Search

Domestic wastewater is a potential medium for microbial cultivation because it contains abundant non-toxic inorganic salts and organic nutrients. However, studies of the feasibility of using wastewater as medium have focused on removal rates, while ignoring changes in biomass composition. Therefore, this study investigated the feasibility of growing Chlorella vulgaris in domestic wastewater, while focusing on its nutrient removal rates and biomass composition. Results showed that Chlorella vulgaris growth rate and biomass were significantly promoted by domestic wastewater compared with BG11 medium. The maximum biomass (17.94 × 10 6 cell L −1 ) was obtained when 100% domestic wastewater was used. The highest COD removal rate was 93.6% obtained by 75% of wastewater, while the highest NH 4 + –N and TP removal rates were 98.69% and 86.07% by 25% of wastewater. The harvested biomass was rich in protein (40.9–50.7%) and low in lipids (23.4–28.5%), and both the nutritional quality and quantity of protein and lipid were increased in dilutions. These results indicated that domestic wastewater is a feasible medium for mass-cultivation of Chlorella vulgaris , and 100% dilution is suggested. [ABSTRACT FROM AUTHOR]

2,4,6-trichlorophenol (2,4,6-TCP) aerobic degrading granules were successfully developed in the sequencing batch airlift reactor. The key strategy used in cultivation of the granules was dosing glucose and acetate as co-substrates. After granulation, average concentrations of 2,4,6-TCP and COD in the effluent were less than 8 mg L −1 and 59 mg L −1 , respectively. The removal efficiencies of 2,4,6-TCP and COD were above 93% and 90%, respectively. The specific degradation rate of 2,4,6-TCP peaked at 61 mg 2,4,6-TCP g VSS −1 h −1 when inoculated at the concentration of 400 mg L −1 . The extracellular polymeric substance (EPS) contents of the 2,4,6-TCP aerobic degrading granules were decreased compared with the contents in seed sludge. Two peaks attributed to the protein-like fluorophores were identified by three-dimensional excitation emission matrix (EEM) fluorescence spectra. The decrease of fluorescence parameters, e.g., peak locations, intensities, indicated quenching effect of 2,4,6-TCP on the EPS fluorescence. Meanwhile, the shift of peak position indicated chemical changes of the EPS. [ABSTRACT FROM AUTHOR]

The performance and microbial community changes of an activated sludge sequencing batch reactor were evaluated after exposure to trimethoprim for 51 days. The average chemical oxygen demand, ammonia nitrogen, phosphorus efficiencies were 88.6% ± 0.56%, 90.47% ± 0.29% and 64.25% ± 1.12%, respectively. The protein and polysaccharide contents increased with increasing trimethoprim concentration to protect the cells from the unfavorable conditions. The chemical composition of extracellular polymeric substances increased. For denitrifying bacteria, the read numbers of Pseudomonas , Flavobacterium and Bacillus were both significantly increased from Day 1 to 25 and sharply decreased by Day 50 ( p < 0.05), which is consistent with the tendency of Planctomyces (Anammox). The read number of Paracoccus displayed an increasing trend, whereas Nitrospirales, Nitrospira (nitrite oxidizer) and Nitrosomonadaceae (ammonia oxidizer) were significantly decreased ( p < 0.05). The read number of Rhodocyclaceae (phosphorus oxidizer) was significantly decreased from Day 1 to 25 and sharply increased by Day 50 ( p < 0.05). [ABSTRACT FROM AUTHOR]

An activated sludge sequencing batch reactor (SBR) was fed with synthetic wastewater containing ofloxacin (OFL) for 52 days to study the overall performance of the SBR, the characteristics of extracellular polymeric substances (EPS) and the bacterial community shift. Removal efficiencies of chemical oxygen demand, ammonia nitrogen, phosphorus and OFL were maintained at 90%, 96%, 80% and 65%, respectively. The EPS contents increased with increasing OFL concentration because more EPS was secreted to protect cells from OFL damage. Moreover, the EPS compositions shifted. For denitrifying bacteria, the read number of Pseudomonas and Bacillus sharply decreased initially ( p < 0.05) and increased from Day 25 to Day 50, which agreed with the tendency of Nitrosomonadaceae (ammonia oxidizer), while Paracoccus significantly decreased ( p < 0.05). The read number of Rhodocyclaceae , a phosphorus-accumulating bacterium, increased. Other functional microbes such as Nitrospirales (nitrite oxidizer) and Planctomyces (anammox) sharply decreased under OFL pressure ( p < 0.05). [ABSTRACT FROM AUTHOR]

The multiplicity and heterogeneity of anaerobic ammonia oxidation (anammox) bacteria make their absolute quantification difficult. To reveal the quantitative relationships among the 16S rRNA gene and typical functional genes ( nir , hzo and hzs genes) in the anammox process and their quantitative association with nitrogen removal (ammonium and nitrite), the genes were extracted from four reactors and quantified by real-time quantitative PCR (q-PCR). The Pearson correlation coefficients among the associated genes exceeded 0.96 ( P < 0.01), and the q-PCR results indicated that the relative copy numbers (compared with the level of the hzo gene, which was set as 1) of the hzs gene, nir gene and 16S rRNA gene per cell were 8.00, 25.22 and 157.67, respectively. Nitrogen removal efficiency was directly proportional to the logarithm of the gene concentration, with most of the R 2 values being greater than 0.9. The functional genes, especially hzo and hzs , are more suitable to assess anammox activity with the R 2 values of fitted equations being greater than 0.96. The mRNA quantity did not correlate with the system nitrogen removal performance directly because of different enzyme activities. This study provided valuable reference data to further reveal the molecular mechanism of anammox metabolism. [ABSTRACT FROM AUTHOR]

This study evaluates greenhouse gas emission and the microbial community dynamics during simultaneous nitrification and denitrification (SND) process. Based on CO 2 equivalents, the SND reactor released 4.28 g of greenhouse gases each cycle. 2.91% of the incoming nitrogen load was emitted as N 2 O. The CO 2 and N 2 O emissions mainly occurred in the aerobic stage and CH 4 emissions were consistently near zero. Extracellular polymeric substance (EPS) contents in activated sludge increased during start-up the SND process. High-throughput sequencing showed increases in bacterial species richness, leading to changes in EPS content and composition observed using 3D-EEM fluorescence spectra. For denitrifying bacteria, the relative abundance of Pseudomonas significantly increased during the SND process, while Paracoccus decreased significantly. For phosphorus-accumulating bacteria, the relative abundance of Rhodocyclaceae also significantly increased. The relative abundance of other functional microbes, such as Nitrosomonadaceae (ammonia oxidizer), Nitrospirales (nitrite oxidizer) and Planctomyces (anammox) decreased significantly during the SND process. [ABSTRACT FROM AUTHOR]

This study characterizes the extracellular polymeric substances and bacterial community composition of aerobic granules exposed to cefalexin (CLX). The presence of CLX potentially decreases granular stabilities, resulting in a lowered granule diameter. Chemical oxygen demand and NH 4 + –N removal efficiencies were slightly decreased and the denitrification process was inhibited with CLX addition. Extracellular polymeric substance contents were significantly increased in aerobic granules exposed to CLX. The shifts of fluorescence intensities and peak locations in 3D-EEM fluorescence spectra indicated changes of EPS components. High-throughput sequencing analysis showed aerobic granules with CLX addition in synthetic wastewater had superior diversity of microbial species, and this was the reason that the level and components of EPS changed. The species richness for bacteria was increased from 341 to 352, which was revealed by Chao1. The Shannon index of diversity rose slightly from 3.59 to 3.73 with CLX addition. The abundance of Proteobacteria significantly decreased, while the abundance of Bacteroidetes and Chloroflexi underwent a highly significant increase in aerobic granules exposed to CLX. [ABSTRACT FROM AUTHOR]

• Salinity did not significantly inhibit the removal efficiency of TP and COD (p > 0.05). • Salinity (5 g/L) significantly increased power density by a factor of 4 (p < 0.05). • The highest power density was 16.4 mW m−2 in saline wastewater treatment. • Electrochemically active bacteria predominated in the microbial community. The use of constructed wetlands in combination with microbial fuel cells (CW-MFC) to treat saline wastewater may enhance electricity production by increasing the ionic strength, reducing internal resistance and stimulating microbes to accelerate electron transfer. In this study, salinity did not significantly inhibit the removal of TP and COD, but TN and NH 4 +-N removal efficiencies during saline wastewater treatment (ST) were significantly lower than during non-saline wastewater treatment (NT). However, salinity significantly increased the power density (16.4 mW m−2 in ST and 3.9 mW m−2 in NT, a 4-fold enhancement) by increasing the electron transfer rate and reducing internal resistance (140.29 Ω in ST and 415.21 Ω in NT). The peptides in extracellular polymeric substances (EPS) acted as electron shuttles to promote the migration of electrons and protons in ST. From start-up to stable operation, though the microorganisms in ST were reduced in diversity relative to NT, the proportion of electrochemically active bacteria (EAB), such as Ochrobactrum , significantly increased (p < 0.05) and gradually predominated in the microbial community. [ABSTRACT FROM AUTHOR]