Thomas Pümpel

Heavy metals removal by sand filters inoculated with metal sorbing and precipitating bacteria

Abstract Large volumes of wastewater containing metals such as Cd, Zn, Cu, Pb, Hg, Ni or Co are mainly treated by precipitation processes. However, waters treated in such ways do not always meet regulatory standards. And in many cases, ecotaxes must be paid on the heavy metals load in the discharged water. Therefore, a second polishing treatment is often necessary. In order to be economically acceptable, the technology must be cheap and adapted to the treatment of large volumes. The use of sand filters inoculated with heavy metal biosorbing and bioprecipitating bacteria fulfils these objectives. The system is based on a moving bed sand filter. A biofilm is formed on the sand grains after inoculation with heavy metal-resistant bacteria able to biosorb or to bioprecipitate heavy metals. Passage of the wastewater over these biofilms leads to the binding of the metals to the biofilm and consequently the removal of the metals from the wastewater. The metal-laden biofilm is removed from the sand grains in a sand washer created by an airlift for the continuous movement of the filter bed. The metal-loaded biomass is separated from the sand in a labyrinth on the top of the sand washer. Nutrients and a carbon source are provided continuously in the system in order to promote the regrowth of the biofilm on the sand grains. The reactor can be used for the removal of heavy metals, nitrates and some COD. The obtained biosludge contains heavy metals at concentrations of more than 10% of the dry weight. The treatment of the sludge is also taken into account.

New Insight into Amphotericin B Resistance in Aspergillus terreus

ABSTRACT Amphotericin B (AMB) is the predominant antifungal drug, but the mechanism of resistance is not well understood. We compared the in vivo virulence of an AMB-resistant Aspergillus terreus (ATR) isolate with that of an AMB-susceptible A. terreus isolate (ATS) using a murine model for disseminated aspergillosis. Furthermore, we analyzed the molecular basis of intrinsic AMB resistance in vitro by comparing the ergosterol content, cell-associated AMB levels, AMB-induced intracellular efflux, and prooxidant effects between ATR and ATS. Infection of immunosuppressed mice with ATS or ATR showed that the ATS strain was more lethal than the ATR strain. However, AMB treatment improved the outcome in ATS-infected mice while having no positive effect on the animals infected with ATR. The in vitro data demonstrated that ergosterol content is not the molecular basis for AMB resistance. ATR absorbed less AMB, discharged more intracellular compounds, and had better protection against oxidative damage than the susceptible strain. Our experiments showed that ergosterol content plays a minor role in intrinsic AMB resistance and is not directly associated with intracellular cell-associated AMB content. AMB might exert its antifungal activity by oxidative injury rather than by an increase in membrane permeation.

Treatment of rinsing water from electroless nickel plating with a biologically active moving-bed sand filter

Abstract The MERESAFIN (MEtal REmoval by SAnd Filter INoculation) process presented here was designed to combine the optimum conditions for more than one of the well-known processes of biological metal immobilisation like biosorption and bioprecipitation in a treatment system for industrial waste water. The approach makes use of a continuously operated moving-bed Astrasand® filter which has been inoculated with a mixed population of selected metal biosorbing, bioprecipitating and biodegrading bacteria. One of four pilot plants has been erected at a metal plating company in Vienna (A) to treat waste water from an electroless nickel plating line. In addition to several mg/L of nickel the rinsing water also contains organic acids and inorganic phosphates, which make conventional treatment difficult. Metal laden biomass is continuously removed from the sand grains in the filter and settled in a lamella separator. The thickened biosludge contained 2% of Ni (at only 2–5 mg/L in the feed water), which could be recycled in a shaft furnace. Regeneration of biofilms on the sand is achieved by dosing a cheap carbon source; all other nutrients are available from that specific waste water. For the removal of 0.8 mg/L of nickel the biofilms consumed 8 mg carbon/L and, in addition to 8 mg/L of dissolved oxygen, 3.4 mg NO 3 –N/L as additional electron acceptor. The process was shown to be economically favourable over comparable conventional techniques of metal removal. A further advantage of the biological system is its ability to cleave organo-metal complexes (e.g. nickel lactate in the presented case), to degrade organic molecules like organic acids, surface active substances, etc., often present in industrial waste waters, or to reduce ammonium, nitrite and nitrate. Proposed areas of application comprise the final polishing of industrial and mining water, but also the full treatment of contaminated ground water or drainage water.

Silver tolerance and silver accumulation of microorganisms from soil materials of a silver mine

SummarySilver-tolerant microoganisms were isolated from soil materials of a silver mine. The bacterial count decreased approximately linearly with increasing silver concentration. The fungal count, however, remained almost constant in all flasks, up to a concentration of 1 mM silver. At 10 mM Ag+ (about 1 g/l) and more, neither bacterial nor fungal growth could be observed.All silver-tolerant isolates were tested for silver accumulation capacity. Bacteria accumulated a mean 23 mg Ag+/g dry weight, hyphomycetes 6.7 mg/g dry wt. and yeasts 0.46 mg/g dry wt. The accumulation process of the hyphomycete with the highest accumulation capacity (20 mg/g dry wt.) was shown to be completed after about 30 min. Between 4°C and 80°C the process was nearly independent of temperature; as to the optimum pH, a slight preference for the neutral range was observed. Mycelium destroyed by formaldehyde solution showed the same accumulation pattern. These results would indicate a binding of silver to the surface of the cell.

Lactic acid and methane: Improved exploitation of biowaste potential

This feasibility study investigated a two-step biorefining approach to increase the value gained by recycling of organic municipal solid waste. Firstly, lactic acid was produced via batch fermentation at 37°C using the indigenous microbiome. Experiments revealed an optimal fermentation period of 24h resulting in high yields of lactic acid (up to 37gkg(-1)). The lactic acid proportion of total volatile fatty acid content reached up to 83%. Lactobacilli were selectively enriched to up to 75% of the bacterial community. Additionally conversion of organic matter to lactic acid was increased from 22% to 30% through counteracting end product inhibition by continuous lactic acid extraction. Secondly, fermentation residues were used as co-substrate in biomethane production yielding up to 618±41Nmlbiomethaneg(-1) volatile solids. Digestate, the only end product of this process can be used as organic fertilizer.

A rapid screening method for the isolation of metal-accumulating microorganisms

SummaryAn agar plate screening method was developed for the rapid isolation of heavy metal-accumulating microorganisms and preliminary estimation of their biosorption capacity. The test is based on the visulaization and interpretation of the metal distribution between agar and colonies by chemical preciptitation with hydrogen sulphide or ammonium sulphide. The heavy metals silver, thallium, lead, copper, nickel and cadmium have been tested successfully. The efficiency of the method is demonstrated for isolating silver-accumulating bacterian and estimating silver biosorption capacity.

Bioremediation technologies for metal-containing wastewaters using metabolically active microorganisms.

Publisher Summary Metal wastes represent a critical loss of nonrenewable resources and pose serious health and ecological risk. International agreements and directives issued by various countries prohibit or strictly control the discharge of hazardous materials such as heavy metals into the environment. With stricter statutory limits imposed by international agencies, the conventional physical-chemical methods for the treatment of metal-containing wastewaters are proving to be expensive and inadequate to meet the required standards. From the description of various full scale, pilot-scale, and expanded-laboratory-scale processes presented in the chapter, it is evident that new and exciting prospects exist for the treatment of metal-containing wastewaters using living microorganisms because of toxicity and ubiquity of metals in the environment. Some microorganisms have mechanisms to sequester and immobilize metals, whereas others actually enhance metal solubility. This chapter describes the various mechanisms involved in microbial metal immobilization and evaluates technologies that have been demonstrated at commercial, pilot, and expanded-laboratory scale. Major part of this chapter is based on extensive patent search and reliable data obtained from researchers and inventors across the globe. It is essential that in the near future wastewater treatment and environmental protection become attractive business opportunities rather than statutory requirements.

Removal of nickel from plating rinsing water with a moving-bed sand filter inoculated with metal sorbing and precipitating bacteria

The MERESAFIN (MEtal REmoval by SAnd Filter INoculation) process presented here was designed to combine the optimum conditions for more than one of the well-known processes of biological metal immobilisation like biosorption and bioprecipitation. The approach makes use of a continuously operated moving-bed AstraSand filter which has been inoculated with a mixed population of metal biosorbing and bioprecipitating bacteria. A pilot plant operating at 1 m 3 /h has been erected at a metal plating company in Vienna to treat waste water from an electroless nickel plating line. In addition to several mg/L of nickel the rinsing water also contains some organic acids and inorganic phosphates, which make conventional treatment difficult. The main laboratory experiments as well as preliminary results from the pilot installation are presented.

Mixing non-Newtonian flows in anaerobic digesters by impellers and pumped recirculation

Abstract In this article, a finite volume method based CFD analysis of the mixing of Newtonian and non-Newtonian flows in anaerobic digesters is conducted. The multiple reference frame method is used to model the mixing which is induced by an impeller rotating within a mechanical draft tube. Moreover, the feeding of biomass is considered in the model formulation. Following the validation of the method against reference data, the mixing of cylindrical and egg-shaped digesters is investigated. The distinguishing feature of this article is that the theoretical findings are adopted for the operation of a real-life anaerobic digester. In the context of a case study slurry flows with high total solids concentrations are investigated.

The ‘behaviour’ of five metal biosorbing and bioprecipitating bacterial strains, inoculated in a moving-bed sand filter

In the course of a RTD-project * we tried to remove nickel from a rinsing water of a plating company in Vienna. To this purpose a moving-bed ‘AstraSand’ filter was inoculated with a mixture of five well investigated (Brite-Euram 5350) bacterial strains with a high potential to biosorb and bioprecipitate heavy, metals. Three of the five bacterial strains ( Pseudomonas mendocina As 302, Arthrobacter sp . BP 7/26, Alcaligenes eutrophus CH 34, Pseudomonas fluorescens K 1/8a and Methylobacillus sp . MB 127) could be adapted separately to the waste water before inoculation was carried out using a mixed culture. On the basis of morphological and physiological characteristics of the bacteria—four of the strains stain gram-negative, one gram-positive; the strains use different carbon sources and some of them bear heavy metal resistances—selective agar media were collated to re-isolate the strains out of the mixture. With this simple method it could be shown that one of the strains, which could not be preadapted to the rinsing water by separate cultivation, was able to survive in the waste water when it was precultured together with the other strains. After the inoculation of the non-sterile moving-bed reactor and during its operation the proliferation of autochthonous microorganisms could be observed in the waste water in a high density. Periodically the composition of the biofilm, grown on the sand particles, and of the planktonic microorganisms was investigated. The influence of continous sand regeneration on the growth of the biofilm was documented regarding different operation models. Eutrophic-, oligotrophic-, Cd-resistant-, Ni-resistant-, As-resistant- and methylo Pseudomonas mendocina AS 302 and Pseudomonas fluorescens K 1/8a), and the family Nocardiaceae (like Arthrobacter sp. BP 7/26). Several re-isolates were related to Acinetobacter calcoaceticus BV ALC. Colonies of this species were found on agar plates containing methanol (No. 22) on nickel containing agar plates (No. 26) and, very frequently, on the medium made of the nickel containing waste water (No. 33). Thus, it can be concluded that Acinetobacter calcoaceticus BV ALC as an autochthonous strain takes part in the biofilm of the moving-bed filter for the waste water treatment of the plating company ‘Skolnik’