Assessing coastal waters of American Samoa: territory-wide water quality data provide a critical “big-picture” view for this tropical archipelago

The coastal waters of American Samoa’s five high islands (Tutuila, Aunu’u, Ofu, Olosega, and Ta’u) were surveyed in 2004 using a probabilistic design. Water quality data were collected from the near-shore coastal habitat, defined as all near-shore coastal waters including embayments, extending out to 1/4 mile off-shore. Hydrography and water column samples were collected, and water quality data were compared to the Territorial water quality standards for pH, dissolved oxygen (DO), Enterococcus, chlorophyll a, water clarity, total nitrogen, and total phosphorus. All station measurements for pH, DO, and Enterococcus satisfied the local water quality standards, although some fraction of the Territory could not be assessed for either DO or Enterococcus. With respect to chlorophyll a, 66 ± 18% of Territory coastal waters complied with the standard, while 34 ± 18% failed to comply with the standard. For water clarity, 54 ± 18% of the Territorial waters complied with the standard while 42 ± 7% failed to comply. Territorial waters satisfied the standards for total nitrogen and phosphorus 72 ± 17% and 92 ± 10%, respectively. These data provide the first “big-picture” view of water quality in the near shore region around the high islands of American Samoa. While the picture is encouraging, these data suggest emerging water quality concerns.     

Monsoon-induced changes in the size-fractionated phytoplankton biomass and production rate in the estuarine and coastal waters of southwest coast of India

Changes in the autotrophic pico- (0.2–2 μm), nano- (2–20 μm), and microplankton (>20 μm) biomass (chlorophyll a) and primary production were measured in the estuarine and coastal waters off Cochin, southwest coast of India during the onset and establishment of a monsoon. During this period, the estuary was dominated by nutrient-rich freshwater, whereas the coastal waters were characterized with higher salinity values (>30 psu) and less nutrients. The average surface chlorophyll a concentrations and primary production rates were higher in the estuary (average 13.7 mg m^???3 and 432 mgC m^???3 day^???1) as compared to the coastal waters (5.3 mg m^???3 and 224 mgC m^???3 day^???1). The nanoplankton community formed the major fraction of chlorophyll a and primary production, both in the estuary (average 85 ± SD 8.3% and 81.2 ± SD 3.2%) and the coastal waters (average 73.2 ± SD 17.2% and 81.9 ± 15.7%). Nanoplankton had the maximum photosynthetic efficiency in the coastal waters (average 4.8 ± SD 3.9 mgC mgChl a m^???3 h^???1), whereas in the estuary, the microplankton had higher photosynthetic efficiency (average 7.4 ± 7 mgC mgChl a m^???3 h^???1). The heavy cloud cover and increased water column turbidity not only limit the growth of large-sized phytoplankton in the Cochin estuary and coastal waters but also support the proliferation of nanoplankton community during the monsoon season, even though large variation in nanoplankton chlorophyll a and production exists between these two areas.     

Chemical-mineralogical characterisation of coarse recycled concrete aggregate

The construction industry is now putting greater emphasis than ever before on increasing recycling and promoting more sustainable waste management practices. In keeping with this approach, many sectors of the industry have actively sought to encourage the use of recycled concrete aggregate (RCA) as an alternative to primary aggregates in concrete production. The results of a laboratory experimental programme aimed at establishing chemical and mineralogical characteristics of coarse RCA and its likely influence on concrete performance are reported in this paper. Commercially produced coarse RCA and natural aggregates (16-4 mm size fraction) were tested. Results of X-ray fluorescence (XRF) analyses showed that original source of RCA had a negligible effect on the major elements and a comparable chemical composition between recycled and natural aggregates. X-ray diffraction (XRD) analyses results indicated the presence of calcite, portlandite and minor peaks of muscovite/illite in recycled aggregates, although they were directly proportioned to their original composition. The influence of 30%, 50%, and 100% coarse RCA on the chemical composition of equal design strength concrete has been established, and its suitability for use in a concrete application has been assessed. In this work, coarse RCA was used as a direct replacement for natural gravel in concrete production. Test results indicated that up to 30% coarse RCA had no effect on the main three oxides (SiO2, Al2O3 and CaO) of concrete, but thereafter there was a marginal decrease in SiO2 and increase in Al2O3 and CaO contents with increase in RCA content in the mix, reflecting the original constituent's composition.     

Hospital waste management and toxicity evaluation: a case study

Hospital waste management is an imperative environmental and public safety issue, due to the waste's infectious and hazardous character. This paper examines the existing waste strategy of a typical hospital in Greece with a bed capacity of 400-600. The segregation, collection, packaging, storage, transportation and disposal of waste were monitored and the observed problematic areas documented. The concentrations of BOD, COD and heavy metals were measured in the wastewater the hospital generated. The wastewater's toxicity was also investigated. During the study, omissions and negligence were observed at every stage of the waste management system, particularly with regard to the treatment of infectious waste. Inappropriate collection and transportation procedures for infectious waste, which jeopardized the safety of staff and patients, were recorded. However, inappropriate segregation practices were the dominant problem, which led to increased quantities of generated infectious waste and hence higher costs for their disposal. Infectious waste production was estimated using two different methods: one by weighing the incinerated waste (880 kg day(-1)) and the other by estimating the number of waste bags produced each day (650 kg day(-1)). Furthermore, measurements of the EC(50) parameter in wastewater samples revealed an increased toxicity in all samples. In addition, hazardous organic compounds were detected in wastewater samples using a gas chromatograph/mass spectrograph. Proposals recommending the application of a comprehensive hospital waste management system are presented that will ensure that any potential risks hospital wastes pose to public health and to the environment are minimized.     

Landfill leachate treatment using a rotating biological contactor and an upward-flow anaerobic sludge bed reactor

This paper describes the feasibility of an aerobic system (rotating biological contactor, RBC) and a biological anaerobic system (upward-flow anaerobic sludge bed reactor) at small scale for the treatment of a landfill leachate. In the first phase of the aerobic system study, a cyclic-batch RBC system was used to select perforated acetate discs among three different acetate disc configurations. These discs were chosen on the basis of high COD removal (65%) and biological stability. In the second phase, the RBC system (using four stages) was operated continuously at different hydraulic retention times (HRT), at different rotational speeds, and with varying organic concentrations of the influent leachate (2500-9000mgL(-1)). Forty percent of the total surface area of each perforated disc was submerged in the leachate. A COD removal of about 52% was obtained at an HRT of 24h and a rotational speed of 6rpm. For the anaerobic system, the reactor was evaluated with a volumetric organic load of 3273g-COD m(-3) day(-1) at an HRT of 54, 44, 39, 24 and 17h. At these conditions, the system reached COD removal efficiencies of 62%, 61%, 59%, 44% and 24%, respectively.     

Reusing fly ash in glass fibre reinforced cement: a new generation of high-quality GRC composites

New composite materials based on an alkali-resistant glass-fibre reinforced cement (AR-GRC) system are being developed by using fly ash (FA) produced at coal thermoelectric power plants, and fluid catalytic cracking catalyst residue (FC3R) from the petrol industry as cement replacement materials. These wastes are reactive from the pozzolanic viewpoint, and modify the nature and the microstructure of the cement matrix when a part of the Portland cement is replaced in the formulation of GRC. Several microstructural and mechanical aspects are being studied for AR-GRC systems. The behaviour of composites exposed to ageing shows that the pozzolanic activity of the ground FA added in high amounts and its mixture with the FC3R increase the flexural strength and no evidences of strength decay are observed. Additionally, the fibres due to the high alkalinity of the cementing matrix can be deteriorated. Fibres in the control (only Portland cement) and FC3R containing composites were attacked, whereas composites with FA and their mixture with FC3R show that the fibres have not been attacked, due to the pozzolanic activity of replacing materials that reduce the calcium hydroxide content in the cementing matrix.     

Leachate injection using vertical wells in bioreactor landfills

Leachate recirculation or liquid injection in municipal solid waste landfills offers economic and environmental benefits. The key objective of this study was to carry out numerical evaluation of key design variables for leachate recirculation system consisting of vertical wells. In order to achieve the objective, numerical modeling was carried out using the finite-element model HYDRUS-2D. The following design parameters were evaluated by simulating liquid pressure head on the liner and the wetted width of the waste under steady-state flow conditions: (1) hydraulic conductivities of the waste and vertical well backfill; (2) liquid injection rate and dosing frequency; (3) well diameter, screen height and screen depth; and (4) hydraulic conductivity of the leachate collection system, slope of the leachate collection system and spacing of the leachate collection pipes. The key findings of this study are as follows. The well diameter, hydraulic conductivity of the well drainage pack, and screen height and screen depth of the well have very little effect on the wetted width for a given liquid flux. The wetted width and the injection pressure for a given liquid flux decrease with the increase in the hydraulic conductivity of the waste. The pressure head on the liner increases with the decrease in the vertical distance between the bottom of the well screen and the top of leachate collection system. The liquid injection flux increases with the decrease in hydraulic conductivity of the leachate collection system. Unlike sand (k approximately 10(-4)m/s), pea gravel (k approximately 0.01 m/s) resulted in less than 0.3m pressure head on the liner for all simulations carried out in this study.     

Waste polyvinylchloride derived pitch as a precursor to develop carbon fibers and activated carbon fibers

Polyvinylchloride (PVC) was successfully recycled through the solvent extraction from waste pipe with an extraction yield of ca. 86%. The extracted PVC was pyrolyzed by a two-stage process (260 and 410 degrees C) to obtain free-chlorine PVC based pitch through an effective removal of chlorine from PVC during the heat-treatment. As-prepared pitch (softening point: 220 degrees C) was spun, stabilized, carbonized into carbon fibers (CFs), and further activated into activated carbon fibers (ACFs) in a flow of CO2. As-prepared CFs show comparable mechanical properties to commercial CFs, whose maximum tensile strength and modulus are 862 MPa and 62 GPa, respectively. The resultant ACFs exhibit a high surface area of 1200 m2/g, narrow pore size distribution and a low oxygen content of 3%. The study provides an effective insight to recycle PVC from waste PVC and develop a carbon precursor for high performance carbon materials such as CFs and ACFs.     

Effects of environmental methylmercury on the health of wild birds, mammals, and fish

Wild piscivorous fish, mammals, and birds may be at risk for elevated dietary methylmercury intake and toxicity. In controlled feeding studies, the consumption of diets that contained Hg (as methylmercury) at environmentally realistic concentrations resulted in a range of toxic effects in fish, birds, and mammals, including behavioral, neurochemical, hormonal, and reproductive changes. Limited field-based studies, especially with certain wild piscivorous bird species, e.g., the common loon, corroborated laboratory-based results, demonstrating significant relations between methylmercury exposure and various indicators of methylmercury toxicity, including reproductive impairment. Potential population effects in fish and wildlife resulting from dietary methylmercury exposure are expected to vary as a function of species life history, as well as regional differences in fish-Hg concentrations, which, in turn, are influenced by differences in Hg deposition and environmental methylation rates. However, population modeling suggests that reductions in Hg emissions could have substantial benefits for some common loon populations that are currently experiencing elevated methylmercury exposure. Predicted benefits would be mediated primarily through improved hatching success and development of hatchlings to maturity as Hg concentrations in prey fish decline. Other piscivorous species may also benefit from decreased Hg exposure but have not been as extensively studied as the common loon.     

Leachate recirculation effects on waste degradation: study on columns

The purpose of this study is to determine the impact of leachate recirculation on the degradation of municipal solid wastes (bioreactor concept). The study was carried out using columns containing approximately 50 kg of waste, in order to follow waste degradation over a limited time. Three types of waste were studied: fresh waste of standard composition, fresh waste of fermentable composition and some 8-yr-old waste extracted from a site in France. Measurement of the global parameters, such as chemical oxygen demand (COD), volatile acidity, alkalinity, leachate conductivity, methane potential of the wastes and biogas production monitoring (volume of CO2 and CH4 produced), were carried out. The quantity of oxydizable matter and biogas production was increased by the leachate recirculation, and the duration of the first degradation phases was reduced in all cases. Chloride, ammonium and organic pollution accumulation was observed according to the duration of recirculation. After 400 days of degradation, waste stabilization seemed to be reached for all of the recirculated columns (COD<300 mg/L O2, and methane potential reached).