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Aerobic biodegradation of polyhydroxybutyrate (PHB) was investigated. Mass loss experiments were performed to determine degradation kinetics. Tributyl citrate was blended with some test samples to determine the impact of a natural plasticizer on biodegradation. Effects of biodegradation in the physical, chemical, thermal, and mechanical properties of the materials tested were determined. Plates of different thicknesses (0.24, 1.2, 3.5, and 5.0 mm) were degraded to determine the effect of initial mass:initial surface area ratio on degradation rates. The mass:initial surface area is proportional to the plate thickness. PHB biodegradation rates obtained are dependent on the mass:surface area ratio. Temperature affects the relation of degradation rate to initial mass:initial surface area. PHB in plates up to a thickness of 3.5 mm can degrade completely in compost. Plates with an initial mass:initial surface area ratio of

The marshland upwelling system (MUS) was developed as an onsite wastewater treatment approach for coastal dwellings. The MUS removes fecal bacteria in injected wastewater by utilizing the processes of filtration, straining, adsorption, predation, and die-off through saturated subsurface sediments. The objective of this research was to evaluate the long-term sustainability of the MUS by evaluating removal efficiency of fecal bacteria from raw wastewater and assessing the system background recovery after the MUS stopped operation. Based on 32-month monitoring on an MUS site located in Bayou Segnette Canal Waterway, Louisiana, we found that the MUS compared well with other constructed wetland systems. The MUS showed an enhanced efficacy of fecal bacteria removal after long-time operation due to the deposition of solid particles from primary wastewater and the growth of biofilm in subsurface over time. Moreover, the background recovery study indicates that the subsurface environment has recovered com...

The effectiveness of the marshland upwelling system (MUS) installed in a low-background salinity area was investigated for the removal of fecal bacteria from domestic wastewater. It was hypothesized that travel distance required to meet the treatment objectives would be greater under low-salinity conditions. A suite of three injection regime (flow rate/frequency; 18.9 L/min-15 min/h; 0.95 L/min-15 min/h; and 1.9 L/min-15 min/h) studies was performed over a 1.25-year period to investigate the impact of injection flow rate on the removal of fecal coliforms and Escherichia coli from domestic wastewater injected into the MUS system. Each injection regime resulted in removal efficiencies greater than 99.9% for fecal coliforms and E. coli. The 18.9 L/min study (10 times design flow rate) tested the upper hydraulic loading limit of the system and resulted in eventual system channelization. First-order removal rate constants were estimated as 2.5–2.6 and 1.5–1.7 m–1 for the 0.95 and 1.9 L/min studies, respectivel...

Polarized optical microscopy, scanning electron microscopy, and X-ray microprobe analysis were used to investigate the effect of sea water on phosphogypsum (PG):cement composites. Thin surface sections were taken from 85%: 15% PG:cement composites that had been submerged under natural seawater conditions for 1 month and 70%:30% PG:cement composites that had been submerged under natural seawater conditions for 1 year. The optical microscopy results revealed a crystalline layer of carbonates on the surface of the 70%:30% composites, which was absent on the 85%:15% composites. Microprobe analyses indicated that the carbonates, in the form of CaCO3, were formed from Ca2+ and CO32− contained in the seawater, not from the composites. This CaCO3 coating may act as a physical barrier to seawater intrusion into the composites, preventing block degradation. The polarized optical and scanning electron microscopy images of the 85%:15% composites showed surface disruption, which is hypothesized to be caused b...