Reactive transport simulation in a tropical horizontal subsurface flow constructed wetland treating domestic wastewater.

A promising approach to the simulation of flow and conversions in the complex environment of horizontal subsurface flow constructed wetlands (HSSF-CWs) is the use of reactive transport models, in which the transport equation is solved together with microbial growth and mass-balance equations for substrate transformation and degradation. In this study, a tropical pilot scale HSSF-CW is simulated in the recently developed CWM1-RETRASO mechanistic model. The model predicts organic matter, nitrogen and sulfur effluent concentrations and their reaction rates within the HSSF-CW. Simulations demonstrated that these reactions took place simultaneously in the same (fermentation, methanogenesis and sulfate reduction) or at different (aerobic, anoxic and anaerobic) locations. Anaerobic reactions occurred over large areas of the simulated HSSF-CW and contributed (on average) to the majority (68%) of the COD removal, compared to aerobic (38%) and anoxic (1%) reactions. To understand the effort and compare computing resources needed for the application of a mechanistic model, the CWM1-RETRASO simulation is compared to a process-based, semi-mechanistic model, run with the same data. CWM1-RETRASO demonstrated the interaction of components within the wetland in a better way, i.e. concentrations of microbial functional groups, their competition for substrates and the formation of intermediary products within the wetland. The CWM1-RETRASO model is thus suitable for simulations aimed at a better understanding of the CW system transformation and degradation processes. However, the model does not support biofilm-based modeling, and it is expensive in computing and time resources required to perform the simulations.

Safety studies of a recently developed microbicidal contraceptive gel (UniPron) in female baboons (Papio anubis).

To identify any toxicity on the vaginal epithelium, liver and kidney following UIniPron administration, ten healthy female olive baboons (Papio anubis) of reproductive age and of proven fertility were used. Five baboons were each treated with 15 g of UniPron intravaginally twice a week for 20-weeks and venous blood collected before and after each treatment. Venous blood was collected from five control animals as in the experimental females, but these control animals were not given any treatment. The endpoints that were evaluated included clinical chemistry profiles on kidney and liver functions and vaginal histopathology. Female baboons treated with 15 g of UniPron intravaginally showed no detectable adverse effects on clinical chemistry profiles investigated and vaginal histopathology. Repeated intravaginal exposure of female baboons to UniPron did not induce detectable vaginal irritation and there were no detectable histological changes. We conclude that administration of UniPron into baboon vagina did not cause any detectable toxicity.