Plant Traits for Phytoremediation in the Tropics

Water is a limited and valuable resource.Singapore has four national sources of water supply,one of which is natural precipitation.Pollutants collected in stormwater runoff are deposited into drainage systems and reservoirs.Major nutrient pollutants found in local stormwater runoff include nitrate and phosphate,which may cause eutrophication.Bioretention systems are efficient in removing these pollutants in the presence of plants.This paper discusses plant traits that can enhance the phytoremediation of nutrient pollutants in stormwater runoff for application in bioretention systems.The plant species studied showed variations in chlorophyll florescence,leaf greenness,biomass production,and nitrate and phosphate removal.In general,dry biomass was moderately correlated to nitrate and phosphate removal(r=0.339–0.501).Root,leaf,and total dry biomass of the native tree species showed a moderate to strong correlation with nitrate removal(r=0.811,0.657,and 0.727,respectively).Leaf dry biomass of fastgrowing plants also showed a moderate to strong relationship with the removal of both pollutants(r=0.707 and 0.609,respectively).Root dry biomass of slow-growing plants showed a strong relationship with phosphate removal(r=0.707),but the correlation was weaker for nitrate removal(r=0.557).These results are valuable for choosing plants for application in bioretention systems.

Modeling 3D Ex-Filtration Process of a Soak-Away Rain Garden

This paper presents a three-dimensional (3D) model developed using COMSOL Multiphysics to understand the 3D ex-filtration process of a soak-away rain garden. With a design hyetograph of 3-month average rainfall intensities of Singapore, it is found that the average vertical ex-filtration rate that is obtained by dividing the average vertical ex-filtration (drained through bottom of the soak-away rain garden, averaged over the simulation period = 720 min, and expressed in m3) by the surface area of the soak-away rain garden and the simulation time step is almost constant regardless of increase in saturated hydraulic conductivity (K) of the in-situ soil and the surface area of the soak-away rain garden as a percentage of catchment area. However, as depth to groundwater table which is measured from bottom of the filter media increases, in between 0.5 m and 1 m of depth to groundwater table, the average vertical ex-filtration rate decreases significantly (by around 15 - 20 mm/hr) and the decrease is almost twice, compared with that between 1 m and 1.5 m of depth to groundwater table. Furthermore, this study shows that for a given K of in-situ, K of filter media, and depth to groundwater table, as the surface area of the soak-away rain garden increases, the horizontal flow coefficient which is defined as the ratio between total horizontal ex-filtration (drained through sides of the soak-away rain garden, summed over the simulation period, and expressed in m3) and total vertical ex-filtration (drained through bottom of the soak-away rain garden, summed over the simulation period, and expressed in m3) decreases. Moreover, for a given surface area of the soak-away rain garden, K of in-situ, and depth to groundwater table, the horizontal flow coefficient decreases as K of the filter media increases. However, it is found that for a given surface area of the soak-away rain garden, K of in-situ, and K of filter media, the horizontal flow coefficient increases as depth to groundwater table increases.

Multiple Regression Model of a Soak-Away Rain Garden in Singapore

Under the possible hydrological conditions, with a design hyetograph of 3-month average rainfall intensities of Singapore, multiple regression equations on hydrological processes, specifically on overflow volume, average vertical ex-filtration rate and horizontal flow coefficient, of a soak-away rain garden are established based on simulated results of a mathematical model. The model that is based on Richard’s equation is developed using COMSOL Multiphysics. The regression equation on overflow volume and the regression equation on log of horizontal flow coefficient show a very strong relationship with the independent variables (saturated hydraulic conductivity of the filter media, saturated hydraulic conductivity of the in-situ soil, depth to groundwater table, and surface area of the soak-away rain garden). The coefficients of determination of the fitted equations on overflow volume and log of horizontal flow coefficient were 0.992 and 0.986, respectively. However, the regression equation on average vertical ex-filtration rate has high p-values (p-values > significance level, α = 0.01) for saturated hydraulic conductivity of the in-situ soil and surface area of the soak-away rain garden. Thus, forward stepwise regression was used to develop the best regression equation on average vertical ex-filtration rate with saturated hydraulic conductivity of the filter media and depth to groundwater table. The coefficient of determination of the fitted equation was found to be 0.911. These easy to use regression equations will be of great utility for local mangers in the design of soak-away rain gardens.

Easy-to-Use Look-Up Hydrologic Design Charts of a Soak-Away Rain Garden in Singapore

As catchments become urbanized due to population growth the impervious surfaces created by buildings and pavements in the expense of permeable soil, depressions, and vegetation cause rainwater to flow rapidly over the landscape. To mitigate the adverse impact of urbanization such as increased flooding and depleted groundwater recharge, around the world, several best management practices, in other words, green infrastructures have been practised, and soak-away rain garden is one of them. However, to have a rapid assessment of soak-away rain gardens on a range of potential hydrologic conditions (e.g., size of the soak-away rain garden, saturated hydraulic conductivity of the in-situ soil, and saturated hydraulic conductivity of the filter media), hydrologic design guidelines or design charts of soak-away rain gardens that are specific for local conditions are not currently available for many regions including Singapore. Thus, in this paper, with a design hyetograph of 3-month average rainfall intensities of Singapore, hydrologic design charts, especially, design charts on overflow volume (as a % of total runoff volume) of soak-away rain gardens are established for a range of potential hydrologic conditions by developing a mathematical model based on Richard’s equation using COMSOL Multiphysics, a finite element analysis and solver software package for various physics and engineering applications. These easy-to-use look-up hydrologic design charts will be of great utility for local managers in the design of soak-away rain gardens.

An Interface to Model 3D Hydrological Process of a Soak-Away Rain Garden

To mitigate the adverse impact of urbanization around the world, several best management practices, in other words green infrastructures, have been used in a way that protect the natural hydrology of the catchment and are more beneficial to the environment. Soak-away rain garden, shallow, landscaped depressions commonly located in parking lots or within small pockets in residential areas, is one of those best management practices or green infrastructures. However, though in the past few decades the mathematical modeling work and the science of computer simulation have enhanced the understanding of hydrological processes, there is still a lack of modeling studies that focus on understanding the three-dimensional (3D) hydrological processes, such as the 3D ex-filtration process of a soak-away rain garden in a sufficient level of details. Thus, this paper develops a 3D mathematical model to represent the hydrological processes of a soak-away rain garden using COMSOL Multiphysics Java API, a Java-based interface of COMSOL Multiphysics. The developed model is demonstrated with a design hyetograph of 3-month average rainfall intensities of Singapore.

Effect of ozone on the performance of a hybrid ceramic membrane-biological activated carbon process

Two hybrid processes including ozonation-ceramic membrane-biological activated carbon （BAC） （Process A） and ceramic membrane-BAC （Process B） were compared to treat polluted raw water. The performance of hybrid processes was evaluated with the removal efficiencies of turbidity, ammonia and organic matter. The results indicated that more than 99% of particle count was removed by both hybrid processes and ozonation had no significant effect on its removal. BAC filtration greatly improved the removal of ammonia. Increasing the dissolved oxygen to 30.0 mg/L could lead to a removal of ammonia with concentrations as high as 7.80 mg/L and 8.69 mg/L for Processes A and B, respectively. The average removal efficiencies of total organic carbon and ultraviolet absorbance at 254 nm （UV254, a parameter indicating organic matter with aromatic structure） were 49% and 52% for Process A, 51% and 48% for Process B, respectively. Some organic matter was oxidized by ozone and this resulted in reduced membrane fouling and increased membrane flux by 25%-30%. However, pre-ozonation altered the components of the raw water and affected the microorganisms in the BAC, which may impact the removals of organic matter and nitrite negatively.

Role of water chemistry on estrone removal by nanofiltration with the presence of hydrophobic acids

Hydrophobic acid organic matter （HpoA） extracted from treated effluent has been known to improve the rejection of steroid hormone estrone by reverse osmosis （RO） and nanofiltration （NF） membranes. In this study, the effects of solution chemistry （solution pH and ionic strength） on the estrone rejection by NF membrane with the presence of HpoA were systematically investigated. Crossflow nanofiltration experiments show that the presence of HpoA significantly improved estrone rejection at all pH and ionic strength levels investigated. It is consistently shown that the ＂enhancement effect＂ of HpoA on estrone rejection at neutral and alkaline pH is attributed to the binding of estrone by HpoA macromolecules via hydrogen bonding between phenolic functional groups in feed solutions, which leads to an increase in molecular weight and appearance of negative charge. The membrane exhibited the best performance in terms ofestrone rejection at pH 10.4 （compared to pH 4 and pH 7） as a result of strengthening the electrostatic repulsion between estrone and membrane with the presence of HpoA. At neutral pH level, the ability of HpoA macromolecules to promote estrone rejection became stronger with increasing ionic strength due to their more extended conformation, which created more chances for the association between estrone and HpoA. The important conclusion of this study is that increasing solution pH and salinity can greatly intensify the ＂enhancement effect＂ of HpoA. These results can be important for NF application in direct/indirect potable water reuse.

Intense,wideband optical waveform generation by self-balanced amplification of fiber electro-optical sideband modulation

We demonstrate a simple method to obtain accurate optical waveforms with a gigahertz-level programmable modulation bandwidth and a watt-level output power for wideband optical control of free atoms and molecules.Arbitrary amplitude and phase modulations are transferred from microwave to light with a low-power fiber electro-optical modulator.The sub-milliwatt optical sideband is co-amplified with the optical carrier in a power-balanced fashion through a tapered semiconductor amplifier(TSA).By automatically keeping TSA near saturation in a quasi-continuous manner,typical noise channels associated with pulsed high-gain amplifications are efficiently suppressed.As an example application,we demonstrate interleaved cooling and trapping of two rubidium isotopes with coherent nanosecond pulses.

Photocatalytic degradation of the acetaminophen by nanocrystal-engineered TiO_(2)thin film in batch and continuous system

Un-biodegradable pharmaceuticals are one of the major growing threats in the wastewaters.In the current study,TiO_(2)thin film photocatalysts were designed by nanocrystal engineering and fabricated for degradation of the acetaminophen(ACE)in a photocatalytic reaction under UV light irradiation in batch and continuous systems.The photocatalyst was prepared by sputtering and then engineered by thermal treatment(annealing at 300℃(T300)and 650℃(T650)).The annealing effects on the crystallinity and photocatalytic activity of the TiO_(2)film were completely studied;it was found that annealing at higher temperatures increases the surface roughness and grain size which are favorable for photocatalytic activity due to the reduction in the recombination rate of photo-generated electron-hole pairs.For the continuous system,a flat plate reactor(FPR)was designed and manufactured.The photocatalytic performance was decreased with the increase of flow rate because the higher flow rate caused to form the thicker film of the liquid in the reactor and reduced the UV light received by photocatalyst.The reusability and durability of the samples after 6 h of photocatalytic reaction showed promising performance for the T650 sample(annealed samples in higher temperatures).

Application of proteomics in environmental science

Proteomics involves the separation of proteins,identification of the amino acid sequence of the interested or target proteins,study of the function of the proteins,modification,structure and ultimate assignments to functional pathways in the cell.The proteomic investigations have contributed greatly to human diseases studies,new drugs discovery researches,and environmental science in recent years.This article provides a review on the development of the main proteomic technologies,including both the gel based and non-gel based technologies,and their applications in environmental science.Proteomic technologies have been utilized in the environmental stresses studies to analyze the induction or reduction of proteins at expression level and identify the target proteins to investigate their function in response to environmental stresses,such as high or low pH,oxidation stress,and toxic chemicals.Such protein responses are also helpful to understand the mechanisms of some cellular activities and the functions of some proteins.