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 substance is described for separating wastewater to be treated into sludge and clear water phases and removing trace substances from the clear water phase by adsorption; this substance contains a polymer system as a flocculant, and at least one alkaline earth solution containing carbon and Ca ions and / or Mg ions. According to the invention, the carbon is proposed to be present in a polymer surface-modified form as activated carbon, carbon black, graphite, graphene and / or fullerene, forming a polymer-carbon complex, and the substance 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, comprising a polymer system, for example in solution form, as a flocculant, carbon and at least one alkaline earth solution comprising Ca ions and / or Mg ions.

[0002] Especially in the context of municipal and industrial wastewater treatment, the term "trace substances" refers to undesirable substances dissolved in water, also known as micropollutants. These trace substances are primarily synthetic substances present in wastewater at concentrations ranging from nanograms to several micrograms per liter. Trace substances dissolved in wastewater typically 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 remain in the water cycle long-term and therefore pose a significant problem, particularly for drinking water supply.Of particular concern are substances that, due to their toxicity or known biological effects, can influence water quality and water use. Examples of environmentally relevant trace substances associated with the discharge of wastewater from treatment plants into receiving waters, or in connection with the determination of water quality parameters, include benzotriazole, diclofenac, and metoprolol. These very common trace substances, as well as any related metabolites, cannot be removed from wastewater in conventional three-stage treatment plants, or only insufficiently, as can be demonstrated by their regular detection in water samples.

[0003] Therefore, 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 primarily used in the industrial sector, 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] In size-selective processes, pressure-driven membrane filtration, which is carried out as part of a full-flow treatment, is particularly important. A disadvantage of this method is the high pressures of almost 70 bar required. However, this is not technically feasible for the treatment of municipal wastewater in larger catchment areas, as the daily wastewater volumes are far too high to justify full-flow treatment. Furthermore, the associated high energy and investment costs are many times higher than those of conventional wastewater treatment, making the use of such filtration processes for municipal wastewater uneconomical.

[0005] In addition, activated carbon is used, for example, as an adsorbent to purify wastewater of various trace substances, etc. Accordingly, suitable products are known (CN109553175A, CN108557973A, US8021556B2) which, in addition to a polymer system as a flocculant and alkaline earth solutions, also include activated carbon particles. When using such powdered activated carbon particles (PACs), the adsorbent is thus disposed of via the sludge line together with the adsorbate formed from the trace substances, etc. Other relevant documents are CN 108 409 056 A, CN 107 915 290 A, US 2019 / 084843 A1 and CN 106 745 351 A. A disadvantage is that when using PAH-containing agents for wastewater treatment in conventional wastewater treatment plants, the separation of the wastewater into sludge and clear water phases is often inadequate. Furthermore, certain bacteria in the sludge phase or an unbalanced calcium carbonate equilibrium, etc., can occur.Insufficient acid buffering capacity of the wastewater being treated hinders the formation of sludge flocs of a consistency necessary for efficient separation. This leads to an undesirable PAH slip of up to 30% of the total amount of PAHs used, resulting in the discharge of pollutant-laden activated carbon into the receiving water body or the effluent of the wastewater treatment plant. Consequently, the prescribed limit of a maximum of 1 milligram of pollutant-laden PAHs per liter in the effluent of the wastewater treatment plant cannot be regularly met when using known agents.

[0006] 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 sewage 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.

[0007] The invention solves the stated problem by providing the carbon, selected in particular from activated carbon, carbon black, graphite, graphene and / or fullerene, in a polymer-surface-modified form, forming 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 composition according to the invention are specified in the dependent claims.

[0008] Surprisingly, it has been shown that, due to the polymer-based surface modification or the formation of a polymer-carbon complex, the adsorption capacity is not only not impaired but even improved, and that the adsorbed micropollutants are more readily incorporated into the sludge phase. In combination with at least one alkaline earth solution, this promotes the formation of shear-stable, dense activated sludge flocs with a mean diameter of 150 to 500 µm and an improved sedimentation rate, which is a prerequisite for efficient separation. Flocs are defined as shear-stable if they exhibit a kinematic viscosity greater than 1 cSt or 10⁻⁶ m² / s after shear stress.

[0009] The surface modification of the carbon is achieved by the initial attachment of functional ester groups to the carbon surface as a result of esterification induced by the alcohol(s) and the carboxylic acid(s). These ester groups then allow for the subsequent attachment of the polymer. For this purpose, the carbon can first be suspended in a mixture of an alcohol and a carboxylic acid solution. The resulting carbon suspension is then mixed with a polymer matrix, which may also be in solution, to form the surface modification of the carbon, i.e., the polymer-carbon complex. In principle, the polymer underlying the polymer-carbon complex can be different from the polymer(s) of the polymer system. Preferably, however, the polymer underlying the polymer-carbon complex is a polymer of the polymer system of the composition according to the invention.In this case, it is also possible for the surface modification of the carbon to occur directly during the mixing of the agent according to the invention. The alcohols and carboxylic acids used are thus initially available, according to the invention, for the chemical synthesis of the surface-modified carbons into a polymer-carbon complex and subsequently also serve for suspension stabilization in conjunction with the polymer system, which provides an increased proportion of organic charge carriers. A lack of acid buffering capacity can also be compensated for by the interaction of the components according to the invention, which further promotes a reliable separation of the wastewater into a sludge and a clear water phase.

[0010] It has been found that higher amounts of an alcohol solution, up to 10 wt%, further promote the surface modification of the carbon.

[0011] Furthermore, the surface modification of the carbon can be further promoted by taking place the mixing or esterification at temperatures above 70 °C, while adhering to appropriate maximum temperatures.

[0012] According to the invention, the polymer system 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, contain 10–50 wt% of the inventive agent.

[0013] Preferably, the at least one alkaline earth solution comprises 5–30 wt% of the composition according to the invention. This means that if only one alkaline earth solution is present, it comprises 5–30 wt% of the composition, whereas if several alkaline earth solutions are present, they together comprise 5–30 wt% of the composition. 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. A composition according to the invention particularly preferably comprises two alkaline earth solutions, most preferably a calcium chloride solution and a magnesium chloride solution.

[0014] Preferably, the alcohol solution is based on monohydric and / or polyhydric alcohols, i.e., a mixture of several different alcohols may be provided. More preferably, the alcohol solution is based on either a monohydric, dihydric, or trihydric alcohol. Particularly preferably, the alcohol solution is based on a monohydric alcohol, especially ethanol.

[0015] 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 may also be present. Naturally, a mono-, di-, or tricarboxylic acid may 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 wt% of the composition according to the invention, wherein, if several carboxylic acid solutions are present, they collectively comprise 5–30 wt% of the composition, analogous to the above descriptions in connection with the alkaline earth solutions.

[0016] Preferably, a composition 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 a 20-40% alkaline earth solution, 0.1-10 wt% of a 60-80% alcohol solution, and 5-20% of at least a 0.2-80% carboxylic acid solution.

[0017] More preferably, an agent according to the invention comprises 35 wt% of a polymer system, of which 20 wt% is cationized starch and 15 wt% is a polyamine, 5 wt% is a polyamine surface-modified carbon, in particular a polyamine surface-modified activated carbon, 15 wt% is a 30-40% MgX solution and 15 wt% is a 30-40% CaX solution, wherein X is a chloride, a sulfate and / or a nitrate, 10 wt% is a 70% ethanol solution, and 20 wt% is a 50% citric acid solution.

[0018] An agent according to the invention may in principle contain further components. Preferably, however, an agent 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 solution, at least one alcohol solution, and at least one carboxylic acid solution. Examples of implementation:

[0019] An agent according to the invention 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 comprises 20% cationized 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.

[0020] According to a further embodiment, an agent according to the invention comprises 10% epichlorohydrindimethylamine 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

[0021] In a laboratory experiment (n = 100), wastewater samples were treated with different agents S1 to S4. S1 refers to an agent according to EP2808306B1, consisting of 61 wt% of a polyaluminium chloride solution with 18 wt% Al₂O₃, 20 wt% of a 23% FeCl₂ solution, 3.5 wt% of a 15% solution of cationized starch, 15 wt% of a 33% CaCl₂ solution, and 0.5 wt% of a saturated ascorbic acid solution. S2 refers to a product according to EP3636601B1, wherein the product consists of 40 wt% of a 28% FeCl2 solution, 8 wt% of a 30% ascorbic acid solution, 5 wt% of a 40% CaCl2 solution, 42 wt% of a 36% polyaluminium chloride solution with 18 wt% Al2O3 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 a flocculant, 10 wt% of a 50% epichlorohydrin dimethylamine copolymer solution as a flocculant aid, 15 wt% of a 30% MgCl 2 solution as an 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% epichlorohydrindimethylamine copolymer, 20 wt% a polyamine, 15 wt% a 15% solution of cationized starch, 20 wt% a 33% CaCl2 solution, 10 wt% a MgCl2 solution, 3 wt% a 50% lactic acid solution, 2 wt% a 0.2% fumaric acid solution, 10 wt% polyamine surface-modified C60 fullerene and 10 wt% a 70% ethanol solution.

[0022] The percentage removal of various micropollutants from the wastewater sample was determined according to the table below. 100 ppm of each of agents S1-S3 were tested, either alone or in combination with 15 ppm of activated carbon (AC). Agent S4 was also dosed at 100 ppm. Compared to the other agents S1 to S3, S4 showed improved removal (E). micropollutant category S1 S1+AK S2 S2+AK S3 S3+AK AK S4 E E E E 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 Carbendazime Pesticide 25 21 14 11 11 28 35 84 Benzotriazol Corrosion protection 13 15 18 16 6 19 27 70 Wastewater treatment plant trial

[0023] Furthermore, a composition according to the invention was used in a wastewater treatment plant. The wastewater treatment plant has a design capacity or population equivalent (PE) of 24,000 PE. The influent flow rate was 4,460 m³ per day. The biochemical oxygen demand (BOD₅₀) in the influent was 950 kg per day. The chemical oxygen demand (COD₅₀) in the influent was 1,574 kg per day. The dissolved organic carbon (DOC₅₀) in the influent was 411 kg per day.

[0024] The concentrations C of various micropollutants in nanograms per liter (ng / l) were measured in the influent and effluent of the wastewater treatment plant. A dosage of 100 ppm of the agent S4 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 observed in the effluent of the flow line where agent S4 was dosed, 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 Carbendazime Pesticide 105 7 82 Benzotriazol Corrosion protection 6.090 828 4.872

Claims

1. Agent for separating wastewater to be treated into a sludge phase and a clear water phase, and for the adsorptive removal of trace substances from the clear water phase, with a. a polymer system as a flocculant, 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 a polymer surface-modified form, forming a polymer-carbon complex, and that the agent comprises at least one alcohol solution and at least one carboxylic acid solution as suspension stabilizers for the polymer-carbon complex, and that the polymer-carbon complex is based on a surface modification of the carbon by at least one polymer of the polymer system, and that the polymer system comprises cationized starch, epichlorohydrin dimethylamine copolymer, polydiallyldimethylammonium chloride, polyamine, and / or polyacrylamide.

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 at least one alkaline earth metal solution is formed by a CaX solution and / or an MgX solution, wherein X is a chloride, a sulfate, and / or a nitrate.

4. Agent according to one of claims 1 to 3, characterized in that the alcohol solution is based on monohydric and / or polyhydric alcohols, preferably on a monohydric, dihydric or trihydric alcohol, more preferably on a monohydric alcohol, and particularly preferably on ethanol.

5. Agent according to one of claims 1 to 4, characterized in that the at least one carboxylic acid solution is based on mono-, di-, tri- and / or hydroxycarboxylic acids.

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

7. Agent according to claim 6, characterized in that it comprises a. 35 wt% of a polymer system, of which 20 wt% is cationized starch and 15 wt% is 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, wherein 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.

8. Agent according to claim 6, characterized in that it comprises a. 45 wt% of a polymer system, of which 10 wt% is epichlorohydrin dimethylamine copolymer, 20 wt% is a polyamine, and 15 wt% is cationized starch, b. 10 wt% of a polyamine surface-modified carbon, in particular a polyamine surface-modified C60 fullerene, c. 10% by weight of a 30% magnesium chloride solution and 15-20% by weight of a 33% calcium chloride solution, d. 10 wt% of a 70% ethanol solution, and e. 3% by weight of a 50% lactic acid solution and 2% by weight of a 0.2% fumaric acid solution.