IE910237A1

IE910237A1 - An apparatus for the biological removal of pollutants from¹contaminated solids

Info

Publication number: IE910237A1
Application number: IE23791A
Authority: IE
Inventors: Helmut Pelzer
Original assignee: H P Chemie Pelzer Res & Dev Lt
Priority date: 1991-01-23
Filing date: 1991-01-23
Publication date: 1992-07-29
Also published as: CS18392A3; EP0496198A3; EP0496198A2

Abstract

Equipment is described for the biological removal of pollutants from contaminated solids, in particular soils polluted by hydrocarbons, by bacterial cultures in solid-waste reactors. The inventive solution comprises treating polluted soils in equipment composed of a transport device (2) with revolving endless belt (3) of perforated plates (4) and holders (5) for the flat bed reactors (1) to be transported and base troughs (6) arranged below, and also an irrigation system (7) arranged above enclosed by a casing (11) equipped with heating devices (8) and cooling devices (9) and also exhaust air control devices (10). The base troughs (6) are preferably divided into sections (15). The irrigation system (7) is composed of individually controlled part systems (16). The flat bed reactors (1) are equipped with mixing devices (19). For example, the driving stubs (21) of the shafts (20) of the mixing devices (19) in the flat bed reactors (1) are equipped with toothed wheels (22) and a stationary toothed rack (23) is arranged prior to the transport device (2).

Description

The invention relates to an apparatus for the biological clearance of contaminated solids, such as soils, especially those contaminated with hydrocarbons, using bacterial cultures.

The problem of cleaning contaminated soils has led to the production of various methods and apparatuses, including for example deposition, incineration, biological treatment in situ, biological treatment in beds and chemical washing and extraction procedures.

Revolving drums are used in some biological cleaning procedures. Thus, in accordance with DE OS 38 24 009, balls are formed in the revolving drum from the contaminated earth with the addition of extractive liquid, and the foul liquid is pressed out of these balls using press rollers. The balls are then once more comminuted. Microorganisms can be added to the comminuted soil. 91023/ A multi-step cleaning method is also known, in which the contaminated soils are mixed with a solution in a number of consecutive steps, and the solution with a proportion of the contaminants is drawn off at each step. The corresponding device consists of a homogenisation container based on the principle of the concrete mixer, with a plurality of washing drums arranged one after the other (DE OS 37 26 282).

In a further known clearance method the contaminated material is introduced into an emulsion within a mobile rotating container with helical baffles, and subsequently rinsed in washing devices. The polluted liquid phase is fed into settling basins and there broken down using bacteria.

Furthermore, an apparatus for removing pollutants from contaminated earth masses is also known, in which contaminated soil is mixed with water in a rotating free-fall mixer, and bacteria are added. The contaminated washing water passes through several washing devices to a dewatering container, where the suspended substances are flocculated and separated from the water. The contaminated constituents are converted to carbon dioxide and water in a bioreactor at approx 35 degrees Centigrade with the addition of oxygen (WO 89/96992).

Finally, contaminated earth, especially earth which is contaminated with oil, can be regenerated in passing through a chamber where it is heated to the temperature of evaporation of a slurry. The chamber consists of a plurality of stages disposed one above the other and 1 0 2 3/ bonded like bricks, each of which stages contains a trough with chain conveyors for conveying the residue.

The non-condensable vapours are burnt.

All these procedures have specific attendant disadvantages. They require expensive apparatus and are inflexible. In addition some of them are environmentally damaging, lead to considerable amounts of deposited material or are extremely expensive to run, and the cleaned soil may no longer contain any organic components and thus be biologically dead (revolving flue ovens, pyrolysis chambers).

The object of the invention is to develop an apparatus for the biological removal of pollutants from contaminated solids, especially earth masses contaminated with hydrocarbons, using bacteria in solid reactors, in which apparatus a plurality of transportable reactors filled with polluted soils can be cleaned simultaneously, with optimal exploitation of the reaction solution and treatment, and in which the escape of liquid or gaseous pollutants into the environment can be avoided.

This object is achieved in accordance with the invention by a process in which the solids which are contaminated with hydrocarbons are biologically cleaned of the pollutants using microorganisms and nutrient salt solutions or water (or a mixture of same) in an apparatus which consists of a conveying device with a moving endless belt of perforated metal, catchpoints for stackable bed reactors which are to be transported, collecting troughs disposed thereunder, and a wetting system disposed thereabove, which apparatus is enclosed within a housing which is provided with heating/cooling devices and air exhaust control devices.

The invention also provides apparatus for the biological removal of pollutants from contaminated solids, especially earth masses polluted with hydrocarbons, using bacterial cultures, characterised in that the apparatus comprises a conveying device with a moving endless belt of perforated metal, catchpoints for the stackable bed reactors to be transported, collecting troughs disposed beneath said belt and a wetting system disposed thereabove, and is enclosed within a housing provided with heating, cooling and air exhaust control devices.

The conveying device can be a horizontal plate conveyor or a chain conveyor supported by heavy load-bearing rollers. The bed reactors are moved within the apparatus by the conveying device and remain on the endless belt throughout the entire reaction time. A completed passage is simultaneously the end of the dwell time in the apparatus and of the reaction time in the bed reactor.

The wetting system located above the conveying device is designed as a spraying system or consists of nozzle devices. The wetting system consists of individually controlled sub-systems, by means of which the solids to be treated are sprayed at set intervals with nutrient solutions or water or with a mixture of both. 91023/ The water or the liquid with the nutrient salt flows through the sieve-like perforated base of the bed reactors and through the endless belt of perforated metal into the collecting troughs disposed thereunder. The collecting troughs are preferably divided into sections, so that collection of the liquid in the individual sections allows the attainment of true cross-current or cross-counter-current procedures for the permeation of the reaction solutions through the solid which is to be treated, and thus optimal use of the nutrient solution and optimal treatment of the solid are made possible. The liquid caught in the collecting troughs is filtered in a filtering device and is recycled into the wetting system.

The bed reactors are provided with mixing devices. The driving ends of the shafts of these mixing devices are equipped with toothed wheels and a fixed toothed or chain rack is disposed before the conveying device.

The driving ends of the shafts of the mixing devices are provided with said toothed wheels before they are mounted on the conveying device. When the bed reactors are placed on the conveying device, these wheels engage for example the toothed rack and, as a result of the horizontal motion of the reactor past the toothed rack, the shafts are turned by the turning motion of the toothed wheels.

Instead of the fixed toothed or chain rack, independently driven moving toothed or roller chains can be used, which permit a rotation speed of the shafts of the mixing devices that is largely independent of the velocity of the bed reactors.

The shafts of the mixing devices can also be externally driven by mobile drive motors.

In order to avoid environmental contamination by liquid or evolved gaseous substances, the apparatus is contained within a housing with an air exhaust control, in which heating and cooling devices are also contained.

In the following the apparatus of the invention will be described in more detail with reference to an exemplary embodiment. Figures 1 and 2 show the side elevation and plan view respectively of the layout of this apparatus with a plate conveyor and Figures 3 and 4 show a variation with a chain conveyor.

Before the bed reactors (1) which have just been filled with contaminated soil, and to which microorganisms have been added, are placed on the horizontal plate conveyor (2), they are provided with appropriate toothed wheels (22) at the driving ends (21) of the shafts (20) of the mixing devices (19), and then passed by fork lift to the beginning of the moving endless belt (3) with catchpoints (5) for the stackable bed reactors (1) which are to be transported. When the bed reactors (1) are put into place, the toothed wheels (22) engage the fixed toothed rack (23) in front of the plate conveyor (2) and as a result of the horizontal motion of the reactor (1) past the fixed toothed rack (23) the shafts (20) of the mixing device (19) are turned by the rotation of the toothed wheels (22), thereby agitating the soil. < ·-**· π a υ I Nutrient solutions for the microorganisims and water are released separately by a spraying system (17) through individually controlled.sub-systems (16) at set intervals above the filled bed reactor (1) and then mixed. The required temperature of about 15 to 35 degrees Celcius is maintained by the heating (8) and cooling (9) devices. The flat bed reactors (1) are moved on by the plate conveyor (2).

The liquid (nutrient solution and water) flows through the sieve-like perforated bases of the bed reactors (1) and through the preforated metal (4) of the endless belt (3) into the collecting troughs (6) arranged below, which troughs are divided into several sections (15), so that true cross counter-current procedures for the permeation of the reaction solution through the solid to be treated are achieved. The liquid caught in the collecting troughs (6) is fed through a filtering device (28) and recycled into the shower system (17). Waste gases which develop are caught and removed by an air exhaust control device (10) .

After a complete passage, when the end of the plate conveyor (2) is reached, the reaction time and the dwell time of the treated soil in the apparatus are ended. The bed reactors with newly contaminant-free soil are now removed by fork lift. The treated soil can now be harmlessly returned to a natural environment.

Claims

1. Apparatus for the biological removal of pollutants from contaminated solids, especially earth masses polluted with hydrocarbons, using bacterial cultures, characterised in that the apparatus comprises a conveying device with a moving endless belt of perforated metal, catchpoints for the stackable bed reactors to be transported, collecting troughs disposed beneath said belt and a wetting system disposed thereabove, and is enclosed within a housing provided with heating, cooling and air exhaust control devices.

2. Apparatus in accordance with Claim 1, characterised in that the conveyor device is a horizontal plate conveyor .

3. Apparatus in accordance with Claim 1 or 2, characterised in that the conveyor device is a chain conveyor supported on heavy load-bearing rollers.

4. Apparatus in accordance with Claim 1, characterised in that the collecting troughs are divided into sections . - ©10 2

5. Apparatus in accordance with Claim 1, characterised in that the wetting system consists of individually controlled sub-systems.

6. Apparatus in accordance with Claim 1 or 5, characterised in that the wetting system is a spraying system.

7. Apparatus in accordance with one of Claims 1, 5 and 6, characterised in that the wetting system consists of spray nozzles.

8. Apparatus in accordance with one of Claims 1 and 4 to 7, characterised in that a filtering device is installed between the collecting troughs and the wetting system.

9. Apparatus in accordance with Claim 1, characterised in that the bed reactors are equipped with mixing devices .

10. Apparatus in accordance with one of Claims 1,2 and 9, characterised in that the driving ends of the shafts of the mixing devices in the bed reactors are provided with toothed wheels, and that a fixed toothed rack is disposed in front of the conveying device.

11. Apparatus in accordance with one of Claims 1, 3, 9 and 10, characterised in that a fixed chain rack is disposed in front of the conveying device.

12. Apparatus in accordance with one of Claims 1, 2, 9 and 10, characterised in that a moving endless toothed chain with a separate drive is disposed in front of the conveying device.

13. Apparatus in accordance with one of Claims 1, 2, 9 and 11, characterised in that a moving endless roller chain with a separate drive is disposed in front of the conveying device.

14. Process for the biological removal of pollutants from contaminated solids, characterised in that the contaminated solids are filled into stackable bed reactors with permeable bases, are charged with microorganisms and are further charged by a wetting system with nutrient solution for the microorganisms and/or water, and are mixed by mixing devices integrated into the bed reactors, are placed and retained on a conveying device having an endless belt of perforated metal, and further treated at 15 to 35 degrees Celsius until the contaminants have been completely decomposed, and that the liquid flowing out through the bases of the bed reactors and through the perforated metal of the endless belt is caught by collecting troughs lying thereunder, filtered and discarded or refed through a circulatory system into the treatment system for the solids.

15. Apparatus for the biological removal of pollutants from contaminated solids, using bacterial cultures, substantially as herein described with reference to or as illustrated in the accompanying drawings.

16. Process for the biological removal of pollutants from contaminated solids, using bacterial cultures, substantially as herein described with reference to or as illustrated in the accompanying drawings. Dated this the 23rd day of January, 1991 F. R. KELLY & CO. BY ^EXECUTIVE 27 Clyde Road,,-Ballsbridge, Dublin 4 AGENTS FOR^-TflE APPLICANTS H.P. CHEMIE PELZER RESEARCH & DEVELOPMENT LTD. 2 Sheets