Investigation on evaluation criteria of backwashing effects for a pilot-scale BAF treating petrochemical wastewater

<p>Parameters for evaluation criteria of air–water backwashing effects of a pilot-scale biological aerated filter (BAF) treating petrochemical wastewater were investigated. The parameters included the suspended solids (SS) and specific oxygen uptake rate (SOUR) of the backwashing effluent, recovery of the BAF after backwashing, and the removal of the biomass/bioactivity attached on the filter media after backwashing. Results showed that the weight of the total sludge produced in the backwashing effluent increased with the increase in water-backwashing intensity, while the total SOUR of backwashing effluent rose notably with the increase of air-backwashing intensity. The optimal backwashing intensity of 14 L/(m²<b>_·</b>s) for air and 4 L/(m²<b>_·</b>s) for water were obtained. When the BAF was backwashed on this condition, the BAF recovered with high average removal of chemical oxygen demand (COD) and ammonia nitrogen of 14.3% and 50.3%, respectively. High amount of biomass removal at 15.8% and low level of bioactivity removal at 8.8% attached on the filter media were also found. Concentrations of the benzene, toluene, ethylbenzene and (<i>o</i>-, <i>m</i>-, <i>p</i>-) xylenes (BTEX) and phenol in the backwashed sludge were analyzed, showing that the backwashing was essential to remove some aromatic compounds adsorbed in the microorganisms.</p

Nitrogen Removal and N₂O Accumulation during Hydrogenotrophic Denitrification: Influence of Environmental Factors and Microbial Community Characteristics

Hydrogenotrophic denitrification is regarded as an efficient alternative technology of removing nitrogen from nitrate-polluted water that has insufficient organics material. However, the biochemical process underlying this method has not been completely characterized, particularly with regard to the generation and reduction of nitrous oxide (N₂O). In this study, the effects of key environmental factors on hydrogenotrophic denitrification and N₂O accumulation were investigated in a series of batch tests. The results show that nitrogen removal was efficient with a specific denitrification rate of 0.66 kg N/(kg MLSS·d), and almost no N₂O accumulation was observed when the dissolved hydrogen (DH) concentration was approximately 0.40 mg/L, the temperature was 30 °C, and the pH was 7.0. The reduction of nitrate was significantly affected by the pH, temperature, inorganic carbon (IC) content, and DH concentration. A considerable accumulation of N₂O was only observed when the pH decreased to 6.0 and the temperature decreased to 15 °C, where little N₂O accumulated under various IC and DH concentrations. To determine the microbial community structure, the hydrogenotrophic denitrifying enrichment culture was analyzed by Illumina high-throughput sequencing, and the dominant species were found to belong to the genera <i>Paracoccus</i> (26.1%), <i>Azoarcus</i> (24.8%), <i>Acetoanaerobium</i> (11.4%), <i>Labrenzia</i> (7.4%), and <i>Dysgonomonas</i> (6.0%)

Additional file 1: Figure S1. of Bacteriophage–prokaryote dynamics and interaction within anaerobic digestion processes across time and space

Spatiotemporal changes in (A) richness of phages, (B) richness of prokaryotes, (C) the α-diversity of phages and (D) the α-diversity of prokaryotes. BJ Beijing samples, QD Qingdao samples, Ningbo-M: samples from Ningbo anaerobic digester maintained at mesophilic temperature, and Ningbo-T samples from Ningbo anaerobic digester maintained at thermophilic temperature. Figure S2. Proportions of phages based on their detection frequencies in anaerobic digesters. Figure S3. The most abundant phages detected in Beijing samples as functions of (A) time and their average relative abundance in samples across (B) space. Figure S4. Association networks generated from (A) Beijing, (B) Ningbo-T, (C) Ningbo-M, and (D) Qingdao samples. Modules with equal or less than five nodes were omitted. Positive linkages are shown in red edges, while negative linkages are shown in blue edges. Spearman’s correlation coefficients are indicated by line width. Figure S5. Association networks generated according to seasons: (A) winter, (B) spring, (C) summer, and (D) autumn. Modules with equal or less than five nodes were omitted. Positive linkages are shown in red edges, while negative linkages are shown in blue edges. Spearman’s correlation coefficients are indicated by line width. Table S1. Dissimilarity tests of Mrpp, Anosim, and Adonis on community structures. Table S2. Measurements of physicochemical properties related to process performance. Table S3. Taxonomic information of Euryarchaeota OTUs. Table S4. Major properties of association networks. Table S5. Dissimilarity of phage communities between months represented as β-diversity. Boldface values indicate dissimilarities between two consecutive months. (DOCX 5058 kb