Agent for separating effluent into a sludge and a clarified water phase and for adsorptive removal of trace substances from the clear water phase

Abstract

A means for separating wastewater to be treated into a sludge and a clear water phase, and for the adsorptive removal of trace substances from the clear water phase, is described. The means comprises a polymer system as a flocculant, carbon, and at least one alkaline earth solution containing Ca ions and / or Mg ions. According to the invention, it is proposed that the carbon be present as activated carbon, carbon black, graphite, graphene, and / or fullerene in a polymer-surface-modified form, forming a polymer-carbon complex. The means also includes an alcohol solution and at least one carboxylic acid solution as a suspension stabilizer for the polymer-carbon complex.

Description

[0001] The invention relates to a means for separating wastewater to be treated into a sludge and a clear water phase and for the adsorptive removal of trace substances from the clear water phase, with a polymer system, for example in solution form, as a flocculation aid, carbon and at least one alkaline earth solution comprising Ca ions and / or Mg ions.

[0002] Particularly in the context of municipal and industrial wastewater treatment, the term "trace substances" refers to undesirable substances dissolved in water, also known as micropollutants. Such trace substances are primarily synthetic substances that are present, for example, in wastewater in concentrations ranging from nanograms to several micrograms per liter of water. Trace substances dissolved in wastewater generally originate from various products used in households, public facilities, industry, and agriculture. Such products can include pharmaceuticals, biocides or pesticides, detergents and cleaning agents, cosmetics, and building materials. Due to their persistence and accumulation in biological tissues, they persist in the water cycle over the long term and therefore pose a significant problem, not least for drinking water production.Of particular concern are those substances that, due to their toxicity or known biological effects, can affect water quality and water use. Environmentally relevant trace substances associated with the discharge of wastewater from wastewater treatment plants into receiving waters or in connection with the determination of water quality parameters include benzotriazole, diclofenac, and metoprolol. However, these very common trace substances, as well as any associated metabolites, cannot be removed from wastewater in conventional three-stage wastewater treatment plants, or can only be removed inadequately. This is demonstrated by their regular detection in water samples.

[0003] In order to effectively remove trace substances remaining after treatment in conventional wastewater treatment plants, which are highly water-soluble and poorly biodegradable, adsorption processes based on adsorptive phases are used in industrial applications, in addition to oxidative or size-selective processes. The latter can be achieved, for example, using granular activated carbon (GAC) as a fixed bed.

[0004] Pressure-driven membrane filtration, which is carried out as part of a full-flow treatment process, is particularly important for size-selective processes. The disadvantage is that high pressures of almost 70 bar are required. However, this is not technically feasible for the treatment of municipal wastewater in larger catchment areas, as the respective daily wastewater volumes are far too high to allow full-flow treatment. In addition, the associated high energy and investment costs are many times higher than those of conventional wastewater treatment, making the use of such filtration processes uneconomical for municipal wastewater.

[0005] In addition, activated carbon, for example, is used as an adsorbent to purify wastewater of various trace substances, etc. Accordingly, corresponding agents are known (CN109553175A, CN108557973A, US8021556B2), which, in addition to a polymer system as a flocculant, alkaline earth solutions, and activated carbon particles are also included. When using such powdered activated carbon particles (PAH), the adsorbent is disposed of via the sludge line together with the adsorbate formed by the trace substances, etc.

[0006] The disadvantage is that when agents containing PAHs are used for wastewater treatment in conventional wastewater treatment plants, the separation of the wastewater to be treated into a sludge and a clear water phase is often inadequate. Furthermore, certain bacteria in the sludge phase, an imbalance in the lime-carbonic acid balance, or a lack of acid buffer capacity in the wastewater to be treated can hinder the formation of sludge flocs in the form required for efficient separation. Overall, this leads to undesirable PAH slippage of up to 30% of the total amount of PAHs used, which is reflected in the entry of contaminated activated carbon into the receiving water or the wastewater treatment plant effluent. As a result, the prescribed limit of a maximum of 1 milligram of contaminated PAHs per liter in the wastewater treatment plant effluent cannot regularly be met when using known agents.

[0007] There is therefore a need for a means of the type described above which, when used in the biological treatment of municipal wastewater by conventional wastewater treatment plants, not only enables a reliable separation of the wastewater to be treated into a sludge and a clear water phase, but also an effective removal of trace substances from the clear water phase.

[0008] The invention achieves this objective by providing the carbon, selected in particular from activated carbon, carbon black, graphite, graphene, and / or fullerene, in a polymer-surface-modified form to form a polymer-carbon complex, and by comprising at least one alcohol solution and at least one carboxylic acid solution as a suspension stabilizer for the polymer-carbon complex. Further advantageous embodiments of the agent according to the invention are specified in the subclaims.

[0009] Surprisingly, it has been shown that, due to the polymer-based surface modification or the formation of a polymer-carbon complex, on the one hand, the adsorption capacity is not impaired but actually improved, and on the other hand, an increased incorporation of the adsorbed micropollutants into the sludge phase occurs. In conjunction with the at least one alkaline earth solution, the formation of shear-stable, dense activated sludge flocs with an average diameter of 150 to 500 µm and an improved sedimentation rate is promoted as a prerequisite for efficient separation. Flocs are referred to as shear-stable if they have a kinematic viscosity of more than 1 cSt or 10 -6 < m 2 < *s -1 < after shear stress.

[0010] The surface modification of the carbon occurs because, as a result of esterification caused by the alcohol(s) and the carboxylic acid(s), functional ester groups are initially bound to the carbon surface, which then allow the polymer to be bound. For this purpose, the carbon can first be suspended in a mixture of an alcohol and carboxylic acid solution, after which the carbon suspension thus formed is mixed with a polymer matrix, which can also be in solution form, to form the surface modification of the carbon, i.e. to form the polymer-carbon complex. In principle, the polymer underlying the polymer-carbon complex can be a different polymer from the polymer(s) of the polymer system. However, the polymer underlying the polymer-carbon complex is preferably a polymer of the polymer system of the agent according to the invention.In this case, it is also possible for the surface modification of the carbon to occur directly during mixing of the agent according to the invention. The alcohols and carboxylic acids used are thus initially available for the chemical synthesis of the surface-modified carbons into a polymer-carbon complex and subsequently also serve to stabilize the suspension in conjunction with the polymer system, which provides an increased proportion of organic charge carriers. A lack of acid buffer capacity can also be compensated for by the interaction of the components according to the invention, which further promotes reliable separation of the wastewater into a sludge and a clear water phase.

[0011] It has been found that higher amounts of an alcohol solution of up to 10 wt% further promote the surface modification of the carbon.

[0012] In addition, the surface modification of the carbon can be further promoted by mixing or esterification at temperatures above 70 °C, while maintaining appropriate maximum temperatures.

[0013] The polymer system preferably comprises cationized starch, epichlorohydrin dimethylamine copolymer, polydiallyldimethylammonium chloride, polyamine, and / or polyacrylamide. This means that the polymer system can also be formed from a mixture of these polymers. The polymer system can, in particular, comprise 10-50% by weight of the agent according to the invention.

[0014] Preferably, the at least one alkaline earth solution comprises 5-30 wt.% of the agent according to the invention. This means that if only one alkaline earth solution is present, it comprises 5-30 wt.% of the agent, whereas if several alkaline earth solutions are present, they comprise a total of 5-30 wt.% of the agent. The at least one alkaline earth solution is formed in particular by a CaX solution and / or an MgX solution, where X is a chloride, a sulfate, and / or a nitrate. Particularly preferably, an agent according to the invention comprises two alkaline earth solutions, particularly preferably a calcium chloride solution and a magnesium chloride solution.

[0015] The alcohol solution is preferably based on mono- and / or polyhydric alcohols, meaning that a mixture of several different alcohols can be provided. Even more preferably, the alcohol solution is based on either a mono-, di-, or trihydric alcohol. The alcohol solution is particularly preferably based on a monohydric alcohol, in particular ethanol.

[0016] Preferably, the at least one carboxylic acid solution is based on mono-, di-, tri-, and / or hydroxycarboxylic acids. Accordingly, a mixture of different carboxylic acid solutions can also be present. Naturally, a mono-, di-, or tricarboxylic acid can also simultaneously be a hydroxycarboxylic acid, for example, in the case of citric acid. Particularly preferably, the at least one carboxylic acid solution comprises 5-30% by weight of the agent according to the invention. If several carboxylic acid solutions are present, these solutions comprise a total of 5-30% by weight of the agent, analogous to the above statements in connection with the alkaline earth solutions.

[0017] Preferably, an agent according to the invention comprises 10 - 50 wt% of a polymer system, 0.1 - 10 wt% of a polymer-surface-modified carbon, 5 - 30 wt% of at least one 20 - 40% alkaline earth metal solution, 0.1 - 10 wt% of a 60 - 80% alcohol solution, and 5 - 20% of at least one 0.2 - 80% carboxylic acid solution.

[0018] More preferably, an agent according to the invention comprises 35% by weight of a polymer system, of which 20% by weight is cationized starch and 15% by weight of a polyamine, 5% by weight of a polyamine surface-modified carbon, in particular a polyamine surface-modified activated carbon, 15% by weight of a 30-40% MgX solution and 15% by weight of a 30-40% CaX solution, where X is a chloride, a sulfate and / or a nitrate, 10% by weight of a 70% ethanol solution, and 20% by weight of a 50% citric acid solution.

[0019] A composition according to the invention can, in principle, contain further components. However, it is preferably provided that a composition according to the invention consists exclusively of a polymer system, a polymer-carbon complex based on a polymer-surface-modified carbon, at least one alkaline earth metal solution, at least one alcohol solution, and at least one carboxylic acid solution. Examples of implementation:

[0020] An agent according to the invention for separating wastewater to be treated into a sludge and a clear water phase and for adsorptive removal of trace substances from the clear water phase comprises 20% cationified starch, 15% of a polyamine, 15% of a 30% calcium chloride solution, 15% of a 30% magnesium chloride solution, 20% of a 50% citric acid, 5% polyamine surface-modified activated carbon and 10% of a 70% ethanol solution.

[0021] According to a further embodiment, an agent according to the invention comprises 10% epichlorohydrin dimethylamine copolymer, 20% of a polyamine, 15% of a 15% solution of cationized starch, 20% of a 33% calcium chloride solution, 10% of a 30% magnesium chloride solution, 3% of a 50% lactic acid solution, 2% of a 0.2% fumaric acid solution, 10% polyamine surface-modified C 60 fullerene and 10% of a 70% ethanol solution. Test results: Laboratory experiment

[0022] In laboratory tests (n = 100), wastewater samples were treated with different agents S1 to S4. S1 refers to an agent according to EP2808306B1, which consists of 61 wt% of a polyaluminum chloride solution with 18 wt% Al 2 O 3 , 20 wt% of a 23% FeCl 2 solution, 3.5 wt% of a 15% solution of cationized starch, 15 wt% of a 33% CaCl 2 solution, and 0.5 wt% of a saturated ascorbic acid solution. S2 refers to an agent according to EP3636601B1, wherein the agent consists of 40 wt% of a 28% FeCl 2 solution, 8 wt% of a 30% ascorbic acid solution, 5 wt% of a 40% CaCl 2 solution, 42 wt% of a 36% polyaluminium chloride solution with 18 wt% Al 2 O 3 and 5 wt% of a polyamine solution with an active substance content of 85%.S3 refers to an agent according to EP3974394A1, wherein the agent consists of 65 wt% of a polyaluminium chloride solution with 18 wt% Al 2 O 3 as flocculant, 10 wt% of a 50% epichlorohydrin dimethylamine copolymer solution as flocculant, 15 wt% of a 30% MgCl 2 solution as alkaline earth solution and 10 wt% of a 70% ethanol solution. S4 refers to an agent according to the invention which consists of 10 wt% epichlorohydrin dimethylamine copolymer, 20 wt% of a polyamine, 15 wt% of a 15% solution of cationized starch, 20 wt% of a 33% CaCl 2 solution, 10 wt% of a MgCl 2 solution, 3 wt% of a 50% lactic acid solution, 2 wt% of a 0.2% fumaric acid solution, 10 wt% polyamine surface-modified C 60 fullerene and 10 wt% of a 70% ethanol solution.

[0023] The percentage removal of various micropollutants from the wastewater sample was determined according to the table below. 100 ppm of each of the agents S1-S3 were tested alone or in combination with 15 ppm of activated carbon (AC). Agent S4 was also dosed at 100 ppm. An improved removal (E) was observed for S4 compared to the other agents S1 to S3: Micropollutant category S1 S1+AK S2 S2+AK S3 S3+AK AK S4 E E E F E E E E [%] [%] [%] [%] [%] [%] [%] [%] Carbamazepin drug 11 15 13 14 18 20 38 73 Diclofenac drug 5 34 7 9 15 17 34 67 Metoprolol Medicines 16 26 21 34 13 19 49 97 Ethinylestradiol Estrogen 3 8 10 15 20 33 38 72 Estradiol Estrogen 4 19 7 8 15 24 31 68 Carbendazim pesticide 25 21 14 11 11 28 35 84 Benzotriazol Corrosion protection 13 15 18 16 6 19 27 70 Wastewater treatment plant experiment

[0024] In addition, an agent according to the invention was used in a wastewater treatment plant. The wastewater treatment plant has a capacity or population equivalent (PE) of 24,000 PE. The influent flow was 4,460 m³ per day. The biochemical oxygen demand (BOD 5,ad ) in the influent was 950 kg per day. The chemical oxygen demand (COD Ad ) in the influent was 1,574 kg per day. The dissolved organic carbon (DOC Ad ) in the influent was 411 kg per day.

[0025] The concentrations C of various micropollutants in nanograms per liter (ng / l) were measured in the inlet and outlet of the wastewater treatment plant. A dosage of 100 ppm of the agent S4 according to the invention, specified according to the above composition, was carried out in a separate flow line (index 1), whereas no dosage was carried out in parallel in a different flow line (index 2). As can be seen from the table, reduced pollutant concentrations were detected in the outlet of the flow line in which dosing with agent S4 was carried out compared to the untreated flow line. Micropollutant category C ZU,dM [ng / L] C Ab,dM,1 [ng / L] C AB,dM,2 [ng / L] Carbamazepin drug 502 69 432 Diclofenac drug 920 126 598 Metoprolol drug 261 3 149 Ethinylestradiol Estrogen 25 1 6 Estradiol Estrogen 53 2 8 Carbendazim pesticide 105 7 82 Benzotriazol Corrosion protection 6090 828 4.872

Claims

1. A means for separating wastewater to be treated into a sludge and a clear water phase and for the adsorptive removal of trace substances from the clear water phase, comprising a. a polymer system as a flocculation aid, b. carbon, and c. at least one alkaline earth solution comprising Ca ions and / or Mg ions, characterized in that the carbon is present in polymer-surface-modified form to form a polymer-carbon complex, and that the agent comprises at least one alcohol solution and at least one carboxylic acid solution as suspension stabilization for the polymer-carbon complex.

2. Agent according to claim 1, characterized in that the carbon is selected from activated carbon, carbon black, graphite, graphene and / or fullerene.

3. Agent according to claim 1 or 2, characterized in that the polymer-carbon complex is based on a surface modification of the carbon by at least one polymer of the polymer system.

4. Agent according to one of claims 1 to 3, characterized in that the polymer system comprises cationified starch, epichlorohydrin dimethylamine copolymer, polydiallyldimethylammonium chloride, polyamine and / or polyacrylamide.

5. Agent according to one of claims 1 to 4, characterized in that the at least one alkaline earth solution is formed by a CaX solution and / or a MgX solution, where X is a chloride, a sulfate and / or a nitrate.

6. Agent according to one of claims 1 to 5, characterized in that the alcohol solution is based on mono- and / or polyhydric alcohols, preferably on a mono-, di-, or trihydric alcohol, more preferably on a monohydric alcohol, particularly preferably on ethanol.

7. Agent according to one of claims 1 to 6, characterized in that the at least one carboxylic acid solution is based on mono-, di-, tri- and / or hydroxycarboxylic acids.

8. Agent according to one of claims 1 to 7, characterized in thatit comprises a. 10-50% by weight of a polymer system, b. 0.1-10% by weight of a polymer-surface-modified carbon, c. 5-30% by weight of at least one 20-40% alkaline earth metal solution, d. 0.1-10% by weight of a 60-80% alcohol solution, and e. 5-20% of at least one 0.2-80% carboxylic acid solution.

9. Means according to claim 8, characterized in that it comprises a. 35 wt% of a polymer system, of which 20 wt% is cationized starch and 15 wt% of a polyamine, b. 5 wt% of a polyamine-surface-modified carbon, in particular a polyamine-surface-modified activated carbon, c. 15 wt% of a 30-40% MgX solution and 15 wt% of a 30-40% CaX solution, where X is a chloride, a sulfate and / or a nitrate, d. 10 wt% of a 70% ethanol solution, and e. 20 wt% of a 50% citric acid solution.

10. Means according to claim 8, characterized in thatit comprises a. 45 wt% of a polymer system, of which 10 wt% epichlorohydrin dimethylamine copolymer, 20 wt% of a polyamine and 15 wt% cationized starch, b. 10 wt% of a polyamine surface-modified carbon, in particular a polyamine surface-modified C60 fullerene, c. 10 wt% of a 30% magnesium chloride solution and 15-20 wt% of a 33% calcium chloride solution, d. 10 wt% of a 70% ethanol solution, and e. 3 wt% of a 50% lactic acid and 2 wt% of a 0.2% fumaric acid.