Herein, a preparation of a mixed-phase titanium dioxide (TiO₂) thin layer on glass beads was developed using the modified spray method. This approach was determined to be affordable and easy to operate. Optimum conditions were investigated for the photodegradation of wastewater generated from textile dyeing by TiO₂-coated glass beads as a catalyst using the central composite design (CCD). An increase in the direct dye photodegradation rate was observed at lower direct dye concentrations when TiO₂ dosages were increased, and the initial pH value was decreased. The optimal conditions involving TiO₂ dosage, pH, UV intensity, and dye concentrations were 3 g/L, 5.0, 3000 µW/cm², and 50 mg/L, respectively, when administered at ambient temperatures. For the batch experiments, the direct dye removal efficiency at 93.7% was achieved within 24 h. The average direct dye removal efficiency was 67.8% and could be up to 80.2% when using a fixed-bed photocatalysis reactor during 30 d of continuous operation. The reused catalyst’s degradation efficiency was not significantly changed, indicating its capability for repeated reuse and the excellent stability of immobilized TiO₂ onto the glass beads. This study additionally found that high temperatures could increase the efficiency of color removal.

Hydrogen sulfide (H₂S) is a toxic and corrosive component that commonly occurs in biogas. In this study, H₂S removal from swine-waste biogas using sulfur-oxidizing Paracoccus versutus CM1 immobilized in porous glass (PG) and polyurethane foam (PUF) biofilters was investigated. Bacterial compositions in the biofilters were also determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The biofilters were first tested on a laboratory scale under three space velocities (SV): 20, 30, and 40 h⁻¹. Within 24 h, at an SV of 20 h⁻¹, PG and PUF biofilters immobilized with P. versutus CM1 removed 99.5% and 99.7% of H₂S, respectively, corresponding to the elimination capacities (EC) of 83.5 and 86.2 gm⁻³ h⁻¹. On a pilot scale, with the horizontal PG-P. versutus CM1 biofilter operated at an SV of 30 h⁻¹, a removal efficiency of 99.7% and a maximum EC of 113.7 gm⁻³ h⁻¹ were achieved. No reduction in methane content in the outlet biogas was observed under these conditions. The PCR-DGGE analysis revealed that Paracoccus, Acidithiobacillus, and Thiomonas were the predominant bacterial genera in the biofilters, which might play important roles in H₂S removal. This PG–P. versutus CM1 biofiltration system is highly efficient for H2S removal from swine-waste biogas.

Conversion of Pennisetum purpureum × Pennisetum americanum (Napier Pak Chong1) press cake into biobutanol using Clostridium beijerinckii TISTR 1461 was proposed as an alternative to combustion in this study. The optimum conditions for biobutanol fermentation were determined using a full factorial design and a central composite design of experiment. The studied factors were initial pHs (5.50–6.50) and sugar concentrations (40–60 g/L), while butanol yield (g/g reducing sugar utilized) was specified as the optimization response. The results showed that the suitable enzyme loading of alkali-pretreated press cake (at 3% w/w NaOH, 10% substrate loading, boiling at 90 °C, with a reaction time of 1 h) was 10 FPU/g biomass, which provided a glucose yield of 345 mg/g pretreated press cake. The optimized pH and reducing sugar concentration were 6.08 and 43 g/L, respectively. At these conditions, the maximum butanol yield from the hydrolysate of NaOH-pretreated press cake was 0.135 g/g reducing sugar utilized (0.30 g/g glucose utilized). Apart from the possibility of generating much less pollution, it was estimated that using the same amount of press cake, butanol production could possibly have a value comparable to that obtained from combustion for electricity production. A new concept for overall Napier Pak Chong1 grass utilization was also presented.