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BACKGROUND The simultaneous treatment of selenite and phenol containing wastewater in batch and continuous systems, inoculated with pellets of Phanerochaete chrysosporium, was evaluated in this study. RESULTS Synthetic oil refinery wastewater containing 15 mg L-1 selenite and 100 - 600 mg L-1 phenol was used in batch incubations for 5 days. Orange-red colored pellets developed during selenite incubations in the presence of up to 400 mg L-1 of phenol, which confirms the formation of elemental selenium with removal efficiencies ranging from 57 - 78.5% and 75 - 90.8% for, respectively, phenol and selenite. Continuous experiments in two upflow fungal pelleted bioreactors (30 oC, pH 4.5, hydraulic retention time of 16.7 h) fed the synthetic oil refinery wastewater containing phenol or phenol with selenite were performed for 38 days. The maximum removal efficiency of phenol in the fungal bioreactor was 100% (up to day 26). CONCLUSION The selenite mass balance showed the overall maximum removal efficiency of selenite in the presence of phenol was 67.3%. The critical phenol and selenite loading rates of the upflow bioreactors were ~12 and 4.3 mg L-1.h-1, respectively.

We consider the relationship between taxes and the size of the underground economy in New Zealand. Previous studies indicate that a positive relationship exists in this and certain other countries. We address the following question: "Is the response of the underground economy to an increase in taxes the same as its response to a decrease in taxes?" To answer this question we modify an existing methodology for testing for both "timing symmetry" and "pattern symmetry". Paying careful attention to the non-stationarity and cointegration of our annual data, we test for the presence of such symmetry in the tax-evasion relationship for New Zealand. We find that although the effect on the underground economy of an upward movement in the effective tax rate is numerically greater than that of a downward tax movement, this difference is not statistically significant in either the short-run or the long-run. Elasticity and multiplier calculations allow us to quantify some of the effects of changes in taxation policy on hidden output.