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

Impact analysis of hydraulic loading rate and antibiotics on hybrid constructed wetland systems: Insight into the response to decontamination performance and environmental-associated microbiota

Hybrid constructed wetlands (HCWs) are a promising solution for water ecology and environmental treatment, not only for conventional types of water pollution but also for antibiotics. Among the critical parameters for wetlands, the hydraulic loading rate (HLR) is especially important given the challenges of antibiotics treatment and frequent extreme rainfall. To investigate the removal performance of different HLRs on nutrients and antibiotics, as well as the response of antibiotics to nutrient removal, and the impact of HLRs on microbial communities, new HCWs with vertical flow constructed wetlands (VFCWs) and floating constructed wetlands (FCWs) in series were built. The results of the study showed that: (1) HCWs are highly effective in removing chemical oxygen demand (COD), NH4+-N, NO2--N, and total phosphorus (TP) at low HLR (L_HLR), with removal efficiencies as high as 97.8%, 99.6%, 100%, and 80.5%. However, high HLR (H_HLR) reduced their removal efficiencies; (2) The average removal efficiency of fluoroquinolones (FQs) under different HLRs was consistently high, at 99.9%, while the average removal efficiency of macrolides (MLs) was 96.3% (L_HLR) and 88.4% (H_HLR). The removal efficiency of sulfonamides (SAs) was susceptible to HLRs, and the removal of antibiotics occurred mainly in the rhizosphere zone of wetland; (3) High concentrations of antibiotics in HCWs were found to inhibit and poison plant growth and to reduce the removal efficiency of TP by 12%. However, they had a minor effect on the removal efficiency of carbon and nitrogen nutrients; (4) H_HLR altered the diversity and abundance of microbial communities in different compartments of the wetland and also reduced the relative abundance of Bacillus, Hydrogenophaga, Nakamurella, Denitratisoma and Acidovorax genera, which are involved in denitrification and phosphorus removal processes. This alteration in microbial communities was one of the main reasons for the reduced performance of nitrogen and phosphorus removal.

Microbial granules on reactors performance during organic butyrate digestion: clean production

This critical review for anaerobic degradation of complex organic compounds like butyrate using reactors has been enormously applied for biogas production. Biogas production rate has a great impact on: reactor granulation methanogenesis, nutrient content, shear velocity, organic loading and loss of nutrients taking place in the reactor continuously. Various technologies have been applied to closed anaerobic reactors to improve biogas production and treatment efficiency. Recent reviews showed that the application of closed anaerobic reactors can accelerate the degradation of organics like volatile fatty acid-butyrate and affect microbial biofilm formation by increasing the number of methanogens and increase methane production 16.5 L-1 CH4 L-1 POME-1. The closed anaerobic reactors with stable microbial biofilm and established organic load were responsible for the improvement of the reactor and methane production. The technology mentioned in this review can be used to monitor biogas concentration, which directly correlates to organic concentrations. This review attempts to evaluate interactions among the: degradation of organics, closed anaerobic reactors system, and microbial granules. This article provides a useful picture for the improvement of the degradation of organic butyrate for COD removal, biogas and methane production in an anaerobic closed reactor.

A review on the pollution assessment of hazardous materials and the resultant biorefinery products in Palm oil mill effluent

The voluminous nature of palm oil mill effluent (POME) is directly associated with environmental hazards and could be turned into biorefinery products. The POME, rich in BOD, COD, and oil and grease, with few hazardous materials such as siloxanes, fatty acid methyl ester, and phenolic compounds that may significantly increase the risk of violating the effluent quality standards. Recently, the application of chemical and biological risk assessment that can use electrochemical sensors and microalgae-like species has gained paramount attention towards its remediation. This review describes the existing risk assessment for POME and recommends a novel assessment approach using fish species including invasive ones as suitable for identifying the toxicants. Various physico-chemical and biological treatments such as adsorption, coagulation-flocculation, photo-oxidation, solar-assisted extraction, anaerobic digestion, integrated anaerobic-aerobic, and microalgae cultivation has been investigated. This paper offers an overview of anaerobic technologies, with particular emphasis on advanced bioreactors and their prospects for industrial-level applications. To illustrate, palmitic acid and oleic acid, the precursors of fatty acid methyl ester found in POME pave the way to produce biodiesel with 91.45%. Although there are some challenges in attaining production at an economic scale, this review offers some opportunities that could help in overcoming these challenges.

Optimization of operating parameters for biogas production using two-phase bench-scale anaerobic digestion of slaughterhouse wastewater: Focus on methanogenic step

The objective of the present study was an optimization of operating parameters and the performance of the methanogenesis reactor in phased anaerobic digestion (AD) of slaughterhouse wastewater at 37.5°C. Accordingly, the feedstock of the methanogenic reactor was effluent from the hydrolytic-acidogenic reactor operating at HRT of 3-days and OLR of 1789 mg/L. The methanogenesis phase was also investigated at different hydraulic retention time (HRT) values ranging from 12 to 3 days at 3-day intervals, and organic loading rates (OLR) of 149, 199, 298, and 596 mg of COD/L. The methanogenesis reactor effluent concentrations of TN, TP, PO4- 3, SO4- 2, and S2- 2 were ranging between 424-464, 83-117, 63-86, 130-197, and 0.98-1.02 mg/L, respectively. The removal efficiencies of TN and TP were vary from 10-17% to 17-21%, respectively. The average biogas production was 125 ± 16, 150 ± 10, 185 ± 4, and 154 ± 17 mL at HRT of 12, 9, 6, and 3 days, respectively. Methane quality (%) and yield (mg/L of COD) were 55-67% and 0.02-0.03, respectively. Furthermore, the average stability indicator parameter values of (total volatile fatty acid (TVFA) = 520 ± 19 mg/L, total alkalinity (TotA) = 1424 ± 10 mg/L, TVFA:TotA. Ratio = 0.36, salinity = 1172 mg/L, pH = 6.92) and performance indicator parameters removal efficiency (RE) for (chemical oxygen demand (COD) = 81%, volatile solid (VS) RE = 95%, biogas production = 185 ± 4 mL, methane yield = 0.03 per mg COD consumed) were achieved at HRT of 6 days and OLR of 298 mg of COD/L. Low removal efficiencies of TP and TN at all HRT/OLR were observed for the methanogenic reactor signifying further treatment system.

Research on removal of fluoroquinolones in rural domestic wastewater by vertical flow constructed wetlands under different hydraulic loads

Antibiotics had attracted more and more attention in recent years due to their harmfulness. Fluoroquinolones (FQs), one class of antibiotics widely used in human and veterinary medicine, were found in various water bodies in China. Therefore, in order to found an efficient method for removing FQs in rural domestic wastewater and optimize the process parameters, ceramsite and soil were applied in vertical flow constructed wetlands (VFCWs) to study the effects of different hydraulic loads and different substrates on the removal of FQs and conventional pollutants. The results showed the VFCW-D filled with 45 cm soil layer and 15 cm ceramasite layer had the highest removal efficiency of conventional pollutants and FQs under low hydraulic load. Nevertheless, the removal efficiency of conventional pollutants was significantly declined for the VFCWs which contained soil substrates under high hydraulic load due to the soil pores were clogged by the accumulation of organic matter. Finally, VFCW-A filled with 60 cm ceramasite layer revealed good ability to remove conventional pollutants and FQs under high hydraulic load. Deinococcus played a vital role here due to its excellent removal effect on conventional pollutants. The microbial composition in the substrate changed greatly after adding antibiotics under high hydraulic load. Devosia, Pseudorhodoferax, Cellvibrio, Bosea, Caulobacter, Acinetobacter, Zoogloea, Arcobacter, Dechloromonas, Flavobacterium, Nakamurella, Chloroplast, Clostridium_sensu_stricto_1, Pelosinus, UTCFX1 and Hypnocyclicus became the new dominated genera and were essential to remove pollutants. In summary, VFCW was an effective system to remove fluoroquinolones in rural domestic wastewater.

Microbial community composition in different carbon source types of biofilm A/O-MBR systems with complete sludge retention

In this study, the three biofilm-anoxic-oxic-MBR systems were operated in parallel using different carbon source feed types. The three systems were operated with complete sludge retention to compare microbial community composition and system efficiency. High average removal of ammonia and COD was obtained in the three reactors. However, total nitrogen and total phosphorus removal efficiency were significantly higher in the VFAs feed systems when compared with the glucose feed system. The highest and most stable BNR efficiency was observed when acetate was used as a carbon source. The qPCR analysis revealed that ammonium oxidizing bacteria, denitrifiers and total bacteria were all highest in the acetate feed system followed by the propionate feed system. Moreover, among all carbon source types, the PUS-biofilm could maintain a higher degree of abundance of total bacteria than the sludge biomass. Meanwhile, ammonium oxidizing bacteria and denitrifiers were enriched in the sludge biomass rather than in the PUS-biofilm. The results of illumina sequencing revealed that acetate followed by propionate were favourable to the growth of microorganisms that were associated with the BNR process, which was the main reason for the high efficiency of nutrient removal in the acetate and propionate feed systems.

Treatment of landfill leachate using single-stage anoxic moving bed biofilm reactor and aerobic membrane reactor

Landfill leachate (LFL) is one of the most serious environmental problems due to the high concentrations of toxic and hazardous matters. Although several physical, chemical, methods have been tested, biological processes and single or multiple-stage combinations of them have been receiving more attention due to their cost-effective and environmentally-friendly manner. The present work recommended coupling of conventional single-stage A/O with moving bed biofilm reactor and membrane bioreactor (AnoxMBBR/AeMBR) for LFL treatment. The system performance was evaluated for 233 d under varying nitrate concentrations (100-1000 mgNO₃^--N/L), sludge retention time (SRT) (30-90 d), and HRT (24-48 h) in AnoxMBBR, and constant SRT (infinite) and HRT (48 h) in the AeMBR. The best system performances were observed at 1000 mgNO₃^--N/L concentration, SRT of 90 d and HRT of 48 h, and the average removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), and nitrate‑nitrogen (NO₃^-N) were 74.2%, 99.7%, and 89.1%, respectively. Besides, the AeMBR was achieved above 99% NH₄⁺-N removal and not adversely affected by varying operation conditions of AnoxMBBR. A slight increase in selected phthalic acid ester (PAE) concentrations (diethyl phthalate (DEP), di (2-Ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP)) was detected in the AnoxMBR, and complete PAEs removal was attained in the AeMBR. Mg, Al, Si, Na, Fe was detected by SEM-EDX analyses in both biofilm of AnoxMBBR and the cake layers of AeMBR. Nitrobacter and Nitratireductor which showed a relatively high abundance played an important role in the removal of NH₄⁺-N and COD in LFL. The results confirmed that the proposed sequence is efficient for COD removal, nitrogen removal, and PAEs being an acceptable treatment for landfill leachates.

Potential Utilisation of Dark-Fermented Palm Oil Mill Effluent in Continuous Production of Biomethane by Self-Granulated Mixed Culture

Two-stage anaerobic digestion of palm oil mill effluent (POME) is a promising method for converting the waste from the largest agricultural industry in Southeast Asia into a clean and sustainable energy. This study investigates the degradation of acid-rich effluent from the dark fermentation stage for the production of biomethane (BioCH4) in a 30-L continuous stirred-tank reactor (CSTR). The continuous methanogenic process was operated with varied HRTs (10 - 1 day) and OLRs (4.6-40.6 gCOD/L.d-1) under thermophilic conditions. Methanothermobacter sp. was the dominant thermophilic archaea that was responsible for the production rate of 4.3 LCH4/LPOME.d-1 and methane yield of 256.77 LCH4kgCOD at HRT of 2 d, which is the lowest HRT reported in the literature. The process was able to digest 85% and 64% of the initial POME's COD and TSS, respectively. The formation of methane producing granules (MPG) played a pivotal role in sustaining the efficient and productive anaerobic system. We report herein that the anaerobic digestion was not only beneficial in reducing the contaminants in the liquid effluent, but generating BioCH4 gas with a positive net energy gain of 7.6 kJ/gCOD.

A pilot-scale study on the treatment of landfill leachate by a composite biological system under low dissolved oxygen conditions: Performance and microbial community

In this work, a pilot-scale low dissolved oxygen (DO) composite biological system (LDOCBS) composed of an anoxic rotating biological contactor (RBC) and four aeration tanks with gradient aeration was used to treat landfill leachate for 88 d. The maximum removals of 85.65%, 99.92% and 84.06% for chemical oxygen demand (COD), ammonia (NH₄⁺-N) and total nitrogen (TN) were achieved, respectively. The three-dimensional exaction and emission matrix (3D-EEM) fluorescence spectroscopy revealed that the biodegradability of leachate was significantly improved by the LDOCBS. Mass balance calculations showed that the COD removal and denitrification process mainly occurred in RBC while 1# contributed primarily to nitrification. High-throughput sequencing analysis indicated that denitrifying bacteria with highly relative abundances of 46.45%-53.81% played key roles in organic degradation and nitrogen removal. This work could add some guiding insights into the cost-efficient treatment of landfill leachate by the composite biological system.

Influence of reflux ratio on two-stage anoxic/oxic with MBR for leachate treatment: Performance and microbial community structure

A lab-scale two-stage Anoxic/Oxic with MBR (AO/AO-MBR) system was operated for 81 days for leachate treatment with different reflux ratio (R). The best system performances were observed with a R value of 150%, and the average removal efficiencies of chemical oxygen demand, ammonia and total nitrogen were 85.6%, 99.1%, and 77.6%, respectively. The microbial community were monitored and evaluated using high-throughput sequencing. Proteobacteria were dominant in all process. Phylogenetic trees were described at species level, genus Thiopseudomonas, Amaricoccus, Nitrosomonas and Nitrobacter played significant roles in nitrogen removal. Co-occurrence analyzing top 20 genera showed that Nitrosomonas-Nitrobacter presented perfect positive relationship, as well as Paracoccus-Brevundimonas and Pusillimonas-Halobacteriovorax.

Novel approach of adaptive laboratory evolution: triggers defense molecules in Streptomyces sp. against targeted pathogen

Adaptive laboratory evolution by competition-based co-culture: triggers and enhance specific bioactive molecules against targeted pathogen.

Influence of temperature on volatile fatty acid production and microbial community structure during anaerobic fermentation of microalgae

The objectives of this study were to investigate the effect of operating temperature on volatile fatty acids (VFAs) production from microalgal biomass, and to clarify the relationships between VFAs accumulation at different temperatures and the corresponding bacterial communities. The VFA yields were 0.10±0.017, 0.12±0.008, and 0.34±0.009 g/g VS at 35, 45, and 55 °C, respectively. The proportion of acetic acid decreased from 85.6% to 65.8% as operating temperature increased, whereas that of propionic acid increased from near 0% to 15.5% and that of iso-valeric acid remained relatively stable (10.2-11.2%). Bacterial communities at different operating temperatures consisted mostly of the phyla Proteobacteria, Bacteroidetes, and Firmicutes, which can degrade organic compounds effectively. Bacillus sp. was more predominant at 55 °C than at mesophilic temperatures, suggesting that this microorganism contributed significantly to the higher hydrolysis rate and VFA yield at this operating temperature.

454-Pyrosequencing Reveals Microbial Community Structure and Composition in a Mesophilic UAFB System Treating PTA Wastewater

To well understand the community structure and composition of mesophilic microorganisms in anaerobic system fed with PTA wastewater, an up-flow anaerobic fixed bed reactor was continuously run at 33 and 37 °C for 75 and 60 days, respectively. Both fluorescence in situ hybridization analysis and 454-pyrosequencing were applied to investigate the microbial distinction within mesophilic ranges. A preferable performance was achieved at 37 than 33 °C. The taxonomic complexities of two samples were further compared at phylum, class, and genus levels. Notably, microbial diversity differed a lot and the change of populations was observed mainly in the shared OTUs. Genus level analysis showed that when temperature was increased to 37 °C, the abundance of Thauera and Hydrogenophaga (β-Proteobacteria) decreased by 93.75 and 61.47 %, respectively, whereas that of Syntrophorhabdus (δ-Proteobacteria) increased from 4.93 to 16.01 %. Furthermore, the dominant archaeal Methanobacterium at both temperatures indicated the prevailing contribution of hydrogenotrophic methanogens in mesophilic anaerobic system.