Diffusional properties of methanogenic granular sludge: 1H-NMR Characterisation
The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22degreesC with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion coefficients of H2O in the investigated series of mesophilic aggregates were found to be 51 to 78% lower than the self-diffusion coefficient of free water. Interestingly, self-diffusion coefficients of H2O were independent of the aggregate size for the size fractions investigated. Diffusional transport occurred faster in aggregates growing under nutrient-rich conditions (e.g., the bottom of a reactor) or at high (55degreesC) temperatures than in aggregates cultivated in nutrient-poor conditions or at low (10degreesC) temperatures. Exposure of aggregates to 2.5% glutaraldehyde or heat (70 or 90degreesC for 30 min) modified the diffusional transport up to 20%. In contrast, deactivation of aggregates by HgCl2 did not affect the H2O self-diffusion coefficient in aggregates. Analysis of NMR images of a single aggregate shows that methanogenic aggregates possess a spin-spin relaxation time and self-diffusion coefficient distribution, which are due to both physical (porosity) and chemical (metal sulfide precipitates) factors.
| Main Authors: | , , , , , |
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| Format: | Article/Letter to editor biblioteca |
| Language: | English |
| Subjects: | biofilms, coefficients, fatty-acid degradation, mass-transfer, molecular-diffusion, nmr, nuclear-magnetic-resonance, porous-media, spin-echo, transport processes, |
| Online Access: | https://research.wur.nl/en/publications/diffusional-properties-of-methanogenic-granular-sludge-1h-nmr-cha |
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