AGENT FOR PRECIPITATING SUSPENDED AND DISSOLVED SUBSTANCES IN MUNICIPAL WASTEWATER TO BE TREATMENT

Description

[0001] The invention relates to agents for precipitating suspended and dissolved substances in municipal wastewater to be treated with a mixture comprising at least one flocculant for phosphate precipitation, comprising Fe(II)X and / or Fe(III)X and / or AlX and / or polymeric compounds thereof, where X is either Cl and / or a sulfate and / or a nitrate, at least one organic polymer as a flocculant aid, comprising cationified starch and / or epichlorohydrin dimethylamine copolymer and / or polydiallyldimethylammonium chloride and / or polyamines and / or polyacrylamides and / or a mixture of these substances and for influencing the charge distribution and determining the charge of the flocculant at least one alkaline earth solution comprising Ca ions and / or Mg ions.

[0002] EP2808306B1 discloses a method for precipitating suspended solid particles in municipal wastewater to be treated. The method is a mixture containing, among other ingredients, a flocculant for phosphate precipitation, such as iron or aluminum salts, which converts the dissolved phosphate content in the wastewater into insoluble phosphates. To achieve improved solid-liquid separation of the precipitated substances, a polymeric flocculant is used, which promotes the formation of macroflocs and thus increases the sedimentation rate of the precipitated substances. The charge and thus the effect of the flocculant can be modified by adding alkaline earth solutions.However, especially in the case of wastewater with a high microbial load, the problem arises that after the use of the agent known from the state of the art, a significant residue of microorganisms remains in the wastewater, which is why further measures, such as chlorine, ozone, UV treatments, etc., must be carried out after precipitation to treat the biologically treated wastewater.

[0003] The bactericidal effect of alcohol is well known in the art, with high-proof alcohols in the range of 50-80% being used primarily. Due to the water content, alcohol can penetrate the cell membrane of the microorganism, where it denatures proteins, including membrane proteins. This leads to the destruction of the cell structure. Although alcohol has a strong bactericidal effect, its use is limited to surface cleaning agents due to the high concentration required. Adding alcohol to wastewater to be treated would result in extreme dilution of the alcohol and thus render it ineffective.

[0004] CN108773890A shows an agent according to the generic term, wherein the agent may contain ethanol.

[0005] The invention is therefore based on the object of proposing a means of the type described at the outset which enables targeted control of wastewater-specific microorganisms, such as pathogenic or multi-resistant bacterial groups, without having to provide a separate process step for this purpose.

[0006] The invention solves the stated problem in that the mixture comprises 30 - 80 wt% of a polymeric AIX solution comprising between 10 and 30 wt% Al 2 O 3 or 30 - 80 wt% of an AlCl 3 solution as a flocculant, 5 - 30 wt% of a 40 - 60% epichlorohydrin dimethylamine copolymer solution as a flocculant, 1 - 15 wt% of a 20 - 40% MgCl 2 solution as an alkaline earth solution, and 5 - 30 wt% of a 60 - 80% ethanol solution. In principle, the agent comprises, in addition to the monohydric alcohol according to the invention, a flocculant which converts dissolved phosphates into undissolved phosphates, an organic polymer as a flocculant aid which promotes the formation of macroflocs consisting of various undissolved substances, such as cell residues, undissolved phosphates, etc., and an alkaline earth solution which influences the charge distribution of the flocculants or determines their charge.It has been shown that by combining the monohydric alcohol with the flocculant, the flocculant, and the alkaline earth solution, even low mass concentrations of a monohydric alcohol, namely 5-30 wt%, are sufficient to achieve a disinfecting effect. Surprisingly, the combination of alcohol and the remaining components achieves a greatly improved charge balance both between the substances precipitated by the flocculant and thus undissolved and the flocculant, as well as between the undesirable microorganisms and the flocculant, thus promoting the formation of macroflocs between these components, which sediment during solid-liquid separation.Furthermore, the charge change caused by the components can alter the cell membrane of the microorganisms in such a way that even a low concentration of the monohydric alcohol is sufficient to promote the destruction or degradation of the microorganisms. The bactericidal or disinfecting effect of the alcohol is therefore synergistically enhanced by the components of the agent, in contrast to a pure alcohol solution with a concentration of 5 - 30 wt%, as demonstrated in the comparative experiments described below. Although the addition of the alcohol increases the viscosity of the agent, which has a fundamentally detrimental effect on efficient solid-liquid separation due to the resulting increased flow resistance, the combination of the alcohol with the alkaline earth solution improves the flocculation aid to the extent that particularly large macroflocs can form.The size of the macroflocs increases more rapidly than their viscosity, which nevertheless increases the sedimentation rate and thus improves solid-liquid separation. Another advantage is that the increased viscosity of the agent prevents the escape of any substances escaping from the ruptured bacterial cell membrane, thus promoting the stabilization and binding of these substances into a single macrofloc.

[0007] Series of tests have shown that methanol, ethanol, propanol and / or butanol or a mixture of these monohydric alcohols have the strongest bactericidal effect in the concentration range 5 - 30 wt%.

[0008] A fundamental difficulty in disinfecting microorganisms in a wastewater treatment process lies in the targeted destruction or elimination of only certain microorganisms. Therefore, microorganisms relevant for nitrification and denitrification, as well as for biological phosphorus elimination, should not be destroyed or eliminated. Such beneficial microorganisms can utilize EPS (extracellular polymeric substances), a gel-like biofilm surrounding the microorganism that binds dirt or pollutant particles, for wastewater treatment. The Ca ions and / or Mg ions in the alkaline earth solution stabilize the EPS and protect it from binding by the flocculant, thus preventing macrofloc formation and thus the separation of the beneficial microorganisms.The best results are achieved when the agent contains 30-80 wt% of a polymeric AIX solution containing between 10 and 30 wt% Al 2 O 3 as a flocculant, 5-30 wt% of a 40-60% epichlorohydrin dimethylamine copolymer solution as a flocculant, 1-15 wt% of a 20-40% MgCl 2 solution as an alkaline earth metal solution, and 5-30 wt% of a 60-80% ethanol solution. A polyaluminum chloride solution can be used as the polymeric AIX solution.

[0009] Similarly good results are obtained from a composition comprising 30 - 80 wt% of an AlCl 3 solution as a flocculant, 5 - 30 wt% of a 40 - 60% epichlorohydrin dimethylamine copolymer solution as a flocculant, 1 - 15 wt% of a 20 - 40% MgCl 2 solution as an alkaline earth solution, and 5 - 30 wt% of a 60 - 80% ethanol solution.

[0010] In order to create a surface-to-volume ratio of the macro flocs which, on the one hand, despite the increased viscosity of the agent, enables the fastest possible sedimentation of the macro flocs and, on the other hand, an effective destruction of undesirable microorganisms such as filamentous bacteria or other pathogenic or multi-resistant bacterial groups, it is proposed that the agent comprise 30 - 80 wt% of a polyaluminium chloride solution containing 18 wt% Al 2 O 3 as a flocculant, 5 - 30 wt% of a 50% epichlorohydrin dimethylamine copolymer solution as a flocculation aid, 1 - 15 wt% of a 30% MgCl 2 solution as an alkaline earth solution, and 5 - 30 wt% of a 70% ethanol solution. Example:

[0011] An agent according to the invention for precipitating suspended and dissolved substances in municipal wastewater to be treated comprises 60 wt% of a polyaluminium chloride solution containing 18 wt% Al 2 O 3 as a flocculant, 17 wt% of a 50% epichlorohydrin dimethylamine copolymer solution as a flocculant, 6 wt% of a 30% MgCl 2 solution as an alkaline earth solution, and 17 wt% of a 70% ethanol solution.

[0012] In order to investigate the effectiveness of the exemplary embodiment, the sedimentation behavior of a wastewater suspension mixed with the agent and the germ reduction caused by the agent were investigated and compared with reference samples. Sedimentation behavior using settling test

[0013] To determine the sedimentation behavior, a standardized, state-of-the-art settling test was conducted in a 1000 mL measuring cylinder. All samples, with the exception of untreated wastewater sample 1, were spiked with 50 ppm of a corresponding additive described in more detail below.

[0014] The test was carried out with an untreated wastewater sample 1, with a wastewater sample 2 mixed with an agent according to the exemplary embodiment, with a wastewater sample 3 mixed with a non-inventive agent according to the exemplary embodiment, wherein the ethanol solution was replaced with water, with a wastewater sample 4 mixed with 12% EtOH, and with a wastewater sample 5 mixed with an inventive agent according to the exemplary embodiment, wherein 60 wt% of an AlCl 3 solution was used as the flocculant instead of the polyaluminum chloride solution. Wastewater sample 4 has the same EtOH content as wastewater samples 2 and 5, which contain 50 ppm of an agent with 17 wt% of a 70% ethanol solution.

[0015] The results are in Fig. 1It can be seen that wastewater sample 2 with the agent according to the exemplary embodiment and wastewater sample 5 with the agent according to the exemplary embodiment, wherein 60 wt% of an AlCl 3 solution was used as the flocculant instead of the polyaluminum chloride solution, sedimented the fastest despite increased viscosity. Since the sedimentation curves of wastewater samples 2 and 5 are almost identical, they are represented by only one sedimentation curve for reasons of clarity.

[0016] The improved sedimentation behavior of wastewater samples 2 and 5 is also confirmed by Fig. 2 which clarifies the Fig. 1 calculated sedimentation velocities. Accordingly, wastewater samples 2 and 5 have the highest sedimentation velocities at 2.24 m / h. Quantitative evaluation of colony forming units (CFU)

[0017] In this experiment, 100 µL of each of five different samples was applied to a universal culture medium, incubated at 26°C for 24 hours, and then counted. The result from untreated wastewater sample 1 served as a reference for calculating the relative bacterial reduction. The results are presented in the following table: Sample designation Germ load [%] Germ reduction [%] Untreated wastewater sample 1 100 0,00 Wastewater sample 2 with 50 ppm of the agent according to the invention according to the embodiment 16,98 83,02 Wastewater sample 3 with 50 ppm of the agent according to the embodiment, where the ethanol solution was replaced by water 39,01 60,99 Wastewater sample 4 with 50 ppm 12% EtOH 119,01 -19,01 Wastewater sample 5 with 50 ppm of the agent according to the embodiment, whereby 60 wt% of an AlCl 3 solution was used instead of the polyaluminium chloride solution 15,74 84,26

[0018] As can be seen from the table, wastewater sample 4, which only contains EtOH, surprisingly led to an increase in the microbial load compared to the untreated wastewater sample 1. This is probably due to the fact that the diluted alcohol no longer has any disinfectant effect, but can actually be used as a carbon source by the microorganisms. By adding the remaining components (flocculant, flocculant aid, alkaline earth solution) to the EtOH according to the exemplary embodiment (wastewater sample 2), a microbial reduction of 83.02% can be achieved. In contrast, the microbial reduction in wastewater sample 3 with 50 ppm of the agent not according to the exemplary embodiment, where the ethanol solution was replaced with water, shows a microbial reduction of only 60.99%.By combining EtOH, which alone has a negative effect on germ reduction, with the remaining components of the agent according to the invention (flocculant, flocculant aid, alkaline earth solution), a surprisingly greatly improved germ-reducing effect of more than 20% can be achieved compared to wastewater sample 3. A similarly strong effect is produced by an agent according to the invention, in which 60 wt% of an AlCl 3 solution was used as the flocculant instead of the polyaluminum chloride solution (wastewater sample 5).

Claims

1. Agent for precipitating suspended and dissolved substances in municipal waste water to be treated with a mixture comprising a. at least one flocculant for phosphate precipitation comprising Fe(II)X and / or Fe(III)X and / or AIX and / or polymeric compounds thereof, wherein X is either Cl and / or a sulfate and / or a nitrate b. at least one organic polymer as flocculating aid, comprising cationized starch and / or epichlorohydrin dimethylamine copolymer and / or polydiallyldimethylammonium chloride and / or polyamines and / or polyacrylamides and / or a mixture of these substances c. and for influencing the charge distribution and determining the charge of the flocculating aid at least one alkaline earth solution comprising Ca ions and / or Mg ions characterized in that the mixture comprises 30 - 80 wt% of a polymeric AIX solution comprising between 10 and 30 wt% Al2O3, or 30 - 80 wt% of an AlCl3 solution as flocculant, 5 - 30 wt% of a 40 - 60% epichlorohydrin dimethylamine copolymer solution as flocculating aid, 1 - 15 wt% of a 20 - 40% MgCl2 solution as alkaline earth solution, and 5 - 30 wt% of a 60 - 80% ethanol solution.

2. Agent according to claim 1, characterized in that a polyaluminium chloride solution is provided as the polymeric AIX solution.

3. Agent according to claim 1 or 2, characterized in that it comprises 30-80wt% of a polyaluminium chloride solution comprising 18wt% of Al2O3 as flocculant, 5-30wt% of a 50% epichlorohydrin dimethylamine copolymer solution as flocculating aid, 1-15wt% of a 30% MgCl2- solution as alkaline earth solution, and 5-30wt% of a 70% ethanol solution.