Energy dissipation estimates in oscillating grid setup: LDV and PIV measurements

The dissipation of turbulent kinetic energy has been increasingly used as a scaling parameter to integrate microbiological accrual and metabolic rates with fluid-flow motion in natural and engineered aquatic ecosystems. The estimation of turbulent kinetic energy under field conditions and the generation of energy dissipation rates under controlled laboratory conditions with microbiological organisms are necessities required to integrate environmental/ecological laboratory protocols with a moving fluid in the environment. Turbulent fluid-flow conditions were generated in an oscillating grid setup, and turbulence variables were quantified using laser-Doppler velocimetry (LDV) and particle image velocimetry (PIV) measuring techniques. The rate of dissipation of the turbulent kinetic energy in the setup ranged from 10⁻⁹ to 10⁻⁴ m²/s³ and was similar to the levels of energy dissipation commonly reported in engineered and natural aquatic ecosystems. Time-averaged velocities were close to zero with the root-mean-square velocity ratios about 1, indicating nearly isotropic fluid-flow conditions in the setup. The velocity spectra, obtained by stationary LDV measurements for the vertical and horizontal velocity components across the setup revealed the existence of inertial subrange with the frequency power scaling law of “ω ^−5/3.” The estimated Eulerian frequency spectrum followed the theoretical functional relation and confirmed the applicability of inertial dissipation method for the estimation of turbulent kinetic energy dissipation rates. PIV was used for a direct estimation of dissipation by evaluating spatially distributed velocity gradients. The direct dissipation estimate in conjunction with the estimated Eulerian frequency spectrum provided evaluation of a “universal” constant, α, commonly used for the estimation of an energy dissipation rate over the inertial subrange of the Eulerian spectrum. The results demonstrated a range of values, rather than a universal constant, of α with a lognormal probability distribution for vertical and horizontal velocity components. In order to encompass a 0.955 probability range under the lognormal distribution the universal constant, α, should be in the range 2.91 ≥ α _u ≥ 0.43 and 4.44 ≥ α _w ≥ 0.42 for horizontal and vertical velocity components, respectively.     

Degradation of microcystins using immobilized microorganism isolated in an eutrophic lake

The final purpose of our series of studies is to establish a biological removal method of cyanobacteria and their toxic products using immobilized microorganisms that can lyse cyanobacteria and decompose microcystins. To establish the biological removal method in non-point areas and water purification plants, as the first step, we explored bacteria active against the cyanobacterial hepatotoxin microcystin in the present study. Eleven active bacteria were isolated from samples taken from Lakes Tsukui and Sagami, Japan. Among 3 strains (B-9 to B-11) with degradative activity, strain B-9 exhibited the strongest activity. The 16S rDNA sequence of the strain B-9 showed the highest similarity to that of Sphingomonas sp. Y2 (AB084247, 99% similarity). Microcystins-RR and -LR were completely degraded by strain B-9 (SC16) within 1d, which led to an immobilized microorganism with a polyester resin. The degradation of microcystin-RR in a bioreactor using the immobilized strain B-9 was observed and microcystin-RR (> 90%) was completely degraded after 24 h. Microcystin-RR was added to the lake water at regular intervals and the degradation after 24 h was observed in the bioreactor over a 72-d period. An over 80% removal efficiency continued for 2 months, showing that the life of the immobilized B-9 in terms of activity was at least 2 months under the optimized conditions. From these results, this immobilized B-9 is feasible for the practical treatment of microcystins in non-point areas and water purification plants.     

Health-care waste management in Lao PDR: a case study.

This study investigated the health-care waste (HCW) management at each health-care facility level at two selected sites in the Lao People's Democratic Republic (Lao PDR): Vientiane Municipality; and Bolikhamxay province. It focused on the amount of HCW, its segregation and the factors influencing HCW management, particularly segregation procedures. A high proportion of incorrectly segregated medical waste was found at each level of health-care facility. Re-segregation revealed 39, 62, 57 and 37% at national hospital, provincial hospital, district hospital and health centre level, respectively, was poorly segregated. The mean of generated HCW was 0.62 kg/bed per day (Vientiane Municipality) and 0.38 kg/bed per day (Bolikhamxay) at two study sites. A higher proportion of medical waste (MW) from the inpatient department at the primary health-care level was found. Thus, HCW management at primary health-care facilities needs more attention and should be better understood.     

Nitrification model with an inhibitory effect of sea water

A dynamic model of nitrification including bacterial growth equations was developed for the understanding of nitrification in estuaries. Sensitivity analysis based on the model revealed that not only maximum specific growth rates of nitrifiers but also yield constants and initial bacterial concentrations have great effect on the nitrification process.Batch experiments were carried out in order to investigate nitrification rates and an inhibitory effect on nitrification by sea water. The maximum specific growth rate of ammonia oxidizing bacteria in fresh water was estimated as 0.04 (h^?1) using a nonlinear regression method. The sea water content of 10%, 25%, 50% and 100% reduced the maximum specific growth rate of ammonia oxidizing bacteria to 0.027, 0.016, 0.0085 and 0.0028 (h^?1) respectively. The effect of sea water on nitrification was interpreted as noncompetitive inhibition. The computed results of inhibition of nitrification based on the noncompetitive inhibition model are presented.     

Detoxification of hexachlorobenzene by dechlorination with potassium-sodium alloy

Dechlorination of hexachlorobenzene (HCB) was achieved by a liquid potassium–sodium (K–Na)-alloy. HCB in a cyclohexane/benzene solution (22 mmol/l, 4.67 g/l as chlorine) was dechlorinated by almost 100% after a 30-min reaction, indicating high reactivity of K–Na alloy and high proton donating power of cyclohexane. Decreasing orders of chlorobenzenes identified after a 15-min reaction, by amount were 1,2,3,4- > 1,2,3,5- > 1,2,4,5- for tetrachlorobenzenes, 1,2,4- > 1,2,3- > 1,3,5- for trichlorobenzenes, and 1,4- > 1,3- > 1,2- for dichlorobenzenes. It was hypothesized that once one chlorine atom in HCB was replaced with a proton, the adjacent chlorine atom to the proton tended to be replaced with another hydrogen atom. A total of 63 PCBs formed via the Wurtz–Fittig reaction were identified as by-products in the sample after a 15-min reaction. Among PCBs found, 2,3^′,4^′,5-tetrachlorobiphenyl, which was a product from 1,2,4-trichlorobenzene formed via the Wurtz–Fittig reaction, was detected in relatively high concentration (48.9 nmol/ml). The sample obtained from a reaction mixture after 30 min contained only 14 PCBs in trace amounts, indicating that the PCBs formed were also further dechlorinated by K–Na alloy. Non-chlorinated compounds––such as methylbenzene, dimethylbenzene, dimer of tetrahydrofuran, and dicyclohexyl (dimer of cyclohexane)––were also identified in the samples. A method using K–Na alloy developed in the present study dechlorinated satisfactorily HCB at room temperature.     

Enantioselective recognition of mono-demethylated methoxychlor metabolites by the estrogen receptor

Metabolites of methoxychlor such as 2-(p-hydroxyphenyl)-2-(p-methoxyphenyl)-1,1,1-trichloroethane (mono-OH-MXC) and 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (bis-OH-MXC), have estrogenic activity. Mono-OH-MXC is a chiral compound in which the carbon atom bridging two benzene rings is the chiral centre. In previous studies the estrogenic activity of racemic mono-OH-MXC has been measured, and the activity of each enantiomer of this compound has not yet been elucidated. In this study, we evaluated the estrogen receptor-binding activity of each enantiomer of mono-OH-MXC to clarify the enantioselective recognition by the estrogen receptor. (S)-mono-OH-MXC showed 3-fold higher binding activity than that of the (R) enantiomer. The activity of bis-OH-MXC was only 1.7-fold higher than that of (S)-mono-OH-MXC. This result suggests that the one hydroxy group and the orientation of the CCl3 group of mono- and bis-OH-MXCs are important for the interaction with the estrogen receptor. The result also points out the estrogenic activity of methoxychlor after metabolic activation in vivo, which predominantly produces the (S)-mono-OH-MXC, may be higher than estimated from the in vitro activity of racemic mixtures.     

Residues of pharmaceutical products in recycled organic manure produced from sewage sludge and solid waste from livestock and relationship to their fermentation level

In recent years, sludge generated in sewage treatment plants (STPs) and solid waste from livestock being utilized is useful for circulation of nourishment in farmlands as recycled organic manure (ROM). In this study, we determined the residue levels and patterns of 12 pharmaceutical products generated by human activity in the ROMs produced from human waste sludge (HWS), sewage sludge (SS), cattle manure (CM), poultry manure (PM), swine manure (SM) and horse manure (HM).The kind and number of pharmaceutical products detected in ROMs were different. Fluoroquinolones (FQs) were detected at high levels in HWS and SS samples. In addition, the detection frequency and concentration levels of sulfonamides (SAs) in PM and SM were high. Moreover, high concentrations of chlortetracycline (CTC) were found in only SM. These differences reflect specific adherence adsorption of the pharmaceutical products to different livestock and humans. Moreover, it was found that the concentrations of pharmaceutical products and fermentation levels of ROMs had significant positive correlation (r = 0.41, p = 0.024).When the fermentation test of ROM was conducted in a rotary fermentor in a lab scale test, the residue levels of pharmaceutical products decreased effectively except carbamazepine (CBZ). The rates of decrease were in the case of tetracyclines (TCs): 85-92%, FQs: 81-100%, erythromycine: 67%, SAs: 79-95%, trimethoprim: 86% and CBZ: 37% by 30 d. Pharmaceutical products that can be decomposed by fermentation process at the lowest impact of residual antibiotic activities may therefore be considered as environmentally friendly medicines.     

Monitoring of PAHs and alkylated PAHs in aquatic organisms after 1 month from the Solar I oil spill off the coast of Guimaras Island, Philippines

Following the oil spill accident of the Solar I tanker in 2006 off the coast of Guimaras Island in the Philippines, polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs in some aquatic organisms were investigated at Luzaran in Guimaras and Taklong Islands, which were heavily polluted with spilled oil, immediately and 1 month after the accident. The concentrations of total PAHs were 11.9–52.3 ng/g dry weight in fish. Meanwhile, total PAH concentrations in shellfish were 38.0–3,102 ng/g dry weight in Luzaran and 128–236 ng/g dry weight in Taklong. Pyrene, phenanthrene, and fluoranthene were dominant in most fish and chrysene in all shellfish. Significantly higher concentrations of all alkylated homologs were detected in shellfish than in fish. These differences had two possible causes, that is, the differences between fish and shellfish could be attributed to the uptake routes and/or their metabolizing abilities.