Process for taking samples of wastewater for analyzing and sampler for carrying out the process

Abstract

The invention relates to a process for taking samples of wastewater for analyzing, comprising: (a) feeding wastewater from a wastewater reservoir (3) to a sampler (1) having at least one chamber (7, 19, 25; 103, 107, 111, 117) from which samples are taken; (b) taking samples from the at least one chamber (7, 19, 25; 103, 107, 111, 117); (c) supplying the samples to an analyzing device (31, 34, 41) through a sampling line (33, 35, 43; 119); (d) flushing the sampler (1) and / or the sampling line (33, 35, 43; 119) with an inert gas having a high turbulent flow at regular intervals for removing deposits of salts and algae. The invention further relates to a sampler (1) for carrying out the process.

Description

[0001] Process for taking samples of wastewater for analyzing and sampler for carrying out the process

[0002] Specification

[0003] The invention relates to a process for sampling wastewater for analyzing. The invention further relates to a sampler for carrying out the process.

[0004] Strongly polluted wastewater, which may be obtained for example in industrial processes, often contains organic pollution, which exceeds the capacity of common wastewater treatment plants or which may poison bacteria in the . For this reason it is necessary to continuously analyze the wastewater and determine the organic pollution. This allows for example to mix several wastewater fractions in such a way that wastewater with a lower pollution is mixed with stronger polluted wastewater to achieve a wastewater that can be handled by the wastewater treatment plant. To analyze the organic pollution of the wastewater, usually the total organic carbon (TOC), the volatile organic carbon (VOC) and non-purgeable organic carbon (nPOC) are measured.

[0005] For analyzing the wastewater, it is necessary to take samples either continuously or in predefined intervals. Particularly for continuous measurements, suitable analyzers are connected to a sampler, in which samples are continuously taken from the wastewater.

[0006] However, due to the strong pollution, dirt contained in the waste water may precipitate on surfaces and may block lines to the analyzers. Additionally, components contained in the wastewater may react and form polymers that precipitate on surfaces and additionally, algae and salts like calcium carbonate may deposit on surfaces. All of these deposits on surfaces may block lines or change flow rates which may lead to wrong measurement. Further, if such deposits peel away, the particles thereby formed may block lines or damage analyzers.

[0007] A filterless water treatment apparatus with a separator for separating water and oil is shown in KR-B 101810362. To operate the water treatment continuously and safely, the oxygen demand of the bacteria used in the water treatment can be set by the size of bubbles supplied to the wastewater to be treated.

[0008] A setup for treating wastewater including measuring TOCs in the wastewater is described for example in WO-A 2018 / 017723. To avoid large particles to enter the analyzers, it is known for example from CN-A 104730267 to use filters.

[0009] A process for analyzing microplastics in sewage based on TOC measurement is described in KR-B 10-2545564. Here filters are used to obtain a sample. JP-B 446046 describes measuring the biochemical oxygen demand concentration as an indicator of organic pollution in wastewater. However, this is an indirect method and only can be used for determining the organic matter but cannot be used for measuring TOC, VOC and nPOC.

[0010] Depending on the sensitivity of the analyzers used for determining TOC, VOC and nPOC, it may be necessary to remove particles from the wastewater. For this purpose, multiple different mesh filters may be necessary having the disadvantages that fine filters will block too fast and coarse filters will not protect the system. Additionally, even if flushed at regular intervals, the deposits in filters will implement huge memory effects on the measurements, which lead to wrong results.

[0011] It is a further disadvantage that despite using filters algae may grow in the samplers and in lines to the analyzers, and salts, for example calcium carbonate will deposit on surfaces and may have an effect on the flow rate. Particularly in sampling lines, deposits may loosen, for example by shocks or flow changes, and block the respective line. Such blockage is difficult to remove and may often result in a complete change of the line.

[0012] An additional disadvantage of the formation of algae may be that algae usually produce carbon dioxide which may negatively influence measurements.

[0013] Therefore, it is an object of the present invention to provide a process and a sampler for taking samples of wastewater for analyzing, which can operate without filters and allows for a continuous measurement without blocking of lines and possible wrong measurements due to formation of algae and deposits on surfaces in the sampler.

[0014] This object is achieved by a process for taking samples of wastewater for analyzing, comprising:

[0015] (a) feeding wastewater from a wastewater reservoir to a sampler having at least one chamber from which samples are taken;

[0016] (b) taking samples from the at least one chamber;

[0017] (c) supplying the samples to an analyzing device through a sampling line;

[0018] (d) flushing the sampler and / or the sampling line with an inert gas having a high turbulent flow at regular intervals for removing deposits of salts and algae.

[0019] A sampler for carrying out the process comprises at least one chamber connected to a sampling line through which wastewater can flow to an analyzing device a feed line for feeding wastewater into the sampler and a gas line connected to the sampler and / or the sampling line for flushing the sampler and / or the sampling line with the inert gas.

[0020] The process is particularly suitable for wastewater that contains at least one pollutant that can significantly impact the efficacy of filtration methods. This impact on the efficacy of the filtration method is given particularly by at least one of algal proliferation, mineral scaling and polymer accumulation.

[0021] Algal proliferation is often driven by nutrient enrichment, particularly by elevated levels of nitrogen and phosphorus. During filtration, small algal cells can easily bypass filtration systems, leading to subsequent growth within in the wastewater sampling. This uncontrolled proliferation can result in biofouling, where algae adhere to internal surfaces of pipes and filters and, ultimately, may cause hydraulic blockages. Additionally, decomposition of algal biomass can lead to further degradation of water quality, contributing to false measurements.

[0022] Mineral scaling particularly occurs in wastewater streams with high caustic content, where precipitation of minerals like calcium carbonate may occur. This precipitation results in significant scaling within pipes. Over time, these deposits can accumulate and restrict fluid flow. Further the deposits may cause structural damage to the piping infrastructure. Effective management of mineral scaling often requires the implementation of regular maintenance protocols and the application of chemical treatments aimed at mitigating deposition.

[0023] Particularly in industrial wastewaters sticky polymers may be present. These sticky polymers are a substantial challenge for filtration systems, because they can rapidly adhere to filter media, leading to clogging and diminished flow rates. In regions of low hydraulic velocity, larger polymer aggregates may form, exacerbating blockage issues. To counteract these effects, presently frequent maintenance of filtration systems is necessary, and alternative technologies, such as membrane filtration or advanced oxidation processes may be employed to enhance these challenging contaminants.

[0024] Therefore, presently, addressing these pollutants necessitates a comprehensive strategy that includes pretreatment processes, continual monitoring, and the potential use of chemical additives to prevent buildup and mitigate blockages in wastewater systems.

[0025] Surprisingly it has shown that flushing with an inert gas with a high turbulent flow has a better effect on removing deposits of salts like calcium carbonate and algae than a liquid has. Therefore, the inventive process allows to omit filters and the problems caused by the present processes that all use filters can be avoided.

[0026] The inert gas used for flushing the sampler and / or the sampling line may be any gas, which is inert to the components that may be comprised in the deposits. Particularly gases that do not promote the growth of algae. Particularly preferably, the inert gas used for flushing is nitrogen. By flushing with the inert gas, remaining water forms drops, which help to clean the inner walls of the sampler due to the high turbulent flow. For achieving the high turbulent flow, it is preferred that the inert gas has a flow velocity of at least 15 m / s. When starting flushing, the flow of water preferably is set such that the velocity of the water increases to at least 3 m / s, particularly to at least 4 m / s. After a while, the gas flow will reach a velocity of 15 to 20 m / s.

[0027] Besides the advantage that using an inert gas allows for flushing the lines with a high flow with high turbulence, using an inert gas has the additional advantage that in difference to using a liquid for flushing no remainders of the inert gas may accumulate in the sampler and / or sampling line or, if some of the gas accumulates in the sampler and / or sampling line, this would not result in inaccuracies of the analyzes because in difference to an organic solvent or water as flushing liquid, the inert gas has no influence on the amount of components in the waste water, particularly on the amount of organic carbon. If an organic solvent is used as flushing liquid, remainders which accumulated in the sampler will be washed out by the wastewater and, thus, increase the amount of organic carbon in the waste water, and, if water is used as flushing liquid, the additional water washed out by the wastewater may dilute the wastewater and, thus, result in a measured amount of organic carbon, which is too low.

[0028] Further, due to the highly turbulent flow, deposits formed on walls of the sampler and / or the sampling lines will break into small pieces, which prevents blockage.

[0029] If samples are taken continuously, flushing the sampler and / or the sampling lines with an inert gas is carried out at predetermined intervals. The intervals preferably are selected such that the thickness of the deposits on surfaces of the sampler and / or the sampling lines does not exceed a value at which the flow rate of the sample to the analyzer is affected negatively. Suitable intervals for flushing may be determined for example by experiments which show the grow rate of the deposits. Alternatively, it is possible to use either glass or transparent plastics as a material for at least parts of the sampler or to provide inspection glasses through which the formation of deposits can be observed.

[0030] If, on the other hand, samples are taken at regular intervals, it is particularly preferred to flush the sampler and / or sampling lines with the inert gas after taking a predefined number of samples, particularly after each sample taken by the sampler.

[0031] To reduce or even to avoid growth of deposits, particularly by algae, salts, e.g. calcium carbonate, it is preferred to maintain turbulent flows, particularly in the sampling lines. Particularly in lines with small diameters, like common sampling lines, for achieving a turbulent flow, high pressures are needed. Further, the necessary flow velocity results in huge sample flows. For this reason, particularly if only small samples are needed for analyzing, flushing the sampling lines with an inert gas is preferred. Further, particularly if analyzers are used which may be damaged by particles contained in the waste water, it may be necessary to provide filters either in the sampling line or, preferably, at the inlet of the sampling line, by which the particles are retained in the waste water and waste water free of particles enters the sampling line.

[0032] For operating the sampler without filters, it is necessary to design the sampler in such a way that dirt contained in the wastewater does not block lines and passages in the sampler. Further, the sampler should be designed in such a way that formation of deposits, particularly deposits of dirt, algae and salts are reduced or even avoided.

[0033] For this purpose, it is particularly necessary to design lines and passages of the sampler in such a way that blocking by dirt is avoided. This can be achieved for example by a sufficient large diameter. For this reason, it is preferred that lines in the sampler have an inner diameter of in a range from 4 to 25 mm, more preferred an inner diameter in a range from 7 to 20 mm and particularly an inner diameter in a range from 8 to 15 mm, for example an inner diameter of 10 mm.

[0034] Further, as also valves tend to block by dirt particles in the waste water or by deposits formed by algae and / or salts, it is preferred to design the sampler without valves or common pressure regulators in all parts, which may come into contact with wastewater.

[0035] Depending on the analyzers used for analyzing the wastewater, it may be necessary that sampling lines, connecting the analyzer and the sampler have smaller diameters. In this case, generally it is not possible to omit a filter at the inlet of the sampling line or in the sampling line.

[0036] Particularly if lines are used having an inner diameter of at least 10 mm, the necessary turbulence for reducing or even avoiding formation of deposits can be achieved by the wastewater flowing with a minimum flow velocity of at least 1 m / s. Preferably, the wastewater has a minimum flow velocity in a range from of 1 to 3 m / S7

[0037] Depending on the values to be measured, for accurate measurements it further may be necessary to provide a constant sample flow. Particularly for measuring the VOC, it is necessary to provide a constant flow of the waste water from which the volatile organic carbons to be measured are extracted. For this reason, it is preferred that the wastewater flows through the at least one chamber of the sampler with a constant flow velocity.

[0038] For achieving a constant sample flow, in one embodiment of the invention, the sampler comprises an upper vessel having an inlet for feeding wastewater into the upper vessel and a draining pipe extending into the upper vessel and with an opening at a position in the upper vessel such that a constant filling level can be established in the upper vessel, a purger being connected to the upper vessel with a pinhole tube, which intrudes into the wastewater in the upper vessel, when the upper vessel is filled with wastewater, the pinhole tube having a plurality of openings through which the wastewater can flow from the upper vessel into the pinhole tube, wherein the purger is established such that the wastewater flows in counter current to a gas stream for purging volatile components from the wastewater, and a lower vessel being connected to the purger such that wastewater can flow from the purger into the lower vessel, wherein the upper vessel encloses a first chamber, which is connected by a first sampling line to a device for measuring total organic carbon (TOC) and / or the purger encloses a second chamber, which is connected by a second sampling line to a device for measuring volatile organic carbon (VOC) and / or the lower vessel encloses a third chamber, which is connected by a third sampling line to a device for measuring non-purgeable organic carbon (nPOC).

[0039] By providing the draining pipe in the upper vessel, a constant filling level in the upper vessel is achieved. Wastewater flows into the upper vessel through the inlet until a filling level is achieved which corresponds to the position of the opening of the draining pipe. As soon as the wastewater reaches the opening into the draining pipe, the wastewater flows into the draining pipe. For avoiding an increase of the filling level above the opening of the draining pipe and establishing a constant filling level, the diameter of the draining pipe is selected such that in each case the amount of wastewater that can flow through the draining pipe out of the upper vessel can be larger than the amount of wastewater fed into the upper vessel.

[0040] By establishing the constant filling level in the upper vessel, it is possible to provide a constant flow of wastewater into the at least one chamber to ensure correct analyzes of the wastewater. The constant flow velocity is achieved by hydrostatic pressure in the upper vessel with constant filling level, because due to the constant filling level, the hydrostatic pressure and, thus the flow velocity, remain constant. This arrangement has the additional advantage, that no apparatuses like pumps, valves or pressure regulators are needed for providing a constant flow velocity and, thus a constant volume flow.

[0041] The tube having a plurality of openings through which the wastewater can flow may directly extend into the upper vessel through the bottom of the upper vessel. However, for maintenance purposes and for an easier connection of the purger, it is preferred that a communicating chamber is connected to the upper vessel such that wastewater can flow into the communicating chamber and the filling level of the wastewater in the communicating chamber corresponds to the filling level in the upper vessel, wherein the pinhole tube extends into the communicating chamber.

[0042] To avoid large particles to enter the purger, it is preferred that the openings in the pinhole tube have a diameter that is at least 1 mm smaller than the diameter of the pinhole tube. Preferably, the pinhole tube comprises openings having a diameter in a range from 1 to 5 mm, more preferred in a range from 3 to 5 mm and particularly in a range from 4 to 5 mm. The pinhole tube further comprises a plurality of openings to ensure that even in case an opening is blocked, wastewater can flow into the purger and, thus, the sampling can continue.

[0043] In the purger, the wastewater is brought into contact with a gas stream which purges volatile components including volatile organic carbon from the wastewater. The gas stream containing the volatile components then can be analyzed for determining the amount of VOC.

[0044] For continuously determining of the amount of volatile components in the wastewater it is further important to provide a continuous flow of the wastewater through the purger to allow calculating the relation of the amount of volatile components to the amount of wastewater.

[0045] To analyze the volatile components contained in the wastewater, it is necessary to purge them completely from the wastewater. This is achieved by an intense contact of the gas stream with the wastewater flowing through the purger. For this purpose, a large boundary layer between the wastewater and the gas stream must be provided. This preferably is achieved by equipping the purger with a large number of plates arranged one above the other, wherein the wastewater flows along one plate to an edge of the plate, flows over the edge of the plate onto the plate below. The gas stream flows in countercurrent to the wastewater so that the gas stream passes the wastewater falling from one plate to the plate below and thus is mixed with the wastewater and purges volatile components from the wastewater. Further, due to the movement of the water in the purger, the surface continuously changes, so that volatile components can diffuse easier from the wastewater into the gas stream. In contrast to conventional trays as used in columns, such a design also is applicable for small streams of gas and wastewater. Using such trays has the additional advantage that in contrast to bubble trays, sieve trays or valve trays or in contrast to random packings or structured packings, no passages are provided which may block by particles contained in the wastewater or by deposits of algae and / or salts.

[0046] After passing the wastewater and absorbing the volatile components from the wastewater, the gas stream is withdrawn from the purger through a gas outlet. For removing condensable components from the gas stream, it is preferred that the gas outlet is connected to a cooler and droplet separator for removing condensable components from the gas stream containing the volatile components, and the second sampling line is connected to the cooler. By cooling and condensing condensable components it is ensured that only the volatile components are fed into the analyzer for analyzing the volatile components and particularly for determining the amount of VOC in the wastewater.

[0047] The gas used for purging the volatile components from the wastewater may be any suitable gas which is inert to the components contained in the wastewater and which further does not affect the analysis of the volatile components. Suitable gases for example are noble gases like helium or argon, carbon dioxide or nitrogen. Particularly preferably as gas for purging the volatile components is nitrogen. The condensable components removed from the gas stream in the cooler and droplet separator may also be analyzed in a suitable analyzer or may be removed and particularly returned into the wastewater downstream the sampler.

[0048] Since the volatile components are removed from the wastewater in the purger, the analyzer for determining the TOC is connected to the upper vessel, which contains the wastewater still comprising the total carbon compounds, including total organic carbon and total inorganic carbon. For this reason, if it is intended to analyze the total carbon including the total inorganic carbon or the total organic carbon and the total inorganic carbon, the respective analyzers are connected to the upper vessel.

[0049] Further, if it is intended to determine also the pH-value of the wastewater, a pH-sensor also is connected to the upper vessel, because this is the only vessel of the sampler, which contains the wastewater in an unchanged composition.

[0050] The wastewater leaving the sample still contains non-purgeable components, particularly non-purgeable organic carbon (nPOC). For analyzing the nPOC contained in the waste water, the third sampling line is connected to the lower vessel, so that wastewater can be withdrawn from the lower vessel and delivered to an analyzer for analyzing the nPOC.

[0051] Depending on the desired analysis of the wastewater, the sampler can be used for example for taking samples for determining at least one of the total composition of the wastewater, the TOC, the VOC, the total inorganic carbon (TIC), the volatile inorganic carbon (VIC), the nPOC, the non-purgeable inorganic carbon (nPIC), the chemical oxygen demand (COD), and the pH-value.

[0052] After flowing through the sampler, the wastewater collected in the lower vessel is returned into the wastewater stream.

[0053] If a sampling line is connected to the upper vessel or to the lower vessel to take samples of the wastewater, it is preferred to provide a filter at the inlet of the respective first or third sampling line to avoid particles entering and blocking the sampling line. As dirt, particularly particles collect on the filter, it is necessary to flush the filter at predefined intervals, if samples are continuously taken through the sampling lines. If samples are taken discontinuously, the filter may be flushed after a predefined number of samples taken, preferably after each sample taken from the sampler. Depending on the time needed for carrying out the analysis, it is possible to flush the sampling line and the filter during operation of the analyzer.

[0054] In another embodiment, the sampler comprises at least three chambers being connected in such a way that the wastewater in the chambers flows alternately from top to bottom and from bottom to top. For this purpose, it is preferred, that the chamber have a vertical orientation. In a particularly preferred embodiment, the sampler comprises four chambers. For taking samples, the wastewater flows through an inlet into the first chamber. The inlet preferably is arranged at the bottom of the first chamber, so that the waste water flows from the bottom to the top of the first chamber. The top of the first chamber is connected to the top of a second chamber. At the top of the second chamber further a gas outlet is provided. In the second chamber the wastewater flows from top to bottom and gas that may be contained in the wastewater rises in the form of bubbles, collects at the top of the second chamber and can be removed through the gas outlet.

[0055] The bottom of the second chamber is connected to the bottom of a third chamber. For taking samples for analyzing the wastewater, a sampling line extends into the third chamber. The sampling line may either extend into the third chamber from any suitable position, preferably from the top or the bottom of the third chamber and particularly from the top of the third chamber. To avoid particles that may block the sampling line enter the sampling line, it is preferred to provide a filter at the inlet of the sampling line. To remove particles accumulated in the filter, it is preferred to flush the filter in regular intervals. If samples are taken discontinuously, it is preferred to flush the filter after each sample taken from the third chamber.

[0056] Flushing the filter and the sampling line preferably is carried out with an inert gas, particularly nitrogen. As the filter usually is flushed countercurrent to the flow of the wastewater, the inert gas enters the third chamber through the filter during flushing. At least a part of the inert gas may flow countercurrent to the wastewater and enter the second chamber. In the second chamber the inert gas is separated from the waste water, collects at the top and also can be removed through the gas outlet at the top of the second chamber.

[0057] The third chamber preferably is connected to a fourth chamber by a connection that connects the top of the third chamber with the top of the fourth chamber. In the fourth chamber, the wastewater again flows from top to the bottom an is withdrawn from the sampler at the bottom of the fourth chamber.

[0058] If it is intended to analyze the pH-value of the waste water, it is preferred to arrange the pH- detector in the first chamber, because in the first chamber, the used pH-detector is not influenced by the inert gas used for flushing the filter of the sampling line.

[0059] Analyzers used with this sampler preferably are analyzers having an integrated pump which collects a sample through the sampling line from the sampler.

[0060] Independent of the sampler used for taking the wastewater samples, for analyzing the wastewater, any suitable analyzers and analyzing processes known to the skilled person can be used, for example gas chromatography, high pressure liquid chromatography and / or infrared spectroscopy. Detectors used for analysis, particularly are flame ionization detectors. Further, independent of the sampler used, besides using an inert gas for flushing the filter at the inlet of the sampling line, also any other flushing medium may be used. However, flushing media that change the composition of the wastewater only can be used for flushing filters of sampling lines which are not followed by further positions for taking samples because in this case the flushing medium would falsify the results obtained by the analysis. Therefore, if the sampling line is followed by further positions for taking samples, for example further sampling lines, it is preferred to flush the filter with an inert gas that has no influence on the composition of the wastewater and on further analyses.

[0061] Embodiments of the invention are shown in the figures and explained in more detail in the following description.

[0062] In the figures:

[0063] Figure 1 shows a sampler in a first embodiment;

[0064] Figure 2 shows an upper vessel of the sampler of figure 1 in more detail;

[0065] Figure 3 shows a sampler in a second embodiment.

[0066] A sampler in a first embodiment is shown in figure 1 .

[0067] For taking samples to be analyzed, a sampler 1 is connected to a wastewater reservoir 3 by a feed line 5. The wastewater reservoir 3 may be a wastewater tank as shown here or a wastewater pipe through which wastewater is transported either to a wastewater tank or to a wastewater processing site, for example a wastewater purification plant.

[0068] The feed line 5 is connected with the wastewater reservoir 3 in such a way that wastewater can flow from the wastewater reservoir 3 into the feed line 5. This can be achieved for example by arranging the feed line 5 at the bottom of the wastewater reservoir 3 or by immersing the feed line 5 into the wastewater in the wastewater reservoir 3 as shown here. If the wastewater reservoir is a wastewater pipe, the feed line 5 preferably branches off the wastewater pipe so that the wastewater can flow through the feed line 5 to the sampler 1 .

[0069] The feed line 5 ends in an upper vessel 7 of the sampler 1. To avoid foaming of the wastewater when the upper vessel 7 is filled with wastewater, the feed line 5 preferably immerses into the water when the upper vessel 7 is filled, as shown here. To achieve a constant filling level in the upper vessel 7, a draining pipe 9 extends into the upper vessel 7. The draining pipe 9 comprises an opening 11 at the position of the desired filling level in the upper vessel 7. If wastewater is filled into the upper vessel 7 and the filling level reaches the opening 11 of the draining pipe 9, the wastewater flows into the draining pipe and is returned into the wastewater reservoir 3. To allow the wastewater in the draining pipe 9 to flow only driven by gravity, the upper vessel 7 is located above the wastewater reservoir 3. If the wastewater reservoir 3 is a wastewater pipe, it is also possible to arrange the upper vessel 7 at any height in respect to the wastewater pipe, as long as it is possible that the end of the draining pipe 11 through which the wastewater flows out of the upper vessel 7 is below the upper vessel 7. This also applies if the wastewater reservoir 3 is a wastewater tank as shown here and the draining pipe 9 does not return the wastewater into the wastewater tank but to any other place being located below the upper vessel 7.

[0070] If the upper vessel 7 is located above the wastewater reservoir 3, a pump 13 is arranged in the feed line 5, to feed the waste water through the feed line 5 into the upper vessel 7.

[0071] The upper vessel 7 is connected to a communicating chamber 15 in such a way that the filling level in the upper vessel 7 and in the communicating chamber 15 is the same. A pinhole tube 17 extends into the communicating chamber 15 and ends in a purger 19, so that wastewater can flow from the communicating chamber 15 through the pinhole tube 17 into the purger 19. Due to the constant filling level in the upper vessel 7 and the communicating chamber 15, which is achieved by feeding at least such an amount of wastewater into the upper vessel 7 as leaves the upper vessel 7 through the communicating chamber 15 and the pinhole tube 17, the volume flow of the waste water flowing through the pinhole tube 17 into the purger 19 remains constant.

[0072] In the purger 19 the wastewater is brought into contact with a gas stream to purge volatile components from the wastewater into the gas. For this purpose, plates 21 are arranged in the purger 19 in such a way that the wastewater is fed through the pinhole tube 17 onto the uppermost plate 21 , flows along the plate 21 to the edge of the plate and then falls onto the plate 21 below this plate. This repeats until the wastewater reaches the bottom of the purger 19.

[0073] The gas stream is fed into the purger 19 by a gas feed 23 at the bottom of the purger 19 and flows in countercurrent to the wastewater from the bottom of the purger 19 to the top of the purger 19. By this arrangement, the gas stream passes the wastewater each time it falls from one plate 21 onto the plate below and absorbs volatile components. Further, by the movement of the wastewater in the purger 19, the surface of the wastewater continuously changes, which allows the volatile components to be transferred from the wastewater into the gas stream more easily.

[0074] After having passed the purger 19 and being freed of the volatile components, the wastewater flows into a lower vessel 25. To reduce or even to avoid foam formation, the bottom of the purger 19 is connected to a dip tube 27, which immerges into the wastewater in the lower vessel 25, if filled with wastewater.

[0075] To achieve a constant filling level, a second draining pipe 29 is connected to the lower vessel 25 in the same manner as the draining pipe 9 is connected to the upper vessel 7. As soon as the filling level in the lower vessel 25 reaches the opening of the second draining pipe 29, the wastewater flows into the second draining 29 pipe and is withdrawn from the lower vessel 25. The second draining pipe 29 either may be connected to the draining pipe 9, so that waste water withdrawn from the lower vessel 25 flows into the draining pipe 9 and then back into the wastewater reservoir 3 or, alternatively, the second draining pipe 29 may be arrange in such a way that the wastewater directly flows back into the wastewater reservoir 3.

[0076] For a regular operation of the sampler, it is important, that the upper vessel 7, the purger 19 and the lower vessel 25 are arranged one above the other, particularly in such a way that the pinhole tube 17 and the dip tube 27 can be straight without any bends.

[0077] For determining the TOC in the wastewater, a first analyzer 31 is connected to the upper vessel 7 by a first sampling line 33. Due to the small amount of wastewater needed for determining the TOC, the first sampling line 33 usually has an inner diameter that may block by particles in the wastewater. For this reason, it is preferred that a sample filter 36 is connected to the end of the first sampling line 33 that enters into the upper vessel 7.

[0078] A second analyzer 34 for determining the VOC is connected to the purger 19 by a second sampling line 35. To separate condensable components from the gas stream containing the VOC, a cooler and droplet separator 37 is arranged in the second sampling line 35. In the cooler and droplet separator 37, the gas stream is cooled and, due to cooling, the condensable components condense and then are separated from the gas stream. This ensures, that no condensable components are fed into the second analyzer 34 for measuring the VOCs and only the VOCs are analyzed. For cooling of the gas stream in the cooler and droplet separator 37 any suitable cooling medium may be used. Preferably, the cooling medium used for cooling is air.

[0079] To remove particles or droplets from the gas stream which may not be removed in the cooler and droplet separator 37, and which are entrained in the gas stream, an additional filter 39 may be provided. The additional filter 39 may be particularly relevant if an analyzer is used which may be damaged by particles or droplets. Preferably, the filter 39 is a heated filter to prevent blocking the analyzer if a salty liquid is purged. By using the heated filter, which preferably is operated at a temperature in a range from 120 to 150 °C, particularly in a range from 12 to 140 °C, the salt is filtered from the liquid and it is avoided that salt passes over in the gas phase.

[0080] To avoid condensation and blocking in the second sampling line 35, this line is may be heated by heat tracing 38.

[0081] If it is further intended to analyze nPOCs, a third analyzer 41 may be connected to the lower vessel 25 by a third sampling line 43.

[0082] To avoid blocking by deposition of algae and salts or of other components contained in the wastewater, it is preferred that particularly the feed line 5, the pinhole tube 17 and the dip tube 27 have a diameter of more than 10 mm. Further, to avoid formation of deposits, particularly of algae and salts, it is preferred that the flow velocity in the feed line 5 is at least 1 to 3 m / s.

[0083] Further, to remove deposits, particularly in the feed line 5, a gas feed 45 is provided. By feeding an inert gas, particularly nitrogen, into the feed line 5, deposits which may form in the feed line 5 can be removed. For this purpose, it is important that the gas flow of the inert gas is highly turbulent. To remove deposits from the whole feed line 5, it is preferred to provide one connection of the gas feed 45 with the feed line 5 upstream the pump 13 and one connection of the gas feed 45 with the feed line 5 downstream the pump 13. As the inert gas fed into the feed line 5 downstream the pump 13 enters the upper vessel 7, it is important that the upper vessel 7 comprises a gas outlet 47, through which gas can be withdrawn from the upper vessel 7.

[0084] The upper vessel 7 of the sampler 1 is shown in more detail in figure 2.

[0085] If it is intended to measure the pH-value of the wastewater, it is preferred, that a pH-sensor 49 extends into the upper vessel 7. If, however, an analyzer is connected to the upper vessel 7, which regularly is back-flushed with an acid, for example common analyzers for measuring the TOC, the pH-sensor cannot be used at least during the back-flushing. On the other hand, the acid used during back-flushing enters the upper vessel 7 and is mixed with the wastewater contained in the upper vessel 7 and, therefore, falsifies the pH-value even in times between the back-flushing processes. For this reason, if an analyzer is used that is back-flushed with an acid, it may be advantageous to provide the pH-sensor in the feed line 5 or, alternatively, in the wastewater reservoir 3.

[0086] As can be seen in figure 2, the pinhole tube 17 comprises a plurality of openings 51. The openings 51 are distributed over the whole pinhole tube 17 extending in the communicating chamber 15. By providing the plurality of openings 51 , it is ensured that even if an opening is blocked, for example by particles contained in the waste water or by deposits of algae and / or salts, the wastewater still flows with a constant flow rate into the purger 19. For flushing the pinhole tube 17 with an inert gas, it may be possible to connect the pinhole tube 17 to a gas feed.

[0087] Further, for emptying the upper vessel, for example for maintenance purposes, a connection 53 is provided. Besides for emptying, the connection 53 also may be used for connecting a source for cleaning agent for cleaning the sampler 1 .

[0088] A second embodiment of a sampler is shown in figure 3.

[0089] For sampling wastewater, the sampler 1 shown in figure 3 comprises an inlet 101 through which wastewater is fed into a first chamber 103 at the bottom of the first chamber 103. In the first chamber 103, the wastewater flows upwards to the top 105 of the first chamber 103. At the top 104, the first chamber 103 is connected to a second chamber 107. At the bottom, the second chamber 107 end in a connecting tube 109, which connects the bottom of the second chamber 107 with the bottom of a third chamber 111. Finally, the third chamber 111 is connected at its top 113 with the top 115 of a fourth chamber 117. The bottom of the fourth chamber 117 is connected to a waste outlet to remove the wastewater from the sampler.

[0090] By this connection of the first to fourth chambers 103, 107, 111 , 117, the wastewater enters the first chamber 103 at the bottom, flows upwards in the first chamber 103, passes to the top of the second chamber 107, flows downwards in the second chamber 107, then through the connecting tube 109 into the third chamber 111 , flows upwards in the third chamber 111 , passes to the top 115 of the fourth chamber 117, flows downwards in the fourth chamber, and is removed through the waste outlet at the bottom of the fourth chamber 117.

[0091] For analyzing the wastewater, for example for measuring the TOC, a sampling line 119 extends into the third chamber 111. To avoid particles blocking the sampling line 119, a sample filter 121 is provided at the inlet of the sampling line 119.

[0092] Due to the flow pattern of the wastewater in the sampler 1 , gaseous components collect at the top of the second chamber 107 and can be removed through a gas outlet 123. Further, if a gaseous flushing medium is used for back-flushing the analyzer and the sampling line 119, if some of the gaseous flushing medium flows counter the flow direction of the wastewater, this gaseous flushing medium also collects at the top of the second chamber and can be removed from the second chamber 107 through the gas outlet 123.

[0093] For measuring the pH-value of the wastewater, a pH-sensor 120 extends into the first chamber 103. Placing the pH-sensor into the first chamber 103 has the advantage that the pH of the wastewater is not influenced by washing agents used for back-flushing the sampling line 119, because even if some of the washing agent flows counter the flow of the wastewater, the flow distance through the second chamber 107 is sufficiently long, so that the washing agent and the wastewater mix and the washing agent is withdrawn from the sampler with the wastewater that flows through the sampler 1.

[0094] T o remove algae and / or salt deposits, which may form on surfaces of the sampler, an air breather 125 is provided to prevent syphon effect.

[0095] As an alternative, the inlet 101 may be connected to a gas feed to supply the inert gas for flushing the sampler 1 through the inlet 101. In this case, the inert gas flows in the same direction as the wastewater. To remove the deposits, the velocity and the pressure of the inert gas must be high enough to provide a highly turbulent flow that removes the deposits from surfaces of the sampler 1 .

Claims

Claims1 . A process for taking samples of wastewater for analyzing, comprising:(a) feeding wastewater from a wastewater reservoir (3) to a sampler (1 ) having at least one chamber (7, 19, 25; 103, 107, 111 , 117) from which samples are taken;(b) taking samples from the at least one chamber (7, 19, 25; 103, 107, 111 , 117);(c) supplying the samples to an analyzing device (31 , 34, 41 ) through a sampling line (33, 35, 43; 119);(d) flushing the sampler (1 ) and / or the sampling line (33, 35, 43; 119) with an inert gas having a high turbulent flow at regular intervals for removing deposits of salts and algae.

2. The process according to claim 1 , wherein the inert gas is nitrogen.

3. The process according to claim 1 or 2, wherein at least in the sampling line (33, 35, 43; 119), the wastewater flows with a flow velocity of at least 5 m / s.

4. The process according to any of claims 1 to 3, wherein the wastewater flows through the at least one chamber (7, 19, 25; 103, 107, 111 , 117) of the sampler (1 ) with a constant flow velocity.

5. The process according to any of claims 1 to 4, wherein an upper vessel (7) is provided in which a constant filling level is established and the water flows from the upper vessel (7) into the at least one chamber (19) and the constant flow velocity is achieved by hydrostatic pressure in the upper vessel (7) with constant filling level.

6. A sampler for carrying out the process according to any of claims 1 to 5, comprising at least one chamber (7, 19, 25; 103, 107, 111 , 117) connected to a sampling line through which wastewater can flow to an analyzing device (31 , 34, 41) a feed line (5) for feeding wastewater into the sampler (1) and a gas line connected to the sampler (1) and / or the sampling line for flushing the sampler (1 ) and / or the sampling line (33, 35, 43; 119) with an inert gas.

7. The sampler according to claim 6, wherein the sampler (1 ) comprises an upper vessel (7) having an inlet for feeding wastewater into the upper vessel (7) and a draining pipe (9) extending into the upper vessel (7) and with an opening (11) at a position in the upper vessel (7) such that a constant filling level can be established in the upper vessel (7),a purger (19) being connected to the upper vessel (7) with a pinhole tube (17), which intrudes into the wastewater in the upper vessel (7), when the upper vessel (7) is filled with wastewater, the pinhole tube (17) having a plurality of openings (51) through which the wastewater can flow from the upper vessel (7) into the pinhole tube (15), wherein the purger (19) is established such that the wastewater flows in counter current to a gas stream for purging volatile components from the wastewater, and a lower vessel (25) being connected to the purger (19) such that wastewater can flow from the purger (19) into the lower vessel (25), wherein the upper vessel (7) encloses a first chamber, which is connected by a first sampling line (33) to a device for measuring total organic carbon and / or the purger (19) encloses a second chamber, which is connected by a second sampling line (35) to a device for measuring volatile organic carbon and / or the lower vessel (25) encloses a third chamber, which is connected by a third sampling line (43) to a device for measuring non- purgeable organic carbon.

8. The sampler according to claim 7, wherein a communicating chamber (15) is connected to the upper vessel (7) such that wastewater can flow into the communicating chamber (15) and the filling level of the wastewater in the communicating chamber (15) corresponds to the filling level in the upper vessel (7), wherein the pinhole tube (17) extends into the communicating chamber (15).

9. The sampler according to claim 7 or 8, wherein the purger (19) comprises a gas outlet, the gas outlet being connected to a cooler and droplet separator (37) for removing condensable components from the gas stream containing the volatile components and the second sampling line (35) is connected to the cooler and droplet separator (37).

10. The sampler according to claim 6, wherein the sampler comprises at least three chambers (103, 107, 111 , 117) being connected in such a way that the wastewater in the chambers (103, 107, 111 , 117) flows alternately from top to bottom and from bottom to top.11 . The sampler according to claim 10, wherein the bottom of the first chamber (103) is connected to a wastewater inlet (101).

12. The sampler according to claim 10 or 11 , wherein the sampling line (119) extends into the third chamber (111).

13. The sampler according to any of claims 6 to 12, wherein a sample filter (121 ) is provided at the inlet of the sampling line (33, 43; 119).

14. The sampler according to any of claims 6 to 13, wherein a device for measuring the pH- value is provided in the first chamber.

15. The sampler according to any of claims 6 to 14, wherein a predetermined flow rate of the wastewater in the sampling line (33, 43; 119) is set by the inner diameter of the sampling line (33, 43; 119).

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