Hydrogen is a promising alternative of clean energy carrier which can be biologically produced from glycerol-rich waste an abundant and economic source of substrate. However, continuous hydrogen-producing systems still need to be improved and in particular by manipulating the only few available operating conditions. The aim of this study was to investigate the effect of the two main operational parameters, ie. pH and hydraulic retention time (HRT) on hydrogen yields and microbial community structures. For that, a continuous stirred tank reactor (CSTR) was first inoculated with an enriched mixed microflora and was then fed with glycerol. A strong influence of these two operational parameters was shown on hydrogen yields where the maximum yield (0.58 ± 0.13 mol H2 mol-1 glycerol) was achieved at pH 5.5-HRT 12 h and was 28.5 times higher than the minimum (0.02 ± 0.02 mol H2 mol-1 glycerol) obtained at pH 5.0-HRT 14 h. Changes in most dominant microbial populations were mainly influenced by the pH. Interestingly, HRT parameter related to changes in the metabolic patterns and influenced the composition of subdominant Version postprint

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An Ultic Haploxeralf soil collected from ridges built into the slopes of the Coastal Mountain Range of Central Chile was used in applications of humic and fulvic acids (HFA) extracted from sludge from sewage treatment plants, in combination with gypsum (CaSO 4 ). A total of 12 treatments were applied by combining four doses of HFA (0, 20, 30 and 40 t ha -1 ) with three doses of gypsum (0, 1.2 and 6.0 t ha -1 ). The effect of these treatments was assessed using three indicators of the degree of soil aggregation: macroporosity (MA), bulk density (Da) and microinfiltration (MI). The experiment was set up in a laboratory using a completely randomised design (CRD). Factorial variance analysis was also performed using two factors: gypsum in three doses and HFA in four doses. For all three indicators, MA, Db and MI, it can be seen that there is interaction between the HFA treatments and the gypsum treatments in the studied soil. The macroporosity increased with HFA treatments with 20 or 30 t ha -1 (9%) and with gypsum of 1.2 t ha -1 plus 20 t ha -1 HFA (11%). It can also be seen that the gypsum treatments have no effect on Db when HFA is not applied. Microinfiltration is the variable that shows the greatest effects from the treatments applied. The results also clearly show that high amounts of HFA (40 t ha -1 ) and of gypsum (6.0 t ha -1 ) cancel out the differential effects and cause negative effects on the three indicators for the studied soils. The use of liquid humus and its combination with calcium sulphate (20/1.2 t ha -1 ) improves soil aggregation.

A 10 1 anaerobic fluidized bed reactor (AFBR) was designed and constructed, using beach sand as the solid support for the biomass. Considering the complexity of this type of system, previously to the startup, several experiences were performed in a series of minireactors, such as: determination of the bed expansion and the feed distribution. The startup was made increasing gradually the organic load rate (OLR), using the alkalinity ratio (α) and the removal of the organic load, as mg/l of COD, as leading parameters. The system attained a COD removal of over 85%, for an OLR of 3.4 [kg COD/m3·d]. The best removal of 92% was obtained at an OLR of 1.04 [kg COD/m3·d], with a hydraulic retention time (HRT) of 12 hours. The best gas production of 1.8 [m3 of biogas/m3·d], equivalent to a production of 0.16 [m3/kg CODremoved], was obtained at an (HRT) of 4.8 hours. The best startup results were obtained using Ethanol as the Carbon source.

Background: Constructed wetlands are a promising, cheap and effective wastewater treatment in small communities. The studies on these systems have been reported mainly from cold, tropical or subtropical climate regions. In this work we constructed a pilot plant with six horizontal subsurface flow constructed wetlands (HSSF CWs) with a surface area of 2 m 2 and a depth of 0.6 m each, planted with Typha latifolia or Scirpus sp., and filled with gravel (G) or fine gravel (FG) of 2.8 and 1.2 cm of diameter respectively, continuously fed with raw domestic wastewater. This experimental setup was evaluated over 280 days for the removal of organic matter and nutrients in a Mediterranean climate, near Valparaíso, Chile. The removal of total COD, NH4