The development and evaluation of a microstill with conductance detection for low level ammonia monitoring in chloraminated water.

Monitoring low levels of ammonia in chloraminated water can be challenging but is important for effectively managing potable water disinfection. The lower the concentration of free ammonia that can be determined, the tighter the control at the disinfection point, which supports better maintenance of chloramine residuals in the distribution system. In this study a micro-distillation technique was used to selectively separate ammonia into a boric acid solution allowing determination by conductance (i.e., micro-distillation and conductance measurement instrument - Micro-DCMI). The optimised technique had a linear calibration range of 0.01-60 mg NH3 L-1 with a limit of detection (LOD) of 0.014 mg L-1 and limit of quantification (LOQ) of 0.045 mg L-1. With the optimum operational parameters of 80 °C distillation temperature, 0.3 L min-1 air flow rate, 0.1 mol L-1 boric acid concentration and 8 min pre-concentration time, a sample throughput of 7 samples per hour was achieved. A laboratory comparison between Micro-DCMI and the standard ammonia selective electrode method was conducted on water samples obtained from a chloraminated drinking water distribution system. The results showed that the ratios of the free ammonia values determined by Micro-DCMI and an ammonia selective electrode were between 0.82 and 1.2 for 11 water samples. A custom-built automated analytical system was evaluated at a water treatment plant in Australia and the results compared favourably with the in plant online ammonia ion selective analyser. This study indicated that the Micro-DCMI method was a simple, robust and low cost online monitoring system suitable for determining low concentration ammonia to manage chloramination.

Lipid Biomarker and Isotopic Study of Community Distribution and Biomarker Preservation in a Laminated Microbial Mat from Shark Bay, Western Australia.

Modern microbial mats from Shark Bay present some structural similarities with ancient stromatolites; thus, the functionality of microbial communities and processes of diagenetic preservation of modern mats may provide an insight into ancient microbial assemblages and preservation. In this study, the vertical distribution of microbial communities was investigated in a well-laminated smooth mat from Shark Bay. Biolipid and compound-specific isotopic analyses were performed to investigate the distribution of microbial communities in four distinct layers of the mat. Biomarkers indicative of cyanobacteria were more abundant in the uppermost oxic layer. Diatom markers (e.g. C25 HBI alkene, C20:4ω6 and C20:5ω3 polar lipid fatty acids (PLFAs)) were also detected in high abundance in the uppermost layer, but also in the deepest layer under conditions of permanent darkness and anoxia, where they probably used NO3 (-) for respiration. CycC19:0, an abundant PLFA of purple sulfur bacteria (PSB), was detected in all layers and presented the most (13)C-depleted values of all PLFAs, consistent with photoautotrophic PSB. Sulfur-bound aliphatic and aromatic biomarkers were detected in all layers, highlighting the occurrence of early sulfurisation which may be an important mechanism in the sedimentary preservation of functional biolipids in living and, thus, also ancient mats.