Start-Up of Chitosan-Assisted Anaerobic Sludge Bed Reactors Treating Light Oxygenated Solvents under Intermittent Operation.

Quality of the granular sludge developed during the start-up of anaerobic up-flow sludge bed reactors is of crucial importance to ensure the process feasibility of treating industrial wastewater such as those containing solvents. In this study, the microbial granule formation from suspended-growth biomass was investigated in two chitosan-assisted reactors. These reactors operated mimicking industrial sites working with night closures treating a mixture of ethanol, ethyl acetate, and 1-ethoxy-2-propanol. Each reactor operated under different hydrodynamic regimes typical from UASB (R1: <0.15 m h-1) and EGSB (R2: 3 m h-1). High soluble COD removal efficiencies (>90%) accompanied by rapid formation of robust anaerobic granules were achieved at both up-flow velocity levels. After three weeks from the start-up, mean size diameters of 475 µm and 354 µm were achieved for R1 and R2, respectively. The performance of the process was found to be stable for the whole operational period of 106 days treating intermittent OLR up to 13 kg COD m-3 d-1. A memory dose of chitosan at day 42 was beneficial to guarantee good quality of the granules by offsetting the negative impact of intermittent water supply on the granular size. Methanocorpusculum was identified as the dominant archaea at both up-flow velocities. Acetobacterium, Geobacter and Desulfovibrio bacteria were also abundant, demonstrating its role on the degradation of light-oxygenated solvents.

Removal of acetone from air emissions by biotrickling filters: providing solutions from laboratory to full-scale.

A full-scale biotrickling filter (BTF) treating acetone air emissions of wood-coating activities showed difficulties to achieve outlet concentrations lower than 125 mg C m-3, especially for high inlet concentrations and oscillating emissions. To solve this problem, a laboratory investigation on acetone removal was carried out simulating typical industrial conditions: discontinuous and variable inlet concentrations and intermittent spraying. The results were evaluated in terms of removal efficiency and outlet gas emission pattern. Industrial emissions and operational protocols were simulated: inlet load up to 70 g C m-3 h-1 during 2 cycles of 4 h per day and intermittent trickling of 15 min per hour. The outlet gas stream of the pollutant was affected by intermittent spraying, causing a fugitive emission of pollutant. Complete removal efficiency was obtained during non-spraying. Average removal efficiencies higher than 85% were obtained, showing the feasibility of BTF to treat acetone. The outlet gas stream showed a clear dependence on the pH of the trickling liquid, decreasing the removal at pH < 5.5. Thus, a proper control of alkalinity, with regular NaHCO3 addition, was required for successful operation. The laboratory findings were fruitfully transferred to the industry, and the removal of acetone by full-scale BTF was improved.

Modeling of copper fixed-bed biosorption from wastewater by Posidonia oceanica.

Biosorption of copper from aqueous solutions by Posidonia oceanica was investigated in batch and fixed-bed experiments. Batch experiments were conducted to evaluate the removal equilibrium at pH 5.0 and 6.0; experimental data were fitted to Langmuir model with maximum uptake capacities of 56.92 and 85.78 mg g(-1), respectively. Five column experiments were carried out at different feed concentrations. Breakthrough times and continuous sorption isotherm were obtained from breakthrough curves. Differences among batch and continuous isotherms were observed; the maximum uptake capacity in dynamic conditions was found in 56.70 mg g(-1) for final pH between 5.0 and 5.5. The biosorbent was regenerated with HCl. Hydrodynamic axial dispersion was estimated by tracing experiments at different velocities using LiCl as tracer. A mass transport model including convection-dispersion and sorption processes was successfully applied to breakthrough curve modeling. Results indicate that P. oceanica can be used as an effective biosorbent for copper removal.