Granulation and microbial community dynamics in the chitosan-supplemented anaerobic treatment of wastewater polluted with organic solvents

The effect of chitosan on the development of granular sludge in upflow anaerobic sludge blanket reactors (UASB) when treating wastewater polluted with the organic solvents ethanol, ethyl acetate, and 1-ethoxy-2-propanol was evaluated. Three UASB reactors were operated for 219 days at ambient temperature with an organic loading rate (OLR) of between 0.3 kg COD m−3 d−1 and 20 kg COD m−3 d−1. One reactor was operated without the addition of chitosan, while the other two were operated with the addition of chitosan doses of 2.4 mg gVSS−1 two times. The three reactors were all able to treat the OLR tested with COD removal efficiencies greater than 90%. However, the time required to reach stable operation was considerably reduced in the chitosan-assisted reactors. The development of granules in the reactors with chitosan was accelerated and granules larger than 2000 μm were only observed in these reactors. In addition, these granules exhibited better physicochemical characteristics: the mean particle diameter (540 and 613 μm) was approximately two times greater than in the control reactor (300 μm), and the settling velocities exceeded 35 m h−1. The extracellular polymeric substances (EPS) in the reactors with the chitosan was found to be higher than in the control reactor. The protein-EPS content has been correlated with the granule size. The analyses of the microbial communities, performed through denaturing gradient gel electrophoresis and high-throughput sequencing, revealed that the syntrophic microorganisms belonging to genus Geobacter and the hydrogenotrophic methanogen Methanocorpusculum labreanum were predominant in the granules. Other methanogens like Methanosaeta species were found earlier in the chitosan-assisted reactors than in the control reactor

Properties of Mortars Mixed with Polystyrene and Hemp Fiber Wastes

When polystyrene (PS) and hemp fiber waste were mixed into the sand aggregate, some physical-mechanical properties of mortar changed. The PS and hemp fiber were tested as partial replacements for sand in mortar with three designated percentages of 2.5, 5.0 and 10.0% by mass. The properties of mortar with PS were found to be better than that of the mortar with hemp fiber. The water absorption of mortar with PS was comparable with the reference mortar but lower than that of mortar with hemp fiber. The compressive strength of the mortar with PS was higher than that with hemp fiber whereas the tensile strength of the mortar with 2.5% PS and hemp fiber was comparable and was higher than that of the reference mortar. The thermal conductivity of a wall plastered by mortar containing PS decreased as the PS content was increased, whereas the thermal conductivity of a wall plastered by mortar containing hemp fiber increased as the hemp fiber content was increased. Thick crack was detected in the reference wall while hair line crack occurred from the wall plastered with PS and hemp fiber mortars. The results indicated that 10.0% PS could be used as a partial replacement for sand in mortar with an improvement in some of the properties of the mortar

Enhanced production of reducing sugars from paragrass using microwave-assisted alkaline pretreatment

The main aims of this study were to examine the effectiveness of pretreatment methods for enhancing the conversion of Brachiara mutica (paragrass) lignocellulose into valuable reducing sugars by enzymatic hydrolysis. The pretreatments studied included alkali alone, microwave-assisted alkali, acid alone, and microwave-assisted acid. It was found that the application of microwave irradiation during alkaline pretreatment with an alkali-to-biomass ratio of 5% (w w−1) for 30 min at 120 °C markedly increased the total reducing sugar (TRS) yield after enzymatic hydrolysis from 316 mg g−1 dry pretreated paragrass without microwave irradiation to 750 mg g−1 dry pretreated paragrass with microwave irradiation. In particular, the microwave-assisted alkaline pretreatment markedly increased xylose production and enhanced the enzymatic digestibility of cellulose. The concentrations of 5-hydroxymethylfurfural (HMF) and furfural after the microwave-assisted pretreatment were well below 1.0 kg m−3, the suggested threshold concentration of furfurals where yeast inhibition may begin

Shifts in bacterial and archaeal community structures during the batch biomethanation of Ulva biomass under mesophilic conditions

Mesophilic biomethanation of Ulva biomass was performed in a batch bioreactor, and a high organic removal of 77% was obtained on the basis of chemical oxygen demand (COD) after a month of operation. The estimated methane yield was 0.43??0.02L CH4/g CODremoved which is close to the theoretical methane potential. Transitions of bacterial and archaeal community structures, associated with process performance data, were investigated using a combination of molecular fingerprinting and biostatistical tools. During the operation, archaeal community structure had no significant changes while bacterial community structure shifted continuously and dynamically. The reactor completely stabilized volatile fatty acids (primarily acetate and propionate) accumulated from the acidogenesis phase, with Methanosaeta- and Methanolinea-related microbes respectively being the main aceticlastic and hydrogenotrophic methanogens. Methanolinea- and Syntrophobacter-related populations were likely the key members to form a syntrophic propionate-degrading consortium. A Methanolinea-related population was likely the dominant methane producer in the experimental reactor.close0