Sumate Chaiprapat

Effects of pH adjustment by parawood ash and effluent recycle ratio on the performance of anaerobic baffled reactors treating high sulfate wastewater

The objective of this study was to compare the performance of anaerobic baffled reactor (ABR) treating concentrated rubber latex wastewater under different pH adjustment substances and recycling ratios (R). Two ABRs, one received wastewater pretreated with NaOH and the other with ash, were operated at 35 degrees C under identical HRTs from 10 to 1.25d. Results show that both ABRs had highest COD and sulfate removal efficiencies at HRT 10d (averaged 82.71% and 96.16% of ABR-NaOH, and 80.77% and 96.60% of ABR-Ash, respectively), where majority of the influent COD and sulfate were removed by the first compartment of the ABR at all conditions tested. Increasing R (0, 0.3 and 0.5) raised the hydraulic loading on the system and resulted in a drop of organic removal efficiency and methane yield. Translocation of sulfate reducing bacteria and methanogens in the ABRs caused by increased organic loading and effluent recycle is discussed. The results show great potential of parawood ash as a pH adjustment substance for acidic wastewaters.

Effects of inoculum to substrate ratio, substrate mix ratio and inoculum source on batch co-digestion of grass and pig manure.

Biochemical methane potential (BMP) assay was conducted at 35 °C to evaluate the effects of inoculum to substrate ratio (ISR) and substrate mix ratio between para-grass and pig manure co-digesting using different inocula. Rubber latex digester (RLD) inoculum showed higher methanogenic activity (41.4 mL CH4/gVS) than pig farm digester (PFD) inoculum (37.3 mL CH4/gVS). However, the maximum methane yields, occurred at the highest para-grass mix ratio (G), were 369.6, 437.6, 465.9 and 442.6 mL CH4/gTSadded for RLD inoculum, versus 332.4, 475.0, 519.5 and 521.9 mL/gTSadded for PFD inoculum at ISR 1, 2, 3, and 4, respectively. HPr, HBu and HVa appeared at higher G, corresponding to substrates higher biodegradability. Response surface indicated that higher ISR and G had a significantly positive impact on methane yield. It suggested the use of higher ISR, i.e. 3 or 4, for BMP assay of these co-substrates. Dominant species of fermentative bacteria in each inoculum was tested by DGGE.

Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms

Removal of hydrogen sulfide (H2S) from biogas was investigated in a biochar column integrated with a bench-scale continuous-stirred tank reactor (CSTR) treating sulfate-laden wastewater. Synthetic wastewater containing sulfate concentrations of 200-2000mg SO42-/L was used as substrate, and the CSTR was operated at an organic loading rate of 1.5g chemical oxygen demand (COD)/L·day and a hydraulic retention time (HRT) of 20days. The biochar was able to remove about 98.0 (±1.2)% of H2S for the ranges of concentrations from 105-1020ppmv, especially at high moisture content (80-85%). Very high H2S adsorption capacity (up to 273.2±1.9mg H2S/g) of biochar is expected to enhance the H2S oxidation into S0 and sulfate. These findings bring a potentially novel application of sulfur-rich biochar as a source of sulfur, an essential but often deficient micro-nutrient in soils.

Enhancing digestion efficiency of POME in anaerobic sequencing batch reactor with ozonation pretreatment and cycle time reduction

Ozonation pretreatment was applied to palm oil mill effluent (POME) prior to anaerobic digestion using the anaerobic sequencing batch reactor (ASBR). Ozonation increased BOD/COD by 37.9% with a COD loss of only 3.3%. At organic loads of 6.48-12.96 kg COD/m(3)/d, feeding with non-ozonated POME caused a system failure. The ozonated POME gave significantly higher TCOD removal at loadings 6.52 and 9.04 kg COD/m(3)/d but failed to sustain the operation at loading 11.67 kg COD/m(3)/d. Effects of cycle time (CT) and hydraulic retention time (HRT) were determined using quadratic regression model. The generated response surface and contour plot showed that at this high load conditions (6.52-11.67 kg COD/m(3)/d), longer HRT and shorter CT gave the ASBR higher organic removal efficiency and methane yield. The model was able to satisfactorily describe the relationship of these two key operating parameters.

Bio-desulfurization of biogas using acidic biotrickling filter with dissolved oxygen in step feed recirculation.

Triple stage and single stage biotrickling filters (T-BTF and S-BTF) were operated with oxygenated liquid recirculation to enhance bio-desulfurization of biogas. Empty bed retention time (EBRT 100-180 s) and liquid recirculation velocity (q 2.4-7.1 m/h) were applied. H2S removal and sulfuric acid recovery increased with higher EBRT and q. But the highest q at 7.1 m/h induced large amount of liquid through the media, causing a reduction in bed porosity in S-BTF and H2S removal. Equivalent performance of S-BTF and T-BTF was obtained under the lowest loading of 165 gH2S/m(3)/h. In the subsequent continuous operation test, it was found that T-BTF could maintain higher H2S elimination capacity and removal efficiency at 175.6±41.6 gH2S/m(3)/h and 89.0±6.8% versus S-BTF at 159.9±42.8 gH2S/m(3)/h and 80.1±10.2%, respectively. Finally, the relationship between outlet concentration and bed height was modeled. Step feeding of oxygenated liquid recirculation in multiple stages clearly demonstrated an advantage for sulfide oxidation.

Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes

Methane production potential of tropical fruit wastes, namely lady-finger banana peel, rambutan waste and longan waste were compared using BMP assay and stoichiometric modified Buswell and Mueller equation. Methane yields based on volatile solid (VS) were in the order of ground banana peel, chopped banana peel, chopped longan waste, and chopped rambutan waste (330.6, 268.3, 234.6 and 193.2 mLCH4/gVS) that corresponded to their calculated biodegradability. In continuous operations of banana peel digestion at feed concentrations based on total solid (TS) 1-2%, mesophilic single stage digester run at 20-day hydraulic retention time (20-day HRT) failed at 2%TS, but successfully recovered at 1.5%TS. Pre-hydrolysis thermophilic reactor (4-d HRT) was placed as pre-treatment to mesophilic reactor (20-d HRT). Higher biogas (with an evolution of H2) and energy yields were obtained and greater system stability was achieved over the single stage digestion, particularly at higher solid feedstock. The best performance of two stage digestion was 68.5% VS destruction and energy yield of 2510.9kJ/kgVS added at a feed concentration of 2%TS.

Effect of pH, OLR, and HRT on performance of acidogenic and methanogenic reactors for treatment of biodiesel wastewater

AbstractTwo-stage anaerobic process was studied in order to treat biodiesel wastewater. The first stage represented acidogenic reactor while the second stage was methanogenic reactor. The effect of pH, hydraulic retention time (HRT), and organic loading rate (OLR) on performance of both reactors was investigated. The optimum condition was examined using response surface methodology with the Box–Behnken Design. In the acidogenic reactor, the optimum pH, HRT, and OLR were 6.48, 16 h, and 26 g COD/(l d), respectively. High VFA production of 9.35 g/l was achieved with the low methane production. In the methanogenic reactor, the optimum pH, HRT, and OLR were 6.95, 30 h, and 6 g COD/(l d), respectively. Biogas production of 19.1 l/d was obtained with the methane content of 66%. VFA was completely consumed. In comparison, the two-stage system showed higher efficiency (COD removal, biogas production, and methane yield) than the one-stage system.

Relationship of Substrate and Inoculum on Biochemical Methane Potential for Grass and Pig Manure Co-Digestion

The effects of substrate mix ratio and inoculum/substrate ratio (ISR) on biochemical methane potential of para-grass (PG) and pig manure (PM) were investigated in batch test that maintained temperature at 35±1 oC and continuously shaked at 120 rpm. Cumulative methane production data at different mix ratios and ISRs were evaluated and fitted with Gompertz equation to derive methane production potential (mL) and maximum methane production rate (mL/d). The maximum and average methane yields at each respective ISR of 1, 2, 3, and 4 were [413.0, 315.5], [539.7, 455.6], [590.3, 472.5], and [593.1, 473.5] mL/gVSadded. Relationship of ISR and PG mix ratio to specific methane yield were expressed in quadratic regression model. The generated response surface showed that methane yield was elevated at higher ISR and higher PG mix ratio. This suggests a careful investigation at different ISR and substrate mix ratios should be performed in order to develop a realistic biochemical methane potential of anaerobic co-digestion.

Use of wood vinegar to enhance 5-aminolevulinic acid production by selected Rhodopseudomonas palustris in rubber sheet wastewater for agricultural use

This study aimed to produce inexpensive 5-aminolevulinic acid (ALA) in a non-sterile latex rubber sheet wastewater (RSW) by Rhodopseudomonas palustris TN114 and PP803 for the possibility to use in agricultural purposes by investigating the optimum conditions, and applying of wood vinegar (WV) as an economical source of levulinic acid to enhance ALA content. The Box–Behnken Design experiment was conducted under microaerobic-light conditions for 96 h with TN114, PP803 and their mixed culture (1:1) by varying initial pH, inoculum size (% v/v) and initial chemical oxygen demand (COD, mg/L). Results showed that the optimal condition (pH, % inoculum size, COD) of each set to produce extracellular ALA was found at 7.50, 6.00, 2000 for TN114; 7.50, 7.00, 3000 for PP803; and 7.50, 6.00, 4000 for a mixed culture; and each set achieved COD reduction as high as 63%, 71% and 75%, respectively. Addition of the optimal concentration of WV at mid log phase at 0.63% for TN114, and 1.25% for PP803 and the mixed culture significantly increased the ALA content by 3.7–4.2 times (128, 90 and 131 μM, respectively) compared to their controls. ALA production cost could be reduced approximately 31 times with WV on the basis of the amount of levulinic acid used. Effluent containing ALA for using in agriculture could be achieved by treating the RSW with the selected ALA producer R. palustris strains under the optimized condition with a little WV additive.

Cultivation of Chlorella sp. Using Industrial Effluents for Lipid Production

This work aims to investigate microalgal growth and lipid production from Chlorella sp. on different digester effluents from seafood factory, starch factory and palm oil mill. Results under 32 cultivation days showed that the effluent from seafood factory gave the highest microalgal growth (0.9956±0.2121 g/L) followed by starch factory and palm oil mill (0.8622±0.0391 and 0.2611±0.0444 g/L, respectively). Although higher nitrogen and phosphorus in medium stimulated growth, turbidity of the palm oil mill effluent showed a negative impact. In addition, phosphorus concentration in the medium positively affected the lipid content in cells. The seafood effluent with total phosphorus of 45.24±3.80 mg/L yielded highest lipid content at 26.96±1.58% compared to starch factory (22.10±2.61). The digester effluent from seafood factory was found more suitable for Chlorella sp. cultivation due to the high mass production, oil content and lipid productivity.