Title:
|
Investigation into dynamic membranes and integration with anaerobic bioreactors
|
Dynamic Membranes (DM) are considered as low-cost alternatives to conventional membranes and offer the possibility of higher flux and lower resistance when carefully applied. The development of this technique was investigated under batch, semi-continuous and continuous studies. Given the variety of materials that could form the support for DM, three potential materials of same pore size but different make were trialled. Batch trials was set up to test the materials before selection of the nylon mesh as the material of choice based on resistance and permeate turbidity. Subsequent investigations on nylon mesh established the limit for substrate TSS concentration (< 5g TSS L-1), below which changes in TMP could be kept low. Tests were carried out using the two modes of operation: Constant flux and constant pressure (gravity - induced flow). In constant flux operation, the TMP rose significantly when the substrate TSS reached 5 g L-1. For constant TMP operation, the flux level did not significantly improve with increased head, indicating that cake layer resistance was the dominant mechanism for DM filtration. Semi-continuous tests explored the possibility of pre-forming the DM under set conditions using a range of flux from 5 to 15 L m -2 h-1, and despite the longer time it took for the DM to form at the lowest flux, it was observed that lower formation flux resulted in stable filtration erformance and solids retention, and permeate turbidity was similar in all cases. Long term studies for the integration of DM with functional anaerobic digesters was carried out by setting up AF digesters and granular digesters for the treatment of tomato wastewater and an external DM for the polishing of the effluent solids. Flux values of around 20 L m-2 h-1 was achieved, whereas the permeate turbidity was generally less than 40 NTU although periods of instability resulted in higher permeate turbidities. The digestate type was shown to influence on DM structure and performance even in an external configuration.
|