Simultaneous Carbamazepine and Phosphate Removal from a Moving-Bed Membrane Bioreactor Effluent by the Electrochemical Process: Treatment Optimization by Factorial Design.

Pharmaceutical and personal care products are frequently used in various fields and released into water bodies from the outlets of wastewater treatment plants. These products can harm the environment and human health even at low concentrations. Carbamazepine (CBZ), the most persistent pharmaceutical, has frequently been found in surface waters that bypassed the secondary treatments of conventional activated sludge. In addition, the treatment of phosphate in wastewater by the electrochemical process has recently attracted much attention because of its ability to remove, recover, and prevent environmental problems associated with eutrophication. This study proposes using the electrochemical process as an advanced oxidation process to simultaneously treat CBZ and phosphate from the moving-bed membrane bioreactor effluent. The study includes a long-term survey of CBZ treatment efficiency and common parameters of synthetic wastewater in the moving-bed membrane bioreactor system. Afterward, the electrochemical process is applied as an advanced oxidation process for the simultaneous removal of CBZ and phosphate from the moving-bed membrane bioreactor. Under the investigated conditions, CBZ has proven not to be an inhibitor of microbial activity, as evidenced by the high extent of chemical oxygen demand and nutrient removal. Using a factorial design, the electrochemical process using Pt/Ti as anode and cathode under optimal conditions (reaction time-80 min, bias potential-3 V, and electrode distance-1 cm) resulted in as high as 56.94% CBZ and 95.95% phosphate removal, respectively. The results demonstrated the ability to combine an electrochemical and a moving-bed membrane bioreactor process to simultaneously remove CBZ and phosphate in wastewater.

Effect of Operational Parameters on the Removal of Carbamazepine and Nutrients in a Submerged Ceramic Membrane Bioreactor.

Pharmaceuticals and personal care products have raised significant concerns because of their extensive use, presence in aquatic environments, and potential impacts on wildlife and humans. Carbamazepine was the most frequently detected pharmaceutical residue among pharmaceuticals and personal care products. Nevertheless, the low removal efficiency of carbamazepine by conventional wastewater treatment plants was due to resistance to biodegradation at low concentrations. A membrane bioreactor (MBR) has recently attracted attention as a new separation process for wastewater treatment in cities and industries because of its effectiveness in separating pollutants and its tolerance to high or shock loadings. In the current research, the main and interaction effects of three operating parameters, including hydraulic retention time (12-24 h), dissolved oxygen (1.5-5.5 mg/L), and sludge retention time (5-15 days), on removing carbamazepine, chemical oxygen demand, ammonia nitrogen, and phosphorus using ceramic membranes was investigated by applying a two-level full-factorial design analysis. Optimum dissolved oxygen, hydraulic retention time, and sludge retention time were 1.7 mg/L, 24 h, and 5 days, respectively. The research results showed the applicability of the MBR to wastewater treatment with a high carbamazepine loading rate and the removal of nutrients.

Human health-risk assessment based on chronic exposure to the carbonyl compounds and metals emitted by burning incense at temples.

Health effects resulting from the smoke of carbonyl compounds (aldehydes and ketones) and metal-containing incense particles at temples during incense burning periods were evaluated at temple A (without incense reduction activities) and B (with incense reduction activities), Nantou County, in 2018. The predominant size fractions of particles were PM1, PM1-2.5, and PM2.5-10 at both temples. The total particle mass at temple A was approximately 1.1 times that of temple B due to incense reduction at temple B. The most abundant metal elements in all particle size fractions at both temples were Fe, Al, and Zn. Metal species of incense smoke are divided into three groups by hierarchical cluster analysis and heatmaps, showing higher metal contents in groups PM1, PM18-10, and PM18-2.5 at temple A. In contrast, higher metal contents were observed in PM18-10 and PM2.5-1 at temple B. Most of the carbonyl species were formaldehyde and acetaldehyde, released during incense burning periods, with concentrations ranging from 6.20 to 13.05 µg/m3 at both temples. The total deposited fluxes of particle-bound metals at temples A and B were determined to be 83.00% and 84.82% using the International Commission on Radiological Protection (ICRP) model. Health-risk assessments revealed that the risk values of metals and carbonyls were above recommended guidelines (10-6) at temple A. Since worshippers and staff are exposed to incense burning environments with poor ventilation over a long period, these toxic organic compounds and metals increase health risks in the respiratory tract. Therefore, incense reduction is important to achieve healthy temple environments.

The photocatalytic degradation of methylene blue by green semiconductor films that is induced by irradiation by a light-emitting diode and visible light.

This study develops a low-energy rotating photocatalytic contactor (LE-RPC) that has Cu-doped TiO2 films coated on stainless-steel rotating disks, to experimentally evaluate the efficiency of the degradation and decolorization of methylene blue (MB) under irradiation from different light sources (visible 430 nm, light-emitting diode [LED] 460 nm, and LED 525 nm). The production of hydroxyl radicals is also examined. The experimental results show that the photocatalytic activity of TiO2 that is doped with Cu2+ is induced by illumination with visible light and an LED. More than 90% of methylene blue at a 10 mg/L concentration is degraded after illumination by visible light (430 nm) for 4 hr at 20 rpm. This study also demonstrates that the quantity of hydroxyl radicals produced is directly proportional to the light energy intensity. The greater the light energy intensity, the greater is the number of hydroxyl radicals produced. IMPLICATIONS: The CuO-doped anatase TiO2 powder was successfully synthesized in this study by a sol-gel method. The catalytic abilities of the stainless-steel film were enhanced in the visible light regions. This study has successfully modified the nano-photocatalytic materials to drop band gap and has also successfully fixed the nano-photocatalytic materials on a substratum to effectively treat dye wastewater in the range of visible light. The results can be useful to the development of a low-energy rotating photocatalytic contactor for decontamination purposes.

Remediation of trichloroethene (TCE)-contaminated groundwater by persulfate oxidation: a field-scale study.

This study uses a trichloroethene (TCE)-contaminated site to determine the efficacy of persulfate oxidation for the treatment of TCE-contaminated groundwater. The main objectives of this study are: (1) to evaluate the efficacy of TCE treatment using persulfate with different injection strategies; (2) to determine the persistence of persulfate in the aquifer; (3) to determine the radius of influence (ROI) and transport distance of persulfate and (4) to determine the impact of persulfate on indigenous microorganisms during remediation. TCE concentrations are 0.26 mg L-1 in P143 and 0.361 mg L-1 in P146 and the microbial numbers are 6.1 × 103 CFU mL-1 in P143 and 4.4 × 104 CFU mL-1 in P146, before persulfate is injected. The results of the pilot study show that persulfate eliminates TCE. 100% of TCE is removed in P146 and 95% in P143. Single injection of a total amount of 275 kg of 5% persulfate produces better TCE removal than two half persulfate injections in sequence. The transport distance of persulfate ranges from 3.6 to 4.5 m. Persulfate also persists for 14 days in the aquifer. After persulfate is injected, the total bacterial counts decrease slightly to 2.4 × 103 CFU mL-1 in P143 and 1.8 × 103 CFU mL-1 in P146. When persulfate is consumed, the total bacterial counts increase but there is no recovery of the microbial community. The results show that sequential injections of a large amount of persulfate are suggested to maintain good long-term performance for TCE treatment.

Verification of enzymes deterioration due to Cu(II) presence in an enhanced biological phosphorus removal system.

This study experimentally demonstrated that polyphosphate accumulating organisms (PAOs) losing the abilities of anaerobically synthesizing polyhydroxyalkanoates and aerobically taking up phosphate under Cu(II) presence was due to the inhibition of enzyme activities of acetyl-CoA synthases (ACS) and polyphosphate kinase (PPK), respectively. ACS activity tests showed the apparent maximum specific activity (Vmax) of ACS decreased with increasing Cu(II) concentration, revealing Cu(II) is a mixed inhibitor for ACS. Inhibition coefficients showed Cu(II) has a higher affinity for free ACS than for ACS-coenzyme A complex. PPK activity tests showed the Vmax substantially decreased with increasing Cu(II) concentration, revealing Cu(II) is also a mixed inhibitor for PPK. Inhibition coefficients showed Cu(II) more easily bound to free PPK than to PPK-Adenosine triphosphate complex. Experimental data also showed the aerobic mechanism of PAOs taking up phosphate was completely interrupted when 3mgL(-1) of Cu(II) was added.

Influence of sludge retention time on tolerance of copper toxicity for polyphosphate accumulating organisms linked to polyhydroxyalkanoates metabolism and phosphate removal.

This study explored the influence of sludge retention time (SRT) on tolerance of copper invasion for polyphosphate accumulating organisms (PAOs) in an enhanced biological phosphorus removal (EBPR). The experimental data showed the anaerobic polyhydroxyalkanoates (PHA) storage for the sludge at 10d SRT was less influenced by copper invasion than those at 5d and 15d SRTs. The reaction of PAOs aerobically taking up phosphate for the sludge at 5d or 15d SRT almost ceased at 2 mg Cu L(-1), whereas PAOs in the sludge at 10d SRT retained half of the ability to take up phosphate. Both the PHAs degradation and synthesis rates decreased with increasing copper concentration, regardless of the SRTs. However, the copper inhibition of the former was greater than that of the later.

Metabolic influence of lead on polyhydroxyalkanoates (PHA) production and phosphate uptake in activated sludge fed with glucose or acetic acid as carbon source.

Sludge in a sequential batch reactor (SBR) system was used to investigate the effect of lead toxicity on metabolisms of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) communities fed with acetic acid or glucose as their sole carbon source, respectively. Results showed that the effect of lead on substrate utilization of both PAOs and GAOs was insignificant. However, lead substantially inhibited both of phosphate release and uptake of PAOs. In high concentration of acetic acid trials, an abnormal aerobic phosphate release was observed instead of phosphate uptake and the release rate increased with increasing lead concentration. Results also showed that PAOs could normally synthesize polyhydroxybutyrate (PHB) in the anaerobic phase even though lead concentration was 40 mg L(-1). However, they could not aerobically utilize PHB normally in the presence of lead. On the other hand, GAOs could not normally metabolize polyhydroxyvalerate (PHV) in both the anaerobic and aerobic phases.

Effect of heavy metals on nitrification performance in different activated sludge processes.

To understand the toxic effect of heavy metals on the nitrification mechanisms of activated sludge, this study identified the specific ammonia utilization rate (SAUR) inhibited by Pb, Ni and/or Cd shock loadings. Seven different heavy metal combinations (Pb, Ni, Cd, Pb+Ni, Ni+Cd, Pb+Cd, and Pb+Ni+Cd) with seven different heavy metal concentrations (0, 2, 5, 10, 15, 25, and 40 ppm, respectively) were examined by batch experiments, where the activated sludge was taken from either sequencing batch reactor (SBR) or anaerobic-anoxic-oxic (A(2)O) processes. The experimental results showed the SAUR inhibition rate was Ni>Cd>Pb. No significant inhibition in the nitrification reaction of the activated sludge was observed even when as much as 40 ppm Pb was added. In addition, no synergistic effect was found when different heavy metals were simultaneously added in different concentrations, and the overall inhibition effect depended on the heavy metal with the highest toxicity. Further, first order kinetic reaction could model the behavior of SAUR inhibition on activated sludge when adding heavy metals, and the SAUR inhibition formula was derived as (SAURmax-SAURmin) x e-ric+SAURmin. On the other hand, the heavy metal adsorption ability in both the activated sludge system was Pb=Cd>Ni. The specific adsorption capacity of activated sludge on heavy metal increased as the heavy metal concentration increased or the mixed liquid volatile suspended solid (MLVSS) decreased. The batch experiments also showed the heavy metal adsorption capacity of the SBR sludge was larger than the A(2)O sludge. Finally, the most predominant bacteria in the phylogenetic trees of SBR and A(2)O activated sludges were proteobacteria, which contributed to 42.1% and 42.8% of the total clones.

Interaction of chlorine concentration and shear stress on chlorine consumption, biofilm growth rate and particle number.

Eleven test runs (including two replicates) were carried out to explore the interaction of shear stress and chlorine concentration on the growth of heterotrophic microorganisms. Experimental results revealed that influent chlorine concentration and shear stress had no interaction on biofilm formation. Biofilm bacterial numbers decreased with the increase of influent chlorine concentration. Increasing the shear stress up to a specific level could significantly reduce the potential of biofilm formation. A strong interaction on bacterial quality or chlorine consumption rate of bulk water existed. With non-chlorinated and lower chlorinated conditions, the specific growth rate of biofilm increased with the increase of shear stress. However, an inverse relation occurred at higher chlorine conditions. No significant interaction of chlorine concentration and shear stress existed for particle numbers with 2-5, 5-15, 50-100 and >100 microm diameters. However, a significant interaction existed on particle numbers of 15-25 and 25-50 microm diameters.

Simulation of biofilm formation at different assimilable organic carbon concentrations under lower flow velocity condition.

A simulation model was established in this study to evaluate the impacts of assimilable organic carbon concentration on the growth of biofilm and bulk bacteria under lower flow velocity conditions. The experimental results showed that the growth trends of heterotrophic plate count bacteria of biofilm and bulk bacteria were coincident with the pattern of logistic growth model. The effects of the assimilable organic carbon level on the (specific) growth rates of biofilm and bulk bacteria were quite significant, and the higher the assimilable organic carbon level was, the higher the (specific) growth rate was. There was a growth and decline relationship between the maximum quantities of biofilm and bulk water bacteria at steady state. The maximum growth rate of biofilm bacteria exponentially increased with the increase of assimilable organic carbon level. The length of time that the maximum growth rate occurred was inversely decreased with the increase of assimilable organic carbon level. Some results of this study support the inference that the increase of bulk bacteria results mainly from the release or detachment of biofilm bacteria, not from the growth itself.

Impact of flow velocity on the dynamic behaviour of biofilm bacteria.

The impact of flow velocity (FV) on the growth dynamics of biofilms and bulk water heterotrophic plate count (HPC) bacteria in drinking water distribution systems was quantified and modeled by combining a logistic growth model with mass balance equations. The dynamic variations in the specific growth and release rates of biofilm bacteria were also quantified. The experimental results showed that the maximum biofilm biomass did not change when flow velocity was increased from 20 to 40 cm s(-1), but was significantly affected when flow velocity was further increased to 60 cm s(-1). Although the concentration of biofilm bacteria was substantially reduced by the higher shear stress, the concentration of bacteria in the bulk fluid was slightly increased. From this it is estimated that the specific growth rate and specific release rate of biofilm bacteria had doubled. The specific release (detachment) rate was dependent on the specific growth rate of the biofilm bacteria.