Somkiet Techkarnjanaruk

Enhancement of biogas production from swine manure by a lignocellulolytic microbial consortium.

Anaerobic digestion of lignocellulosic wastes is limited by inefficient hydrolysis of recalcitrant substrates, leading to low biogas yield. In this study, the potential of a lignocellulolytic microbial consortium (LMC) for enhancing biogas production from fibre-rich swine manure (SM) was assessed. Biochemical methane potential assay showed that inoculation of structurally stable LMC to anaerobic digestion led to increase biogas production under mesophilic and thermophilic conditions. The greatest enhancement was observed at 37°C with a LMC/SM ratio of 1.5:1 mg VSS/g VS leading to biogas and methane yields of 355 and 180 ml/g VS(added) respectively, equivalent to 40% and 55% increases compared with the control. The LMC was shown to increase the efficiency of total solid, chemical oxygen demand removal and degradation of cellulose and hemicelluloses (1.87 and 1.65-fold, respectively). The LMC-supplemented process was stable over a 90 d biogas production period. This work demonstrates the potential of LMC for enhancing biogas from lignocellulosic wastes.

Effects of hydraulic retention time and carbon to nitrogen ratio on micro-pollutant biodegradation in membrane bioreactor for leachate treatment.

This research investigated the biodegradation of the micro-pollutants in leachate by the membrane bioreactor (MBR) system under six treatment conditions, comprising two C/N ratios (6, 10) and three hydraulic retention time (HRT) durations (6, 12, 24h). The experimental results indicated that the C/N 6 environment was more advantageous to the bacterial growth. The bacterial communities residing in the sludge were those of heterotrophic bacteria (HB), heterotrophic nitrifying bacteria (HNB) and ammonia oxidizing bacteria (AOB). It was found that HB and HNB produced phenol hydroxylase (PH), esterase (EST), phthalate dioxygenase (PDO) and laccase (LAC) and also enhanced the biodegradation rate constants (k) in the system. At the same time, AOB promoted the production of HB and HNB. The findings also revealed that the 12h HRT was the optimal condition with regard to the highest growth of the bacteria responsible for the biodegradation of phenols and phthalates. Meanwhile, the longer HRT duration (i.e. 24h) was required to effectively bio-degrade carbamazepine (CBZ), N,N-diethyl-m-toluamide (DEET) and diclofenac (DCF).

Microbial Communities and Their Performances in Anaerobic Hybrid Sludge Bed-Fixed Film Reactor for Treatment of Palm Oil Mill Effluent under Various Organic Pollutant Concentrations

The anaerobic hybrid reactor consisting of sludge and packed zones was operated with organic pollutant loading rates from 6.2 to 8.2 g COD/L day, composed mainly of suspended solids (SS) and oil and grease (O&G) concentrations between 5.2 to 10.2 and 0.9 to 1.9 g/L, respectively. The overall process performance in terms of chemical oxygen demands (COD), SS, and O&G removals was 73, 63, and 56%, respectively. When the organic pollutant concentrations were increased, the resultant methane potentials were higher, and the methane yield increased to 0.30 L CH4/g CODremoved. It was observed these effects on the microbial population and activity in the sludge and packed zones. The eubacterial population and activity in the sludge zone increased to 6.4 × 109 copies rDNA/g VSS and 1.65 g COD/g VSS day, respectively, whereas those in the packed zone were lower. The predominant hydrolytic and fermentative bacteria were Pseudomonas, Clostridium, and Bacteroidetes. In addition, the archaeal population and activity in the packed zone were increased from to 9.1 × 107 copies rDNA/g VSS and 0.34 g COD-CH4/g VSS day, respectively, whereas those in the sludge zone were not much changed. The most represented species of methanogens were the acetoclastic Methanosaeta, the hydrogenotrophic Methanobacterium sp., and the hydrogenotrophic Methanomicrobiaceae.

Diversity of purple nonsulfur bacteria in shrimp ponds with varying mercury levels

This research aimed to study the diversity of purple nonsulfur bacteria (PNSB) and to investigate the effect of Hg concentrations in shrimp ponds on PNSB diversity. Amplification of the pufM gene was detected in 13 and 10 samples of water and sediment collected from 16 shrimp ponds in Southern Thailand. In addition to PNSB, other anoxygenic phototrophic bacteria (APB) were also observed; purple sulfur bacteria (PSB) and aerobic anoxygenic phototrophic bacteria (AAPB) although most of them could not be identified. Among identified groups; AAPB, PSB and PNSB in the samples of water and sediment were 25.71, 11.43 and 8.57%; and 27.78, 11.11 and 22.22%, respectively. In both sample types, Roseobacter denitrificans (AAPB) was the most dominant species followed by Halorhodospira halophila (PSB). In addition two genera, observed most frequently in the sediment samples were a group of PNSB (Rhodovulum kholense, Rhodospirillum centenum and Rhodobium marinum). The UPGMA dendrograms showed 7 and 6 clustered groups in the water and sediment samples, respectively. There was no relationship between the clustered groups and the total Hg (HgT) concentrations in the water and sediment samples used (<0.002–0.03 μg/L and 35.40–391.60 μg/kg dry weight) for studying the biodiversity. It can be concluded that there was no effect of the various Hg levels on the diversity of detected APB species; particularly the PNSB in the shrimp ponds.

Nitrogen removal of anammox cultures under different enrichment conditions.

Anammox bacteria in sludge from an anoxic tank of a municipal wastewater treatment plant at Nongkhaem, Bangkok, Thailand were enriched in two sequencing batch reactors (SBRs; SBR-1 and SBR-2), under different conditions. SBR-1 was open to the atmosphere, while SBR-2 was closed and flushed with a mixture of 95% argon and 5% CO2 during the fill period in order to provide strict anaerobic conditions. The specific nitrogen removal rates of SBR-1 and SBR-2 were 0.43 g N/g VSS-d and 2.59 g N/g VSS-d, respectively. Denaturing gradient gel electrophoresis (DGGE) analyses showed differences in band patterns among the Nongkhaem sludge and the two enrichment cultures. Based on fluorescent in situ hybridization (FISH), the anammox bacteria in both systems were either “Candidatus Brocadia anammoxidans” or “Candidatus Kuenenia stuttgartiensis”. The results from this study demonstrate the potential of alternative anammox systems for nitrogen removal and provide information on the microbial communities of anammox cultures under different enrichment conditions.

Use of fluorochrome-labeled rRNA targeted oligonucleotide probe and tyramide signal amplification to improve sensitivity of fluorescence in situ hybridization

A tyramide signal amplification (TSA) system was used in combination with a conventional fluorochrome-labeled 16S rRNA oligonucleotide probe to increase the sensitivity of fluorescence in situ hybridization. TSA was performed after hybridization resulted in a low fluorescence signal intensity. In contrast to the horseradish peroxidase-tyramide signal amplification (HRP-TSA) system and biotin-tyramide signal amplification (biotin-TSA) system, no additional expensive probe labeling was required. A whole cell hybridization technique was used to compare the fluorescence signal obtained using a monolabeled probe with that obtained using the TSA system. The fluorescence signal of the probe obtained using the TSA system was much higher than that obtained using the monolabeled probe. The technique was successfully applied to the in situ detection of microbial communities in anaerobic sludge. It was demonstrated that TSA resulted in an increased in sensitivity, as the fluorescence signal intensity was much higher than that obtained using a conventional probe.

Enhanced micropollutant biodegradation and assessment of nitrous oxide concentration reduction in wastewater treated by acclimatized sludge bioaugmentation

This research investigated the micropollutant biodegradation and nitrous oxide (N2O) concentration reduction in high strength wastewater treated by two-stage activated sludge (AS) systems with (bioaugmented) and without (non-bioaugmented) acclimatized sludge bioaugmentation. The bioaugmented and non-bioaugmented systems were operated in parallel for 228 days, with three levels of concentrations of organics, nitrogen, and micropollutants in the influent: conditions 1 (low), 2 (moderate), and 3 (high). The results showed that, under condition 1, both systems efficiently removed the organic and nitrogen compounds. However, the bioaugmented system was more effective in the micropollutant biodegradation and N2O concentration reduction than the non-bioaugmented one. Under condition 2, the nitrogen and micropollutant biodegradation efficiency of the non-bioaugmented system slightly decreased, while the N2O concentration declined in the bioaugmented system. Under condition 3, the treatment performance and N2O concentration abatement were substantially lowered as the compounds concentration increased. Further analysis also showed that the acclimatized sludge bioaugmentation increased the bacterial diversity in the system. In essence, the acclimatized sludge bioaugmentation strategy was highly effective for the influent with low compounds concentration, achieving the organics and nitrogen removal efficiencies of 92-97%, relative to 71-97% of the non-bioaugmented system. The micropollutant treatment efficiency of the bioaugmented system under condition 1 was 75-92%, indicating significant improvement in the treatment performance (p < 0.05), compared with 60-79% of the non-bioaugmented system.

Use of aged sludge bioaugmentation in two-stage activated sludge system to enhance the biodegradation of toxic organic compounds in high strength wastewater

This research investigates the toxic organic compounds biodegradation efficiency of two-stage activated sludge systems with (bioaugmented) and without aged sludge bioaugmentation (non-bioaugmented). The influent was a mixture of leachate and agriculture wastewater (1:1, v/v), used as the representative high strength wastewater. The bioaugmented and non-bioaugmented systems were operated in parallel, with three levels (low, moderate, and high) of concentrations of organics, nitrogen, and toxic organic compounds in the influent (conditions 1, 2, and 3). The results showed that both systems could efficiently degrade the organic compounds. Nevertheless, the toxic organic compounds biodegradation efficiency of the bioaugmented system was higher than that of the non-bioaugmented one. The bioaugmentation enhanced the overall removal efficiency under conditions 1 and 2. However, the bioaugmented system became less effective under condition 3. Further analysis indicated that the bacterial groups essential to the toxic organic compounds biodegradation were abundant in the aged sludge, including heterotrophic bacteria, heterotrophic nitrifying bacteria, and nitrifying bacteria. The abundance of the effective bacteria improved the biodegradation and wastewater treatment performance of the bioaugmented system. In essence, the aged sludge bioaugmentation is a viable and eco-friendly solution to improving the treatment efficiency of the biological activated sludge system, despite limited biodegradation efficiency in an elevated compounds-concentration environment.