Hydrogen sulfide oxidation in novel Horizontal-Flow Biofilm Reactors dominated by an Acidithiobacillus and a Thiobacillus species.

Hydrogen Sulfide (H2S) is an odourous, highly toxic gas commonly encountered in various commercial and municipal sectors. Three novel, laboratory-scale, Horizontal-Flow Biofilm Reactors (HFBRs) were tested for the removal of H2S gas from air streams over a 178-day trial at 10°C. Removal rates of up to 15.1 g [H2S] m(-3) h(-1) were achieved, demonstrating the HFBRs as a feasible technology for the treatment of H2S-contaminated airstreams at low temperatures. Bio-oxidation of H2S in the reactors led to the production of H(+) and sulfate (SO(2-)4) ions, resulting in the acidification of the liquid phase. Reduced removal efficiency was observed at loading rates of 15.1 g [H2S] m(-3) h(-1). NaHCO3 addition to the liquid nutrient feed (synthetic wastewater (SWW)) resulted in improved H2S removal. Bacterial diversity, which was investigated by sequencing and fingerprinting 16S rRNA genes, was low, likely due to the harsh conditions prevailing in the systems. The HFBRs were dominated by two species from the genus Acidithiobacillus and Thiobacillus. Nonetheless, there were significant differences in microbial community structure between distinct HFBR zones due to the influence of alkalinity, pH and SO4 concentrations. Despite the low temperature, this study indicates HFBRs have an excellent potential to biologically treat H2S-contaminated airstreams.

An evaluation of the performance and optimization of a new wastewater treatment technology: the air suction flow-biofilm reactor.

In this laboratory study, a novel wastewater treatment technology, the air suction flow-biofilm reactor (ASF-BR) - a sequencing batch biofilm reactor technology with a passive aeration mechanism - was investigated for its efficiency in removing organic carbon, nitrogen and phosphorus, from high-strength synthetic wastewaters. A laboratory-scale ASF-BR comprising 2 reactors, 350 mm in diameter and 450 mm in height, was investigated over 2 studies (Studies 1 and 2) for a total of 430 days. Study 1 lasted a total of 166 days and involved a 9-step sequence alternating between aeration, anoxic treatment and settlement. The cycle time was 12.1 h and the reactors were operated at a substrate loading rate of 3.60 g filtered chemical oxygen demand (CODf)/m2 media/d, 0.28 g filtered total nitrogen (TNf)/m2 media/d, 0.24 g ammonium-nitrogen (NH4-N)/m2 media/d and 0.07 g ortho-phosphate (PO4-P)/m2 media/d. The average removal rates achieved during Study 1 were 98% CODf, 88% TNf, 97% NH4-N and 35% PO4-P. During Study 2 (264 days), the unit was operated at a loading rate of 2.49 g CODf/m2 media/d, 0.24 g TNf/m2 media/d, 0.20 g NH4-N/m2 media/d and 0.06 PO4-P/m2 media/d. The energy requirement during this study was reduced by modifying the treatment cycle in include fewer pumping cycles. Removal rates in Study 2 averaged 97% CODf, 86% TNf, 99% NH4-N and 76% PO4-P. The excess sludge production of the system was evaluated and detailed analyses of the treatment cycles were carried out. Biomass yields were estimated at 0.09 g SS/g CODf, removed and 0.21 g SS/g CODf, removed for Studies 1 and 2, respectively. Gene analysis showed that the use of a partial vacuum did not affect the growth of ammonia-oxidizing bacteria. The results indicate that the ASF-BR and passive aeration technologies can offer efficient alternatives to existing technologies.

Optimization of a horizontal-flow biofilm reactor for the removal of methane at low temperatures.

UNLABELLED: Three pilot-scale, horizontal-flow biofilm reactors (HFBRs 1-3) were used to treat methane (CH4)-contaminated air to assess the potential of this technology to manage emissions from agricultural activities, waste and wastewater treatment facilities, and landfills. The study was conducted over two phases (Phase 1, lasting 90 days and Phase 2, lasting 45 days). The reactors were operated at 10 degrees C (typical of ambient air and wastewater temperatures in northern Europe), and were simultaneously dosed with CH4-contaminated air and a synthetic wastewater (SWW). The influent loading rates to the reactors were 8.6 g CH4/m3/hr (4.3 g CH4/m2 TPSA/hr; where TPSA is top plan surface area). Despite the low operating temperatures, an overall average removal of 4.63 g CH4/m3/day was observed during Phase 2. The maximum removal efficiency (RE) for the trial was 88%. Potential (maximum) rates of methane oxidation were measured and indicated that biofilm samples taken from various regions in the HFBRs had mostly equal CH4 removal potential. In situ activity rates were dependent on which part of the reactor samples were obtained. The results indicate the potential of the HFBR, a simple and robust technology, to biologically treat CH4 emissions. IMPLICATIONS: The results of this study indicate that the HFBR technology could be effectively applied to the reduction of greenhouse gas emissions from wastewater treatment plants and agricultural facilities at lower temperatures common to northern Europe. This could reduce the carbon footprint of waste treatment and agricultural livestock facilities. Activity tests indicate that methanotrophic communities can be supported at these temperatures. Furthermore, these data can lead to improved reactor design and optimization by allowing conditions to be engineered to allow for improved removal rates, particularly at lower temperatures. The technology is simple to construct and operate, and with some optimization of the liquid phase to improve mass transfer, the HFBR represents a viable, cost-effective solution for these emissions.

A horizontal flow biofilm reactor (HFBR) technology for the removal of methane and hydrogen sulphide at low temperatures.

A novel horizontal flow biofilm reactor (HFBR) has been adapted and tested for its efficiency in treating hydrogen sulphide (H(2)S) and methane (CH(4)) gas. Six pilot-scale HFBR reactors were commissioned, three each treating CH(4) and H(2)S respectively. The reactors were operated at 10 °C, often typical of ambient temperatures in Ireland, and were simultaneously dosed with an air mixture containing the gas in question and with synthetic wastewater (SWW). Three reactors (HFBR 1, 2 and 3), treating an air mixture containing CH(4), were operated over three phases (Phases 1-3) lasting 180 days in total. During each phase the air mixture flow rate (AFR) and the plastic media top plan surface area (TPSA) loading rate to HFBR 1, 2 and 3 were 1.2 m(3)/m(3)/h and 0.6 m(3)/m(2) TPSA/h respectively. In Phase 1 the reactors were operated in triplicate and were loaded with 8.6 g CH(4)/m(3) reactor/h (4.3 g CH(4)/m(2) TPSA/h) and a synthetic wastewater (SWW) similar to domestic sewage at 10 °C. During Phase 2 (reactors also operated in triplicate) the effect of temperature on the reactor performance was examined. During Phase 3 the reactors were operated independently in order to examine the effects of omitting organic carbon and adding additional nitrogen in the form of nitrate-nitrogen (NO(3)-N), rather than ammonium-nitrogen (NH(4)-N). During Phase 3, CH(4) removal efficiencies (RE) of up to 92.8% were achieved at an empty bed retention time (EBRT) of 50 min, equating to a maximum removal of 8.0 g CH(4)/m(3) reactor/h. Three additional reactors (HFBR 4, 5 and 6) were used to treat an air mixture containing H(2)S and were loaded at an AFR of 15 m(3)/m(3) reactor/h (7.5 m(3)/m(2) TPSA/h) with an average H(2)S loading rate of 3.34 g H(2)S/m(3) reactor/h (1.67 g H(2)S/m(2) TPSA/h). After 50 days of operation, the RE reached 100% for all three reactors at an EBRT of 4 min. In each reactor, profile samples of biofilm, air and liquid were taken periodically from various regions of the HFBR. These allowed detailed description of removal processes and optimisation of the reactors by detailing changes in air, liquid and biofilm composition as air moved through the reactor.

Mother-infant interaction and child development after rooming-in: comparison of high-risk and low-risk mothers.

One hundred and seventy-two low-income women were interviewed prenatally to determine risk for later mistreatment of their children. High-risk and low-risk women were then randomly assigned at delivery to either limited or extended postpartum contact with their newborns over the first two days after birth. Mother-infant interaction observations were performed at 48 hours and at one, three, six, twelve and eighteen months postpartum. Infants were tested at nine months with the Bayley Scales of Infant Development. Results indicated that outcome following extended mother-infant postpartum contact varies with maternal risk status and measures employed for evaluation. Low-risk extended-contact mother-infant pairs differed from low-risk controls in observed interaction while high-risk extended-contact and controls did not differ from each other in interaction. High-risk extended-contact infants were more advanced in motor development than control infants at nine months, however, while low-risk extended contact and control infants did not differ in development.