DE19616953A1 - Water treatment adsorption agent regenerated in situ - Google Patents

Abstract

The novelty is that in a process and assembly (a) an adsorption agent bearing a load of impurities is regenerated by a retro-fitted cleaning and decontamination assembly (b) the retro-fit assembly facilitates the in-situ regeneration of the adsorption agent; (c) in-situ regeneration prevents damage that might otherwise occur during transport of the agent to a treatment installation; and (d) the regeneration takes place within the reactor in which the adsorption agent treats water (e.g. ground water, waste water, process water), in normal operation. Preferably (e) the regeneration process uses electrolysis generating hydrogen at the cathode, the gas being surrendered to microorganisms; (f) the cathode is surrounded by an ion-exchange membrane from the rest of the reaction vessel, and discharging the gas to a reactor outlet pipe (g) the specific choice of membrane at the reactor outlet prevents the ingress of microorganisms from the reaction vessel into the pipes and the mixing vessel, during cleaning and decontamination operations; (h) as soon as the adsorption agent is fully laden, cleaning and decontamination commences by creating conditions within the reactor which enable the microorganisms to convert the load (without heavy metals) into minerals.

Description

The performance according to the invention is characterized in that certain structure Changes in the adsorbent after pollutant absorption and at subsequent decontamination can be prevented.

This applies to adsorbents in filters for cleaning water (groundwater, Process water, waste water, etc.) were used.

It is possible that the decontamination of the adsorbent depends on the Pollutant characteristics carried out in one or more process steps becomes.

Current status

For the regeneration of the adsorbent, mostly activated carbon, both thermal treatment as a classic process, as well as newer biotechnology cal cleaning process (two-stage process and device for biological Regeneration of loaded activated carbon, A.Bartetzko &P.J.Janietz; biotechnology and environmental protection, Wiesbaden July 1995) applied. These procedures require the transport of the adsorbent loaded with pollutants from the filter in the reactor in which the decontamination takes place.

Structural changes in the adsorbent arise largely from the mechanical Stress

• 1. when removing from the filter,
• 2. during transport to the place of the decontamination process, as well
• 3. when returning, including loading the filter with the processed one Adsorbent.

The result is very fine-grained abrasion, which must be discarded because it is the cause for clogging pipes and filters. This separation means Loss of quantity and thus loss of capacity of the respective batch and must can be compensated for by purchasing adsorbents.

The loss of fine grain or sludge is estimated at various companies dealing with foundation engineering and / or environmental technology, about 3-6% of the total amount when replacing the adsorb completely once means of a filter (approx. 10 m³).

New process

Preventing the unfavorable structural changes of the invention Adsorbent can be done by decontaminating the adsorbent in place and place in the used water / waste water filter by an appropriate device respectively.

In the description of the device according to the invention it is assumed that during the filtering process, the inlet of the water / waste water to be cleaned is depressurized from above is done. This inevitably means that the purified water in the lower Section of the filter body is removed.

When switching the filter from "cleaning the water / waste water" to "the "Decontamination of the adsorption material" according to the invention becomes this Reverse flow direction, d. H. the process water for the decontamination process is pumped into the filter container at the bottom and runs in the upper part of the filter container depressurized.

It is also possible with little effort, the "decontamination according to the invention  of the adsorbent "to realize in a reverse flow direction in the area to start decontamination in which a higher Pollutant concentration is present.

For the formation of a fluidized bed in the filter container, it is more favorable if the flow direction of the process water with the direction of movement of the ascending Oxygen bubbles match, otherwise the flow direction of the process would water against the rising oxygen bubbles.

The turbulence additionally causes the shear forces to develop forming biofilm is torn on the particles of the adsorbent and so Excess and dead biomass from the reaction space (filter container) can be carried out.

Furthermore, it is also possible to carry out this decontamination in a horizontal position Perform filter container after the decontamination device has been installed.

For this purpose, the following devices are either in the lower part of the filter container to be installed later or during production:

• - Electrodes for the anodic generation of finely divided oxygen bubbles. Titanium coated with ruthenium dioxide in expanded metal form should be used as the electrode material.
  The hydrogen gas possibly generated at the cathode is removed from the reactor chamber with a trap (pipe or membrane). The cathode is encapsulated by an ion exchange membrane from the rest of the reaction space.
• - closable sampling openings in the filter container wall, which made it possible Lichen, based on samples, the degree of decontamination of the adsorbent to be determined analytically.

The following must be installed in the upper part of the filter container:

• - A valve that catches gas generated during cleaning can be so that there is no excess pressure in the filter container.
• - Openings for attaching sensors or measuring electrodes for the measurement of pH, temperature, redox potential / oxygen and the conductivity of the Process water in the reaction space.

The conductivity measurement is done to prevent one for the micro organisms toxic salt concentration in the process water arises. If exceeded the process computer switches a pump to supply fresh water on.

The following are other devices for controlling the decontamination process outside of the filter container for the decontamination necessary and become integrated in the supply or discharge.

Process water outlet

• - Device (weir or self-cleaning filter) for returning particles of the adsorbent in the reaction chamber (filter container), which is flushed out and which lead to blockages in the pipes or in the mixing vessel.
• - Integrated mixing vessel with dosing devices for nutrient salts acid / alkali for pH regulation
• - A further filter removes dead microorganisms from the Process water removed.

A circulation pump for the closed process water circuit is also closed to install. The performance data of the pump depend on the flow resistance including the liquid column of the filter filled with the adsorbent. If it is the construction form and the already existing internals of the Filter container, it would be beneficial for the efficiency of the decontamination, not to clean the adsorbent in a fixed bed reaction space, but the Buoyancy caused by the ascending, finely divided oxygen bubbles at the Grains of the adsorbent arise, and the flow rate of the process water to build a fluidized bed in the reaction space and during decontamination (Holst J., Martens B., Gulyas H. Greiser N. & Sekoulvl. (1991) J.Environ. Engineering 12 (2) pp. 194-208).

All measurement results regarding the decontamination process are carried out by one process computer evaluated and on the basis of process-dependent, selectable target values converted into control commands for the individual actuators.

Decontamination usually begins when the loading capacity of the Adsorbent was reached, that is, if only very little or no more pollutants are absorbed.

The supply for the water / wastewater as well as the discharge are below broken and the additional devices for decontamination of the adsorption means are connected.

End of decontamination

The end of decontamination for halogen-containing pollutants can be recognized by that the pH remains constant. When these pollutants are broken down, u. a. Halo hydrogen that must be neutralized by lye. If no Halogenated pollutants are more present because pollutant degradation stops the pH value no longer changes.

For other pollutants, the end of decontamination can be recognized by that the content of nutrients in the process water no longer drops because the Microorganisms due to the lack of C source their metabolism and their Adjust propagation.

In parallel, samples of the adsorbent are analyzed analytically for the status of Decontamination examined.

Description of the devices

The cleaning and decontamination device consists of the following components:
Electrodes ( 2 ) are located in the lower part of the filter container ( 1 ). Oxygen bubbles generated at the anode are generated for the microorganisms from the water itself.

A collecting device on the cathode, which is seldom encapsulated with an ion exchange membrane, conducts gases (e.g. hydrogen) from the reaction space. In the upper area (cover) there are measuring electrodes for pH ( 3 ), temperature ( 4 ), redox potential ( 5 ) and conductivity ( 6 ). Also in the upper part of the filter container at the highest point, a valve ( 7 ) is installed with which the gas generated during the decontamination can be collected. Lockable sampling openings ( 9 ) are provided in the wall of the container. Existing assembly openings or removal or loading openings ( 8 ) can also be used for sampling.

At the lowest point of the filter container, possibly on an existing line, a closable drain opening ( 10 ) for the process water of the decontamination must be provided.

From a storage tank ( 12 ) by means of a pump ( 13 ) an addition ( 11 ) of fresh water when z. B. the determined via the conductivity ( 6 ) salt concentration could be toxic to the microorganisms. At the same time it is achieved with the help of the process computer that only the really necessary amount of water is supplied to the system by an optimal dosage.

The outlet ( 15 ), which may also be combined with a line already present on the filter container, is to be provided with a device ( 14 ) which is designed as a weir or self-cleaning filter, which prevents particles of the adsorbent from being washed out of the filter container that lead to blockages in the system. The drain is led into a mixing vessel ( 18 ) via a material-impermeable line ( 16 ) in which there is a sampling point ( 17 ).

The mixing vessel is used to adjust the pH value, the optimal nutrient salt concentration, and the amount of oxygen for cleaning and decontamination. With the aid of a pump ( 20 ) controlled by a pH electrode ( 19 ), acid / alkali is metered in from a storage vessel.

The pH to be set depends on the organisms used. The optimum oxygen content, which is 9.2 mg O² / l at 21 ° C, is set by adding a H²O² solution from a storage vessel via a controlled pump ( 21 ).

Nutrient salts are metered from the reservoir into the mixing vessel via the pump ( 23 ). The pump is controlled so that there is always a sufficient concentration of nitrogen and phosphate at the sampling point ( 17 ). The distribution of the added substances takes place with a motor-driven agitator ( 24 ). In the mixing vessel, which is also closed in such a way that no stripping effects can occur, there is a valve ( 25 ) for the gas discharge and the outlet ( 26 ) for the process water from the system. As a check there is a sampling point in the drain ( 27 ).

In the mixing vessel there is an addition lock ( 30 ) for microorganisms which are propagated in the fermenter, as a carrier of the decontamination process. By adding sufficient microorganisms, which are selected for the existing pollutants, it is possible to start the decontamination process, ie the microbial degradation of the pollutants, in the entire filter container after a short start-up time.

This makes it possible to shorten the time for decontamination. Aerobic bacteria of the genera Pseudomonas, Acinobacter, Rhodococcos, Alcanigenes, Thiobacillus, Bacillus, Xanthobacter and other pollutants Strains as pure cultures or mixed cultures that are isolated and on the way mineralizing pollutants have been particularly adapted to Decontamination process to carry out on the adsorbent.

Instead of the mixing vessel with the agitator, a mixing section can also be installed in which all the devices described are arranged one behind the other, and appropriate baffles cause turbulence.

The circuit stream is returned to the filter container through a line ( 28 ) with a regulated pump ( 29 ).

Claims (4)

1. Use and application of a retrofittable cleaning and decontamination device for adsorbent loaded with pollutants, which enables this cleaning and decontamination immediately in the respective reaction container to carry out the structural changes that occur when transporting the Adsorbent for cleaning and decontamination arise avoid, the pollutant loading of the adsorbent takes place in reaction instead of containers in which water (groundwater, wastewater, process water, etc.) is cleaned. 2. The method and device according to claim 1, characterized in that for the safe discharge of gases (e.g. hydrogen), which are used in the electro chemical - oxygen supply of microorganisms at the cathode arise, the cathode through an ion exchange membrane from the rest Reaction container is separated and provided with a pipe that the Allows gas discharge from the reactor vessel. 3. The method and device according to claim 1 to 2, characterized in that that through a specific membrane at the outlet of the reaction vessel prevents micro. during cleaning and decontamination organisms from the reaction vessel into the piping and into the Mixing vessel can get. 4. The method and device according to claim 1 to 3, characterized in that immediately after loading the adsorbent with pollutants The decontamination is started by conditions in the reaction containers are created that allow the microorganisms that Mineralize pollutants (without heavy metals) immediately. That’s it possible the adsorption reactor for water / wastewater treatment to operate continuously without the use time of this reactor by the Having to insert a decontamination phase when the Loading capacity of the adsorbent has been reached.