Hydraulic performance of a proposed in situ photocatalytic reactor for degradation of MTBE in water.

Methyl tert-butyl ether (MTBE) groundwater remediation projects often require a combination of technologies resulting in increasing the project costs. A cost-effective in situ photocatalytic reactor design, Honeycomb II, is proposed and tested for its efficiency in MTBE degradation at various flows. This study is an intermediate phase of the research in developing an in situ photocatalytic reactor for groundwater remediation. It examines the effect of the operating variables: air and water flow and double passages through Honeycomb II, on the MTBE removal. MTBE vaporisation is affected by not only temperature, Henry's law constant and air flow to volume ratio but also reactor geometry. The column reactor achieved more than 84% MTBE removal after 8 h at flows equivalent to horizontal groundwater velocities slower than 21.2 cm d⁻¹. Despite the contrasting properties between a photocatalytic indicator methylene blue and MTBE, the reactor efficiency in degrading both compounds showed similar responses towards flow (equivalent groundwater velocity and hydraulic residence time (HRT)). The critical HRT for both compounds was approximately 1 d, which corresponded to a velocity of 21.2 cm d⁻¹. A double pass through both new and used catalysts achieved more than 95% MTBE removal after two passes in 48 h. It also verified that the removal efficiency can be estimated via the sequential order of the removal efficiency of one pass obtained in the laboratory. This study reinforces the potential of this reactor design for in situ groundwater remediation

Uveitis and Gender: The Course of Uveitis in Pregnancy

The hormonal and immunological changes in pregnancy have a key role in maintaining maternal tolerance of the semiallogeneic foetus. These pregnancy-associated changes may also influence the course of maternal autoimmune diseases. Noninfectious uveitis tends to improve during pregnancy. Specifically, uveitis activity tends to ameliorate from the second trimester onwards, with the third trimester being associated with the lowest disease activity. The mechanism behind this phenomenon is likely to be multifactorial and complex. Possible mechanisms include Th1/Th2 immunomodulation, regulatory T-cell phenotype plasticity, and immunosuppressive cytokines. This clearly has management implications for patients with chronic sight threatening disease requiring systemic treatment, as most medications are not recommended during pregnancy due to lack of safety data or proven teratogenicity. Given that uveitis activity is expected to decrease in pregnancy, systemic immunosuppressants could be tapered during pregnancy in these patients, with flare-ups being managed with local corticosteroids till delivery. In the postpartum period, as uveitis activity is expected to rebound, patients should be reviewed closely and systemic medications recommenced, depending on uveitis activity and the patient's breastfeeding status. This review highlights the current understanding of the course of uveitis in pregnancy and its management to help guide clinicians in managing their uveitis patients during this special time in life