Othman Al-Mashaqbeh

Effect of media type and particle size on dissolved organic carbon release from woody filtration media.

Sequential batch leaching tests were used to evaluate the mass of DOC released from composted garden organics (yard waste), pine and hardwood under pseudo-equilibrium conditions. All media showed an initial rapid decline in DOC values followed by a slower rate during later time periods. Greater than 50% of the DOC leached occurred within the initial time period (<24 h). The mass of DOC leached varied significantly between the materials and to a lesser degree between different particle size ranges. The pine had the lowest leached DOC fraction (2.8-4.8 mg/g), while the hardwood (21-27 mg/g) and compost (13.6-32.7 mg/g) were significantly greater. The type and processing of the woody material incorporated into these systems can have a significant impact on the treated stormwater.

A one-stage cultivation process for the production of poly-3-(hydroxybutyrate-co-hydroxyvalerate) from olive mill wastewater by Haloferax mediterranei.

Olive mill wastewater (OMW), a highly polluting waste from the olive oil industry, was utilized as sole carbon source for the production of polyhydroxyalkanoate (PHA) by extremely halophilic Haloferax Mediterranei (H. mediterranei) in a one stage cultivation step. H. mediterranei showed remarkable cell growth and tolerated the inhibitory effect of polyphenols present in medium containing 25% of OMW. H. mediterranei cultivation conditions were optimized in medium containing 15% OMW by investigating several parameters that affect the production of PHA. The highest polymer yield (0.2g/L) and PHA content (43% PHA/cell dry mass) were achieved at 37°C, 170rpm and 22% salt concentration. Analysis of the produced PHA revealed the production of copolyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) containing 6.5mol% 3-hydroxyvalerate (3HV). The production of PHBHV was observed without the need for fermentation step or adding external carbon source. The PHBHV displayed reduced melting points at 140.1°C and 154.4°C when compared to homopolymer polyhydroxybutyrate.

Simple models for the release kinetics of dissolved organic carbon from woody filtration media.

The mechanisms and kinetics of dissolved organic carbon (DOC) release from woody materials (pine, hardwood and compost) under non-equilibrium leaching conditions was examined through batch and column tests. Mechanistically based kinetic models (first and second order) had a low predictive power for DOC release compared to those based solely on regression (Elovitch, power law). The DOC release data showed a bi-phasic response, with an early period of rapid release (<24h) controlled by film diffusion followed by a slower rate controlled by intra-particle diffusion. After flow interruption, DOC release was primarily controlled by intra-particle diffusion; however, the specific rate parameters generally varied with each flow cycle and between different wood types.

Non-equilibrium zinc uptake onto compost particles from synthetic stormwater.

Zinc uptake onto different particle size compost was evaluated in batch and column studies using a synthetic stormwater to quantify sorption capacity and kinetics. The results showed that the pseudo equilibrium time for uptake increased from 2h to greater than 120h as the particle size of compost increased from 75μm to 6.75mm. This was due to intra-particle diffusion becoming a rate limiting process as the particle size increased. Column effluent data with 1.18mm particles could be fitted by Freundlich isotherm while that from the 4.75mm particles and a mixed particle size columns showed rate limited sorption with tailing and could not be adequately fitted using an equilibrium based isotherm. The results have established rate-limited sorption in amended filtration media due to larger particles under these flow conditions. This needs to be accounted for in the design of these filtration media and during performance modelling.

Hydraulics stability of compost-based filtration media

The longevity of compost-based storm water filtration systems has not been widely studied. Hydraulic conductivity measurements of compost amended sand media (20% and 50% v/v) within columns were undertaken. The results show that the filtration media in both columns had a reduction in the total saturated hydraulic conductivity. A tracer test showed there was no blockage due to biological or chemical fouling of the compost-sand (20% v/v) media. Particle size distributions results for the compost-sand (50% v/v) media suggest that there was minor degradation of compost particles. It appears gas production causing physical blockage was the most likely cause of the decline. It is recommended that compost filters are not run continuously but have drying periods which would allow any gas build-up to escape.

Occurrence of rate limited sorption in stormwater biofiltration systems

Batch and column studies were conducted using synthetic stormwater with mixtures of 0.6 mm glass beads and compost particles of either 1.18 or 4.75 mm. Batch tests showed that rate limited uptake of zinc occurred onto both particle sizes. The column containing the 1.18 mm particles could be fitted by a Freundlich sorption isotherm while the other column exhibited a diffuse front and tailing and could not be modelled using equilibrium isotherms. The sorption capacity of the compost for zinc was estimated at 12.5 mg/g and 9.1 mg/g for the 1.18 mm and 4.75 mm particle size fractions, respectively.