H-1 NMR characterisation of the diffusional properties of methanogenic granular sludge

The diffusive properties of mesophilic methanogenic granular sludge have be en studied using diffusion analysis by relaxation time separated pulsed fie ld gradient nuclear magnetic resonance (DARTS PFG NMR) spectroscopy. NMR me asurements were performed at 22 degrees C with 10 mi granular sludge at a m agnetic field strength of 0.5 T (20 MHz resonance frequency for protons). S pin-spin relaxation (T-2) time measurements indicate that three H-1 populat ions can be distinguished in methanogenic granular sludge beds, correspondi ng to water in three different environments. The T-2 relaxation time measur ements clearly differentiate the extragranular water (T-2 approximate to 10 00 ms) from the water present in the granular matrix (T-2 = 40-100 ms) and bacterial cell associated water (T-2 = 10-15 ms). Self-diffusion coefficien t measurements at 22 degrees C of the different H-1-water populations as th e tracer show that methanogenic granular sludge does not contain one unique diffusion coefficient. The observed distribution of self-diffusion coeffic ients varies between 1.1 x 10(.9) m(2)/s (bacterial cell associated water) and 2.1 x 10(.9) m(2)/s (matrix associated water). (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.