Fungal based nitrogen and phosphorus concentration reduction in wastewater.

摘要

This research project investigated the development of a fungal nitrogen a phosphorus wastewater treatment system. Fungi were isolated from a unit process at the Gold Bar Wastewater Treatment Plant. A subset of the isolates were tested using batch reactors to determine the initial kinetic description of nitrogen and phosphorus decrease from wastewater. Test conditions evaluated included: aerobic, microaerophilic and anoxic atmospheres; pH; dilute wastewater; mixed culture; and successive inoculations. Additional testing was performed using batch and fed-batch attached growth systems with surface to volume ratios of 25 and 50 m2 m-3. It was found that the fungi isolated were capable of a single-step direct ammonium (NH4 +) concentration decrease pathway. This nitrogen decrease system was most active using a microaerophilic environment. A zero-order kinetic model best fit the NH4+ decrease data. Calculated NH 4+ substrate utilisation rates ranged between 0.033 to 0.08 mg-N L-1 hr-1 for the five fungal species tests. However, with suspended growth conditions NH4+ decrease suffered from variable performance. The attached growth NH4 + decrease tests saw a 50% decrease in the variation of the NH4+ utilisation rates. NH4 + utilisation rates observed for the attached growth decrease were also in the range of 0.031 to 0.076 mg-N L-1 hr-1. Fungi were shown to be capable of phosphate (o-PO43-) concentration decrease from wastewater. It was also found that the oxygen tension has a clear role in fungal o-PO43- decrease. Fungi will reduce the concentration of o-PO43- under all three oxygen tensions tested. However, the mechanism of uptake and final biochemical destination of o-PO43- cannot be stated with the data collected. However the data support different mechanisms for the concentration decrease, especially for anoxic uptake and that energy requirements were substantially less than conventional bacterial o-PO 43- systems. The COD to o-PO43- decrease ratio was estimated to be 6.5 g COD:1 g of o-PO4 3-. The major issue for further development of fungal nitrogen and phosphorus treatment technology, the slow substrate utilisation rates, may be addressed by increasing the microbial mass.