| Semi-continuous anaerobic digestion and aerobic composting processes were used to investigate the feasibility of treating biosolids from a land based aquaculture facility. The investigation was divided into three phases: characterization and respirometeric evaluation of biochemical methane production potential (BMP) of aquaculture biosolids, laboratory-scale batch fed anaerobic digestion of aquaculture solids without and with dilution, and respirometric evaluation of aerobic compostability of raw and digested biosolids. The characterization and BMP evaluation of aquaculture biosolids suggested that these can be anaerobically digested. Following the characterization and BMP evaluation a semi-continuous anaerobic digestion study at volatile solids (VS) loading of 0.6, 1.2, and 1.8 Kg VS/m3.d was conducted. The digester performed well up to the loading rate of 1.2 Kg VS/m3 .d. It was observed that the digester performance was adversely impacted due to increase in ammonia concentration at the loading 1.8 Kg VS/m 3.d. However, the anaerobic digestion of diluted biosolids led to the increased level of volatile fatty acids (VFA) in the form of propionic acid at the same VS loading rate. This also adversely affected the performance of anaerobic digester. A parallel respirometric evaluation of the aerobic composting process of the aquaculture biosolids blended with paper sludge showed a rapid oxygen uptake and low reduction of VS and moisture content with significant loss of nitrogen. This suggested the unsuitability of treating raw aquaculture biosolids using aerobic composting. In contrast, the anaerobically digested biosolids blended with paper sludge showed potential of aerobic composting. Overall it was concluded that an integrated treatment system including anaerobic digestion followed by aerobic composting of digested solids can be used for the management of the aquaculture biosoilds. |
