Enrichment of 15N/14N in wastewater-derived effluent varies with operational performance of treatment systems: implications for isotope monitoring in receiving environments.

Stable nitrogen isotope ratios are routinely used to trace the dispersion and assimilation of wastewater-derived N in receiving environments, but few isotope studies have investigated wastewater treatment plants and ponds themselves. An improved understanding of N isotope compositions in effluent will help assess treatment plant processes and performance and will help trace sources of excess nutrients in receiving environments. Here, we assess N budgets and treatment processes in seven wastewater treatment plants and wastewater stabilisation ponds in northern Australia based on concentrations and isotope ratios of N in effluent. We show that δ15N values in effluent are linked to treatment type, effectiveness of conversion of ammonia and levels of gaseous N emissions. These relationships suggest that N isotope monitoring of wastewater treatment plants and ponds can provide an integrated assessment of treatment performance and gaseous N emissions on a pond- or plant-wide scale that is not readily available through other methods. Our findings further imply that monitoring N isotope ratios in receiving environments cannot be assumed to be universally effective as their sensitivity to uptake of wastewater-derived N will vary with the characteristics of individual treatment systems. Paradoxically, N isotope monitoring is less effective where treatment systems are functioning poorly and where monitoring needs are the greatest.

Changes in activities-specific balance confidence of active unilateral transtibial prosthesis users after provision of a self-aligning ankle foot.

BACKGROUND: Self-aligning ankle feet have an increased range of motion and are marketed to improve compliance over uneven terrain and increase function and balance; however, much of the existing literature focuses on the biomechanical aspect of these prostheses as opposed to patient-reported measures. OBJECTIVE: To compare activities-specific balance confidence (ABC), health-related quality of life (HR-QoL), perceived mobility, gait speed, and step length before and after provision of a self-aligning ankle foot in the active unilateral transtibial prosthesis user. STUDY DESIGN: Retrospective analysis of prospectively collected data. METHODS: Patient-reported and functional measures were captured for 85 users who were provided with a self-aligning ankle foot. Measures were recorded immediately before self-aligning ankle foot provision and again at 6 months afterward. The primary outcome was the ABC Score, along with the following secondary measures; HR-QoL using EQ-5D-5L Health Index Prosthetic Limb User Survey of Mobility and 10-meter timed walk test. RESULTS: The median age of the cohort was 55.2 years old and 71% were males, with the majority having their transtibial amputation due to trauma. There was a statistically significant improvement in ABC from 76 to 86% (p < 0.001) with a medium effect size. There was no statistically significant improvement in HR-QoL (p = 0.051), Prosthetic Limb User Survey of Mobility (p = 0.043), time taken to walk 10 m (p = 0.15) and step length (p = 0.003). CONCLUSIONS: Self aligning ankle feet increased ABC and step length with no detrimental effect on HR-QoL, perceived mobility or walking speed in those with a unilateral trans-tibial amputation.