final content of the micropollutants after electrolysis. A degree of decomposition of ≥ 95, 90, or ≥ 80% is particularly preferred.

[0078] According to a further embodiment of the method according to the invention, the method is operated as a flow-through process, for example, by connecting multiple cells in series. This eliminates the need for a collection container, and the purified sample can leave the continuous arrangement at its end.

[0079] In this way, the method according to the invention can be easily integrated into an industrial production process.

[0080] Continuous processes offer the general advantage that the sample can be passed through the device in which the electrolysis is to be carried out. The sample containing micropollutants can be continuously introduced into one or more electrochemical cells connected in series and, after electrolysis, discharged from these cells again. This means that the sample flows through the device in which the electrolysis takes place in a flow-through process, with at least one suitable inlet and at least one suitable outlet being provided. In a preferred embodiment of this configuration, a constant volume flow can be provided with which the sample is introduced into the corresponding device and discharged from it again.

[0081] A flow-through process also offers the advantage of continuous mixing of the sample. Since the degradation of micropollutants occurs at the electrodes or on the electrode surfaces, saturation can quickly occur in this area. Therefore, a uniform degradation of micropollutants within the sample can be better ensured using a flow-through process. Ideally, mineralization of the micropollutants is achieved.

[0082] Alternatively, the process can also be used as a batch process, i.e., in a discontinuous process. The sample to be purified, the quantity of which is limited by the container containing the electrochemical cell, is added to the system and removed from it as a whole after the process is completed.

[0083] The sample can be liquid manure, slurry, silage sap, or other animal excrement, especially farm animals such as cattle, pigs, and poultry, such as chickens and turkeys. If these liquids are purified using the method according to the invention, the resulting product is a high-quality fertilizer. This can be spread on fields without the risk of introducing harmful amounts of micropollutants into the environment and thus potentially into the groundwater.

[0084] According to the process according to the invention, hydrogen is produced when the electrolysis is carried out.

[0085] Electrolysis is a redox reaction in which hydrogen can be produced at the cathode. This hydrogen can be collected and reused if necessary. A diaphragm membrane, for example, can be used to separate the hydrogen for use. In the diaphragm process, the cathode chamber is separated from the anode chamber by a porous partition wall that is permeable to current and cations.

[0086] According to a further embodiment of the process according to the invention, the resulting hydrogen is used as an energy source for carrying out the electrolysis.

[0087] The hydrogen obtained during electrolysis can be used as a storable energy source, for example, within a fuel cell. According to this embodiment, the process according to the invention can partially generate the energy required to carry out the electrolysis itself. This makes the process particularly economically important, as it reduces energy costs.

[0088] The features, properties and advantages described for the method according to the invention apply accordingly to the use described herein.

[0089] Further advantages emerge from the figure and the following description of preferred embodiments. They show: Fig. 1 shows the concentration curve of the two antibiotics sulfadimidine and tetracycline in a bovine urine sample. Examples of implementation

[0090] Antibiotics of the sulfonamide or tetracycline class are used in large quantities in both human and veterinary medicine. In this study, one representative of each of these classes (sulfadimidine and tetracycline) was used to test the functionality of the method according to the invention. Electrochemical cell

[0091] The electrolytic degradation of the antibiotics was carried out in a bovine urine sample in a single-chamber electrochemical cell operated in batch mode. A Pb / PbO2 electrode was used as the anode and a steel electrode as the cathode. The active surface area of ​​both electrodes was 120 cm². 2 , with the electrode gap adjusted to 7 mm.

[0092] In each experiment, a 270 ml bovine urine sample was spiked with 10 ppm each of tetracycline and sulfadimidine and then electrochemically degraded. No further additives were added to the urine sample to increase its conductivity, as this sample already had a conductivity of 31.2 mS.

[0093] A Degussa TG 411 power converter was used as the power supply source. The current density was set to 30 mA / cm 2 To analyze the amount of degraded antibiotics, a 2 ml sample was taken from each experiment at different time intervals and analyzed by UV spectroscopy and HPLC-MS / MS. Anode preparation

[0094] For the electrochemical degradation experiments, a planar anode with an active surface of about 120 cm 2 manufactured.

[0095] For this purpose, pieces of lead foil were electrochemically coated with lead dioxide. The lead foil was sanded with various sandpapers. The surface was then cleaned with a 50% acetic acid solution, acetone, and deionized water. After the cleaning process, the lead foil was placed in a 30% sulfuric acid solution (96% sulfuric acid from Merck, Germany) for 45 minutes at 65°C. The electrochemical coating with lead dioxide was then carried out in a molar sulfuric acid solution using a stainless steel cathode at a current density of 60 mA / cm 2 (Rectifier TG 411 from Degussa) for 4 hours at 65°C. Sample preparation by solid phase extraction (SPE)

[0096] The bovine urine degradation samples, with an initial sulfamethidine and tetracycline concentration of 10 ppm, were analyzed by Eurofins WEJ. Contaminants GmbH (Hamburg, Germany).

[0097] Two standard solutions were used for sample preparation. The tetracycline standard solution consisted of 10 ppm demeclocycline as an internal standard and four other tetracyclines dissolved in a mixture of water / acetonitrile / formic acid (89.9 / 10 / 0.1 vol%).

[0098] The sulfamethazine standard solution consisted of 1 ppm sulfamethoxazole D4 as internal standard and 25 other sulfonamides in water / acetonitrile / formic acid (89.9 / 10 / 0.1 vol%).

[0099] For sample preparation, 10 µl of the current urine sample was mixed with 10 µl of the standard solution. Then, 970 µl of a mixture of water / acetonitrile / formic acid (89.9 / 10 / 0.1 vol%) was added, and the sample preparations were transferred to analysis vials. HPLC-MS / MS analysis

[0100] The urine samples were analyzed by HPLC-MS / MS by Eurofins WEJ Contaminants GmbH, Hamburg, Germany. A Sciex API 5500 QT LC-MS / MS system was used, and a Thermo Scientific™ ACCUCORE™ XL C18 reversed-phase LC column (150 x 4.6 mm, 4 µm) was used as the analytical column. Electron spray ionization (ESI) was used for ionization in positive measurement mode. Results

[0101] The samples containing antibiotics were first electrochemically treated at a current density of 25 mA / cm 2 decomposed, pre-purified by solid-phase extraction, and then analyzed by HPLC-MS / MS. The following table lists the reactor conditions, such as the average voltage U, current I, temperature T, and degradation rate. The degradation rates are given in percent for the HPLC-MS / MS methods at 5 and 30 min degradation times. PH value Temperature in C° U to V I in A J in mA / cm 2 Degradation rate in % after 5 min. Degradation rate in % after 30 min. 2 45 9,6 3 25 HPLC: 59 HPLC: 97 Electrochemical degradation of bovine urine samples

[0102] In degradation experiments at different current densities (10, 30 and 40 mA / cm 2 ) showed that degradation can be accelerated with increasing current density. However, they also found that no significant difference could be detected between 30 and 40 mA / cm. Therefore, the subsequent experiments were carried out at 30 mA / cm 2 The results for different current densities are not shown.

[0103] In the degradation experiments, 270 ml of a bovine urine sample, which was spiked with 10 ppm of tetracycline and sulfadimidine, was irradiated at 30 mA / cm 2 decomposed. The degradation sample was then analyzed as described by HPLC-MS / MS by Eurofins WEJ Contaminants GmbH, Hamburg, Germany. The corresponding degradation curves are Fig. 1 shown.

[0104] As in Fig.As can be seen in Figure 1, 90% degradation of sulfadimidine in the bovine urine sample was achieved after 60 minutes. Tetracycline, on the other hand, was degraded by 90% after just 40 minutes and more than 95% after 60 minutes.

[0105] By optimizing the electrode surface by structuring both electrodes, 90% degradation was achieved after just 20 minutes. These results are not shown here. discussion

[0106] The two antibiotics were thus successfully decomposed in the wastewater sample by electrochemical processes.

[0107] The experiments also demonstrated that it is not necessary to additionally increase the conductivity of the urine sample. Thus, degradation could also be detected in the alkaline sample.

[0108] It has been demonstrated that electrochemical processes using lead / lead oxide electrodes can be used to treat wastewater directly on-site, for example, in agriculture, to degrade pharmaceuticals or other pollutants. These electrochemical degradation processes can be used to ensure that contaminants and pharmaceuticals, especially antibiotics, are removed before fertilizer application, preventing them from being released into the environment or the food chain. This ensures that not only pharmaceutical residues can be degraded, but also improves hygiene and prevents antibiotic resistance.

Claims

[1] A process for the degradation of micropollutants in wastewater, sewage sludge filtrates and the like by generating hydrogen as an energy source of the process, the process comprising the following steps: - Provision of an electrochemical cell, - Provision of a sample containing micropollutants, - Conducting electrolysis on the electrochemical cell with the sample to degrade the micropollutants to obtain a purified sample, - Separation and, if necessary, storage of the hydrogen produced in electrolysis and - Use of the resulting hydrogen as an energy source to carry out electrolysis, characterized by that the electrolysis at a current density of 25 to -35 mA / cm 2 is carried out. [2] Method according to claim 1, characterized by that the hydrogen is separated by means of a diaphragm membrane. [3] Method according to one of the preceding claims, characterized by that the micropollutants are medicinal products, in particular antibiotics or hormone preparations, wherein the antibiotics are preferably selected from the group consisting of sulfonamides, tetracyclines, macrolides and / or derivatives thereof. [4] Method according to one of the preceding claims, characterized by that the sample is selected from the group consisting of wastewater, in particular hospital, nursing home or agricultural wastewater, dry urinals, sewage sludge filtrate. [5] Method according to one of claims 1 to 3, characterized by that the sample is an agricultural wastewater sample from animal and / or plant breeding and in particular a urine, slurry, liquid manure or silage sample. [6] Method according to one of the preceding claims, characterized bythat the electrolysis is carried out on a cathode made of steel, in particular stainless steel. [7] Method according to one of the preceding claims, characterized by that the electrolysis is carried out at a voltage of at least 3 V, preferably of at least 10 V, in particular of about 15 V and in particular in a range of preferably 7 to 10 V, ie of 7, 8, 9 or 10 V. [8] Method according to one of the preceding claims, characterized by that the process is operated continuously or as a batch process.

Images