Method for producing an algae lysis-water concentration mixture

Abstract

Method for producing an algae lysis water concentration mixture for dosing into raw water to obtain test water for testing a water treatment plant, simulating the organic load of a natural body of water, comprising the following steps: a) Formation of an algae-water concentration mixture from Chlorella vulgaris algae contained in water, b) Lysis of Chlorella vulgaris algae using ultrasound, characterized by the fact that c) the formation of an algae-water concentration mixture from Chlorella vulgaris algae contained in water is carried out in such a way that Chlorella vulgaris algae cultivated in fermenters with a cell density of higher than 2*10^9 cell / ml are used, d) the lysis of the Chlorella vulgaris algae is carried out for such a long lysis period that the value of dissolved organic carbon reaches its maximum, e) that the lysis time is determined by preliminary tests.

Description

[0001] The invention relates to a method for producing an algae lysis water concentration mixture for dosing into raw water to obtain test water for testing a water treatment plant, wherein an organic load of a natural body of water is simulated.

[0002] The term "water treatment facility" refers to both a complete, non-stationary emergency water supply system and a single module thereof. The aforementioned single module can be a pretreatment module. In the pretreatment module, chemicals (flocculants, activated carbon, etc.) can be added or particles removed. The aforementioned single module can also be a treatment module. In the treatment module, dissolved salts or organic substances can be removed.

[0003] From an article (WATZELT, Timo; REIFER, Elke; Federal Ministry of Defence: Implementation of a testing procedure for the evaluation of prefiltration technologies for drinking water treatment from surface waters. In: Military Science Research. 2023. pp. 1-154. URL: https: / / www.bmvg.de / de / aktuelles / wehrforschung-zeitenwende-jahresbericht-2022-veröffentlicht-5725588 [accessed on 2025-04-28]. - The 2022 annual report describes a generic process. This process is used to produce an algae lysis water concentration mixture for addition to raw water to obtain test water for testing a water treatment plant, thereby simulating the organic pollution of a natural body of water. The steps are: • Formation of an algae-water concentration mixture from Chlorella algae contained in water, • Lysis of Chlorella algae using ultrasound.

[0004] The algae lysis water concentrate mixture contains algae cells, cell fragments, biopolymers, and humic substances. The high-molecular-weight organic compounds are released through ultrasound-assisted cell disruption (lysis) of the microalgae. Test water prepared with the algae lysis water concentrate mixture exhibits similar filter-blocking properties to algae-laden surface water.

[0005] Another method of this type is known from a dissertation (“Mini-plant and bench-scale studies on the fouling mechanisms as well as the responsible organic foulants during direct filtration of algal-containing waters using hollow-fiber membranes”, University of Duisburg-Essen, DOI:10.17185 / duepublico / 74599, URN: urn:nbn:de:hbz:464-20210805-141455-1). The dissertation investigates fouling scenarios in polyethersulfone hollow fiber (HF) membrane modules that occur during the filtration of various microalgae-containing suspensions. The intensity and type of fouling are correlated with the membrane retention and the characteristics of the respective feed suspension, i.e., the cell state of the microalgae and the organic components of the suspension.For this purpose, experiments were carried out with four different microalgae species, which were simultaneously present in two very different cell states: firstly as intact cells in the so-called growth phase, and secondly as lysed cells, i.e., dead and partially destroyed.

[0006] According to DIN 2001-3, non-stationary emergency water supply systems must be able to operate for several days without any loss of performance using raw water from surface water containing up to 10 mg / l of dissolved organic carbon (DOC). However, they must also remain functional, albeit with reduced performance, at DOC levels of up to 20 mg / l. To demonstrate that a water treatment system meets the requirements of the relevant DIN standard, reproducible test water samples are needed for testing the system.

[0007] DE10 2017 009 538 B4 of the same applicant discloses a method for producing an inorganic particle test water with which an inorganic turbidity load of natural surface waters is simulated.

[0008] The object of the invention is to develop a generic process for producing an algae lysis-water concentration mixture in such a way that high reproducibility is achieved with simple production.

[0009] This problem is solved according to the invention by the features of claim 1.

[0010] The advantages of the invention are described below, beginning with a description of the basic effects before discussing the inventive idea. In ultrasonic lysis, the algae-water concentration mixture is subjected to ultrasound. The ultrasound causes the algae to be killed by destroying their cell walls. This ultrasound-assisted cell disruption (lysis) releases high-molecular-weight organic compounds. Cell fragments, released organelles and their fragments, as well as released biopolymers, humic substances, building blocks, nonpolar amphiphilic substances, and organic acids are generated. In a test water sample, these exhibit similar filter-blocking properties to algae-laden surface water. Over the course of the ultrasonic lysis, the DOC value rises steadily to a maximum value. After reaching this maximum value, the DOC value decreases.It is assumed that dissolved carbon beyond the maximum value passes into the gas phase, which is undesirable.

[0011] A surprising effect arises from the fact that the lysis of the Chlorella vulgaris algae is carried out for a specific duration until the dissolved organic carbon (DOC) level in the algae lysis-water mixture reaches its maximum. Studies have shown that when the DOC level reaches its maximum in the algae lysis-water mixture, the lysis has reached an optimal degree of decomposition. At this point, no living algal cells can be detected. This optimal degree of decomposition results in high filter clogging in test water produced from the algae lysis-water mixture, thus ensuring effective testing, as performance degradation is more readily apparent when testing a water treatment system.

[0012] The maximum DOC value can be determined, for example, by continuously measuring the DOC value over the duration of the lysis.

[0013] Chlorella vulgaris algae cultivated in fermenters are used. Chlorella vulgaris algae can also be cultivated fermentatively because they are able to utilize sugars as an energy source by altering their metabolism. The fermentative cultivation of this algae species allows for a high cell density.

[0014] The lysis time is determined through preliminary tests. Inaccuracies are reduced while reproducibility is increased, as the lysis time, using a manageable parameter, reflects the maximum DOC value. Continuous measurement of the DOC value throughout the lysis process would be more complex and less accurate because the ultrasonic lysis of the dissolved organic carbon continues until the maximum DOC value is actually reached. It is important to note that the operating parameters of the preliminary test, such as the ultrasonic power, the flow rate along the sonotrode, and the cell density, must match those of the subsequent process for producing an algae lysis-water concentration mixture.

[0015] According to an advantageous embodiment of the invention, the resulting algae lysis-water concentration mixture is deep-frozen for later use. The algae can be obtained in larger quantities and frozen for future test water. As studies have shown, freezing does not lead to any loss of quality in the test water production. A frozen product has the advantage of rapid availability of the algae lysis-water concentrate for test water production, independent of "fresh" algae deliveries and their shelf life. It is available at any time.

[0016] An embodiment of the invention is explained in more detail below with reference to the figures. These figures are shown as simple schematic diagrams: Fig. 1 a lysis container for producing an algae lysis water concentration mixture for a test water; Fig. 2 a freezer containing a frozen portion block of an algae lysis water concentration mixture; Fig. 3 a test water basin with test water for testing a water treatment plant.

[0017] The Fig. Figure 1 shows a lysis container 11 for producing an algae lysis water concentration mixture 18 for dosing to raw water to obtain test water for testing a water treatment plant, whereby an organic load of a natural body of water is simulated, with the steps: a) Formation of an algae-water concentration mixture from Chlorella vulgaris algae contained in water, b) Lysis of Chlorella vulgaris algae using ultrasound, c) Continue the lysis of the Chlorella vulgaris algae for a lysis period until the value of dissolved organic carbon, hereinafter referred to as DOC (dissolved organic carbon) value, in the algae lysis water concentration mixture has reached its maximum.

[0018] The lysis vessel 11 has a water inlet 12 and an algae inlet 13 for filling the lysis vessel 11 with water and an algae suspension. A ready-made algae lysis-water concentration mixture 18 can be removed via a dispensing port 19. Furthermore, the lysis vessel 11 has a recirculating lysis unit 16 with a metering pump 16a, a sonotrode 16b, and a stirrer 17. The sonotrode 16b is arranged inside a flow body and is surrounded by the volumetric flow (the illustration of the sonotrode 16b in Fig. (Figure 1 is simplified). The stirrer 17 compensates for temperature and compositional differences. The cooling device 15 counteracts the heat input from the sonotrode 16b into the algae / algae lysis water mixture. The cooling device 15 has an outer cooling jacket for the lysis vessel 11. Additionally, a speed-controlled stirrer 17 is located inside the lysis vessel 11.

[0019] Fig. Figure 2 shows a freezer 40 with a frozen portion block (only one of several portion blocks is shown) of a frozen algae lysis water concentration mixture 18' for later use.

[0020] The Fig. Figure 3 shows a test water tank 21 containing test water 28 for testing a water treatment unit 30. The water treatment unit 30 is a pretreatment module used to filter out particles. The test water tank 21 is a collapsible tank with a capacity of 15 m³. 3Test water. The test water tank 21 includes a water inlet 22 for supplying drinking water quality water and a dosing inlet 23 for an algae lysis water concentration mixture. The test water tank 21 includes a temperature control unit 25. The test water 28 can be drawn off via the test water outlet 29. A stirrer 27 ensures uniform temperatures and compositions. The test water used in the water treatment unit is discharged via the outlet 29.

[0021] The following describes the process of testing a water treatment plant: • Sterile and fermentatively cultivated Chlorella vulgaris algae from a microalgae farm are used. The cell density is higher than 2*10^9 cells / ml. • In a preliminary test, the lysis time after which the maximum DOC value is reached is first determined. The lysis tank holds 80 L of the algae-water concentration mixture. The flow rate of the dosing pump 16a is set to 80 L / h. The sonotrode 16b is set to a sound power level of 1,000 W. The parameter pair of 80 L / h flow rate and 1,000 W sonotrode power results in a permissible temperature increase while still ensuring good algae lysis. A maximum temperature of 30°C for lysis is not exceeded. This preserves the algae organic matter. In the lysis tank 11, the algae lysis-water concentration mixture is stirred and cooled to below 5°C. • The ultrasound ruptures the algal cell wall. The algal plasma (chlorophyll-a molecules) is released. Polysaccharides are then broken down into increasingly smaller macromolecules. These macromolecules can cause blockages in water treatment systems during subsequent testing. • Using the DOC values ​​recorded over time in the algae lysis-water concentration mixture, a lysis time of 11 hours is determined. This determined lysis time is then used to prepare the algae lysis-water concentration mixture, using the same settings. These settings include, for example, the volume and cell density of the algae-water concentration mixture, the flow rate, the sonotrode power, and the temperatures. • The prepared algae lysis-water concentration mixture is frozen. At a later time, the algae lysis-water concentration mixture is thawed to create a test water sample. • To prepare a test water sample, 15 m 3 Tap water purified with candle filters (for example: 1. candle filter with a pore size of 5µm and 2. candle filter with a pore size of 0.5µm connected in series) was poured into the test water container. • A calculated amount of the algae lysis water concentration mixture is added to the test water container 21 via the dosing unit 23. • This is followed by a several-hour “maturation period of the test water”, during which the blocking properties of the test water increase. • The test water is used for testing.

[0022] The following modifications can be made in deviation from and / or addition to the illustrated embodiment: • In addition to monitoring, a flow meter can be installed in the lysis container 11 in the recirculation unit 16. • The water treatment unit is a pretreatment module. Alternatively, the water treatment unit could also be, for example, a complete, non-stationary emergency water supply system. • When stirring and tempering the test water mixture to 25 °C, a maximum clogging occurs, depending on the amount of algae lysis-water concentration mixture added. The time window for testing a water treatment system can preferably be chosen to take this maximum clogging into account. • Over time, the blocking properties decrease. To ensure consistently high blocking properties of the test water over time, the algae lysis water concentration mixture, cooled to below 5°C, can be added as needed. • In this example, no additives are added. Alternatively, a humic acid extract could be added directly to the test water container. • In the exemplary embodiment, the prepared algae lysis-water concentration mixture is deep-frozen for later use. Alternatively, the prepared algae lysis-water concentration mixture can also be used directly to produce test water. • According to Fig. In step 1, a single sonotrode 16b is used. To increase the ultrasound power and reduce the lysis time, for example, another sonotrode could be connected in series. Further process-related variations of energy input via ultrasound are possible. Reference symbol list 11 lysis containers 12 Water supply 13 Algae input 15 Cooling unit 16. Circulation unit 16a Dosing pump 16b Sonotrode 18 Algae lysis water concentration mixture 21 test water containers 22 Water supply 23. Dosing of the algae lysis water concentration mixture 25 Cooling equipment 27 stirrers 28 test waters 29 Test water sampling 30 Water treatment plant 39 Discharge of the treated water 40 deep freezer

Claims

[1] Method for producing an algae lysis water concentration mixture for addition to raw water to obtain test water for testing a water treatment plant, simulating the organic load of a natural water body, comprising the steps: a) Formation of an algae-water concentration mixture from Chlorella vulgaris algae contained in water, b) Lysis of Chlorella vulgaris algae using ultrasound, characterized by the fact that c) the formation of an algae-water concentration mixture from Chlorella vulgaris algae contained in water is carried out in such a way that Chlorella vulgaris algae cultivated in fermenters with a cell density of higher than 2*10^9 cell / ml are used, d) the lysis of the Chlorella vulgaris algae is carried out for such a long lysis period that the value of dissolved organic carbon reaches its maximum, e) that the lysis time is determined by preliminary tests. [2] Method according to claim 1, characterized by , that the resulting algae lysis water concentration mixture is deep-frozen for later use.

Images