IMPROVING THE PERFORMANCE OF ANAEROBIC DIGESTERS AT WASTE-WATER TREATMENT WORKS - THE COUPLED CROSS-FLOW MICROFILTRATION DIGESTER PROCESS

Trials at a wastewater treatment works indicate that cross-flow microf iltration, using flexible woven fibre tubes, could significantly enhan ce the performance of anaerobic digesters. The cross-flow microfiltrat ion unit decouples the solids residence time from the liquid residence time and thus enables the volumetric throughput of the digester to be significantly increased while maintaining a constant solids residence time and volatile solids destruction. In trials on a pilot-plant dige ster, the volumetric throughput was almost doubled, from 70 to 130 l d (-1), while the solids residence time was maintained at 26 days. The e conomic feasibility of the coupled system was evaluated, using permeat e flux data obtained from a cross-flow microfiltration unit coupled to a full-scale digester. The evaluation indicates that the coupled proc ess is economically favourable when compared to conventional digester systems. The coupled system is currently being developed into a full-s cale process. A full-scale CFMF unit is being constructed and will be coupled to a full-scale digester. Over a three year project the long-t erm reliability and operability of the process will be investigated, t ogether with its effect on digester fluid dynamics and biomass viabili ty.