Full-scale study on high-rate low-temperature anaerobic digestion of agro-food wastewater: process performances and microbial community.

The fast-growing global population has led to a substantial increase in food production, which generates large volumes of wastewater during the process. Despite most industrial wastewater being discharged at lower ambient temperatures (<20 °C), majority of the high-rate anaerobic reactors are operated at mesophilic temperatures (>30 °C). High-rate low-temperature anaerobic digestion (LtAD) has proven successful in treating industrial wastewater both at laboratory and pilot scales, boasting efficient organic removal and biogas production.

Combined Stochastic and Deterministic Processes Drive Community Assembly of Anaerobic Microbiomes During Granule Flotation.

Advances in null-model approaches have resulted in a deeper understanding of community assembly mechanisms for a variety of complex microbiomes. One under-explored application is assembly of communities from the built-environment, especially during process disturbances. Anaerobic digestion for biological wastewater treatment is often underpinned by retaining millions of active granular biofilm aggregates.

Microbial Community Redundancy and Resilience Underpins High-Rate Anaerobic Treatment of Dairy-Processing Wastewater at Ambient Temperatures.

High-rate anaerobic digestion (AD) is a reliable, efficient process to treat wastewaters and is often operated at temperatures exceeding 30°C, involving energy consumption of biogas in temperate regions, where wastewaters are often discharged at variable temperatures generally below 20°C. High-rate ambient temperature AD, without temperature control, is an economically attractive alternative that has been proven to be feasible at laboratory-scale. In this study, an ambient temperature pilot scale anaerobic reactor (2 m) was employed to treat real dairy wastewater at a milk processing plant, at organic loading rates of 1.

Reactor configuration influences microbial community structure during high-rate, low-temperature anaerobic treatment of dairy wastewater.

Low temperature anaerobic digestion remains in its infancy, despite increasing interest for the treatment of complex wastewaters. In this study, the feasibility of low-temperature anaerobic treatment of dairy wastewater was assessed during a 443-day laboratory-scale bioreactor trial. The bioreactors were operated in triplicate at organic loading rates of 7.

Biological Phosphorus Removal During High-Rate, Low-Temperature, Anaerobic Digestion of Wastewater.

We report, for the first time, extensive biologically mediated phosphate removal from wastewater during high-rate anaerobic digestion (AD). A hybrid sludge bed/fixed-film (packed pumice stone) reactor was employed for low-temperature (12°C) anaerobic treatment of synthetic sewage wastewater. Successful phosphate removal from the wastewater (up to 78% of influent phosphate) was observed, mediated by biofilms in the reactor.

Microbial community structure and dynamics in anaerobic fluidized-bed and granular sludge-bed reactors: influence of operational temperature and reactor configuration.

Methanogenic community structure and dynamics were investigated in two different, replicated anaerobic wastewater treatment reactor configurations [inverted fluidized bed (IFB) and expanded granular sludge bed (EGSB)] treating synthetic dairy wastewater, during operating temperature transitions from 37°C to 25°C, and from 25°C to 15°C, over a 430-day trial. Non-metric multidimensional scaling (NMS) and moving-window analyses, based on quantitative real-time PCR data, along with denaturing gradient gel electrophoresis (DGGE) profiling, demonstrated that the methanogenic communities developed in a different manner in these reactor configurations. A comparable level of performance was recorded for both systems at 37°C and 25°C, but a more dynamic and diverse microbial community in the IFB reactors supported better stability and adaptative capacity towards low temperature operation.

Low-temperature anaerobic digestion for wastewater treatment.

Methanogenesis is an important biogeochemical process for the degradation of organic matter within cold environments, and is associated with the release of the potent greenhouse gas, methane. Cold methanogenesis has been harnessed, in engineered systems, as low-temperature anaerobic digestion (LTAD) for wastewater treatment and bioenergy generation. LTAD represents a nascent wastewater treatment biotechnology, which offers an attractive alternative to conventional aerobic and anaerobic processes.

Quantitative and qualitative analyses of methanogenic community development in high-rate anaerobic bioreactors.

Methanogenic community structure and population dynamics were investigated in two anaerobic reactors treating a dairy wastewater, an Inverted Fluidized Bed (IFB) and Expanded Granular Sludge Bed (EGSB). A combination of real-time PCR, denaturing gradient gel electrophoresis and statistical techniques was employed. Distinct methanogenic communities developed in the IFB and EGSB reactors reflecting step-wise reductions in the applied hydraulic retention time from 72 to 12 h during the 200-day trial.

Microbial community dynamics associated with biomass granulation in low-temperature (15 degrees C) anaerobic wastewater treatment bioreactors.

Granular biofilms underpin the operation of several categories of anaerobic wastewater treatment bioreactors. Recent studies have demonstrated the feasibility of treating both industrial and domestic wastewaters at their discharge temperatures (usually <18 degrees C), thereby avoiding the heating expenses of mesophilic (20-45 degrees C) or thermophilic (45-65 degrees C) treatments. Previous low-temperature trials used mesophilic inocula and little information is available on the viability of low-temperature anaerobic granulation.

Psychrophilic methanogenic community development during long-term cultivation of anaerobic granular biofilms.

Granular biomass was temporally sampled from a cold (4-15 degrees C) anaerobic bioreactor, which was inoculated with mesophilic biomass and used to treat industrial wastewater in a long-term (3.4 year) study. Data from 16S rRNA gene clone libraries, quantitative PCR and terminal restriction fragment length polymorphism analyses indicated that microbial community structure was dynamic, with shifts in the archaeal and bacterial communities' structures observed following start-up and during temperature decreases from 15 to 9.

Quantitative and qualitative analysis of methanogenic communities in mesophilically and psychrophilically cultivated anaerobic granular biofilims.

Anaerobic granulation describes the self-immobilisation of methanogenic consortia into dense, particulate biofilms. This procedure underpins the operation of several categories of high-rate anaerobic wastewater treatment system. Full-scale anaerobic granular sludge plants have been generally operated in the mesophilic (20-45 degrees C) or thermophilic (45-65 degrees C) temperature range.

Long-term (1,243 days), low-temperature (4-15 degrees C), anaerobic biotreatment of acidified wastewaters: bioprocess performance and physiological characteristics.

The feasibility of long-term (>3 years), low-temperature (4-15 degrees C) and anaerobic bioreactor operation, for the treatment of acidified wastewater, was investigated. A hybrid, expanded granular sludge bed-anaerobic filter bioreactor was seeded with a mesophilic inoculum and employed for the mineralization of moderate-strength (3.75-10 kg chemical oxygen demand (COD)m(-3)) volatile fatty acid-based wastewaters at 4-15 degrees C.

Accessing the black box of microbial diversity and ecophysiology: recent advances through polyphasic experiments.

The microbial ecology of a range of anaerobic biological assemblages (granular sludge) from full- and laboratory-scale wastewater treatment bioreactors, and of crop-growing and peat soils, was determined using a variety of 16S rRNA gene-based techniques, including clone library, terminal restriction fragment length polymorphism (TRFLP) and denaturing gradient gel electrophoresis (DGGE) analyses. Fluorescent in situ hybridization (FISH) using 16S rRNA gene-targeted probes was employed to complete a "full-cycle rRNA approach" with selected biomass. Genetic fingerprinting (TRFLP and DGGE) was effectively used to elucidate community structure-crop relationships, and to detect and monitor trends in bioreactor sludge and specific enrichment cultures of peat soil.

New low-temperature applications of anaerobic wastewater treatment.

Low-temperature or psychrophilic (<20 degrees C) anaerobic biological treatment of simple industrial wastewaters has recently been proven feasible as an alternative to more expensive mesophilic (ca. 37 degrees C) technology. We implemented novel expanded granular sludge bed (EGSB)-based bioreactor designs for 27 psychrophilic anaerobic digestion (PAD) trials for the treatment of a broad range of simple and complex synthetic wastewaters representing dairy, food-processing and pharmaceutical sector effluents.

Stability and reproducibility of low-temperature anaerobic biological wastewater treatment.

The reproducibility of low-temperature anaerobic biological wastewater treatment trials was evaluated. Two identical anaerobic expanded granular sludge bed bioreactors were used to treat synthetic volatile fatty acid-based industrial wastewater under ambient conditions (18-20 degrees C) and to investigate the effect of various environmental perturbations on reactor performance and microbial community dynamics, which were assessed by chemical oxygen demand removal or effluent volatile fatty acid determination and terminal restriction fragment length polymorphism analysis, respectively. Methanogenic activity was monitored using specific methanogenic activity assays.

Distribution, localization, and phylogeny of abundant populations of Crenarchaeota in anaerobic granular sludge.

Eight anaerobic granular sludges were surveyed for Crenarchaeota using rRNA gene cloning. Microbial arrangement and substrate uptake patterns were elucidated by fluorescent in situ hybridization and beta imaging. Group 1.

Anaerobic biological treatment of phenolic wastewater at 15-18 degrees C.

Low-temperature, or psychrophilic (<20 degrees C) anaerobic digestion has been proven feasible for the mineralisation of simple wastewaters. In this study, hybrid expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors were used to evaluate the feasibility of psychrophilic digestion for the treatment of phenol-containing wastewater. Efficient chemical oxygen demand and phenol removal were observed at organic and phenol loading rates of 5 kg COD m(-3)d(-1) and 0.

Methanogenic population structure in a variety of anaerobic bioreactors.

The methanogenic community structures of six anaerobic sludges were examined using culture-independent techniques. The sludges were obtained from full-scale and laboratory-scale bioreactors, treating a variety of low- and high-strength, simple and complex wastewaters at psychrophilic (10-14 degrees C), mesophilic (37 degrees C) and thermophilic (55 degrees C) temperatures. Amplified rDNA restriction analysis identified 18 methanogenic operational taxonomic units in the six samples.