Prithvi Simha

Vulnerability assessment of water resources and adaptive management approach for Lesvos Island, Greece

In the Aegean Islands, the continued availability of freshwater resources is of fundamental concern. This study analyzes the freshwater system for the Island of Lesvos by simultaneously conceptualizing various issues surrounding it using vulnerability assessment as a quantitative tool. The endpoint approach to vulnerability assessment was applied by developing a numerical expression based on a set of 25 quantitative and qualitative indicators; the indicators were identified as proxies to reflect the various conspicuous and inconspicuous issues surrounding water resources of the Island. In addition, concurrent visualization of the indicators was carried out by plotting radar charts. The assessment indicated that the Lesvian hydrogeological system has significant vulnerabilities emanating from both natural and anthropogenic pressures in addition to a poor adaptive capacity to counter perturbations; this was corroborated by the composite water vulnerability index which was calculated to be 0.69. Based on the analysis of the assessment results, the priority management targets and existing management optimization tools, the authors propose a quantitative framework that could aid the development of an effective methodology for addressing problems in water resource management; this approach couples adaptive water management with vulnerability assessment. The proposed methodology may represent a tool for identification of better solutions to water management–decision problems and/or provide important insights during decision making in similar environments.

Alkaline dehydration of anion–exchanged human urine: Volume reduction, nutrient recovery and process optimisation

In urine-separating sanitation systems, bacterial urease enzymes can hydrolyse urea to ammonia during the pipe transport and storage of urine. The present study investigated whether it was possible to reduce the urine volume without losing the nitrogen as ammonia. A method for stabilising the urine prior to dehydration was developed. Briefly, fresh human urine was stabilised by passage through an anion-exchanger, added to an alkaline media (wood ash or alkalised biochar), and dehydrated. Urine dehydration was investigated at three temperatures: 40, 45 and 50 °C. The influence of various factors affecting the dehydration process was modelled and the rate of urine dehydration was optimised. Results indicated that 75% (v/v) of the urine has to pass through the ion-exchanger for alkaline stabilisation of urine to occur. At all investigated temperatures, the dehydrator accomplished >90% volume reduction of ion-exchanged urine, > 70% N retention and 100% recovery of P and K. To realise high degree of nutrient valorisation, this study proposes combining source-separation of human urine with alkaline dehydration.