Waste stabilisation ponds (WSP) are an important wastewater treatment technology used by thousands of communities around the world. Unfortunately, phosphorus removal in WSP is generally low and inconsistent. The aim of this work was to investigate biological phosphorus removal by microalgae in WSP. Luxury uptake of phosphorus, which is the accumulation of polyphosphate, is known to occur in microalgae in natural systems such as lakes; however, this mechanism has not previously been studied under WSP conditions. Three methods were used in the laboratory to investigate luxury uptake and it was shown for the first time that luxury uptake of phosphorus can occur in microalgae under typical WSP conditions. Acid-insoluble polyphosphate (AISP) is a form of phosphorus storage and acid soluble polyphosphate (ASP) is used for synthesis of cellular constituents. However, the findings of this thesis indicate that ASP may also act as a form of short term storage. The environmental factors influencing luxury uptake were investigated using laboratory experiments conducted under controlled conditions. The key environmental factors were the phosphate concentration in the wastewater, light intensity and temperature. A higher phosphate concentration increased the amount of ASP accumulation and also resulted in AISP being stored within the cells instead of being consumed for growth. Higher light intensity increased ASP accumulation, but as a consequence of elevated growth, the ASP was rapidly consumed. Temperature influenced the rate of AISP accumulation and little if any was accumulated at low temperatures. The fate of polyphosphate in the sludge layer was also studied and it was shown that polyphosphate was degraded resulting in phosphate release. Therefore, to maximise phosphorus removal the microalgae needs to be harvested. Field work showed that at times the biomass contained almost four times the amount of phosphorus required for growth which confirms that luxury uptake does indeed occur in full-scale WSP. To improve phosphorus removal in WSP both luxury uptake and the biomass concentration need to be maximised simultaneously. With this new understanding of biological phosphorus removal in WSP and the key environmental factors required it may be possible to develop a new phosphorus removal process utilising luxury uptake by microalgae.

An eight-lot residential subdivision in central Wairarapa is being developed to demonstrate the principles of sustainable resource management. Local energy sources for low and high grade use, including electricity sourced from proposed grid-integrated, on-site, distributed generation will supplement imported network electricity. A unique component is an internal loop grid for lot connection that interfaces with the local network through a single connection point. A decision model was designed as a decision-support tool for the development based on the annual supply-demand electrical energy balance, site infrastructure covenants and a range of economic and technology criteria. Solar and wind resources were assessed for potential supply of electricity to the community energy system. Three demand profiles were developed using supplied and estimated electrical demand data; and included assumptions on thermal performance of the houses, the use of low-grade heat, user behaviour, and appliance use. Supply and demand were analysed as daily average profiles by hour for each month of the year. The decision model outputs were designed to give a graphic view of the system options. The accompanying output datasets also enabled a number of scenarios for connection configurations, load management, and economic sensitivity to be explored for their impact on the communal approach to managing energy. The viability of the community energy system is significantly influenced by managing demand level in conjunction with system size, capital cost management, and tariffs for electricity import and export. Energy requirements could be best met in the short term by installing a site-wide mixed generation system of sized capacity between 5 and 11kW, supported by metering and information technology to deliver management data to the residents. Future research opportunities exist to continue monitoring technical, economic and social outcomes from this unique community development. Incentivising private investment in userfocussed energy innovations is an option for New Zealand to consider in the current climate of market-driven large scale electricity developments.