Synthetic Secondary Effluent Research Articles

Acetaminophen removal by peroxymonosulfate catalyzed by C and O co-doped graphitic carbon nitride in synthetic secondary treatment effluent matrix

Catalytic oxidation using carbonaceous materials and peroxymonosulfate (PMS) has attracted attention because of high potential in pharmaceuticals removal. For successful field applications, it is essential to identify the components and characteristics in real water matrices affecting the performance, though it has hardly been elaborated. Therefore, acetaminophen (ACT) removal by C and O co-doped graphitic carbon nitride (COCN) and PMS was investigated in synthetic secondary treatment effluent (SSTE) and compared to that in deionized water (DIW). ACT removal was significantly suppressed in SSTE (20.33 %) compared to that in DIW (94.20 %) under 10 mg/L ACT, 100 mg/L COCN, and 0.5 mM PMS. However, it was enhanced greatly with increasing COCN and/or PMS dose. The reactive species were the same in SSTE and DIW, of which 1O2 from O2− dominantly contributed. However, the amount of them was considerably lower in SSTE than in DIW. ACT removal was slightly affected by the anions in SSTE, such as Cl−, SO42−, and NO3−, at 1.41 × 10−3–0.71 mM. But it was suppressed greatly by 0.71 mM phosphates and by 10 mg/L humic acid and natural organic matter, via consuming hydrophobic and aromatic fractions. It is strongly suggested that the reactivity of COCN/PMS in SSTE was dominantly affected by raised pH and scavenging O2− reducing DOM, which decreased 1O2 generation. The results would significantly contribute to successful practical applications of catalytic systems.

Thin-Film Nanocomposite Membranes with Nature-Inspired MOFs Incorporated for Removing Fluoroquinolone Antibiotics

A nanofiltration membrane functionalized with metal-organic frameworks (MOFs) is promising to enhance micropollutant removal and realize wastewater reclamation. However, the current MOF-based nanofiltration membranes still suffer from severe fouling problems with an indefinable mechanism when used for antibiotic wastewater treatment. Hence, we report a nature-inspired MOF-based thin-film nanocomposite (TFN-CU) membrane to explore its rejection and antifouling behavior. Compared with unmodified membranes, the optimal TFN-CU5 membrane (with 5 mg·mL-1 C-UiO-66-NH2) had high water permeance (17.66 ± 1.19 L·m-2·h-1·bar-1), exceptional rejection for norfloxacin (97.92 ± 2.28%) and ofloxacin (95.36 ± 1.03%), and excellent long-term stability for treating synthetic secondary effluent with antibiotic rejection over 90%. Furthermore, it also showed superior antifouling capability (flux recovery up to 95.86 ± 1.28%) in bovine serum albumin (BSA) filtration after fouling cycles. Deriving from the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approach, the antifouling mechanism between BSA and the TFN-CU5 membrane was mainly attributed to the inhibited adhesion forces because the growing short-ranged acid-base interaction caused repulsive interfacial interactions. It is further revealed that BSA fouling behavior is slightly retarded under an alkaline environment, while strengthened in the presence of calcium ions and humic acid, as well as high ionic strength. In short, the nature-inspired MOF-based TFN membranes possess exceptional rejection and organic fouling resistance, giving insights into the design of antifouling membranes during antibiotic wastewater reclamation.

The role of coagulation on the fate of PFAS, brominated flame retardants and other trace contaminants in tertiary wastewater treatment for phosphorus control

Coagulant dosing to achieve low phosphorus concentrations in wastewater effluents may favour the removal of trace organics such as pharmaceuticals, plasticisers and flame retardants. Nevertheless, the behaviour of trace organics in coagulation processes is currently poorly understood because of the complex interactions between these compounds, the coagulants and dissolved organic matter (DOM). This study assessed the coagulation removal from synthetic secondary effluent of twenty-four compounds including ten PFAS and four brominated flame retardants. Testing involved two coagulants (alum, ferric chloride) and five DOM surrogates (resorcinol, benzoic acid, citric acid, tannic acid, humic acid); DOM surrogates had assorted molecular weights, structures, charges, and hydrophobicity. With coagulant doses of 14 mg Fe/L and 4 mg Al/L, ten trace organics were removed by >30 % in the presence of at least one DOM surrogate. Humic acid effected the highest removals owing to complexation of trace organics and subsequent co-removal by adsorption or sweep floc. For instance, removal extents for three brominated diphenyl ethers were 60 to 75 % with Al and 50 to 88 % with Fe (initial concentration 0.4 to 0.8 ng/L); PFTDA, a long-chain PFAS, was removed by 87 and 91 % with Fe in the presence of tannic or humic acid, respectively (initial concentration 0.03 μg/L). The varying coagulation performance of different treatment works in terms of trace substance removal can be explained because of the site-specific DOM characteristics. Addition of humic acids as complexing agents has the potential to improve the removal of hydrophobic trace substances, including some long-chain PFAS and brominated flame retardants.

Effects of feast-famine nutrient regimes on wastewater algal biofuel communities.

Microalgae accumulate lipids in response to nutrient deprivation, and these lipids are a biodiesel fuel stock. Algal cultivation with secondary wastewater effluent is one proposed platform for biofuel production, which provides nutrients to algae while further polishing wastewater effluent. Algal bioreactors were tested using a feast-famine feeding regiment in simulated secondary wastewater effluent to evaluate the effects on lipid content and algal community structure. Algal polycultures were inoculated into reactors fed with synthetic secondary wastewater effluent at pH 7.5 and 9 and operated under a feast-famine nutrient (N, P, and BOD) supply regime in sequencing batch reactors. Fatty acid methyl ester contents of the reactors were assessed, which showed a decrease in lipid content after the feast-famine cycling (from 12.2% initially to 5.2% after four cycles at pH 9). This decrease in lipid content was not correlated with an increase in carbohydrate storage within biomass, nor an increase in bacterial biomass abundance relative to algal biomass in the reactors. The eukaryotic microbial communities from reactors operated at pH 9 diverged from reactors operated at pH 7.5 during cycling, with the pH 9 reactors becoming dominated by a single Operational Taxonomic Unit aligning to the Scenedesmus genus. These results suggest that high pH and feast-famine nutrient cycling may select for a less diverse algal community with a lower lipid content within a secondary wastewater polishing scheme.

Effects of wastewater composition and reactor operating mode on the removal of micropollutants via electrochemical advanced oxidation

When implementing an electrochemical Advanced Oxidation Process (eAOP) for wastewater treatment, the composition of the wastewater to be treated and the selection of the reactor operating mode are key parameters to be considered given their strong influence on the degradation kinetics, energy consumption, operating costs and environmental impacts. To this end, this study investigated the degradation of carbamazepine (CBZ) in different matrices (i.e., pure water vs. synthetic secondary effluent, high vs. low organic/ion content, single vs. multicomponent systems) and under several reactor operating modes (i.e., batch, fed-batch and continuous). The key findings of this research are (i) the self-cleaning capabilities that naturally occurring ionic species in wastewater (i.e., sulfate and nitrate ions) offer even if present at low concentrations and (ii) the significant performance implications resulting from the reactor operation selection. By combining both insights, this study illustrates the opportunities for developing more efficient eAOPs where no additional chemicals are needed, and hence, where secondary waste streams can be mitigated, while energy consumption is minimized and degradation efficiency is enhanced. In particular, treating CBZ-polluted secondary wastewater effluent in fed-batch mode could lead to up to a 2.1-fold increase in degradation and a 60 % reduction in energy with respect to a batch equivalent, despite the hindering effects that competition reactions from other wastewater constituents entailed.

Comparative Evaluation of Membrane Filtration on the Tertiary Treatment of Synthetic Secondary Effluent

Wastewater reuse is essential for sustainable water management. However, it requires tertiary treatment within the plant to ensure suitable water quality. This project aims to investigate the comparative performance of conventional tertiary treatment (sand filtration) against membrane filtration technology to demonstrate the viability of membrane treatment for wastewater reuse. Sand filtration along with two membrane filtrations, Nano Filtration (NF) and Reverse Osmosis (RO), were tested for their efficiency in removing the target pollutants: chromium, phosphate, and UV-254 from secondary effluent. Standard medium-sized laboratory setups were used. Synthetic secondary effluent was used for comparison among the different treatment processes. The synthetic effluent was compared to the real wastewater to demonstrate the reliability of using synthetic effluent. Evaluation of the role of time and pressure on the treatment efficiency was also examined. Based on the experimental results, RO had the highest removal efficiency for all pollutants with more than 90% removal. The experimental results also showed that synthetic wastewater was reliable in representing the treatability of real wastewater. Time did not seem to have an impact on the quality of filtration. Moreover, as pressure increased there was a slight increase in the efficiency. This trend was observed in all pollutants except UV-254. ANOVA showed different results of the effect of pressure on the removal efficiency in both RO and NF as well as time in NF.

Enhanced removal of nutrients and diclofenac by birnessite sand vertical flow constructed wetlands

The application of constructed wetlands (CWs) in organic micropollutants elimination is receiving increasing attention worldwide. However, acclimatization periods of CWs were long due to uncontrollable biotic factors and external conditions. In this study, manganese oxide was applied to enhance the simultaneous removal of nutrients and diclofenac (DFC) in CWs. To evaluate the treatment performance, two vertical up-flow CWs (VFCWs), with/without (experimental/ control) birnessite-coated sand VFCW, were set up to treat synthetic secondary effluent of the wastewater treatment plant. The removal performance of ammonia was significantly higher in experimental VFCW than that of control during the first 80 d, indicating that experimental VFCW could maintain a stable NH4+-N treatment performance (over 60%) when wastewater contained DFC. After 200 d of operation, the removal efficiency of DFC was achieved 98.5% in experimental VFCWs. The application of birnessite sand increased 12.8% of nitrogen load in the substrate, while phosphorus removal performance was enhanced by 10.0% on account of plant uptake. Though the final nutrients treatment performance was equivalent in experimental and control VFCWs, micro-environments at the middle layer were diverse for microbial communities. This work presents birnessite sand as the potential substrate of VFCWs for treating DFC as well as nitrogen and phosphorus pollutants.

Preparation of effective lithium-ion sieve from sludge-generated TiO2

A potential adsorbent for Li+ extraction from liquid resources is titanium-type lithium-ion sieves (LISs) because of their structural stability and high adsorption capacity. However, the adsorption efficiency and recycling stability of LISs produced with various TiO2 precursors vary significantly. Additionally, traditional TiO2 is often produced using chemical-intensive methods, resulting in large amounts of effluent containing strong acids and high concentrations of chloride/sulfate ions, posing a threat to the environment. Hence, in this study, the LIS precursors, Li2TiO3, were synthesized utilizing novel environment-friendly anatase titania made from flocculated sludges of synthetic secondary sewage effluent (S-LTO) and dye wastewater (D-LTO). The physicochemical characteristics and adsorption capacities of the synthesized LISs were then investigated. The results indicated that sludge-generated LISs could be effectively produced and had a high Li+ adsorption capacity of 35.43 mg/g for S-LTO and 34.97 mg/g for D-LTO. For the synthesized LISs, the adsorption kinetics and isotherms verified a fixed energy-based monolayer chemisorption. Furthermore, the H2TiO3 generated from sludge was extremely stable after acid pickling, reusable (4 regeneration cycles exhibited minimal performance degradation), and highly selective to Li+ in an aqueous medium, suggesting enormous industrial potentials such as seawater and brine for aqueous Li+ recovery.

Characterization of the immobilized algae-based bioreactor with external ceramic ultrafiltration membrane to remove nutrients from the synthetic secondary wastewater effluent

In this study, alginate-immobilization of microalgae combined with continuous/intermittent algae-based membrane bioreactor (A-MBR) and external ceramic membrane was developed to investigate the effect of immobilization on algal growth, nutrient removal, algal organic matter (AOM) and membrane fouling control in synthetic secondary wastewater effluent treatment. First, Chlorella vulgaris and Scenedesmus quadricauda were selected to investigate the treatment performance, AOM characteristics and membrane fouling control between suspended and immobilized microalgae. The results showed the effect of immobilization on two microalgae growth was not significant and nearly complete NO3−-N and PO43−-P removals were achieved by both immobilized microalgae in batch experiments, contributing from algal uptake as well as chemical precipitation. In addition, fluorescence excitation-emission matrix spectra indicated specific intensity of protein- and soluble microbial byproduct-like peaks in AOM derived from immobilized S. quadricauda was lower than C. vulgaris and reduced recently produced AOM from two immobilized microalgae was observed, which would improve membrane fouling control. After 35-day intermittent A-MBR operation with immobilized S. quadricauda, higher concentration of microalgal biomass and 63% NO3−-N and 58% PO43−-P removals were achieved. In addition, alginate-immobilization and intermittent operation for relaxation of membrane showed slower decline of permeate flux under constant pressure mode and therefore, were beneficial for membrane fouling control. Hence, the intermittent A-MBR with immobilized microalgae has potential to cultivate microalgae, provide stable treatment performance to remove nutrients and limit membrane fouling in secondary wastewater effluent treatment.

The role of intraparticle diffusion path length during electro-assisted regeneration of ion exchange resins: Implications for selective adsorbent design and reverse osmosis pretreatment

Inorganic membrane scaling is a major cause of process failure for reverse osmosis (RO). Pretreatment using selective ion exchangers can reduce membrane scaling by removing scale-forming ions such as calcium (Ca2+) and phosphate (P). Ca- and P-selective ion exchangers also enable calcium phosphate recovery via precipitation from spent regenerants enriched with both ions. However, conventional regeneration approaches require substantial chemical and energy inputs. In this study, we designed a RO pretreatment process using electro-assisted regeneration of a column train containing a hybrid anion exchanger (HAIX) and a weak acid cation exchanger (WAC) to selectively remove > 90% Ca2+ and P from synthetic secondary effluent. HAIX and WAC were regenerated using pH 11 catholyte and pH 3 anolyte produced via electrochemical water splitting. HAIX contains ferric oxide nanoparticles (FeOnp) in a parent strong base anion exchanger (SBA). By comparing P regeneration efficiency of HAIX and SBA, we identified that FeOnp dopants reduced intraparticle diffusivity by 85% from SBA to HAIX. However, HAIX exhibited faster column regeneration kinetics than SBA, potentially due to the shortened intraparticle diffusion path length caused by the surface-distributed P in saturated HAIX, which overcompensated for low intraparticle diffusivity. Regenerability enhancement caused by the reduced intraparticle diffusion path length was also confirmed by comparing WAC with shallow-shell WAC (SSWAC), which has surface-distributed carboxylate functional groups. We anticipate that this study will inform selective adsorbent design by identifying strategies to improve regenerability, facilitate process intensification by replacing chemical inputs with electricity, and enhance resource recovery from wastewater.

Optimization of membrane photobioreactor; the effect of hydraulic retention time on biomass production and nutrient removal by mixed microalgae culture

In this study, the effect of hydraulic retention time (HRT) on the performance of microalgae membrane photobioreactor (MpBR) inoculate by mixed culture were with examined on biomass productivity and nutrient removal from synthetic secondary effluent. The optimization of HRT was aimed for the treatment of wastewater in MpBR operating at HRTs between 24 h and 72 h with at a fixed sludge retention times (SRT) of 3 d. The volumetric microalgae production rates were obtained to be from 0.118 g L−1day−1 to 0.064 g L−1day−1, respectively at increasing HRT from 24 h to 72 h at the stable conditions. The total nitrogen (TN) removal rate was calculated to be 5.55 mgL−1day−1 and the phosphate phosphorus (PO4–P) removal rate to 0.40 mgL−1day−1 where the highest biomass production rate was obtained at the HRT of 24 h. Although this work showed the potential use of mixed microalgae culture and membrane in both wastewater treatment and microalgae biomass production, it is looked that the treatment of the secondary effluent has not been able to meet the discharge standards according to EU and general directives unless optimization is made. But bioenergy power, namely lipid and protein ratios of dry biomass under the optimum conditions were also determined and lipid content was 8.94% and the protein content was 34%. Today, when there is a global food shortage, the oil and protein ratio in microalgae biomass obtained by treating wastewater is potentially competitive with traditional agricultural products.

Low voltage iron electrocoagulation as a tertiary treatment of municipal wastewater: removal of enteric pathogen indicators and antibiotic-resistant bacteria

In this paper we analyse the feasibility of low voltage iron electrocoagulation as a means of municipal secondary effluent treatment with a focus on removal of microbial indicators, Antibiotic Resistant Bacteria (ARB) and nutrients. A laboratory scale batch unit equipped with iron electrodes was used on synthetic and real secondary effluent from a municipal wastewater treatment plant. Synthetic secondary effluent was separately assayed with spiked Escherichia coli WR1 and with bacteriophage ΦX174, while real effluent samples were screened before and after treatment for E. coli, Extended Spectrum Betalactamase-producing E. coli, Enterococci, Vancomycin Resistant Enterococci, Clostridium perfringens spores and somatic coliphages. Charge dosage (CD) and charge dosage rate (CDR) were used as the main process control parameters. Experiments with synthetic secondary effluent showed >4log10 and >5log10 removal for phage ΦX174 and for E. coli WR1, respectively. In real effluents, bacterial indicator removal exceeded 3.5log10, ARB were removed below detection limit (≥2.5log10), virus removal reached 2.3log10 and C. perfringens spore removal exceeded 2.5log10. Experiments in both real and synthetic wastewater showed that bacterial removal increased with increasing CD and decreasing CDR. Virus removal increased with increasing CD but was irresponsive to CDR. C. perfringens spore removal increased with increasing CD yet reached a removal plateau, being also irresponsive to CDR. Phosphate removal exceeded 99%, while total nitrogen and chemical oxygen demand removal were below 15% and 58%, respectively. Operational cost estimates were made for power and iron plate consumption, and were found to be in the range of 0.01 to 0.24€/m3 for the different assayed configurations. In conclusion, low voltage Fe-EC is a promising technology for pathogen reduction of secondary municipal effluents, with log10 removals comparable to those achieved by conventional disinfection methods such as chlorination, UV or ozonation.

Bi-Polymer Electrospun Nanofibers Embedding Ag3PO4/P25 Composite for Efficient Photocatalytic Degradation and Anti-Microbial Activity

Using a bi-polymer system comprising of transparent poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP), a visible light active Ag3PO4/P25 composite was immobilized into the mats of polymeric electrospun nanofibers. After nanofibers synthesis, sacrificial PVP was removed, leaving behind rough surface nanofibers with easy access to Ag3PO4/P25 composite. The remarkable photocatalytic efficiency was attained using a PMMA and Ag3PO4/P25 weight ratio of 1:0.6. Methyl orange (MO) was used to visualize pollutant removal and exhibited stable removal kinetics up to five consecutive cycles under simulated daylight. Also, these polymeric nanofibers (NFs) revealed an important role in the destruction of microorganisms (E. coli), signifying their potential in water purification. A thin film fibrous mat was also used in a small bench scale plug flow reactor (PFR) for polishing of synthetic secondary effluent and the effects of inorganic salts were studied upon photocatalytic degradation in terms of total organic carbon (TOC) and turbidity removal. Lower flow rate (5 mL/h) resulted in maximum TOC and turbidity removal rates of 86% and 50%, respectively. Accordingly, effective Ag3PO4/P25 immobilization into an ideal support material and selectivity towards target pollutants could both enhance the efficiency of photocatalytic process under solar radiations without massive energy input.

Process safety and environmental protection: An optimized solid phase denitrification filter by using activated carbon fibers for secondary effluent treatment

This study investigated the denitrification potential of an optimized solid-phase filter with activated carbon fiber (ACF) setting at the top and bottom under hydraulic retention time (HRT) shorter than 60 min from the synthetic secondary effluent. The results showed that, high nitrate removal efficiencies (>99 %) were obtained in reactors filled with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) 3020 at initial stage of start-up. During stable operation under either HRT 40 min or 30 min, the reactor with PHBV 3020 as carrier achieved 90 %–100 % nitrate removal without nitrite accumulation. Moreover, it reached the maximum denitrification rates of 41.8 mg-N/Lh at HRT of 30 min which was significantly higher than that of the reactors filled by ACF/quartz grains and quartz grains at top and bottom. Microbial community in this reactor was dominated by the phylum Proteobacteria as well as Bacteroidetes. The ACF worked as favorable habitat for denitrifying bacteria Hydrogenophaga, Thiothrix, Desulfomicrobium and Sulfurimonas. The genera Ottowia, Limnohabitans, and Propionivibrio attached to ACF at top tended to degrade remaining organics. The optimized solid-phase denitrification filter with ACF showed good application potential for nitrate removal from the secondary effluent.

Reducing carbon source consumption through a novel denitratation/anammox biofilter to remove nitrate from synthetic secondary effluent

This study presents a novel denitratation/anammox biofilter (DABF) for nitrate removal from secondary effluent, where denitratation (NO3–→NO2–) is coupled with anammox (NO2– +NH4+→N2) instead of denitritation (NO2–→N2). Total nitrogen (TN) was removed by 81.90% in this DABF when the average effluent TN concentration was 7.82 mg/L. Meanwhile, organic carbon source consumption and backwash sludge production in the DABF were reduced by 63% and 70%, respectively, compared to conventional denitrifying biofilter (DNBF). Nitrogen banlance analysis indicates that 93% of the nitrogen gas produced in DABF was via anammox. Batch tests confirmed that the DABF biofilm reduced nitrite using ammonium as the electron donor, and accumulated nitrite during denitratation, thus providing nitrite for the anammox bacteria. Moreover, high-throughput sequencing approach also revealed that the anammox bacteria Candidatus Brocadia dominated the community, which could also be responsible for the stable processes in DABF by interacting with the other denitrifying bacteria.

Pyrrhotite-sulfur autotrophic denitrification for deep and efficient nitrate and phosphate removal: Synergistic effects, secondary minerals and microbial community shifts

Pyrrhotite-sulfur autotrophic denitrification (PSAD) system, using mixture of pyrrhotite and sulfur particle as electron donor, was studied through batch, column and pilot experiments. Treating synthetic secondary effluent at HRT 3 h, the PSAD system obtained the effluent with NO3−-N 0.28 ± 0.14 mg·L−1 and without PO43−-P to be detected. Thiobacillus was the most abundant autotrophic denitrification bacteria; autotrophic, heterotrophic and sulfate-reducing bacteria coexisted in the PSAD system; phosphate was mainly removed in forms of graftonite, dufrenite, ardealite. The H+ produced in the SAD could accelerate the PAD through promoting pyrrhotite dissolution, and iron ions produced in the PAD could accelerate the SAD through Fe3+/Fe2+ shuttle. Because of the synergistic effects between the pyrrhotite and sulfur, the PSAD system removed nitrate and phosphate deeply and efficiently. It is a promising way to meet the stringent nitrogen and phosphorus discharge standards and to recover phosphorus resources from wastewater.

Effect of algae acclimation to the wastewater medium on the growth kinetics and nutrient removal capacity.

Algal treatment methods have been widely used in nutrient removal studies. However, in most cases, the experimental conditions have not been fully complied with actual conditions. For instance, the effect of algae acclimation to wastewater medium on cell growth and removal efficiency has generally been ignored in laboratory scale experiments. This paper investigates the effect of acclimation on cell growth and nutrient uptake rates of Arthrospira platensis and Chlorella vulgaris. For this purpose, batch reactors, which contained the synthetic secondary effluent, had been inoculated by acclimated algae cells and the growth parameters were measured daily, as well as nutrient concentration. A significant decrease (P < 0.05) in chlorophyll-a content of acclimated A. platensis was observed, although there was no significant change in specific growth rate (μ) and doubling time (dt), in comparison with the non-acclimated ones. Moreover, the acclimation process changed the chlorophyll-a content and kinetic parameters of Chlorella vulgaris. Furthermore, t test results showed a significant increase in removal rate of nitrogen compounds through the acclimation. Residence time of A. platensis and C. vulgaris was also reduced through the acclimation by approximately 50% and 25%, respectively.

Reusability of iron oxyhydroxide agglomerates adsorbent for repetitive phosphate removal

Phosphate release to receiving water bodies promotes eutrophication. Therefore it is a common practice to remove phosphate from domestic wastewater. Yet, the conventional secondary treatment most often require a polishing step as to comply with rigorous regulations. Semi-batch adsorption experiments demonstrated the feasibility of phosphate removal, from synthetic secondary effluent, by adsorption onto iron oxyhydroxide agglomerates (IOAs) in a submerged membrane reactor. Sedimentation of the IOAs, their regeneration and reusability were investigated. Additionally, the reuse of the desorbing solution was examined. Techno-economic evaluation of the cost of chemicals required for synthesis and regeneration of the IOAs is presented. The potential application of the IOAs as a renewable adsorbent was demonstrated by the high adsorption capacity which was not significantly changed with the adsorption/regeneration cycle number (about 93% of initial adsorption capacity was obtained in the fifth adsorption cycle) as well as the lower chemical cost of IOAs regeneration as compared to their synthesis.

Crossflow electrochemical filtration for elimination of ibuprofen and bisphenol a from pure and competing electrolytic solution conditions.

For the first time, a crossflow electrochemical filtration system containing multiwalled carbon nanotubes (MWNTs) blended with buckypaper as a flat sheet dual membrane electrode was investigated for the removal of two contaminants of emerging concern, Ibuprofen and Bisphenol A. Breakthrough experiments revealed that a crossflow configuration could be highly efficient in eliminating both contaminants at applied DC potentials of 2 and 3 V over an extended period, from pure salt electrolyte as well as from synthetic secondary wastewater effluent. The shear flow provided consistent surface coverage resulting in excellent sorption performance. The long residence time of the two contaminants within the membrane (18.3 s) was sufficient enough to allow for almost complete degradation of phenolic aromatic products and quinoid rings and the resulting formation of aliphatic carboxylic acids, which was more evident at a higher applied potential (3 V). The formation of the non-toxic aliphatic carboxylic acids is a clear indication of the superior electrochemical performance of the crossflow mode over the dead-end flow-through system. Moreover, this study provides an in-depth understanding of different factors such as filter surface area and residence time that can greatly affect the removal of the contaminants considered.

E. coli – MS2 bacteriophage interactions during solar disinfection of wastewater and the subsequent post-irradiation period

In this study, the effect of MS2 bacteriophage on the inactivation of its Escherichia coli host was evaluated in an effort to recreate some the main factors governing solar disinfection of wastewater (namely microbial growth, infection, photonic flux). As such, the kinetics of sole MS2 bacteriophage or Escherichia coli and their simultaneous inactivation were investigated in synthetic secondary effluent wastewater and accurately modeled by log-linear and shoulder-log linear models, respectively. The observed inactivation kinetics revealed a minor influence between the microorganisms during the solar treatment phase. However, the simultaneous presence of both strains affected bacterial regrowth during the post-irradiation period. Specifically, our results show minor MS2 increase (1-log) in presence of E. coli, but bacterial survival restriction in presence of the bacteriophage (24- vs. 48-h decay). Experiments conducted at three different temperatures (4, 20 and 37 °C) and two discharge matrices (lake water, seawater) indicate that both healthy cells and non-cultivable bacteria influence population dynamics, with (re)growth under mesophilic temperatures and support of the viral life cycle. Noteworthy cases were observed in lake water (high regrowth levels) and in seawater (no growth). In overall, this study contributes to the deeper understanding of population dynamics (i.e. coliphage-bacteria interactions). In extension, it unveils the capacity of solar exposure as disinfection method and indicates possible health risks associated with enteric viral and bacterial-related diseases due to incomplete solar wastewater disinfection or post-irradiation mishandling.