Optimizing start-up strategies for the two-inflow nitritation/anammox process: Influence on biofilm microbial community composition.

Low-energy nitrogen removal from ammonium-rich wastewater is crucial in preserving the water environment. A one-stage nitritation/anammox process with two inflows treating ammonium-containing wastewater, supplied from inside and outside the wound filter, is expected to stably remove nitrogen. Laboratory-scale reactors were operated using different start-up strategies; the first involved adding nitritation inoculum after anammox biomass formation in the filter, which presented a relatively low nitrogen removal rate (0.171 kg N/m3 · d), at a nitrogen loading rate of 1.0 kg N/m3 · d. Conversely, the second involved the gradual cultivation of anammox and nitritation microorganisms, which increased the nitrogen removal rate (0.276 kg N/m3 · d). Furthermore, anammox (Candidatus Brocadia) and nitritation bacteria (Nitrosomonadaceae) coexisted in the biofilm formed on the filter surface. The abundance of nitritation bacteria (10.5%) in the reactor biofilm using the second start-up strategy was higher than that using the first (3.7%). Thus, the two-inflow nitritation/anammox process effectively induced habitat segregation using a suitable start-up strategy.

Metagenomic insights into the effect of sulfate on enhanced biological phosphorus removal.

Excess phosphorus in water supplies causes eutrophication, which degrades water quality. Hence, the efficient removal of phosphorus from wastewater represents a highly desirable process. Here, we evaluated the effect of sulfate concentration on enhanced biological phosphorus removal (EBPR), in which phosphorus is typically removed under anaerobic-oxic cycles, with sulfate reduction the predominant process in the anaerobic phase. Two sequencing batch EBPR reactors operated under high- (SBR-H) vs. low-sulfate (SBR-L) concentrations for 189 days and under three periods, i.e., start-up, sufficient acetate, and limited acetate. Under acetate-rich conditions, phosphorus removal efficiency was > 90% for both reactors; however, under acetate-limited conditions, only 34% and 91.3% of the phosphorus were removed for the SBR-L and the SBR-H, respectively. Metagenomic sequencing of the reactors showed that the relative abundance of the polyphosphate-accumulating and sulfur-reducing bacteria (SRB) was higher in the SBR-H, consistent with its higher phosphorus removal activity. Ten high-quality metagenome-assembled genomes, including one closely related to the genus Thiothrix disciformis (99.81% average amino acid identity), were recovered and predicted to simultaneously metabolize phosphorus and sulfur by the presence of phosphorus (ppk, ppx, pst, and pit) and sulfur (sul, sox, dsr, sqr, apr, cys, and sat) metabolism marker genes. The omics-based analysis provided a holistic view of the microbial ecosystem in the EBPR process and revealed that SRB and Thiothrix play key roles in the presence of high sulfate.Key points• We observed high phosphorus-removal efficiency in high-sulfate EBPR.• Metagenome-based analysis revealed sulfate-related metabolic mechanisms in EBPR.• SRB and PAOs showed interrelationships in the EBPR-sulfur systems.

Biodegradability of woody film produced by solvent volatilisation of Japanese Beech solution.

To address the problem of marine pollution from discarded plastics, we developed a highly biodegradable woody film, with almost the same components as wood, from the formic acid solution of ball-milled wood. We found that the woody film was not easily degraded by cultured solution of hand bacteria (phylum Proteobacteria was dominant). However, the film was easily biodegraded when in cultured solution of soil (Firmicutes, especially class Bacilli, was dominant) for 4 weeks at 37 °C, or when buried in the soil itself, both under aerobic conditions (Acidobacteria and Proteobacteria were dominant) for 40 days at room temperature and under anaerobic conditions (Firmicutes, especially family Ruminococcaceae, was dominant) for 5 weeks at 37 °C. Moreover, when film was buried in the soil, more carbon dioxide was generated than from soil alone. Therefore, the film was not only brittle but formed of decomposable organic matter. We showed that the film does not decompose at the time of use when touched by the hand, but it decomposes easily when buried in the soil after use. We suggest that this biodegradable woody film can be used as a sustainable raw material in the future.

Enhancement of methane production and phosphorus recovery with a novel pre-treatment of excess sludge using waste plaster board.

A new pre-treatment process for excess sludge is proposed to increase methane production and recover phosphorus by adding waste plaster board as calcium sulfate. The content of calcium sulfate in the plaster granules (PG) used in this study is 99%. When PG and calcium sulfate are added to the excess sludge generated from a municipal wastewater treatment plant, acetate production is enhanced as per sulfate reduction and phosphorus release is reduced via the formation of calcium phosphate. In the continuous pre-treatment experiment performed at 25 °C and for 10 days of sludge retention time (SRT) using calcium sulfate, 1935 ±â€¯395 mg/L of acetate is produced with 1070 ±â€¯255 mg/L of sulfate, which is reduced. Desulfobulbus spp., which can oxidize organic matter to acetate incompletely, have been observed in the pre-treated sludge. The pre-treated sludge has subsequently been used for methophiric anaerobic digestion. The methane yield from the pre-treated sludge is found to be 1.2 times that of the non-pretreated sludge at an SRT of 30 days, indicating that the pre-treatment using PG can improve methane production. Phosphorus is released from the non-pretreated sludge in the digester. Nevertheless, a decrease in phosphorus content has been observed, resulting in the digested sludge containing calcium phosphate that is useful for agriculture.