Effect of Amoxicillin on Nitrogen Oxidation Bacteria Present in Activated Sludge: Respirometry Investigation

Amoxicillin (AMX) is one of the most widely used antibiotics in the world and its presence in wastewater is of great concern for its potential to bacteria selection. However, there is still a gap about the toxicity effect of AMX in nitrifier biomass from activated sludge (AS). This study is based on the implementation of respirometric tests in batches in order to evaluate the toxic effluent toxicity in the nitrification process of AS. The tests were conducted by comparing respiration rates with effluent containing ammonia nitrogen (NH₄⁺-N) and nitrite nitrogen (NO₂^--N) called "reference" and batches containing toxic effluent doped with different concentrations of AMX here called "process." Results with effluent containing concentrations greater than 100 mg L^-1 showed that AMX negatively affected the specific growth rate (μ_m) of ammonia-oxidizing bacteria (AOB) (from 0.50 d^-1 to 0.13 d^-1) and nitrite-oxidizing bacteria (NOB) (from 0.64 d^-1 to 0.15 d^-1). Although there is no total inhibition of populations, these μ_m values are limiting for a feasible development of the nitrification process in AS systems. The removal of AMX decreased from 99 to 37% (liquid phase) when the concentration of AMX increased (20 mg L^-1 to 200 mg L^-1). A decrease in the microbial community AOB and NOB was observed through fluorescent in situ hybridization (FISH), corroborating the results of respirometry. In summary, the study showed that the inhibition of the AS nitrification process occurs in the presence of high concentrations of AMX and the most susceptible group are the NOB.

Successful bio-electrochemical treatment of nitrogenous mariculture wastewater by enhancing nitrogen removal via synergy of algae and cathodic photo-electro-catalysis

Systems with catalytic cathode in microbial fuel cell can achieve high treatment efficiency enhanced by the cathode. Such bio-electrochemical systems have potential applications in treating high-salinity nitrogenous mariculture wastewater. For sustainable development of the mariculture industry, enhancing inorganic nitrogen removal is of vital importance due to the low carbon to nitrogen (C/N) ratio of wastewater and strict discharge standard. Herein, simulated mariculture wastewater (high salinity, low COD/N ratio of 0.5-1.0) was successfully treated in an integrated self-biased bio-electrochemical system, with catalyst (TiO₂/Co-WO₃/SiC) on the cathode and natural-grown algae in the cathode chamber. Satisfactory nitrogen removal (94.05% NH₄⁺-N and 77.35% inorganic nitrogen) and favorable 76.66% removal of organics (UV₂₅₄) were both achieved, with visible light illumination. The NH₄⁺-N in the effluent was below 2 mg L^-1. The synergy of bacteria, algae and cathode, promoted pollutant removal, and made the system sustainable and efficient in treating mariculture wastewater.

Effects of biomass pyrolysis derived wood vinegar on microbial activity and communities of activated sludge

The effects of wood vinegar (WVG) on microbial activity and communities of activated sludge were investigated in a sequencing batch reactor (SBR) process. Results showed that the optimal WVG concentration was 4 μL/L when the pollutants removal efficiency and microbial activity were promoted by a WVG dilution factor of 1000. WVG could reduce the increase in microbial species richness, which led to a more notable variety of microbial species diversity. The enhanced microbial activity and communities were addressed to the promotion of 7 main classes of microbes in Proteobacteria, Bacteroidetes, Acidobacteria, and Nitrospirae phyla. The growth of ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and main genera of denitrifying bacteria (DNB), phosphorus-accumulating organisms (PAOs), and glycogen-accumulating organisms (GAOs) could be promoted by WVG, which improved the sewage treatment effectiveness in a SBR.

Start-up evaluations and biocarriers transfer from a trickling filter to a moving bed bioreactor for synthetic mariculture wastewater treatment

Mariculture wastewater treatment by nitrification requires a long start-up time due to high salinity stress. This study aimed to verify the faster start-up of a trickling filter (TF) compared to a moving bed bioreactor (MBBR) treating synthetic mariculture wastewater, and to investigate the feasibility of transferring mature biocarriers from the TF to a new MBBR (TF-MBBR). The nitrogen removal performance, biofilm physicochemical properties and microbial communities were investigated. The results obtained showed that, the TF started up 41 days faster than the MBBR, despite the richer microbial diversity in the latter. Lower biofilm roughness and protein content as well as higher adhesive force and polysaccharide content in the TF were obtained compared to the MBBR. Adhesive force was found to be negatively correlated with roughness (r = -0.630, p = 0.069). Transmittance assigned to amide II (1538 cm^-1) and amid III (1243 cm^-1) through Fourier transform infrared spectroscopy (FTIR) determination was only obtained in the TF, which was likely related to the faster start-up. Nitrosomonas and Nitrospira were detected as the predominant nitrifiers in both reactors. In addition, the new MBBR, incubated with the mature biocarriers transferred from the TF, had a satisfactory nitrification performance with no lag time. Interestingly, the transfer action increased the microbial diversity and made the biofilm physicochemical characteristics shift toward those of the MBBR. Taken together, the study confirmed that MBBR nitrification start-up can be accelerated via TF and biocarrier transfer.

Impact of ampicillin on the nitrogen removal, microbial community and enzymatic activity of activated sludge

The performance, nitrogen removal rate, extracellular polymeric substances (EPS), microbial community and enzymatic activity of activated sludge have been assessed in a sequencing batch reactor under ampicillin stress. The chemical oxygen demand and ammonia removal kept relatively stable at 0-30 mg/L ampicillin. No obvious nitrite and nitrate accumulation was found in the effluent. However, the oxygen utilization rate, nitrification rate and denitrification rate declined with the increment of ampicillin concentration. The activities of dehydrogenase and microbial enzymes relating to nitrogen removal were inhibited under ampicillin stress. Ampicillin at 20 and 30 mg/L heightened the microbial lactate dehydrogenase release and reactive oxygen species production. Ampicillin promoted the production of EPS, loosely bound EPS and tightly bound EPS and affected their chemical composition. Additionally, the protein/polysaccharide ratios in the EPS and the sludge settleability reduced with the increment of ampicillin concentration. Ampicillin obviously affected the relative abundance of nitrifying- and denitrifying bacteria.

Effect of florfenicol on performance and microbial community of a sequencing batch biofilm reactor treating mariculture wastewater

The effects of florfenicol (FF) on the performance, microbial activity and microbial community of a sequencing batch biofilm reactor (SBBR) were evaluated in treating mariculture wastewater. The chemical oxygen demand (COD) and nitrogen removal were inhibited at high FF concentrations. The specific oxygen utilization rate (SOUR), specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR) and specific nitrate reduction rate (SNRR) were decreased with an increase in the FF concentration from 0 to 35 mg/L. The chemical compositions of loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) could be affected with an increase in the FF concentration. The high-throughput sequencing indicated some obvious variations in the microbial community at different FF concentrations. The relative abundance of Nitrosomonas and Nitrospira showed a decreasing tendency with an increase in the FF concentration, suggesting that FF could affect the nitrification process of SBBR. Some genera capable of reducing nitrate to nitrogen gas could be inhibited by the addition of FF in the influent, such as Azospirillum and Hyphomicrobium.

Removal of nutrients in saline wastewater using constructed wetlands: Plant species, influent loads and salinity levels as influencing factors

This study aims to evaluate how plant species, influent loads and salinity levels affect the removal of nutrients from saline wastewater using constructed wetlands (CWs). CWs planted with Canna indica showed the greatest removal percentages among the four tested species for nitrogen (N) (∼100%) at both low and high influent loads, and ∼100% and 93.8% for phosphorus (P) at low and high influent loads, respectively at an electrical conductivity (EC) of 7 mS/cm (25 °C). The influence of different salinity levels on plant assimilation of N and P varied with their respective concentrations; salinity (e.g., EC at 7, 10 and 15 mS/cm) even enhanced plant absorption of N and P under specific conditions. In conclusion, CWs planted with selected species can be used for the removal of N and P under a range of different salinity levels (e.g., EC at 7, 10 and 15 mS/cm, 25 °C).

Interaction between common antibiotics and a Shewanella strain isolated from an enhanced biological phosphorus removal activated sludge system

With increasing production and consumption, more antibiotics are discharged into wastewater treatment plants and generally cannot be sufficiently removed. Because of the complexities of biological treatment processes, the fates of antibiotics and their effects on microorganisms, particularly those involved in the phosphorus removal system, are still unclear. Here, a Shewanella strain was isolated from an enhanced biological phosphorus removal (EBPR) system and was found to have the ability to remove phosphorus (P) and chemical oxygen demand (CODcr). Antibiotics affected the Shewanella strain through metabolism of the three main intracellular polymers, altering the ability of the strain to remove P and CODcr. These effects varied with the structure and concentration of the antibiotics. The Shewanella strain removed cefalexin and amoxicillin by degradation or adsorption, producing 2-hydroxy-3-phenyl pyrazine from cefalexin. This study enabled the recognition of the effect and removal of antibiotics during wastewater treatment.

Performance evaluation and microbial community of a sequencing batch biofilm reactor (SBBR) treating mariculture wastewater at different chlortetracycline concentrations

The effects of chlortetracycline (CTC) on the performance, microbial activity, extracellular polymeric substances (EPS) and microbial community of a sequencing batch biofilm reactor (SBBR) were investigated in treating mariculture wastewater. Low CTC concentration (less than 6 mg/L) had no obvious effect on the SBBR performance, whereas high CTC concentration could inhibit the chemical oxygen demand (COD) and nitrogen removal of the SBBR. The microbial activity of the biofilm in the SBBR decreased with the increase of CTC concentration from 0 to 35 mg/L. The protein (PN) contents were always higher than the PS contents in both loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) at different CTC concentrations. The chemical compositions of LB-EPS and TB-EPS had obvious variations with the increase of CTC concentration from 0 to 35 mg/L. The high-throughput sequencing revealed the effects of CTC on the microbial communities of the biofilm at phylum, class and genus level. The relative abundances of some genera displayed a decreasing tendency with the increase of CTC concentration from 0 to 35 mg/L, such as Nitrospira, Paracoccus, Hyphomicrobium, Azospirillum. However, the relative abundances of the genera Flavobacterium, Aequorivita, Buchnera, Azonexus and Thioalbus increased with the increase of CTC concentration.