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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. In this study, we demonstrated the feasibility of two full-scale high-rate LtAD bioreactors treating meat processing and dairy wastewater, and the microbial communities in both reactors were examined. Both reactors exhibited rapid start-up, achieving considerable chemical oxygen demand (COD) removal efficiencies (total COD removal >80%) and generating high-quality biogas (CH4% in biogas >75%). Long-term operations (6-12 months) underscored the robustness of LtAD bioreactors even during winter periods (average temperature <12 °C), as evidenced by sustained high COD removal rates (total COD removal >80%). The stable performance was underpinned by a resilient microbial community comprising active acetoclastic methanogens, hydrolytic, and fermentative bacteria. These findings underscore the feasibility of high-rate low-temperature anaerobic wastewater treatment, offering promising solutions to the zero-emission wastewater treatment challenge.

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Municipal wastewater constitutes the largest fraction of wastewater, and yet treatment processes are largely removal-based. High-rate anaerobic digestion (AD) has revolutionised the sustainability of industrial wastewater treatment and could additionally provide an alternative for municipal wastewater. While AD of dilute municipal wastewater is common in tropical regions, the low temperatures of temperate climates has resulted in slow uptake. Here, we demonstrate for the first time, direct, high-rate, low-temperature AD of low-strength municipal wastewater at full-scale. An 88 m3 hybrid reactor was installed at the municipal wastewater treatment plant in Builth Wells, UK and operated for 290 days. Ambient temperatures ranged from 2 to 18 °C, but remained below 15 °C for > 100 days. Influent BOD fluctuated between 2 and 200 mg L-1. However, BOD removal often reached > 85%. 16S rRNA amplicon sequencing of DNA from the biomass revealed a highly adaptable core microbiome. These findings could provide the basis for the next-generation of municipal wastewater treatment.

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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 m3) was employed to treat real dairy wastewater in situ at a milk processing plant, at organic loading rates of 1.3 ± 0.6 to 10.6 ± 3.7 kg COD/m3/day and hydraulic retention times (HRT) ranging from 36 to 6 h. Consistent high levels of COD removal efficiencies, ranging from 50 to 70% for total COD removal and 70 to 84% for soluble COD removal, were achieved during the trial. Within the reactor biomass, stable active archaeal populations were observed, consisting mainly of Methanothrix (previously Methanosaeta) species, which represented up to 47% of the relative abundant active species in the reactor. The decrease in HRT, combined with increases in the loading rate had a clear effect on shaping the structure and composition of the bacterial fraction of the microbial community, however, without affecting reactor performance. On the other hand, perturbances in influent pH had a strong impact, especially when pH went higher than 8.5, inducing shifts in the microbial community composition and, in some cases, affecting negatively the performance of the reactor in terms of COD removal and biogas methane content. For example, the main pH shock led to a drop in the methane content to 15%, COD removals decreased to 0%, while the archaeal population decreased to ~11% both at DNA and cDNA levels. Functional redundancy in the microbial community underpinned stable reactor performance and rapid reactor recovery after perturbations.

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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. Scanning electron microscopy and energy dispersive X-ray analysis revealed the accumulation of elemental phosphorus (∼2%) within the sludge bed and fixed-film biofilms. 4', 6-diamidino-2-phenylindole (DAPI) staining indicated phosphorus accumulation was biological in nature and mediated through the formation of intracellular inorganic polyphosphate (polyP) granules within these biofilms. DAPI staining further indicated that polyP accumulation was rarely associated with free cells. Efficient and consistent chemical oxygen demand (COD) removal was recorded, throughout the 732-day trial, at applied organic loading rates between 0.4 and 1.5 kg COD m(-3) d(-1) and hydraulic retention times of 8-24 h, while phosphate removal efficiency ranged from 28 to 78% on average per phase. Analysis of protein hydrolysis kinetics and the methanogenic activity profiles of the biomass revealed the development, at 12°C, of active hydrolytic and methanogenic populations. Temporal microbial changes were monitored using Illumina MiSeq analysis of bacterial and archaeal 16S rRNA gene sequences. The dominant bacterial phyla present in the biomass at the conclusion of the trial were the Proteobacteria and Firmicutes and the dominant archaeal genus was Methanosaeta. Trichococcus and Flavobacterium populations, previously associated with low temperature protein degradation, developed in the reactor biomass. The presence of previously characterized polyphosphate accumulating organisms (PAOs) such as Rhodocyclus, Chromatiales, Actinobacter, and Acinetobacter was recorded at low numbers. However, it is unknown as yet if these were responsible for the luxury polyP uptake observed in this system. The possibility of efficient phosphate removal and recovery from wastewater during AD would represent a major advance in the scope for widespread application of anaerobic wastewater treatment technologies.

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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. Successful, high-rate, LTAD of sewage and industrial wastewaters (e.g. from the brewery, food-processing and pharmaceutical sectors), with concomitant biogas generation, has been demonstrated at laboratory-scale and pilot-scale. A holistic, polyphasic approach, which integrates bioprocess, physiological and molecular biological datasets has been critical to the development of the LTAD concept.

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BACKGROUND: The reported incidence of adenocarcinoma in patients with Barrett's oesophagus in surveillance programmes varies widely. Great Britain has one of the highest incidence rates of this cancer in the world, but there are no data from Ireland reporting its incidence in patients with Barrett's oesophagus undergoing surveillance. We carried out a study of all such patients at a large District General Hospital in Northern Ireland. METHODS: A retrospective review of all patients with Barrett's oesophagus from January 1986 to March 2004 at Altnagelvin Area Hospital, Derry, Northern Ireland was performed. Barrett's oesophagus was defined as specialized intestinal metaplasia present in the tubular oesophagus. RESULTS: A total of 277 patients had Barrett's oesophagus. Twenty-one patients had adenocarcinoma and two patients had high-grade dysplasia at initial endoscopy and were excluded. Of the remaining 254 patients, 178 were entered into the surveillance programme (127 men, 51 women). The average follow-up period was 3.4 years, resulting in 613 patient-years of follow-up. Three patients developed adenocarcinoma, an incidence of 1/204 patient-years of follow-up. Two of the three patients had early-stage (T1 or T2) cancers detected and are alive and well. A total of 429 surveillance endoscopies were performed, and a marked year-on-year increase in the workload generated as a result of the surveillance programme was observed. CONCLUSIONS: The incidence of adenocarcinoma in patients in Northern Ireland was similar to the incidence reported by other large institutions. Clinical benefit is suggested but is not certain from these data, because of biases that affect surveillance programmes. Large multicentre studies are required to determine whether surveillance is beneficial.

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BACKGROUND: There are various, well-documented, duodenal endoscopic markers caused by the villous atrophy of celiac disease. Another abnormality seen in association with villous atrophy, erosions in the second part of the duodenum, is described. To our knowledge, this finding has not been heretofore described in patients with celiac disease. METHODS: Five patients with celiac disease and erosions were encountered over a period of 2 years. OBSERVATIONS: The erosions were multiple, superficial, and present in the second part of the duodenum but not the duodenal bulb. All 5 patients had findings typical of celiac disease (iron deficiency, osteopenia/osteoporosis), and 4 had at least one other endoscopic marker: scalloped duodenal folds (3), fold loss (2), or mosaic pattern mucosa (2). These patients represented 7% of new cases of celiac disease during the same time period. This pattern of erosion was not observed in over 1200 other patients undergoing upper endoscopy during the study period. CONCLUSIONS: In a European population, the finding of erosions confined to the second part of the duodenum is specific for villous atrophy, although sensitivity is low. Erosions in the second part of the duodenum should be added to the list of endoscopic markers of celiac disease.

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