DD298766A5 - METHOD AND ARRANGEMENT FOR MICROBIAL HEAVY METAL REMOVAL FROM WASTEWATERS - Google Patents

Abstract

The invention relates to a method and an arrangement for the elimination of heavy metals and heavy metal compounds from industrial wastewater by sorption on biomass. Heavy metals and heavy metal compounds are removed by sorption on biomass to relieve the environment and recover valuable materials, with the help of a simple-built technical arrangement. Heavy metals and heavy metal compounds are sorbed at ambient temperature and atmospheric pressure to biomass. The biomass used is attracted to aqueous nutrient media (eg waste water) and suspended in a specific concentration level and p H range in a technical arrangement consisting of a Saeurevorlagebehaelter, a Abwasserdeponiebehaelter, a Biosorptionsreaktor and solid-liquid separation units, the gemaesz Fig. 1 are coupled together introduced. In the technical arrangement, the depletion of the wastewater takes place effectively and economically. The depletion is followed by a recovery of valuable material. Due to the chosen design and dimensioning, the enrichment process of heavy metals and heavy metal compounds from waste waters can be completed in a very short time. {Industrial wastewater; Heavy metal elimination; Microorganism suspension; biosorption; Biosorptionsreaktor; Solid-liquid separation unit; Environmental impact; Wertstoffrueckgewinnung}

Description

For this 1 page drawings

Field of application of the invention

The invention relates to a method and a technical arrangement for the elimination of heavy metals and heavy metal compounds from wastewater for a process in which heavy metals and heavy metal compounds, by biomass drawn on a suitable nutrient medium (eg wastewater) sorptively removed to relieve the environment and for material recovery become.

Characteristic of the known state of the art

The recovery of metals from low concentration solutions serves essentially the following purposes:

1. a further education through the reusability of the recovered metals and ν

2. Wastewater treatment by the removal of heavy metals from the wastewater.

Ideally, a method satisfies both objectives, i. H. the recovery of heavy metals with simultaneous wastewater treatment.

The most common methods used in industrial practice to remove metals from low concentration solutions are:

- Precipitation

- Adsorption

- electrolysis

- Membrane method

- ion exchange method

- known biotechnological processes

When using the precipitation principle for metal disposal, especially due to the low toxicity of the resulting sparingly soluble compounds, the hydroxide precipitation is more widespread and often a good way to remove metals from aqueous waste products. Particular difficulties arise when certain limit values (eg with mercury less than or equal to 0.05 mg mercury / l waste water) must be observed. Another striking feature of the precipitation reactions is that the resulting metal salt precipitates are predominantly in fine or colloidally disperse form. Although the electrostatic repulsive forces are well stabilized, sedimentation is very low

slowly. In order to achieve better sedimentation and filtration, flocculants must be added, whereby mandamit always receives metal salt precipitates contaminated with organic substrates, the work-up of which up to the material is very callous or impossible.

The adsorption is for the removal of heavy metals and heavy metal compounds from low concentrated

metal! old solutions only occasionally applied. Such methods are described for the use of the following

Adsorb substances:

- Lignite (GMA: Glasformen und Maschinen GmbH Firmenunterlagen, A 8580 Röflach)

- Charcoal (JP 58128188)

- Bone coal (JP 7493214)

- peat (DE-OS 2263047)

- Ash (DD-WP 146444)

Carbon black (P.S. Poklonski et al. Tset Metal, 45 [1972], 1, p.40)

- Graphite powder (SU 569316)

However, this disposal principle is only occasionally used for the following reasons. Such reasons are:

- Low absorption capacities of Adsorbersubstanzen

- Short life of the adsorber

- necessary pretreatments of these adsorbents and

- Often not to immediate landfill of the residues.

In addition, electrolytic processes for the recovery of metals from aqueous solutions are known. In particular, they serve the recovery of precious metals from no longer usable electrolytes, contents of rinsing baths and concentrated rinsing waters. These electrolytic processes are not economical for the recovery of base metals at low concentrations.

Of the numerous membrane separation processes in use today for metal enrichment and thus for the disposal of metal-containing solutions, especially reverse osmosis and electrodialysis come into consideration. An advantage of the membrane processes is that the metals dissolved in effluents can be concentrated without salting up the clarified effluent as in the ion exchange processes. The disadvantage is that they have a less selective effect and, depending on the membrane separation process used, further after-treatments are usually necessary to achieve the required effluent qualities.

The problems of the ion exchange processes with solid exchange resins are the regenerability of the resins, especially in the exchange of heavy metals. This and unsatisfactory selectivity have hitherto prevented widespread use of ion exchange resins for heavy metal charging.

By contrast, the ion exchange processes based on liquid ion exchangers, in which a distinction is made between solvent extraction and liquid membrane permeation, are characterized by high flexibility. There are metal-specific liquid ion exchangers to produce and use in complex wastewater possible. The ion exchange processes are also in the future due to high investment and operating costs and because of the remaining after the ion exchange treatment metal concentration, which is especially in the highly toxic metals mercury and cadmium above the required limit concentrations, not applicable everywhere. In addition to the previously mentioned methods, possibilities for the biotechnological removal of heavy metals and heavy metal compounds are also known. Essentially, the ability of biomass to sorb heavy metals and heavy metal compounds is used. The biomass is contacted with the metal-containing wastewater and while adhering to certain pH ranges and temperature ranges, the accumulation of heavy metals and heavy metal compounds on or into the biomass generally takes place over relatively long periods of time. As biomasses various bacteria and / or yeasts are suitable. After separation of the metal-containing biomass from the treated wastewater, by conventional methods such as filtration, Zentrifugaticn u.a. As a rule, the metal recovery or biomass processing takes place via thermal processes. The cultivation of the biomass used can be carried out both in metal-containing wastewater and in special mineral nutrient media. In the biotechnological removal of mercury and 'mercury compounds arise in most known biotechnological processes volatile organic toxic mercury compounds or the uptake rates for heavy metals per gram biomass dry matter are too low and the contact times unreasonably large. In DD 225415, the removal of mercury by sorption on living, dormant or dead microorganisms such as yeasts, bacteria or mixed populations both by a two-step process. During the 1st stage, the biomass is grown on the different substances in a mercury-free mineral medium. In the second stage, the sorptive process is carried out after contacting this biomass with the mercury-containing wastewater after intensive premixing in the alkaline range between pH 7 and 10. A sorption capacity of 78 to 109 mg mercury per g biomass dry substance is achieved, whereby a maximum degree of concentration of biomass can be achieved by a targeted procedural design. According to DD 225418 there is also the possibility of using special mercury-resistant strains of microorganisms either via the o. G. Use two-step process or directly in the mercury-containing wastewater to breed and thus run off cultivation and mercury accumulation in one stage.

Mercury contents of 90 to 100 mg / g biomass dry substance are achieved under similar reaction conditions as in DD 225415

 According to DD 225443, the accumulation of mercury takes place at a pH of between 3 and 8.

Object of the invention

The aim of the invention is the development of a method and an uncomplicated constructed, effective and safe working technical arrangement for this method for the elimination of heavy metals and heavy metal compounds from wastewater by their sorption on biomass to relieve the environment and to recover material from wastewater by means of a simple procedural design.

-3- 298 766 Presentation of the Essence of the Invention

The invention has for its object a method with controlled ratio of biomass suspension flow and wastewater flow and a simple design flexible deployable and operating at low cost and high efficiency technical arrangement for the removal 'η heavy metals and heavy metal compounds from wastewater to relieve the environment and to recover material and to provide, by using microbial Sorptionsprozesse to remove heavy metals and heavy metal compounds to a predetermined residual concentration of industrial wastewater and supply them to a material recovery. The object is achieved in that a set heavy metal waste stream V) and a present in the aqueous phase controlled Biomassesuspensionsstrom V _{2 are} continuously mixed in such a ratio that arise in a Biosorptionsreaktor highly turbulent flow fields. The heavy metal-containing industrial wastewater is collected according to Figure 1 in a functioning as a buffer vessel closed landfill container (2) and adjusted by controlled addition of acid, preferably sulfuric acid to a pH range of 1.5 to 8. Acid reservoir (1) and landfill containers are dimensioned taking into account the material flows necessary for the realization of the method so that they can be used for interruption of the waste water and / or acid supply for a finite time as buffer systems for maintaining the operation of the plant. In the landfill container (2) an intensive mixing of the landfill container with simultaneous pH gradient reduction is realized by suitable technical devices. Continuously adjusted to the pH range of 1.5 to 8, preferably to the pH of 3, adjusted heavy metal wastewater from the landfill container (2) in the head of the Biosorptionsreaktors (3). By means of a regulating device, a defined waste water volume flow (V ₁ ) containing heavy metals is set and kept constant. With the aid of a pump (5) installed in another pipeline system, a defined volume flow (V ₂ ) containing biomass in a certain concentration is simultaneously and continuously passed into the head region of the biosorption reactor (3) and kept constant by a control device (6). The two volume flows Vi and V ₂ are designed in such a way that when the volume flows Vt and V ₂ meet, highly turbulent flow fields (Re much greater than 2300) are formed and thus a thorough mixing takes place.

Surprisingly, it was gefu. Jen, that is completed by such a design of the beidan volume flows V ₁ and V ₂ in the sorption of the sorption process and the accumulation of heavy metals and heavy metal compounds contained in the waste after a short time, a maximum of 10min, at ambient temperature and under normal pressure. Here, the heavy metal contained in the wastewater is sorptively bound in the order of greater than 6 mg per g of suspended Biomassetiockensubstanz and depleted residual heavy metal content in wastewater to less than 1 mg of heavy metal per I wastewater, if the flow rates V ₁ and V ₂ continuously and regulated in such a ratio introduced into each other in the Biosorptionsreaktor that 1 liter of biomass dry substance is used per liter of mixture Vi and V ₂ for 10mg of heavy metal. For example, microorganism strains of the genera Azetobacter, Methylbacillus, Yarrowia, and mixed populations of the species mentioned above can be used as sorbent biomass. The mixture leaving the sorption reactor of suspended biomass laden with heavy metal and the wastewater secured by the heavy metal is fed to a solid-liquid separation by means of conventional separation devices. In this separation device (4), the suspension of wastewater and biomass containing heavy metals passes. After the solid-liquid separation (4), at least one third of the separated heavy metal-laden biomass is fed back via a bypass piping system (7) directly to the biomass suspension stream V ₂ or to the top of the biosorption reactor (3). The recirculation of the partially loaded biomass occurs depending on the achieved degree of loading of the biomass or of the heavy metal concentration of the wastewater once or several times. By re-contacting the partially loaded biomass with the waste water volume flow Vi in the head of Biosorptionsreaktors (3) higher loading of the biomass is achieved with the heavy metal to be disposed of and thus the required degree of waste disposal and economic material recovery from the loaded biomass. In addition, the recirculation of loaded biomass makes it possible to reduce the unladen biomass used in the volumetric flow V ₂ .

embodiments

example 1

For heavy metal fixation of low concentrated solutions and industrial wastewater, the microorganisms Methylobacillus sp. IMET11070 and the gluconic acid producer Acetobacter methanolicus IMET B 346 used before and after acid formation. The cultivation of these biosorbents was carried out according to DD 239191 or EP 0171447 using methanol as C source.

The biosorption was in each case initiated by a biomass suspension with a defined biomass dry matter concentration Cbts in g BTS / I and a metal-containing solution with a known metal ion content in mg Me ^{n +} / I under specification or constant other process parameters, such as pH, temperature, Art the metal-containing medium and residence time in the combined volume flow, mixed together. The homogenization of the volume flows took place in such a way that highly turbulent flow fields (Re much greater than 2300) arise when the two volume flows meet, resulting in an intensive and complete thorough mixing thereof. After a predetermined residence time (t in min) of the biosorbent in the metal-containing aqueous medium, the loaded with the respective heavy metal biomass with an ultrafiltration laboratory module, wherein a single-stage ultrafiltration was operated separated. The filtrate obtained in the biomass separation was examined in each case subsequently for the current heavy metal residual concentration. For the analytical verification of the Me ^{n +} concentration, except for the Hg content, the AAS method and the usual wet chemical digestion method were used. The determination of the mercury concentrations was carried out with the device system A 511 REKANA BV

From the comparison of the respective heavy metal concentrations in the starting solution (C _Me , ₀ ) and in the resulting filtrate after the single-stage ultrafiltration treatment of the homogenized volume flow, precise information can be obtained

both on the achieved sorption or heavy metal uptake rates in mg Me ¹¹ Vg BTS and over limit concentrations, dio in particular in toxic metals such as mercury, are of extraordinary importance derived.

Microorganism: Acetobacter methanolicus (MB58) IMET 8346 Cultivation, Biosorption and Biomass Separation as described above Type of solution: Model solution Heavy metal ion: Mo ²⁺

Process parameters of biosorption

pH = 1.6

t = 10min

Cbts = 2.5g BTS / l

T = 2O ⁰ C

C _Mo = 136 mg / l

Proven sorption rate: 68mg Mo ² Vg BTS uptake rate: 50% of the Mo ^{2+ of} the starting solution

Example 2 Microorganism: Methylobacillus p. M 127IMET 11070 Cultivation, biosorption and biomass separation analog Ex 1 type of solution, metal ion to be sorbed and Parameter setting analogous to example 1

Proven Sorption Rate: 99mg Mo ² Vg DTS

Acquisition rate: 73% of the Mo ^{2+ of} the starting solution Example 3 Microorganism: Acetobacter methanolicus (MB58) IMET B Cultivation, Biosorption and Biomass Separation analog Ex. Type of solution: Model solution Metal ion: Co ²⁺ Process parameters in the biosorption

pH = 3.5

t = 10min Cbts = 3.5g BTS / 1

T = 17 ⁰ C Cco = 583 mg / l

Proven sorption rate: 396mg Co ² Vg BTS uptake rate: 68% of the Co ^{2+ of} the starting solution

Example 4 Microorganism: Methylobacillus p. MB 127IMET11070 Cultivation, biosorption and biomass separation analogous to Example 1 Metal ion: Hg ²⁺ Process Parameters in Biosorption '"

pH = 4

t = 10min

Cbts = 2.54 g BTS / I

C _Hfl = 45mg Hg / l

T = 20 ^° C.

Proven scrub rate: 6-20mg Hg / g BTS uptake rate: up to 44% of the Hg of the starting solution

Claims (4)

1. A method for microwave heavy metal removal from waste water by sorption and accumulation of or in biomass at ambient temperature and atmospheric pressure in weakly basic to acidic range, characterized in that a set heavy metal waste stream V ₁ and a present in the aqueous phase controlled Biomassesuspensionastrom V ₂ continuously in be mixed with one another such that highly turbulent flow fields arise in the biosorption reactor and 1 g biomass dry substance is used per liter of mixture of V ₁ and V ₂ for heavy metal 10mg, so that heavy metals and heavy metal compounds in the order of greater than 6 mg per g of suspended biomass within a Time of a maximum of 10 minutes are bound and after subsequent solid-liquid separation with recirculation of at least one third of the separated heavy metal biomass laden the heavy metal content of the waste water below 0.05 mg heavy metal pr o liter of wastewater is lowered under maximum load of the biomass and the heavy metal is recovered by known work-up methods. 2. The method according to claim 1, characterized in that sorption and accumulation in the biosorption reactor in the pH range of 1.5 to 3 are performed. 3. The method according to claim 1 and 2, characterized by ι jß preferably microorganism strains of the genera Acetobacter, Methylbacillus, Yarrowia and mixed populations of the strains mentioned are used as biosorbents. 4. Arrangement for microwave heavy metal removal from waste water consisting of acid tank, Abwasserdeponiebehälter, Biosorptionreaktor and a device for solid-liquid separation, characterized in that the means for solid-liquid separation with the sorption reactor is coupled so that a bypass piping system at least one third of the separated heavy metal-loaded biomass controlled directly to the biomass suspension flow V ₂ or the head of the Biosorptionsreaktors is fed back.