Palm oil mill effluent (POME) is a highly polluted wastewater that consists of a high organic content of 4-5% total solids; a potential renewable energy source. A waste to energy study was conducted to improve biogas production using POME as substrate by ultrasonication pretreatment at mesophilic temperatures. The effect of temperature on the specific growth rate of anaerobes and methanogenic activity was investigated. Five sets of assays were carried out at operating temperatures between 25 °C and 45 °C. Each set consisted of two experiments using identical anaerobic sequencing batch reactors (AnSBR); fed with raw POME (control) and sonicated POME, respectively. The ultrasonication was set at 16.2 min ultrasonication time and 0.88 W mL-1 ultrasonication density with substrate total solids concentration of 6% (w/v). At 25 °C, biogas production rate and organic matter removal exhibited lowest values for both reactors. The maximum organic degradation was 96% from AnSBR operated at 30 °C fed with sonicated POME and 91% from AnSBR operated at 35 °C fed with unsonicated POME. In addition, the methane yield from AnSBR operated at 30 °C was enhanced by 21.5% after ultrasonication pretreatment. A few normality tests and a t-test were carried out. Both tests indicated that the residuals of the experimental data were normality distributed with mean equals to zero. The results demonstrated that ultrasonication treatment was a promising pretreatment to positively affect the organic degradation and biogas production rates at 30-35 °C.
AIMS: To evaluate the effects of condensed tannins (CTs) fractions of differing molecular weights (MWs) from a Leucaena leucocephala hybrid-Rendang on the rumen protozoal community in vitro.
METHODS AND RESULTS: The effects of unfractionated CTs (F0) and CT fractions of different MWs (F1 > F2 > F3 > F4 > F5) on protozoal population and community were evaluated in vitro using rumen microbes and ground guinea grass as the substrate. Higher-MW CT fractions F1 and F2 significantly (P
Malaysia has a great number of hot springs, especially along the flank of the Banjaran Titiwangsa mountain range. Biological studies of the Malaysian hot springs are rare because of the lack of comprehensive information on their microbial communities. In this study, we report a cultivation-independent census to describe microbial communities in six hot springs. The Ulu Slim (US), Sungai Klah (SK), Dusun Tua (DT), Sungai Serai (SS), Semenyih (SE), and Ayer Hangat (AH) hot springs exhibit circumneutral pH with temperatures ranging from 43°C to 90°C. Genomic DNA was extracted from environmental samples and the V3-V4 hypervariable regions of 16S rRNA genes were amplified, sequenced, and analyzed. High-throughput sequencing analysis showed that microbial richness was high in all samples as indicated by the detection of 6,334-26,244 operational taxonomy units. In total, 59, 61, 72, 73, 65, and 52 bacterial phyla were identified in the US, SK, DT, SS, SE, and AH hot springs, respectively. Generally, Firmicutes and Proteobacteria dominated the bacterial communities in all hot springs. Archaeal communities mainly consisted of Crenarchaeota, Euryarchaeota, and Parvarchaeota. In beta diversity analysis, the hot spring microbial memberships were clustered primarily on the basis of temperature and salinity. Canonical correlation analysis to assess the relationship between the microbial communities and physicochemical variables revealed that diversity patterns were best explained by a combination of physicochemical variables, rather than by individual abiotic variables such as temperature and salinity.
In this study, a two-stage domesticated shear-loop anaerobic contact stabilization (SLACS) system is introduced as a new reactor design to enhance methane productivity with significant reduction in hydrogen sulphide (H2S) synthesis. Due to the rich sulfate content in industrial wastewaters, the initial fermentation phase of anaerobic digestion is highly acidifying and often leads to severe performance losses, digester's instability, and even culture crash. The SLACS system functions as a dissimilatory sulfate reduction - methanogenic reactor consisting of two compartments, a shear-loop anaerobic bed (SLAB) unit and an anaerobic plug flow (APF) unit. The functional role of the SLAB unit is not limited to acidogenesis but also sulfidogenic processes, which curtails H2S generation in the APF unit (methanogenic stage). Experimental observations indicated that pH serves a critical role in the cohabitation of acidogenic and sulfidogenic microbes in the SLAB unit. Although acidogenesis was not influenced by pH within the range of 4.5-6.0, it is vital to stabilize the pH of this unit at 5.4 to establish a steady sulfate reduction of above 75%. The highest desulfurization achieved in this compartment was 88% under a hydraulic retention time (HRT) of 4 h. With an average methane productivity of 256 mL g-1 VS, the methanogenic performance of the two-stage domesticated SLACS system shows a 32% methanogenic proficiency higher than that of the one-stage digestion system. Microbial community structure within the system carried out via Next Generation Sequencing (NGS) provided qualitative data on the sludge's sulfidogenic and methanogenic performance.