Floc-based sequential partial nitritation and anammox at full scale with contrasting N2O emissions

New Activated Sludge (NAS^®) is a hybrid, floc-based nitrogen removal process without carbon addition, based on the control of sludge retention times (SRT) and dissolved oxygen (DO) levels. The aim of this study was to examine the performance of a retrofitted four-stage NAS^® plant, including on-line measurements of greenhouse gas emissions (N₂O and CH₄). The plant treated anaerobically digested industrial wastewater, containing 264 mg N L⁻¹, 1154 mg chemical oxygen demand (COD) L⁻¹ and an inorganic carbon alkalinity of 34 meq L⁻¹. The batch-fed partial nitritation step received an overall nitrogen loading rate of 0.18-0.22 kg N m⁻³ d⁻¹, thereby oxidized nitrogen to nitrite (45-47%) and some nitrate (13-15%), but also to N₂O (5.1-6.6%). This was achieved at a SRT of 1.7 d and DO around 1.0 mg O₂ L⁻¹. Subsequently, anammox, denitrification and nitrification compartments were followed by a final settler, at an overall SRT of 46 d. None of the latter three reactors emitted N₂O. In the anammox step, 0.26 kg N m⁻³ d⁻¹ was removed, with an estimated contribution of 71% by the genus Kuenenia, which constituted 3.1% of the biomass. Overall, a nitrogen removal efficiency of 95% was obtained, yielding a dischargeable effluent. Retrofitting floc-based nitrification/denitrification with carbon addition to NAS^® allowed to save 40% of the operational wastewater treatment costs. Yet, a decrease of the N₂O emissions by about 50% is necessary in order to obtain a CO₂ neutral footprint. The impact of emitted CH₄ was 20 times lower.     

Trace element concentrations in hair of healthy Chinese centenarians

Trace element concentrations, as indicators of micronutrient status of healthy centenarians, have not been widely analyzed. This study aimed to assess trace element concentrations in the hair of healthy centenarians. The effects of gender and age on element concentrations were also investigated. Eleven trace elements (Al, Ba, Cd, Cr, Cu, Fe, Mo, Pb, Se, Sr and Zn) in the scalp hair of 107 healthy Chinese centenarians were examined. The overall reference values (RVs) in mg/kg for the hair concentrations of trace elements in centenarians were as follows: Al, 14.95; Ba, 2.68; Cd, 0.06; Cr, 0.59; Cu, 6.21); Fe, 19.37; Mo, 0.50; Pb, 4.64; Se, 0.37; Sr, 4.84; and Zn, 154.37. Data analysis found that only Cu and Zn concentrations show a normal distribution, and there is no significant difference between males and females in any element except Zn. However, the levels of Al, Cd, Cr, Fe, Mo, Pb decrease and the levels of Ba, Cu, Se, Sr, Zn increase with age in the centenarian cohort. Results also revealed that sufficient Zn and Se concentrations as well as low exposure to heavy metals pollution contribute to the longevity of centenarians. The results imply the possibility of manipulating trace element concentrations, especially Zn and Se concentrations in tissues, as a means for therapeutic modality in geriatric disease.     

Survey of air pollution in Cotonou, Benin--air monitoring and biomarkers

Exposure to genotoxic compounds present in ambient air has been studied in Cotonou, Benin, a city where two-stroke motorbikes are the major form of transportation and gasoline quality is poor. Personal monitoring and biomarkers were used to assess the exposure. Non-smoking taxi-moto drivers (city) and village residents were the study subjects. Benzene exposure was significantly higher in the city, as compared to the village (76.0+/-26.8 microg/m(3) versus 3.4+/-3.0, p=0.0004). Urinary excretion of benzene and S-phenylmercapturic acid (S-PMA) were also highest in subjects living in the city, whereas 1-hydroxypyrene was not different. The level of total polycyclic aromatic hydrocarbons (PAHs), associated with particles, ranged from 76.21 to 103.23 in Cotonou versus 1.55 ng/m(3) for the village. Determination of DNA damage in lymphocytes showed that subjects from the city had elevated number of lesions compared to subjects in the village in terms of bulky DNA adducts, 8-hydroxy-2'-deoxyguanosine and 5-methylcytosine, whereas DNA fragmentations analysed by alkaline gel electrophoresis was not different between the subjects. In conclusion, this study shows that air pollution is pronounced in Cotonou, Bénin and is associated with elevated levels of DNA damage in residents of the city compared to people living in a non-polluted rural village.     

The water quality of the River Thame in the Thames Basin of south/south-eastern England

The water quality of the River Thame, a tributary of the River Thames in the Thames basin, is described in relation to point and diffuse contaminant inputs and runoff from permeable and impermeable bedrock geology with their own characteristic water quality. The data is examined to see if the market town of Aylesbury in the upper part of the catchment influences water quality. Previous studies highlighted the influence of Aylesbury sewage treatment works (STW) on soluble reactive phosphorus (SRP) concentrations in the river before and after phosphorus (P) stripping at the STW. Variations in water quality along the river are described and the study indicates that, apart from SRP, water quality determinants seem to be relatively unaffected by Aylesbury. The Thame water quality is compared with other catchment typologies and it is very similar to that of the main stem of the Thames even though the Thames is mainly Chalk groundwater fed. Differences in water quality largely link to the amount of STW effluent within the rivers and to the endmember compositions of the groundwater and near surface water sources.     

Comparison of anaerobic dechlorinating enrichment cultures maintained on tetrachloroethene,trichloroethene, cis-dichloroethene and vinyl chloride

An anaerobic mixed microbial culture was enriched from soil and groundwater taken from a site contaminated with trichloroethene (TCE). This enrichment culture was divided into four subcultures amended separately with either perchloroethene (PCE), TCE, cis-dichloroethene (cDCE) or vinyl chloride (VC). In each of the four subcultures, the chlorinated ethenes were rapidly, consistently, and completely converted to ethene at rates of 30-50 micromol/l of culture per day, or an average 160 micro-electron equivalents/l of culture per day. These cultures were capable of sustained and rapid dechlorination of VC, and could not dechlorinate 1,2-dichloroethane, differentiating them from Dehalococcoides ethenogenes, the only known isolate capable of complete dechlorination of PCE to ethene. Chloroform (CF) and 1,1,1-trichloroethane, frequent groundwater co-contaminants with TCE and PCE, inhibited chlorinated ethene dechlorination. Most strongly inhibited was the final conversion of VC to ethene, with complete inhibition occurring at an aqueous CF concentration of 2.5 microM. Differences in rates and community composition developed between the different subcultures, including the loss of the VC enrichment culture's ability to dechlorinate PCE. Denaturing gradient gel electrophoresis of amplified bacterial 16S rRNA gene fragments identified three different DNA sequences in the enrichment cultures, all phylogenetically related to D. ethenogenes. Based on the PCR-DGGE results and substrate utilization patterns, it is apparent that significant mechanistic differences exist between each step of dechlorination from TCE to ethene, especially for the last important dechlorination step from VC to ethene.     

Kinetic modelling and microbial community assessment of anaerobic biphasic fixed film bioreactor treating distillery spent wash

Anaerobic digestion, microbial community structure and kinetics were studied in a biphasic continuously fed, upflow anaerobic fixed film reactor treating high strength distillery wastewater. Treatment efficiency of the bioreactor was investigated at different hydraulic retention times (HRT) and organic loading rates (OLR 5-20 kg COD m⁻³ d⁻¹). Applying the modified Stover-Kincannon model to the reactor, the maximum removal rate constant (U_max) and saturation value constant (K_B) were found to be 2 kg m⁻³ d⁻¹ and 1.69 kg m⁻³ d⁻¹ respectively. Bacterial community structures of acidogenic and methanogenic reactors were assessed using culture-independent analyses. Sequencing of 16S rRNA genes exhibited a total of 123 distinct operational taxonomic units (OTUs) comprising 49 from acidogenic reactor and 74 (28 of eubacteria and 46 of archaea) from methanogenic reactor. The findings reveal the role of Lactobacillus sp. (Firmicutes) as dominant acid producing organisms in acidogenic reactor and Methanoculleus sp. (Euryarchaeotes) as foremost methanogens in methanogenic reactor.     

Fish intake and serum levels of organochlorines among Japanese women

This study evaluates background serum levels of selected organochlorine compounds among Japanese women of reproductive age and investigates whether lifestyle factors, especially dietary factors, may be associated with these levels. A cross-sectional study was performed on 80 Japanese women, aged 26-43 years, who complained of infertility and were confirmed not to have endometriosis. The serum levels of total toxic equivalency (TEQ), 18 polychlorinated dibenzo-p-dioxins (PCDDs)/polychlorinated dibenzofurans (PCDFs), 4 coplanar polychlorinated biphenyls (cPCBs), 36 ortho-substituted polychlorinated biphenyls (PCBs), and 13 chlorinated pesticides or their metabolites were measured and data were collected on the women's age, residence, occupation, body mass index (BMI), smoking and alcohol habit and 6 dietary intakes (fish, meats, rice, vegetables, fruits and dairy products). The serum median level of total TEQ was 25.1 pg TEQ/g lipid, that of PCDDs/PCDFs/cPCBs was 11.5 pmol/g lipid, that of PCBs was 0.46 nmol/g lipid, and that of total pesticides was 1.32 nmol/g lipid. The serum levels of total TEQ, PCDDs/PCDFs/cPCBs, PCBs and pesticides were positively associated with age (P for trend=0.003, 0.01, 0.005 and 0.01, respectively) and frequent fish consumption (P for trend=0.002, 0.003, 0.0003 and 0.006, respectively). Other lifestyle factors were not associated with serum organochlorine levels. The present study suggests that Japanese women who consume fish frequently in their reproductive period tend to accumulate organochlorines in their bodies.     

Natural denitrification in the Kakamigahara groundwater basin,Gifu prefecture,central Japan

Although nitrate is recognized as the most common groundwater contaminant due to growing anthropogenic sources, such as agriculture in particular, its adverse effects on human and animal health are debatable. The current issue, however, is to control and reduce nitrate contamination with regards to the long residence time of groundwater within aquifers. Denitrification has recently been recognized for its ability to reduce high nitrate concentrations in groundwater. The Kakamigahara groundwater basin, Gifu prefecture, Japan, witnessed rising levels of nitrate (>12 mg/l NO(3)-N) originating from agricultural sources. Chemical analyses for the determination of major constituents of groundwater and delta(15)N of residual nitrate were performed on representative groundwater samples in order to fulfill two main objectives. One is to investigate the current situation of nitrate groundwater pollution. The second objective is to determine whether the denitrification is a potential natural mechanism, which eliminates nitrate pollution in the Kakamigahara aquifer. Agricultural nitrate contamination of groundwater was obvious from characteristically high concentrations of Ca(2+), Mg(2+), NO(3)(-) and SO(4)(2-). High nitrate concentrations were found on the eastern side of the basin in association with vegetable cultivation fields, and decreased gradually towards the west of the basin along the direction of groundwater flow. The decrease of nitrate concentration was conveniently coupled with increase of HCO(3)(-) (the heterotrophic denitrification product), pH and delta(15)N of residual nitrate (due to isotopic fractionation) from east to west. Therefore, denitrification in situ is continuously removing nitrate from the Kakamigahara groundwater system.     

The long-term evolutions and the regional characteristics of atmospheric methane concentrations in Nagoya, 1983-1997

This study provides information on the long-term evolutions of the atmospheric methane (CH4) concentrations in Nagoya City, Japan, which were analyzed by using the continuous monitoring data observed at the eight observatory stations for 1983-1997. The 15-year records of the atmospheric CH4 concentrations were examined by means of a time-series analysis using a fast Fourier transform with a low-pass filter to elucidate the seasonal cycles and the long-term trends. The annual averages of the CH4 concentrations in Nagoya were 1.85 ppmv (parts per million by volume), 1.91 ppmv, and 1.90 ppmv in 1988, 1995 and 1997, respectively. Moreover, the annual average growth rate showed a drastic decrease from 17 ppbv (parts per billion by volume) year(-1) in 1992 to 2 ppbv year(-1) in 1993, and further down to 7 ppbv year(-1) in 1997. Comparison of the atmospheric CH4 records in Nagoya with those in global air of the northern hemisphere observed at Mauna Loa observatory in Hawaii, USA, allows us to estimate the excess concentration of CH4 in the urban atmosphere of Nagoya, which was 0.17 ppmv in 1988 and 0.15 ppmv in 1997. On a local scale, the atmospheric CH4 concentrations in the northern part of Nagoya City increased until 1992 and then gradually decreased from 1993 to 1997, although those in the south-western urban areas constantly increased at the averaged growth rate of 13 ppbv year(-1) for 1988-1997. The variation of the long-term trends of the CH4 concentrations in Nagoya may be ascribed to the emission changes from the CH4 sources due to the human activities such as waste dumping and landfills.     

Influence of growth conditions on biofilm development and mass transfer at the bulk/biofilm interface

In a long-term study on heterotrophic biofilms in tube reactors, this investigation focused on mass transfer at the bulk/biofilm interface, biofilm density and substrate conversion rates. Several biofilms were cultivated under different substrate and hydrodynamic conditions. Oxygen concentration profiles were measured with microelectrodes in the biofilm and in the boundary layer directly in the biofilm tube reactors. The thickness of the concentration boundary layer was found to depend on the surface structure of the biofilm. The hydrodynamic conditions and the substrate load during the growth phase of the biofilm in biofilm systems are two key parameters that influence the biofilm growth, particularly the structure, density and thickness. The measured substrate conversion rates, biofilm densities and the boundary layer thickness were used to formulate an equation for the mass transfer in biofilm tube reactors.