| Popis: |
The bioleaching process is, besides metallurgy, a promising technology for the decontamination of waste solids and contaminated soils. In this work, bioleaching was executed and evaluated for decontamination and nutrient recovery from heavy metal loaded solids. By comparing the bioleaching behavior of different waste solids (ash, sludge and soil) it was possible to shape process conditions to predict the decontamination of solids before starting the bioleaching process. Two effects are predominantly responsible for a successful decontamination of waste solids. First factor is the matrix of the solid, in particular the thermal pre-treatment. By incinerating waste or sludge the attachment behavior of metals can change. This leads to changes in metal solubility. The second factor is the buffer capacity of the waste solid in aqueous solution. A high buffer capacity leads to the inhibition of microbial activity and a decreasing metal release. The toxicological evaluation of the bioleached solids was done by LAGA and LAWA guidelines and by ecotoxicological tests. With bioleaching process the heavy metal loaded solids can be decontaminated according to LAWA and LAGA guidelines. The occurrence of toxic metal species during the bioleaching process, like chromium VI, can be excluded. The bioleached solids are less ecotoxic than the untreated waste solids. The results show, that the bioleaching process is an economical technology for the decontamination of waste solids. The combination of the bioleaching process with a microbial phosphorus recovery, is a new approach in environmental technology. With the bioleaching process, besides heavy metals, phosphorus can be resolved from phosphorus enriched waste solids, like sewage sludge incineration ash and sewage sludge. These days, the separation of resolved phosphorus from solved heavy metals is realized by costly processes like membrane techniques or volatilization. In this work the combination of the two microbiological processes bioleaching of phosphorus and phosphorus accumulation into biomass by newly AEDS bacterial consortium (Acidithiobacillus enriched digested sludge) is an alternative technique to common physical/chemical processes. The biotechnological process combination is geared to the enhanced biological phosphorus removal (EBPR) in the waste water treatment. In the EBPR phosphate is stored as polyphosphate by special microorganisms into biomass. With the AEDS bacterial consortium phosphorus can be released and recovered in one step. The microbiological principles of the combined phosphorus release and recovery are three metabolic processes:1. Release of phosphorus from sewage sludge incineration ash through bioleaching with Acidithiobacillus ferrooxidans.2. Phosphorus accumulation by polyphosphate accumulating microorganism of Actino-bacteria class.3. Microbiologically induced iron-(III)-phosphate precipitation by Acidithiobacillus fer-rooxidans.The characterization and identification of microorganisms in AEDS bacterial consortium was conducted by using different methods (FTIR, physiological and morphological methods, identification of 16S-rRNA genes and ARDA analysis). By using this variety of methods it was possible to identify up to now unknown polyphosphate accumulating bacteria of Actinobacteria class. The occurring biomass sediment is phosphorus enriched and has low amounts of heavy metals. The accumulated phosphorus is available as polyphosphate and iron-(III)-phosphate. The further characterization of the acidic phosphorus recovery and the identification of the involved microorganisms will be a promising field of future phosphorus recovery research. |
