Tertiary Wastewater Treatment Research Articles

Open the way to turnover frequency determination in (photo)Fenton processes for catalytic activities comparison

The design of new catalysts represents a crucial aspect for future applications of advanced oxidation processes for tertiary wastewater treatment and the development of active catalysts for (photo-)Fenton processes is a sector of enormous interest for both scientific and industrial sectors. Notwithstanding, critical evaluation of the catalytic activity needed to compare different catalysts under the same conditions has been poorly addressed so far in the scientific literature. To date, researchers’ attention has been mainly devoted investigate optimal reaction conditions to degrade a target pollutant in aqueous matrices excluding a critical evaluation of general aspects of catalysis. In this work we report on the necessity of introducing the turnover frequency number determination for each investigated catalyst in order to evaluate the corresponding activity and to improve the benign-by-design approach for further catalytic improvements. For this purpose, we discussed the comparison between two Iminodisuccinic acid-based metal complexes in the phenol degradation through photo-Fenton process. Experiments were carried out under the same reaction conditions ([phenol]=50 mg/L; [H2O2] =5.3 mM; 2 h; UV-C radiation) and the best results were obtained in the presence of Fe-IDS (COD removal = 73 %; TOF=17.6) whereas Cu-IDS is not active for phenol degradation. TOF determination was further discussed considering literature data (phenol degradation using Fe2+ and Fe-EDTA as catalysts) with the scope of enlarge the results discussion on the basis of TOF determination.

Towards the Configuration of a Photoelectrocatalytic Reactor: Part 1-Determination of Photoelectrode Geometry and Optical Thickness by a Numerical Approach.

Photoelectrocatalysis has been highlighted as a tertiary wastewater treatment in the textile industry due to its high dye mineralisation capacity. However, design improvements are necessary to overcome photo-reactors limitations. The present work proposes a preliminary configuration of a photoelectrocatalytic reactor to degrade Reactive Red 239 (RR239) textile dye, using computational fluid dynamics (CFD) to analyse the mass transfer rate, radiation intensity loss (), and its effect on kinetics degradation, over a photoelectrode based on a nanotube. A study to increase the space-time yield (STY) was carried out through mass transfer rate and kinetic analysis, varying the optical thickness () between the radiation entrance and the photocatalytic surface, photoelectrode geometry, inlet flow rate, and the surface radiation intensity. The was determined using a 1D Beer–Lambert-based model, and an extinction coefficient experimentally determined by UV-Vis spectroscopy. The results show that in RR239 solutions below concentrations of 6 mg/L, a woven mesh photoelectrode and an optimal optical thickness of 1 cm is enough to keep the below 15% and maximise the mass transfer and the STY in around 110 g/m-day.

Seasonal variation and spatial distribution of microplastics in tertiary wastewater treatment plant in South Korea

Wastewater treatment plant (WWTP) is proposed to be a point source of microplastics (MPs) that enter aquatic environments. Here, we quantified and characterized MPs down to 20 µm at a tertiary WWTP in Korea over a 1-year period. All wastewater contained MPs during the monitoring period, with concentrations ranging from 114 ± 17–216 ± 65 particles/L for influent and from 0.26 ± 0.29–0.48 ± 0.11 particles/L for effluent. MP abundance in the influents showed significant seasonal differences whereas a seasonal trend was not observed for the effluents, indicating a stable treatment performance (approx. 99.8%) of the WWTP. Spatial surveys of MP distribution in the WWTP showed that most MPs were removed by coagulation-sedimentation and rapid sand filtration, but some MPs still remained in the final effluent to generate the potential annual load of 2.9 × 109 particles and 0.54 kg into the rivers. These findings highlight the importance of long-term monitoring and MP mass quantification that would promote more accurate estimation of the MP load from WWTPs.

Identifying steep pareto fronts in multicomponent adsorption using a novel elliptical method.

Multicomponent adsorption processes are affected by both mixture and process variables viz. feed composition, pH, adsorbent dosage, and adsorbent type. Optimization of multicomponent adsorption processes with multiple objectives is challenging. It is important to accurately identify possible solutions and select the compromise solution that best satisfies the different objectives. Conventional algorithms, when applied to multicomponent adsorption, were found to identify the Pareto front less accurately, thereby necessitating the need for a reliable method. The steep portion of the Pareto front was especially not captured satisfactorily by the different conventional algorithms such as pattern search (PS), Non-dominated Sorting Genetic Algorithm (NSGA-II), and Epsilon-Constraint (EC). This portion assumes importance, if the compromise solution occurs in its vicinity. To address these challenges, a novel bi-objective optimization technique termed as elliptical method (EM) was developed and described in this work. It involves an exhaustive search, provides a well distributed Pareto front, and clearly delineates the steep region. After validating with benchmark problems, EM was applied to batch multi-component adsorption. The two objectives optimized simultaneously were adsorbent loading and percentage removal of the different solutes. The Pareto front and the compromise solution involving the best combination of the two objectives were significantly superior in the elliptical method when compared to those obtained from typical algorithms including epsilon-constraint (EC) method. The Pareto front was also well defined by the elliptical method without discontinuities near the extreme and steep regions. The number of points found by EM in the steeper region for the grade II adsorbent was 10 times greater than those found by the EC method while the PS and NSGA could not delineate this portion. The average time taken (considering both adsorbents) for EM per solution was 0.17s which was at least 30.6% faster than the other methods. The compromise solution with the elliptical method was superior to the other methods. For instance, with grade II adsorbent, the compromise solution from the elliptical method suggested operating conditions that led to a total adsorbent loading and percentage removal of 333.4mg/g and 56.0%. On the other hand, pattern search gave 324.1mg/g and 56.5%, whereas the NSGA-II method gave 321.9mg/g and 53.3%. For this adsorbent, elliptical method's compromise solution was 50% and 20% closer in terms of the Euclidean distance to the utopia point than NSGA and PS methods, respectively. The elliptical method will facilitate reliable wastewater tertiary treatment taking into cognizance the utilization of the adsorbent as well as the percentage purity requirement.

Start-up and microbial mechanisms of low-voltage electrochemically integrated constructed wetlands: Effect of inoculated source

Nitrogen (N) and phosphorus (P) species in wastewater treatment plants (WWTPs) effluents are important sources of nutrient input to water bodies, resulting in deteriorated eutrophication. The combination of electrochemical technology and constructed wetland provides emerging prospects for tertiary treatment of WWTPs effluents. In this work, three bench-scale electrochemically integrated vertical flow constructed wetlands (E-VFCWs) were established in parallel with different inoculated sources. Among them, the E-VFCW inoculated with anaerobic sludge (AN) of a swine wastewater treatment plant exhibited significantly shorter start-up period (9 d), followed by anoxic sludge (A) from a municipal WWTP (18 d), and no inoculum (NI) exhibited the longest start-up duration (30 d). In addition, AN group allowed the highest removal efficiencies (NO3--N (97.0 ± 1.6 %), TN (83.3 ± 4.6 %), and PO43--P (93.3 ± 3.3 %)) in tertiary wastewater treatment, and lower concentrations of SO42--S and total Fe in effluents. Results of microbial structure and Tax4Fun suggested that multi-path metabolisms including H2-, Fe(II)-, and FemSn-dependent denitrification might facilitate NO3--N reduction in E-VFCWs. The microbial mechanisms that AN exhibited the highest denitrification efficiency in the E-VFCWs may include the highest bacterial copies number and the more abundant denitrifying genes. Moreover, it should be noted that electron transfers mediated by sulfur (S) cycle might significantly enhance NO3--N reduction in E-VFCWs, especially in AN group. To conclude, the study offers new microbial insights into N conversion and S cycling patterns in electrochemically integrated systems in response to inoculated source.

Renewable adsorbents from the solid residue of sewage sludge hydrothermal liquefaction for wastewater treatment

Solid residue from hydrothermal liquefaction (HTL) of nutrient rich feedstock presents a promising source to recover valuable nutrients, such as phosphorus, in the solid form. The present work shows for the first time the potential of utilizing the waste residue remaining after nutrients extraction from HTL of sewage sludge, as renewable adsorbents. A parametric study was undertaken to investigate the influence of chemical activation conditions (temperature, residence time, activation agent loading, washing after activation) on raw and partially demineralized HTL solids. Kinetic and equilibrium adsorption investigation was undertaken for the removal of methylene blue (MB) from aqueous solution. For comparison purposes, a commercial activated charcoal (AC) was used. Demineralization was found to have a significant influence in the adsorption capacity of the resultant adsorbents. Three adsorbents were found to follow the Langmuir adsorption model, while the acid washed demineralized adsorbent had higher adsorption capacity than AC and was found to follow the Freundlich adsorption model. The superior performance of the acid washed demineralized adsorbent was verified from the kinetic study where all adsorbents were found to best fit the pseudo-second order model. Adsorption capacities for MB at equilibrium were 367.1, 332.3, 297.4 and 87.6 mg/g, for acid washed demineralized adsorbent, AC, demineralized adsorbent, and raw adsorbent, respectively. Finally, the most promising adsorbents were assessed for their adsorption capacity to remove pharmaceuticals present in a real wastewater treatment effluent. Results indicated ultimate concentration for all targeted compounds below the detection limits for acid washed demineralized adsorbent, AC and demineralized adsorbent. Future implementation of HTL technology in wastewater treatment facilities, will not only provide an efficient way to valorize sewage sludge into bio-crude and nutrients, but can also enhance technology integration by providing the precursors for renewable adsorbents needed in tertiary treatment of wastewater.

Assessment of a Novel Photocatalytic TiO2-Zirconia Ultrafiltration Membrane and Combination with Solar Photo-Fenton Tertiary Treatment of Urban Wastewater

The objective of this study was to assess the combination of a photocatalytic TiO2-coated ZrO2 UF membrane with solar photo-Fenton treatment at circumneutral pH for the filtration and treatment of urban wastewater treatment plant (UWWTP) effluents. Photocatalytic self-cleaning properties were tested with a UWWTP effluent under irradiation in a solar simulator. Then, both the permeates and retentates from the membrane process were treated using the solar photo-Fenton treatment. The UWWTP effluent was spiked with caffeine (CAF), imidacloprid (IMI), thiacloprid (THI), carbamazepine (CBZ) and diclofenac (DCF) at an initial concentration of 100 µg/L each. Retention on the membrane of Pseudomonas Aeruginosa (P. Aeruginosa), a Gram-negative bacterial strain, was tested with and without irradiation. It was demonstrated that filtration of a certain volume of UWWTP effluent in the dark is possible, and the original conditions can then be recovered after illumination. The photocatalytic membrane significantly reduces the turbidity of the UWWTP effluent, significantly increasing the degradation efficiency of the subsequent solar photo-Fenton treatment. The results showed that the membrane allowed consistent retention of P. Aeruginosa at an order of magnitude of 1 × 103–1 × 104 CFU/mL.

Sustainable Alternatives for Tertiary Treatment of Pulp and Paper Wastewater

In this work, different alternatives to conventional tertiary treatment of pulp and paper (P&P) wastewater (WW), i.e., physicochemical coagulation-flocculation, were investigated to enhance the environmental and economic sustainability of industrial wastewater treatment. In particular, following a preliminary characterization of secondary effluents, cloth filtration and adsorption were studied, the former by pilot-scale tests, while the latter at laboratory scale. An economic analysis was finally accomplished to verify the full-scale applicability of the most promising technologies. Cloth filtration showed excellent total suspended solids (TSS) removal efficiency (mean 81% removal) but a very limited influence on chemical oxygen demand (COD) (mean 10% removal) due to the prevalence of soluble COD on particulate COD. Adsorption, instead, led to a good COD removal efficiency (50% abatement at powdered activated carbon—PAC—dosage of 400 mg/L). The economic analysis proved that adsorption would be convenient only if a local low-cost (100 €/ton) adsorbent supply chain was established. Ultrafiltration was considered as well as a potential alternative: its huge capital cost (19 M€) could be recovered in a relatively short timeframe (pay-back time of 4.7 years) if the ultrafiltrated effluent could be sold to local industries.

Nanofiltration as an Efficient Tertiary Wastewater Treatment: Elimination of Total Bacteria and Antibiotic Resistance Genes from the Discharged Effluent of a Full-Scale Wastewater Treatment Plant

Wastewater reuse for agricultural irrigation still raises important public health issues regarding its safety, due to the increasing presence of emerging contaminants, such as antibiotic resistant bacteria and genes, in the treated effluents. In this paper, the potential for a commercial Desal 5 DK nanofiltration membrane to be used as a tertiary treatment in the wastewater treatment plants for a more effective elimination of these pollutants from the produced effluents was assessed on laboratory scale, using a stainless steel cross-flow cell. The obtained results showed high concentrations of total bacteria and target carbapenem and (fluoro)quinolone resistance genes (blaKPC, blaOXA-48, blaNDM, blaIMP, blaVIM, qnrA, qnrB and qnrS) not only in the discharged, but also in the reused, effluent samples, which suggests that their use may not be entirely safe. Nevertheless, the applied nanofiltration treatment achieved removal rates superior to 98% for the total bacteria and 99.99% for all the target resistance genes present in both DNA and extracellular DNA fractions, with no significant differences for these microbiological parameters between the nanofiltered and the control tap water samples. Although additional studies are still needed to fully optimize the entire process, the use of nanofiltration membranes seems to be a promising solution to substantially increase the quality of the treated wastewater effluents.

Evaluation of Membrane Fouling by Microplastic Particles in Tertiary Wastewater Treatment Processes

Microplastic (MP) pollution in aquatic environments poses substantial ecological, human, and economic threats. A common route of entry for MPs into the aquatic environment is through the effluent from wastewater treatment plants (WWTPs). Although membrane technologies as a tertiary treatment step have shown promise in mitigating the efflux of MPs, little is known about how MPs suspended in wastewater effluent affect membrane performance. One reason is that it is challenging to source MPs for filtration experiments which are representative of those found in WWTPs. As such, this study employed a milling and sieving process to create irregularly shaped polyethylene MPs approximately 10 μm in size which were then suspended in effluent wastewater (taken directly from a secondary clarifier tank). Membrane fouling caused by wastewater/MP interactions was investigated via constant pressure filtration experiments using commercial ultrafiltration and microfiltration membranes. It was found that even low concentrations of MPs in the wastewater increased the extent of membrane fouling. Furthermore, a backwashing process was found to significantly mitigate the effect of MP fouling on the membrane surfaces. The results from this study provide important insights into the governing factors for membrane fouling by MPs in water chemistries representative of WWTP effluents.

Ozone reactor combined with ultrafiltration membrane: A new tertiary wastewater treatment system for reuse purpose

In the present research, a new technology using the application of ozone (O³) together with an ultrafiltration (UF) membrane was tested for the tertiary treatment of wastewater. The primary and secondary wastewater-treatment systems were a septic tank and anaerobic filter. The experiment was divided into two stages: the first including only the application of O3 in the reactor, and the second, inclusion of the UF membrane. During the first stage of the study, where only the ozone was applied, a time of 40 min was chosen, with removal levels for chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), total organic carbon (TOC), turbidity and ammonium (NH4+) of 39.5%, 45.4%, 32.4%, 44.85% and 68.4% being recorded. During stage 2, the UF membrane inside the reactor was activated after 40 min of ozonation. The values for the removal of COD, BOD5, TOC, turbidity, NH4+ and total phosphorus were 89.13%, 95.41%, 82%, 93.4%, 14.75% and 79.67%, respectively. The use of O3 + UF removed 100% of total coliforms and viruses from the secondary wastewater. In accordance with North American and European guidelines, the water resulting from the treatment process is fit for reuse. The operating costs can vary between 0.859 € m-3 and 2.440 € m-3 depending on the cost per kWh in each country. The experiments were conducted under batch-mode conditions, further evaluations about the real scale operation would require a previous pilot stage that would develop more tools for operations specifications and their costs. The results recorded here show that the performance of this new reactor design is effective in the tertiary treatment of wastewater, and should be available for use in the near future.

Life Cycle Assessment for Tertiary Wastewater Treatment and Reuse versus Seawater Desalination

Wastewater reuse is now indispensable for meeting the increasing water demand, particularly under conditions of alarming water scarcity, which is now already affecting every continent. The objective of this study is to apply life cycle assessment (LCA) to evaluate the environmental impact and missed opportunity of treating municipal wastewater to tertiary quality and compare it to conventional seawater desalination in the Gulf Corporation Council (GCC) countries, namely: Multistage flash distillation (MSF), multi-effect distillation (MED) and seawater reverse osmosis (SWRO). The study follows the ISO 14040/44 standards and uses a functional unit of 1 Mm3 of tertiary treated effluent (TTE). The modeling concept adopts the cradle-to-gate consequential paradigm. The life cycle inventory is based on fielded data collection, reports, literature and Ecoinvent database processes. The scope includes: infrastructure, grid, materials, energy requirements, chemical additives and sludge disposal; for primary, secondary and tertiary treatment. The life cycle impact assessment is applied on both the characterized and normalized levels using the ReCiPe method. Compared to distillation, TTE exhibits an average reduction of 94% in fossil depletion. For climate change and particulate matter, an average reduction of 79% and 73% can be realized respectively. The large difference is due to energy consumption in desalination, despite that fact that the energy considered is only the allocated portion to distillation in the cogeneration total, using exergy specific power consumption.

Wastewater substrate disinfection for cyanobacteria cultivation as tertiary treatment.

Cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters offers an opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production, mitigation of emitted GHGs and provision of added value products. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H2O2 or Fe(VI), as a preliminary treatment stage upstream a cyanobacteria cultivation photobioreactor. The growth rate of cyanobacterium Synechococcus elongatus PCC 7942, and nitrate and phosphate removal rates, were experimentally assessed in cultivation setups with biologically treated dairy wastewater that had been subjected to a single or a synergetic couple of disinfection techniques. The results showed that filter thickness has a greater effect on disinfection efficiency than filter pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe0/Fe0 cell, was greater than that of NaClO and H2O2. Filtration at ≤ 1.2-μm pore size coupled with chemical disinfection led to unhindered Synechococcus elongatus PCC 7942 growth and efficient nitrate and phosphate removal rates, at dosages, in terms of Concentreation-Time (CT) product,of CT ≥ 270mgmin L-1 for NaClO and CT ≥ 157mgmin L-1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater media. Moreover, the residual iron species can assist in Synechococcus elongatus PCC 7942 harvesting and may enhance photosynthesis rate by increasing light transfer efficiency. Thus, a filtration configuration coupled with chemical disinfection, preferably using ferrates, downstream of sedimentation tank of a secondary biological wastewater treatment stage is proposed as a necessary, efficient and low-cost disinfection technique for full-scale scale implementation of cyanobacteria cultivation as tertiary wastewater processes.

Integrated estrogenic effects and semi-volatile organic pollutants profile in secondary and tertiary wastewater treatment effluents in North China

Endocrine-disrupting effects on aquatic organisms caused by wastewater discharging have raised extensive concerns. However, the efficiency of various wastewater treatment processes to remove estrogenic activity in effluents and the association with organic micropollutants was not well known. We evaluated the estrogenic activity using a well-characterized in vivo bioassay featuring the Chinese rare minnows (Gobiocypris rarus) and analyzed 886 semi-volatile organic compounds (SVOCs) in effluents from four secondary wastewater treatment plants (SWTP A-D) and a tertiary wastewater treatment plant (TTP E) that utilized various common treatment processes in northern China. The final effluents from SWTPs and TTP E all exhibited estrogenic effects, increasing male fish plasma vitellogenin (VTG) contents and estradiol/testosterone (E2/T) ratios. Key regulating genes in the male fish liver including vtg1, vtg3, era, erβ, and cyp19a were upregulated. TTP E demonstrated high performance in reducing estrogenic activity in the effluents, with a reduction of 64% in integrative biomarkers of estrogenic response (IBR). UV disinfection at SWTPs removed IBR by 14%− 33%, while ozone disinfection at TTP E did not reduce IBR. Several SVOCs including alkanes, chlorobenzenes, and phthalates, detected at ng/L to µg/L level, significantly correlated with effluent estrogenic activity. Our findings suggest the necessity and the potential means to improve the efficiency of current wastewater treatment approaches to achieve better protection for aquatic organisms against the joint effects of mixtures of various categories of micropollutants in effluents.

Tertiary treatment of municipal wastewater by a novel flow constructed wetland integrated with biochar and zero-valent iron

To achieve high and stable nutrient removal efficiency for stricter discharge standards, three bench-scale integrated flow constructed wetlands (IFCWs) with different filler medium arrangements were built for tertiary treatment of municipal wastewater. We hypothesized the incorporation of biochar and zero-valent iron (ZVI) into an IFCW could enhance nutrient removal significantly. Results showed that W2 with biochar (89.1 ± 1.5%, 88.1 ± 1.1%, 75.9 ± 4.5%) and W3 with ZVI-biochar (86.4 ± 1.5%, 88.3 ± 0.7%, 91.6 ± 3.8%) had significantly higher removal efficiencies of NH4+-N, TN, and TP than that of the control group (68.8 ± 7.1%, 62.4 ± 4.6%, 68.1 ± 8.0%). Analysis of the microbial community revealed that nitrifiers such as Nitrosomonadales and Nitrospirales were enriched in W2, while denitrifiers like Rhodocyclales, Burkholderiales, Rhizobiales and Pseudomonadales were enriched in W3. Analysis of functional genes demonstrated that the biochar increased the abundance of AOB-amoA, while ZVI-biochar promoted the abundance of nosZ, nirS, nirK and hzsA. Principal component analysis (PCA) indicated that higher NH4+-N removal efficiency mainly resulted from the enhancement of microbial nitrification by biochar, and the improvement of NO3−-N removal efficiency was attributed to the enhanced denitrification and anammox by ZVI.

Solar photo-Fenton at circumneutral pH using Fe(III)-EDDS compared to ozonation for tertiary treatment of urban wastewater: Contaminants of emerging concern removal and toxicity assessment

• Solar photo-Fenton compared to ozonation at pilot plant scale. • Successful CEC removal was achieved (>80%) but less treatment time was required by ozonation. • Acute and Chronic toxicity tests did not provide conclusive results. Solar photo-Fenton (SPF) at circumneutral pH with ethylenediamine-N,N'-disuccinic acid (EDDS) in raceway pond reactor was compared to a well-stablished process (ozonation) in the degradation of five contaminant of emerging concern (CECs, namely Caffeine, Carbamazepine, Diclofenac, Sulfamethoxazole and Trimethoprim) at the initial concentration of 100 μg/L each in urban wastewater treatment plant secondary effluent (UWWE) at pilot scale with natural sunlight. Both were found to be effective in the removal of the target CECs. Ozonation treatment was faster being able to degrade 80% of each CEC in UWWE within the early 15 min (18.0 mgO 3 /L consumed). Acute (using activated sludge, Vibrio fischeri and Daphnia magna) and chronic (using activated sludge at 72 h of sample contact and V. fischeri at 24 h of sample contact) toxicity were also evaluated. Acute toxicity evaluated by activated sludge did not show any toxic effect. V. fischeri gave less sensitive results compared to D. magna tests. Lower toxicity levels for SPF were observed. Highest acute toxicity was observed for D. magna in UWWE treated by ozonation. Relevant chronic toxicity assessed by activated sludge and V. fischeri was observed in almost all analysed samples, despite 80% of the CECs were eliminated. Successful performance of AOPs for CECs removal is not a guarantee of obtaining safe alternative water sources.

Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant.

Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and genes (ARB and ARGs) in wastewaters. The present work aimed to build on the current knowledge about the effects of activated sludge and UV irradiation on antibiotic resistance determinants in biologically treated wastewaters. For that, the microbial community and ARGs' composition of samples collected after preliminary (APT), secondary (AST), and tertiary (ATT) treatments in a full-scale wastewater treatment plant using a modified activated sludge (MAS) system followed by an UV stage (16mJ/cm2) were investigated through culture-dependent and independent approaches (including metagenomics). A total of 24 phyla and 460 genera were identified, with predominance of Gammaproteobacteria in all samples. Pathogenic genera corresponded to 8.6% of all sequences on average, mainly Acinetobacter and Streptococcus. Significant differences (p < 0.05) in the proportion of pathogens were observed between APT and the other samples, suggesting that the secondary treatment reduced its abundance. The MAS achieved 64.0-99.7% average removal efficiency for total (THB) and resistant heterotrophic bacteria, although the proportions of ARB/THB have increased for sulfamethoxazole, cephalexin, ciprofloxacin, and tetracycline. A total of 107 copies/mL of intI1 gene remained in the final effluent, suggesting that the treatment did not significantly remove this gene and possibly other ARGs. In accordance, metagenomic results suggested that number of reads recruited to plasmid-associated ARGs became more abundant in the pool throughout the treatment, suggesting that it affected more the bacteria without these ARGs than those with it. In conclusion, disinfected effluents are still a potential source for ARB and ARGs, which highlights the importance to investigate ways to mitigate their release into the environment.

Applications of Nano-Zeolite in Wastewater Treatment: An Overview

Nano-zeolite is an innovative class of materials that received recognition for its potential use in water and tertiary wastewater treatment. These applications include ion-exchange/sorption, photo-degradation, and membrane separation. The aim of this work is to summarize and analyze the current knowledge about the utilization of nano-zeolite in these applications, identify the gaps in this field, and highlight the challenges that face the wide scale applications of these materials. Within this context, an introduction to water quality, water and wastewater treatment, utilization of zeolite in contaminant removal from water was addressed and linked to its structure and the advances in zeolite preparation techniques were overviewed. To have insights into the trends of the scientific interest in this field, an in-depth analysis of the variation in annual research distribution over the last decade was performed for each application. This analysis covered the research that addressed the potential use of both zeolites and nano-zeolites. For each application, the characterization, experimental testing schemes, and theoretical analysis methodologies were overviewed. The results of the most advanced research were collected, summarized, and analyzed to allow an easy visualization and comparison of these research results. Finally, the gaps and challenges that face these applications are concluded.

Performance evaluation on ultrafiltration as tertiary treatment for rubber glove wastewater

Ultrafiltration (UF) is a promising treatment solution used for tertiary treatment of industrial wastewater. However, membrane fouling is the major problem which limits the performance of the UF in industry. In the present study, the operational and separation performane of ultrafiltration of biologically treated rubber glove wastewater were carried out using innovative developed organic metal membranes. Two types of commercial PolyCera® Titan (70 kDa) and PolyCera® Hydro (100 kDa) flat sheet UF membrane were applied for tertiary treatment of rubber glove wastewater. The physicochemical properties of influent and UF membranes were characterized before and after the treatment process. PolyCera® Titan membranes have slightly higher hydrophobicity, lower permeability and lower fouling tendency as compared to PolyCera® Hydro membrane. PolyCera® Titan gave higher COD, TSS, and color rejection, observed at 66.9%, 73.3%, and 82.4%, respectively. The permeate quality conformed with the regulatory discharge standard, except for the PolyCera® Hydro membrane in which the COD value surpassed the permissible limit. With its promising performance, PolyCera® membranes have great potential to reduce pollutant loading in the wastewater for efficient rubber glove wastewater treatment.

A Natural Microalgae Consortium for the Biological Nutrient Removal in a Upflow Photobioreactor as Tertiary Wastewater Treatment

A Natural Microalgae Consortium for the Biological Nutrient Removal in a Upflow Photobioreactor as Tertiary Wastewater Treatment