Tertiary Treatment Technologies Research Articles

Nature-based solutions for antibiotics and antimicrobial resistance removal in tertiary wastewater treatment: Microbiological composition and risk assessment

This field-scale study evaluates the seasonal effectiveness of employing nature-based solutions (NBSs), particularly surface flow and horizontal subsurface flow constructed wetland configurations, as tertiary treatment technologies for the removal of antibiotics (ABs) and antibiotic resistance genes (ARGs) compared to a conventional treatment involving UV and chlorination. Out of the 21 monitored ABs, 13 were detected in the influent of three tertiary wastewater treatments, with concentrations ranging from 2 to 1218 ng·L-1. The ARGs sul1 and dfrA1 exhibited concentrations ranging from 1 × 105 to 9 × 106 copies/100 mL. NBSs were better at reducing ABs (average 69 to 88 %) and ARGs (2–3 log units) compared to the conventional tertiary system (average 36 to 39 % and no removal to 2 log units) in both seasons. Taxonomic compositions in influent water samples shifted from wastewater-impacted communities (Actinomycetota and Firmicutes) to a combination of plant rhizosphere-associated and river communities in NBS effluents (Alphaproteobacteria). In contrast, the conventional technology showed no substantial differences in community composition. Moreover, NBSs substantially reduced the ecotoxicological risk assessment (cumulative RQs). Furthermore, NBSs reduced the ecotoxicological risk (cumulative RQs) by an average of over 70 % across seasons, whereas the benchmark technology only achieved a 6 % reduction. In conclusion, NBSs present a robust alternative for minimizing the discharge of ABs and ARGs into surface water bodies.

Second life of water and wastewater in the context of circular economy – Do the membrane bioreactor technology and storage reservoirs make the recycled water safe for further use?

In recent years water demand drastically increased which is particularly evident in tourism-burdened mountain regions. In these areas, climate neutral circular economy strategies to minimize human impact on the environment can be successfully applied. Among these strategies, treated wastewater reuse and retaining water in storage reservoirs deserve particular attention. This study aimed to determine if recycled water produced with two circular economy systems, namely membrane bioreactor treatment plant (MBR) with UV-light effluent disinfection and a storage reservoir, is safe enough for further use in green areas irrigation in summer and artificial snow production in winter. The assessment was based on the presence and concentration of antimicrobial agents, antibiotic resistant bacteria, antibiotic resistance genes, bacterial community composition and diversity. The treated water and wastewater was compared with natural water in their vicinity. Both systems fulfill the criteria set by the European Union in terms of reclaimed water suitable for reuse. Although the MBR/UV light wastewater treatment substantially reduced the numbers of E. coli and E. faecalis (from e.g. 32,000 CFU/100 ml to 20 CFU/100 ml and 15,000 CFU/100 ml to nearly 0 CFU/ml), bacteria resistant to ampicillin, aztreonam, cefepime, ceftazidime, ertapenem and tigecycline, as well as ESBL-positive and multidrug resistant E. coli were highly prevalent in MBR-treated wastewater (88.9 %, 55.6 %, 33.3 %, 22.2 % and 11.1 % and 44.4 and 55.6 %, respectively). Applying additional tertiary treatment technology is recommended. Retaining water in storage reservoirs nearly eliminated bacterial contaminants (e.g. E. coli dropped from 350 CFU/100 ml to 10 CFU/100 ml), antibiotic resistant bacteria, resistance genes (none detected in the storage reservoir) and antibiotics (only enrofloxacin detected once in the concentration of 3.20 ng/l). Findings of this study point to the limitations of solely culture-based assessment of reclaimed water and wastewater while they may prove useful in risk management and prevention in wastewater reuse.

Phosphorus removal from ore waste in aqueous solution with different mass of ore waste adsorbent from the Johor mine site

Abstract Mine waste management is becoming a growing global environmental concern for mining industries all over the world. Due to the abundance of ore waste from mining industries, this study aimed to observe the possibility of using ore waste to remove phosphorus from a solution. Although phosphorus is one of the essential elements for plant life, excessive phosphorus in water becomes one of the environmental issues, e.g., eutrophication. This study analysed the prediction contour of removal efficiency with the mass of adsorbent needed under different initial concentrations of solution. The batch experiment used an aqueous solution of 5 mg/L using potassium dihydrogen phosphate (KH2PO4) at different masses of adsorbent (2, 4, 6, 8, 10 g). The highest removal efficiency for phosphorus using 10 g of adsorbent is 54.3%. The data verified that the pseudo-second-order model (0.9976) fitted well. The adsorption between ore waste adsorbent and phosphorus was chemical sorption, whereas the analysis of isotherm models fitted the Freundlich model, with the occurrence of multilayer adsorption on the adsorption surface. The ability of ore waste to remove phosphorus was successful. This approach is one of the alternatives to enhance tertiary wastewater treatment technologies.

How to choose the best tertiary treatment for pulp and paper wastewater? Life cycle assessment and economic analysis as guidance tools

Pulp and paper wastewater (P&P WW) often requires tertiary treatment to remove refractory compounds not eliminated by conventional biological treatment, ensuring compliance with high-quality effluent discharge or reuse standards. This study employs a life cycle assessment (LCA) methodology to compare alternative tertiary treatment technologies for P&P WW and rank them accordingly. The evaluated technologies in the scenarios include inorganic (S1) and organic (S2) coagulation-flocculation, ozonation (O3) (S3), O3+granular activated carbon (GAC) (S4), and ultrafiltration (UF)+reverse osmosis (RO) (S5). The analysis focuses on a P&P wastewater treatment plant (WWTP) in Northeastern Italy. The LCA is complemented by an economic analysis considering each technology's capital and operating costs, as well as potential revenues from internal effluent reuse. Results indicate that S4 (O3+GAC) outranks all the other scenarios in terms of both environmental performance and economic viability, primarily due to the advantages associated with effluent reuse. S5 (UF+RO), which also involves reuse, is limited by the high energy consumption of UF+RO, resulting in increased environmental impacts and costs. The physicochemical scenario S2 (Chem Or), currently utilized in the WWTP under study, remains the best-performing technology in the absence of effluent reuse. In contrast, S3 (O3 alone) exhibits the poorest environmental and economic outcomes due to substantial energy requirements for O3 generation and the inability to reuse the treated effluent directly. Lastly, a sensitivity analysis underscores the strong influence of chemical dosages in S1 and S2 on environmental and economic impacts, which is more significant than the impact of water reuse percentages in S4 and S5. The high electricity cost observed during 2022 negatively affects the energy-intensive scenarios (S3-S5), making coagulation-flocculation (S1-S2) even more convenient.

Harnessing water fleas for water reclamation: A nature-based tertiary wastewater treatment technology

Urbanisation, population growth, and climate change have put unprecedented pressure on water resources, leading to a global water crisis and the need for water reuse. However, water reuse is unsafe unless persistent chemical pollutants are removed from reclaimed water. State-of-the-art technologies for the reduction of persistent chemical pollutants in wastewater typically impose high operational and energy costs and potentially generate toxic by-products (e.g., bromate from ozonation). Nature-base solutions are preferred to these technologies for their lower environmental impact. However, so far, bio-based tertiary wastewater treatments have been inefficient for industrial-scale applications. Moreover, they often demand significant financial investment and large infrastructure, undermining sustainability objectives. Here, we present a scalable, low-cost, low-carbon, and retrofittable nature-inspired solution to remove persistent chemical pollutants (pharmaceutical, pesticides and industrial chemicals). We showed Daphnia's removal efficiency of individual chemicals and chemicals from wastewater at laboratory scale ranging between 50 % for PFOS and 90 % for diclofenac. We validated the removal efficiency of diclofenac at prototype scale, showing sustained performance over four weeks in outdoor seminatural conditions. A techno-commercial analysis on the Daphnia-based technology suggested several technical, commercial and sustainability advantages over established and emerging treatments at comparable removal efficiency, benchmarked on available data on individual chemicals. Further testing of the technology is underway in open flow environments holding real wastewater. The technology has the potential to improve the quality of wastewater effluent, meeting requirements to produce water appropriate for reuse in irrigation, industrial application, and household use. By preventing persistent chemicals from entering waterways, this technology has the potential to maximise the shift to clean growth, enabling water reuse, reducing resource depletion and preventing environmental pollution.

Biochar integrated reactive filtration of wastewater for P removal and recovery, micropollutant catalytic oxidation, and negative CO2 e: Process operation and mechanism.

Biochar (BC) use in water treatment is a promising approach that can simultaneously help address societal needs of clean water, food security, and climate change mitigation. However, novel BC water treatment technology approaches require operational testing in field pilot-scale scenarios to advance their technology readiness assessment. Therefore, the objective of this study is to evaluate the system performance of BC integrated into hydrous ferric oxide reactive filtration (Fe-BC-RF) with and without catalytic ozonation (CatOx) process in laboratory and field pilot-scale scenarios. For this investigation, Fe-BC-RF and Fe-CatOx-BC-RF pilot-scale trials were conducted on synthetic lake water variants and at three municipal water resource recovery facilities (WRRFs) at process flows of 0.05 and 0.6L/s, respectively. Three native and two iron-modified BCs were used in these studies. The commercially available reactive filtration process (Fe-RF without BC) had 96%-98% total phosphorus (TP) removal from 0.075- and 0.22-mg/L TP, as orthophosphate process influent in these trials. With BC integration, phosphorus removal yielded 94%-98% with the same process-influent conditions. In WRRF field pilot-scale studies, the Fe-CatOx-BC-RF process removed 84%-99% of influent total phosphorus concentrations that varied from 0.12 to 8.1 mg/L. Nutrient analysis on BC showed that the recovered BC used in the pilot-scale studies had an increase in TP from its native concentration, with the Fe-amended BC showing better P recovery at 110% than its unmodified state, which was 16%. Lastly, the field WRRF Fe-CatOx-BC-RF process studies showed successful destructive removals at >90% for more than 20 detected micropollutants, thus addressing a critical human health and environmental water quality concern. The research demonstrated that integration of BC into Fe-CatOx-RF for micropollutant removal, disinfection, and nutrient recovery is an encouraging tertiary water treatment technology that can address sustainable phosphorus recycling needs and the potential for carbon-negative operation. PRACTITIONER POINTS: A pilot-scale hydrous ferric oxide reactive sand filtration process integrating biochar injection typically yields >90% total phosphorus removal to ultralow levels. Biochar, modified with iron, recovers phosphorus from wastewater, creating a P/N nutrient upcycled soil amendment. Addition of ozone to the process stream enables biochar-iron-ozone catalytic oxidation demonstrating typically excellent (>90%) micropollutant destructive removals for the compounds tested. A companion paper to this work explores life cycle assessment (LCA) and techno-economic analysis (TEA) to explore biochar water treatment integrated reactive filtration impacts, costs, and readiness. Biochar use can aid in long-term carbon sequestration by reducing the carbon footprint of advanced water treatment in a dose-dependent manner, including enabling an overall carbon-negative process.

Abundance, characteristics, and removal of microplastics in different wastewater treatment plants in a Yangtze River Delta city of China

Microplastics (MPs) have become emerging environmental pollutants worldwide. Wastewater treatment plants (WWTPs) are considered to be the major source and sink of MPs in the terrestrial and aquatic environment. The present study has been carried out for Nanjing, a typical Yangtze River Delta city in China. In this work, the abundance and characteristics of MPs were investigated in the influent of four WWTPs, and the removal effect of different treatment processes was studied in the two advanced tertiary treatment WWTPs. In the influent, the abundance of MPs of industrial WWTPs (IWWTPs) was higher than that of municipal WWTPs (MWWTPs), with a dominant size of 38–63 μm. MP shapes were mainly distributed in fragments and fibers, with polymer species of polypropylene (PP) and polyethylene (PE). In the final effluent, MPs were removed by 93.81 % in IWWTPs versus 88.10 % in MWWTPs, which were mainly influenced by the tertiary treatment technology. The tertiary treatment showed significant differences with the removal efficiency of 61.58 % in IWWTPs, equipped with a high-density sediment tank, and 30.40 % in MWWTPs, equipped with a denitrification filter. This study provides comprehensive information about the MPs' characteristics and fate contained in different sewage of WWTPs and analyzes the tertiary treatment effect of MPs, expecting to provide constructive support for the improvement of management strategies in WWTPs technologies.

Strategic routes for wastewater treatment plant upgrades to reduce micropollutants in European surface water bodies

The European Union is determined to address the problem of contaminants of emerging concern (CEC) occurrence in natural water bodies. However, if a broad range of possible advanced treatment technological solutions exists as well as a variety of possible future conditions, then emission and consequently strategies for wastewater treatment plan (WWTP) upgrade and operation are not easy to anticipate. Here, a strategic foresight exercise was carried out to support decision-making matching anticipated future conditions toward the goal of finding suitable treatment upgrades to control CECs release in the environment. As a result, a roadmap and strategic routes were developed based on the interpretation of drivers for the EU region in the context of Shared Socioeconomic Pathways (SSPs) global change narratives. Screening and ranking of WWTP tertiary and advanced treatment technology upgrades were performed. Analysis of the resulting envisioned strategic routes allowed identifying and confronting core challenges such as the CEC removal agenda, technologies’ performance, requirements for CEC removal and water scarcity. The results also underline opportunities to shape WWTP technological upgrade planning such as: enhancing circular economy solutions in WWTP, water reclamation, and accelerated increase of the technology readiness level of hybrid and nature-based solutions.

Phycobiliprotein recovery coupled to the tertiary treatment of wastewater in semi-continuous photobioreactors. Tracking contaminants of emerging concern.

This study evaluated a tertiary wastewater treatment technology using cyanobacteria to recover value-added phycobiliproteins. The presence of contaminants of emerging concern (CECs) in wastewater, cyanobacterial biomass and pigments recovered were also analyzed. For this, a wastewater-borne cyanobacterium (Synechocystis sp. R2020) was used to treat secondary effluent from a municipal wastewater treatment plant, with and without nutrients supplementation. Then, the stability of phycobiliprotein production was assessed by operating the photobioreactor in semi-continuous mode. Results showed similar biomass productivity with and without nutrients supplementation (153.5 and 146.7 mg L−1 d−1, respectively). Upon semi-continuous operation, the phycobiliprotein content was stable and reached up to 74.7 mg gDW−1. The phycocyanin purity ratio ranged from 0.5 to 0.8, corresponding to food grade (>0.7). Out of 22 CECs detected in secondary effluent, only 3 were present in the phycobiliprotein extracts. In order to identify applications, prospective research should focus on CECs removal during pigment purification.

Inactivation of antibiotic resistant bacteria and elimination of transforming ability of plasmid carrying single and dual drug resistance genes by electro-oxidation using Ti/Sb-SnO2/PbO2 anode

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are one of the major components of environmental antimicrobial resistance (AMR). Wastewater treatment plant is an important source and a contributor of AMR components in environment. The existing tertiary treatment technologies viz., chlorination, ultraviolet treatment and ozonation are not effective in ARB disinfection or ARG removal. Therefore, it is important to evaluate the potential of advanced wastewater treatment technologies in removing ARB and ARGs. In this study, the potential of Ti/Sb-SnO2/PbO2 anode in disinfecting single ARB (pUC19-ampR), dual ARB (pBR322-ampR and tetR), regrowth inhibition, removal of intracellular and extracellular ARGs and loss of transformation efficiency were evaluated. Upto 7 log (99.99 %) removal of single ARB (0.212 min−1) and dual ARB (0.185 min−1) was achieved in 40 min and 35 min, respectively at an applied current density 30 mA cm−2. Scanning electron microscopy images confirmed extensive and irreparable cell damages. Therefore, no re-growth was observed upto 30 days. Agarose gel electrophoresis and qubit analysis confirmed degradation of intracellular and extracellular genetic material. Upto ∼7.5 log (53.14 ± 1.23 %) of intracellular and ∼5.3 log (41.43 ± 0.89 %) of extracellular ampR (pUC19) reduction was observed. Similarly, reduction of intracellular ampR and tetR (pBR322) were ∼6.5 log (55.19 ± 0.92 %) and ∼7.5 log (64.89 ± 2.39 %). While, extracellular ampR and tetR (pBR322) were ∼4.1 log (41.85 ± 1.62 %) and ∼4.9 log (52.49 ± 1.35 %), respectively. Despite low ARG removal efficiency, complete loss of transformation ability of intracellular and extracellular pUC19 and pBR322 was observed. From the results, it is evident that electro-oxidation is effective in disinfecting both the ARB, removal of intracellular and extracellular ARGs. Therefore, EOP is proposed as an effective and promising tertiary treatment technology.

The environmental assessment of tertiary treatment technologies for wastewater reuse by considering LCA uncertainty

Tertiary treatment methods can result in severe environmental impacts that should be taken into consideration when deciding about the best system for wastewater reuse applications beside technical and economic issues. Life cycle assessment (LCA) commonly is used for evaluating the environmental impacts of these methods. Given the importance of uncertainty analysis, it is still an uncommon practice in LCA researches in recent years, especially those focused on tertiary wastewater treatment technologies (TWWTTs). Therefore, the main purpose of this study is to investigate the parameter and input data uncertainty in LCA of TWWTTs. Considering huge amount of data collected for LCA from different sources with various precision, there is high uncertainty in obtained LCA results that could affect the ranking of different methods based on their environmental impacts. The Monte-Carlo based method is used for uncertainty analysis of LCA and it is investigated how it can affect the final ranking of tertiary treatment methods based on their environmental impacts. In present study, LCA is used to study the environmental impacts of 22 tertiary treatment systems used for further treatment of effluent of South of Tehran wastewater treatment plant (WWTP) located at the south of Tehran, Iran. The treated wastewater of this WWTP is planned to be used for different purposes including landscape irrigation and groundwater recharge as well as industrial and non-potable household (toilet flushing) usages. Among the 22 tertiary treatment systems, the best system for each application was chosen, based on the LCA results and the uncertainty of LCA.

Detection and Tertiary Treatment Technologies of Poly-and Perfluoroalkyl Substances in Wastewater Treatment Plants

PFAS are a very diverse group of anthropogenic chemicals used in various consumer and industrial products. The properties that characterize are their low degradability as well as their resistance to water, oil and heat. This results in their high persistence in the environment and bioaccumulation in different organisms, causing many adverse effects on the environment as well as in human health. Some of their effects remain unknown to this day. As there are thousands of registered PFAS, it is difficult to apply traditional technologies for an efficient removal and detection for all. This has made it difficult for wastewater treatment plants to remove or degrade PFAS before discharging the effluents into the environment. Also, monitoring these contaminants depends mostly on chromatography-based methods, which require expensive equipment and consumables, making it difficult to detect PFAS in the environment. The detection of PFAS in the environment, and the development of technologies to be implemented in tertiary treatment of wastewater treatment plants are topics of high concern. This study focuses on analyzing and discussing the mechanisms of occurrence, migration, transformation, and fate of PFAS in the environment, as well the main adverse effects in the environment and human health. The following work reviews the recent advances in the development of PFAS detection technologies (biosensors, electrochemical sensors, microfluidic devices), and removal/degradation methods (electrochemical degradation, enzymatic transformation, advanced oxidation, photocatalytic degradation). Understanding the risks to public health and identifying the routes of production, transportation, exposure to PFAS is extremely important to implement regulations for the detection and removal of PFAS in wastewater and the environment.

Life cycle assessment as decision support tool for water reuse in agriculture irrigation

This study presents a decision support tool that evaluates the environmental efficiency of water reclamation for agricultural irrigation, among other options. The developed tool is published as open source at https://doi.org/10.18167/DVN1/YLP1BA. The objective of this decision support tool is to facilitate the interpretation of the Life Cycle Assessment (LCA) results. This framework was applied to a representative case of reuse of reclaimed water for vine irrigation at the Murviel-Les-Montpellier experimental site (Hérault, France). It was then generalized through modeling assumptions to consider different reuse scenarios.To highlight situations in which the supply of recycled water for irrigation may or may not provide significant environmental benefits, three main parameters were varied: (i) tertiary treatment technologies, (ii) availability of conventional water sources, (iii) energy mix composition.The results show that the environmental impact of reclaimed water depends directly on the type of tertiary treatment technology and the location of the treatment plant in relation to the field and other water sources. The decision support tool has identified where wastewater reuse is clearly an environmentally beneficial source of irrigation among surface and groundwater sources (e.g., WWTP closer to field than river, groundwater too deep, tertiary treatment environmentally beneficial). However, there are many situations where the decision support process cannot distinguish between water reuse for agricultural irrigation and conventional water sources, especially when the nutrient content of treated municipal wastewater is insufficient to offset the negative effects of high energy requirements and chemicals of tertiary treatment.

Environmental persistence, detection, and mitigation of endocrine disrupting contaminants in wastewater treatment plants – a review with a focus on tertiary treatment technologies

Endocrine disrupting chemicals are a group of contaminants that have severe effects on humans and animals when exposed, like cancer and alterations to the nervous and reproductive systems.

Life-cycle assessment of full-scale membrane bioreactor and tertiary treatment technologies in the fruit processing industry.

A life-cycle assessment (LCA) study was completed to assess the environmental impacts of an on-site wastewater treatment system in the fresh-cut fruit processing industry consisting of a membrane bioreactor (MBR), followed by reverse osmosis (RO) and ultraviolet (UV) disinfection. The system boundaries comprised raw materials extraction and processing, transportation, construction, operation, and waste disposal. SimaPro 8.0.4.26 was used as the software tool, supported by two impact assessment methods (ReCiPe v1.11 and TRACI v2.1). Analysis showed that the treatment capacity of the MBR and tertiary technologies contributed the least damage to the ecosystem when compared with the other three scenarios and can provide water for reuse. Treating wastewater in municipal wastewater treatment plants (WWTPs) mitigated eutrophication like the MBR system but resulted in more environmental impacts from climate change and human health when compared with the on-site treatment system. Findings will be informative to stakeholders in the fresh-cut agri-food sector seeking input into selecting the appropriate treatment approach, with water reuse a goal. PRACTITIONER POINTS: Life-cycle analysis was completed on a fruit processing facility using MBR + RO + UV. On site treatment with MBR + RO UV provides least amount of environmental impact. Use of MBR + RO + UV treatment on fruit wastewater allows for water reuse. ReCiPe v1.11 and TRACI v2.1 give similar LCA results, with TRACI recommended for North American analysis.

Performance characterization of a hybrid adsorptive-photocatalytic (APC) oscillatory membrane reactor for micropollutant removal

• Hybrid adsorptive-photocatalytic (APC) oscillatory membrane reactor was tested. • Up to ∼ 2.5 fold increase in diclofenac (DCF) removal was achieved using APC. • Performance of APC reduced only after continuous operation of 100 h. • The operational cost of the APC was estimated ∼ 2.2–4.4 $/m 3 . In order to reduce the operating cost and plant footprint, process intensification (PI) of tertiary treatment technologies is needed for recycling various effluents. In this study, the performance of a hybrid adsorptive-photocatalytic (APC) oscillatory membrane reactor was characterized by quantifying the degradation/ removal of diclofenac (DCF) as a model pollutant. The intensification effect is achieved through the synergy of a hybrid photocatalysis, activated carbon (AC) adsorption and membrane separation combined with flow modulation in a single unit. Commercial TiO 2 nanoparticles were used as a photocatalyst, while AC was immobilized onto a stainless steel (SS) mesh beneath microfiltration (MF) membrane, were used as pollutant adsorption and separation media, respectively. Initially, the individual effect of AC adsorption and photocatalysis on the reactor performance was quantified and subsequently, the combined effect of AC adsorption and slurry photocatalysis in the hybrid configuration was evaluated. In addition, a degradation pathway for DCF removal was proposed. The APC configuration provided significant process enhancement with up to ∼ 2.5 fold increase in DCF removal compared to the removal obtained using AC adsorption or photocatalysis alone. The electrical energy per unit order (EEO) for the process was estimated as ∼ 2.2–4.4 $/m 3 . A decline in system performance was noticed after extended hours of continuous operation (∼100 h) mainly due to saturation of AC coating and decrease in photocatalytic efficiency of TiO 2 due to formation of degradation byproducts. Both the smaller footprint of the design combined with the hybrid configuration and flow modulation can provide an effective PI approach for tertiary treatment for water recycling.

Clarification of Biologically Treated Wastewater in a Clarifier with Suspended Sludge Layer

The article presents the results of an experimental study on the clarification of biologically treated wastewater in a clarifier with a suspended sludge layer. The pilot plant was receiving effluent from trickling filters treating municipal wastewater. An experimental clarifier worked under steady-state conditions considering the influent characteristics and variable operating parameters in terms of flow velocities and height of the suspended layer. From the experimental dependences between different technological parameters it was found that the optimum range of the upward flow velocities providing a dynamic equilibrium of the suspended layer was 0.6–1.4 mm/s. Upward flow velocities below 0.5 mm/s can lead to sludge compaction at the bottom of the unit, while values greater than 1.8 mm/s may cause sludge washout. It was also found that higher suspended layer height values favor higher efficiency of the clarifier and can achieve suspended solids in the discharge of less than 5.0 mg/L; this height should be greater than 0.6 m Technological efficiency of the experimental clarifier was significantly higher than the conventional unit and was comparable with tertiary treatment technologies.

A comprehensive review on the synthesis, performance, modifications, and regeneration of activated carbon for the adsorptive removal of various water pollutants

Rapid urbanization has led to the generation of a large quantum of complex wastewater comprising of recalcitrant organic and inorganic pollutants. The inability of the conventional treatment techniques to bring down the recalcitrant pollutant concentrations below desired standards has paved the way for the emergence of tertiary treatment technologies. Among various tertiary treatment techniques, adsorption is widely preferred due to the ease of operation, high removal performances, and diverse on-field applications. Activated carbon (AC) has found immense popularity due to easy synthesis routes, high stability, large specific surface area (SSA), etc. The synthesis and performance of AC derived from different carbonaceous precursors for pollutants removal, the role of activation techniques, pollutant specific modifications, regeneration techniques, and their disposal, are covered in this article. Trend analysis showed that research on AC derived from agricultural waste and sludge has a high potential for at least another 50 and 25 years, respectively. Most of the precursors are chemically activated to prepare the AC, which may be further modified using the metal impregnation technique for removing specific pollutants. Among various ACs, maximum mean pore volume has been shown by sludge-based AC (1.17 cm3/g) and the maximum mean SSA value has been exhibited by husk-based AC (1339 m2/g). AC is mostly used to treat dyes and metals, followed by pharmaceuticals, pesticides, and other recalcitrant organics. Moreover, by implementing microwave-assisted and biological-based regeneration techniques, the life of the AC can be increased and may serve as an efficient adsorbent for wastewater treatment for a prolonged duration.

Degradation of tetracycline antibiotics by Fe2+-catalyzed percarbonate oxidation

Antibiotics improve the quality of human life but their intrusion into water matrices comes with adverse effects on natural bacterial communities that may result in the proliferation of antibiotic resistant bacteria and antibiotic resistance genes. Hence, antibiotic-laden wastewaters require adequate treatment prior to their release to the natural environment. Herein, we investigate the degradation of tetracycline (TC) antibiotics in aqueous solutions by ferrous ion-catalyzed oxidation in the presence of sodium percarbonate (SPC). Control experiments without Fe 2+ but with SPC, and vice versa resulted in negligible TC removal. The effects of reactant dosing and solution pH on the extent and rate of TC removal were examined. Hydroxyl radicals were the dominant reactive oxygen species (ROS) identified from indirect ROS scavenging experiments and confirmed by electron paramagnetic resonance analysis. Treatment of actual wastewaters was simulated by adding chloride, nitrite, nitrate and ammonium ions to the water matrix at varying concentrations and their effects on TC removal were examined. Negligible impact on TC degradation was noted for N-species while chloride ion accelerated degradation kinetics and reached complete tetracycline abatement in 10 min. Residual chemical analysis showed continued Fe 2+ consumption and H 2 O 2 production even with complete tetracycline elimination. Experimental results showed complete abatement of 0.2 mM TC with k 1 of 9.3 × 10 −2 min −1 and over 40% TOC removal in 45 min of treatment under optimized conditions of 0.5 mM of Fe 2+ , 0.75 mM SPC, at pH 3.0. The study showed the effectiveness of percarbonate oxidation as a tertiary treatment technology and the results can be used in designing treatment systems for wastewaters containing antibiotics and other pharmaceuticals. • Percarbonate oxidation completely removed tetracycline from water. • Reaction kinetics followed the pseudo-first order model. • Chloride ions in solution accelerated tetracycline degradation. • Hydroxyl radicals were the dominant reactive oxygen species.

Abundance and characteristics of microplastics in municipal wastewater treatment plant effluent: a case study of Guangzhou, China.

Wastewater treatment plants (WWTPs) have been proposed as significant sources of microplastics (MPs) in freshwater and estuarine environments. WWTPs, even those with high removal efficiencies, release millions of MPs per plant daily. China is the largest plastic producer worldwide, but only a few studies of MP pollution from WWTPs have been carried out in China. In this work, we present a comprehensive report concerning the MPs in effluent from six WWTPs in Guangzhou, which is the third largest city in China. The six WWTPs employ different treatment processes and serve different populations and types of factories. The average abundance of MPs in the effluents of all six WWTPs was 1.719 ± 1.035 MP/L. Fiber was the most common type of MP in the effluent, accounting for 39.48 ± 6.37% of all MPs. Fourier transform infrared spectroscopy confirmed that 35.7% of the particles were plastics, including polyethylene terephthalate (31.9%), polypropylene (26.6%), and polyethylene (9.7%). The results showed that advanced or tertiary treatment technologies could substantially remove MPs and that the size of the population served was positively associated with the abundance of MPs. The number of textile factories was a key factor contributing to the total release of MPs. In addition, the MP shapes and polymer compositions showed that the occurrence of MP types is regional, varies regionally, and is related to the types of factories in the vicinity. More studies on the effects of specific industries are suggested in order to improve the management of wastewater discharge and reduce MPs presence in the natural environment.