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Denitrification results in the formation of two gaseous end-products: radiatively active greenhouse gas nitrous oxide (N2O) and radiatively inert di-nitrogen (N2). Measuring N2produced by soil microorganisms has historically been difficult because of interference by high background concentrations (780,840 ppm) of atmospheric N2.Here, we applied a new automated technique for simultaneous measurement of the denitrification end-products N2O and N2. We tested the hypothesis that the temperature response function (defined here as Q10) for N2O was greater than for N2under anaerobic conditions in the laboratory. The Q10for N2O was 2.0 and the Q10for N2was 1.4, indicating differences in sensitivity to temperature. Denitrified-N shifted towards N2O as temperature increased. While moisture strongly controls the relative abundance of denitrification end-products, additional experiments are needed to determine how a wider range of temperatures may affect N2O and N2. Results could enhance understanding of temperature controls on N2O production and consumption processes. [ABSTRACT FROM PUBLISHER]

New Zealand has over 1000 anaerobic waste stabilisation ponds treating wastewater from farms and industry. Traditional anaerobic ponds were not designed to optimise anaerobic digestion to produce biogas and are therefore uncovered, releasing biogas to the atmosphere, which can cause odour problems and contributes to GHG emissions. The biogas production and treatment performance of an anaerobic piggery pond retrofitted with a perimeter cover working under field conditions was monitored over a 14 month period. The cover design proved successful in capturing biogas, mitigating odour and GHG issues and coping with New Zealand weather conditions. High solids removal rates (73% and 86% for TS and VS respectively) were achieved. An annual average biogas methane production rate of 0.263 m(3) CH(4)/kgVS(added) was observed, which is similar to gas production rates of mesophilic farm waste digesters, and indicates that the prolonged hydraulic and solids retention times of covered anaerobic ponds can fully compensate for lower operating temperatures. These results suggest that covered anaerobic ponds treating agricultural wastes in New Zealand have great potential to reduce odour and GHG emissions and recover renewable energy, while producing an easy to handle effluent for land irrigation or further treatment.

Waste stabilisation pond (WSP) technology offers some important advantages and interesting possibilities when viewed in the light of sustainable energy and carbon management. Pond systems stand out as having significant advantages due to simple construction; low (or zero) operating energy requirements; and the potential for bio-energy generation. Conventional WSP requires little or no electrical energy for aerobic treatment as a result of algal photosynthesis. Sunlight enables WSP to disinfect wastewaters very effectively without the need for any chemicals or electricity consumption and their associated CO(2) emissions. The energy and carbon emission savings gained over electromechanical treatment systems are immense. Furthermore, because algal photosynthesis consumes CO(2), WSP can be utilised as CO(2) scrubbers. The environmental and financial benefits of pond technology broaden further when considering the low-cost, energy production opportunities of anaerobic ponds and the potential of algae as a biofuel. As we assess future best practice in wastewater treatment technology, perhaps one of the greatest needs is an improved consideration of the carbon footprint and the implications of future increases in the cost of electricity and the value of biogas., ((c) IWA Publishing 2008.)

Two environmental sites in New Zealand were sampled (e.g., water and sediment) for bacterial isolates that could use either arsenite as an electron donor or arsenate as an electron acceptor under aerobic and anaerobic growth conditions, respectively. These two sites were subjected to widespread arsenic contamination from mine tailings generated from historic gold mining activities or from geothermal effluent. No bacteria were isolated from these sites that could utilize arsenite or arsenate under the respective growth conditions tested, but a number of chemoheterotrophic bacteria were isolated that could grow in the presence of high concentrations of arsenic species. In total, 17 morphologically distinct arsenic-resistant heterotrophic bacteria isolates were enriched from the sediment samples, and analysis of the 16S rRNA gene sequence of these bacteria revealed them to be members of the genera Exiguobacterium, Aeromonas, Bacillus, Pseudomonas, Escherichia, and Acinetobacter. Two isolates, Exiguobacterium sp. WK6 and Aeromonas sp. CA1, were of particular interest because they appeared to gain metabolic energy from arsenate under aerobic growth conditions, as demonstrated by an increase in cellular growth yield and growth rate in the presence of arsenate. Both bacteria were capable of reducing arsenate to arsenite via a non-respiratory mechanism. Strain WK6 was positive for arsB, but the pathway of arsenate reduction for isolate CA1 was via a hitherto unknown mechanism. These isolates were not gaining an energetic advantage from arsenate or arsenite utilization, but were instead detoxifying arsenate to arsenite. As a subsidiary process to arsenate reduction, the external pH of the growth medium increased (i.e., became more alkaline), allowing these bacteria to grow for extended periods of time.

The protease activities of 212 strains of rumen bacteria isolated from New Zealand cattle grazing pasture were measured. Thirty-seven per cent of strains had activity greater than or equal to the proteolytic rumen bacterium Prevotella ruminicola and 43 of these isolates were identified by morphology, carbon source utilization, Gram stain, biochemical tests and fermentation end-product analysis. Hierarchical Cluster Analysis showed that the strains formed four clusters: cluster A contained 26 strains and clustered with a reference strain of Streptococcus bovis; cluster C contained three strains and clustered with a reference strain of Butyrivibrio fibrisolvens, while clusters B (10 strains) and D (three strains) did not cluster with any of the remaining rumen bacterial type strains. Further tests identified strains of cluster B as Eubacterium budayi, while cluster D strains most closely resembled B. fibrisolvens and were described as B. fibrisolvens-like. An unclustered strain, C21a, was identified as P. ruminicola. The significance of these proteolytic bacterial populations is discussed in relation to protein breakdown in New Zealand ruminants.

Minimum inhibitory and minimum bactericidal concentrations (MIC, MBC) of tinidazole for 80 New Zealand isolates of anaerobic bacteria were determined. Growth of 95 percent of the isolates was inhibited by 4 micrograms/ml or less of tinidazole. MBC values were the same as, or one dilution higher than, the MIC.