Urban Wastewater Treatment Plants Research Articles

Biopolymeric Composite Columns for Improving Water Quality in a Freshwater Stream Receiving Wastewater Treatment Plant Effluents

AbstractInefficiently treated wastewater, which contains a high concentration of pollutants, is hazardous when it is mixed with the clean water of rivers and lakes. Nitrate in particular is a major global problem that leads to eutrophication and poses a threat to both aquatic ecosystems and human health. To address this issue, this work assessed the efficiency of polymeric cryogel (PC) and biopolymer (EPS)-blended composites (EPS@PC) in removing nitrates. Tests were also conducted to quantify the decrease in phosphate, chloride ions, and chemical oxygen demand (COD) in real water samples taken from the Ankara stream, which receives effluents from both urban (UWTP) and industrial (IWTP) wastewater treatment plants. Five different columns with varying adsorptive properties were prepared, some of which were combined with iron. The EPS-@PC-C5 column demonstrated the highest adsorption ratio for nitrate removal compared to the other tested columns. The EPS@PC-C5 achieved a high removal efficiency of 126.38 mg nitrate/g and showed COD reduction ranging from 60.2 to 94.1%. The removal ratio of chloride concentration varied between 56.0 and 75.7%, while the removal of phosphates ranged from 87 to 99%. Columns composed of EPS (EPS@PC) with both negatively and positively charged ligands are dependable and suitable options for water remediation. Graphical Abstract

Whole Process Analysis and Fate Behavior of Microplastics in Urban Wastewater Treatment Plants, Including their Occurrence Forms, Components, and Removal Efficiency

Microplastics are among the most difficult new pollutants to remove in wastewater treatment plants. In order to explore the occurrence form, size distribution, composition, removal efficiency, migration law, and fate behavior characteristics of microplastic particles in sewage plants, taking a sewage treatment plant in Hohhot as an example, a total of 17 sampling sites were set up. The LAS X software counted the shape, abundance, and size of microplastics and conducted a full-process analysis. The results showed that： fibrous microplastics had the highest abundance and widest distribution and were the main form of existence, accounting for 61.8% of the total abundance； the size of microplastics ranged mainly between 0 and 1.00 mm, and among the four sizes, the abundance of microplastics 0.25 to 0.50 mm in China was the highest, accounting for 32.9%. Among the eight types of plastic components detected, polyester substances （PET, PBT）, cellulose, and polypropylene （PP） were the main components, accounting for 25%, 21%, and 17%, respectively. The influent abundance of the sewage plant was （73 ±5） n·L-1, the effluent abundance was （14 ±2） n·L-1, and the overall removal rate was （80.8 ±12.1）%. Among the three treatment stages of the sewage plant, only the primary treatment played a role in removal, and the abundance of microplastics surged in the secondary treatment. Different structures playing a major role in the removal of microplastics were fine grids （49.2 ±7.4）% and secondary sedimentation tanks （92.4 ±13.9）%. Microplastics mainly existed in the form of fibers, fragments, and films. The proportion of fibers was approximately 70%, and the size of fragments was mainly concentrated between 0.50 and 5.00 mm. Most fragments were in the range of 5.00 mm, accounting for 50%, making them the main form apart from fibrous. The film-like size was mostly concentrated in the range of less than 0.50 mm, accounting for more than 10%. Therefore, improving the removal of small-sized fibrous and film-like microplastics and large-sized fragmented microplastic particles can effectively reduce the pollution risk of microplastics in the environment caused by sewage plant drainage.

Maximizing pollutant removal and greenhouse gas emission reduction in vertical flow constructed wetlands: an orthogonal experimental approach.

Owing to the impact of the effluent C/N from the secondary structures of urban domestic wastewater treatment plants, the denitrification efficiency in constructed wetlands (CWs) is not satisfactory, limiting their widespread application in the deep treatment of urban domestic wastewater. To address this issue, we constructed enhanced CWs and conducted orthogonal experiments to investigate the effects of different factors (C/N, fillers, and plants) on the removal of conventional pollutants and the reduction of greenhouse gas (GHG) emission. The experimental results indicated that a C/N of 8, manganese sand, and calamus achieved the best denitrification efficiencies with removal efficiencies of 85.7%, 95.9%, and 88.6% for TN, NH4+-N, and COD, respectively. In terms of GHG emission reduction, this combination resulted in the lowest global warming potential (176.8mg/m2·day), with N2O and CH4 emissions of 0.53 and 1.25mg/m2·day, respectively. Characterization of the fillers revealed the formation of small spherical clusters of phosphates on the surfaces of manganese sand and pyrite and iron oxide crystals on the surface of pyrite. Additionally, the surface Mn (II) content of the manganese sand increased by 8.8%, and the Fe (III)/Fe (II) and SO42-/S2- on pyrite increased by 2.05 and 0.26, respectively, compared to pre-experiment levels. High-throughput sequencing indicated the presence of abundant autotrophic denitrifying bacteria (Sulfuriferula, Sulfuritalea, and Thiobacillus) in the CWs, which explains denitrification performance of the enhanced CWs. This study aimed to explore the mechanism of efficient denitrification and GHG emission reduction in the enhanced CWs, providing theoretical guidance for the deep treatment of urban domestic wastewater.

Removal of Micropollutants in Water Reclamation by Membrane Filtration: Impact of Pretreatments and Adsorption.

Organic micropollutants (OMPs) present in water and wastewater are in the spotlight because of their potentially harmful effects even at low concentrations and the difficulties of their elimination in urban wastewater treatment plants (UWWTPs). This study explores the impact of some membrane filtration processes on the removal of a group of 11 OMPs with an eye on the effects of two pretreatments (i.e., coagulation and adsorption onto powdered activated carbon (PAC)) and the adsorption of OMPs onto the membranes on the overall removal. For this purpose, ultrafiltration (UF) and nanofiltration (NF) experiments were conducted with selected OMPs spiked in ultrapure water and secondary effluents from UWWTPs. It was observed that the adsorption of OMPs onto the membranes was influenced by the characteristics of the membranes, as well as the presence of effluent organic matter (EfOM). Since adsorption was the dominant mechanism for the rejection of OMPs by UF membranes, a study of the adsorption equilibrium of the micropollutants using UF membrane pieces as the adsorbent was conducted. The adsorption isotherms for the most hydrophobic OMPs fitted the Langmuir model. The efficiency of coagulation and powdered activated carbon (PAC) adsorption coupled with UF were also investigated. Both pretreatments alleviated membrane fouling and improved the rejection of organic and inorganic matter. The PAC pretreatment significantly improved the removal of OMPs in the combined PAC/UF process. The best options for achieving reclaimed water with satisfactory physicochemical quality, nearly devoid of OMPs and microorganisms, and suitable for diverse reuse purposes are either the NF treatment or the combination of PAC/UF.

Nature-based bioreactors: Tackling antibiotic resistance in urban wastewater treatment

The overuse and misuse of antibiotics have accelerated the selection of antibiotic-resistant bacteria, significantly impacting human, animal, and environmental health. As aquatic environments are vulnerable to antibiotic resistance, suitable management practices should be adopted to tackle this phenomenon. Here we show an effective, nature-based solution for reducing antibiotic resistance from actual wastewater. We utilize a bioreactor that relies on benthic (biofilms) and planktonic microbial communities to treat secondary effluent from a small urban wastewater treatment plant (<10,000 population equivalent). This treated effluent is eventually released into the local aquatic ecosystem. We observe high removal efficiency for genes that provide resistance to commonly used antibiotic families, as well as for mobile genetic elements that could potentially aid in their spread. Importantly, we notice a buildup of sulfonamide (sul1 and sul2) and tetracycline (tet(C), tet(G), and tetR) resistance genes specifically in biofilms. This advancement marks the initial step in considering this bioreactor as a nature-based, cost-effective tertiary treatment option for small UWWTPs facing antibiotic resistance challenges.

Treatment of sewage sludge with γ‐ray irradiation for volatile fatty acids and lipid production

AbstractThe production of value‐added products from sewage sludge is considered to be one of the solutions for the sustainable management of sludge in wastewater treatment plants (WWTPs). The presence of carbon, nitrogen, and phosphorus sources has made the sewage sludge of WWTPs a valuable and low‐cost substrate for the production of fermentative products. In the current study, a process was developed for microbial lipid production from two types of sewage sludge from a WWTP in northern Isfahan: anaerobic digester inlet sludge (DIS) and anaerobic digester outlet sludge (DOS). This process was based on the release of volatile fatty acids (VFAs) from the sludge by combinations of γ‐ray irradiation, anaerobic digestion, and acidogenic fermentation followed by utilization of VFAs in a microbial process by the oleaginous yeast Cryptococcus aureus UIMC65. After γ‐ray irradiation, the acidogenic fermentation of the treated sludge released 72% of the organic matter content of the sludge with acidification efficiency of 12% leading to 0.516 g L−1 VFAs. The oleaginous fermentation of the released VFAs for 7 days was accompanied by production of 1.58 g L−1 dry cell biomass with 40% lipid content. The results of this study indicate that the sewage sludge from urban WWTP has the potential to be used for the production of microbial lipids.

Does stricter sewage treatment targets policy exacerbate the contradiction between effluent water quality improvement and carbon emissions mitigation? An evidence from China

Rapid expansion and upgrading of wastewater treatment facilities globally, driven by stricter wastewater policies, significantly contribute to carbon emissions. China has contributed 30 % of carbon emissions in the world, 1 % of which comes from wastewater treatment, necessitating more understanding of the impact of policies, especially the stringent “10-Point Water Plan” policy. From a micro perspective, this study uses the difference-in-differences method to analyze the impact of wastewater treatment policies on water and carbon issues in China’s 2894 wastewater treatment plants (WWTPs), and delves into the heterogeneity, and mechanisms across various dimensions. The results show that stricter sewage treatment policy decrease effluent concentration of the chemical oxygen demand (COD) by 2.35 %, and also cause a 1.74 % rise in carbon emissions per 10,000 m3 of wastewater treated, intensifying the short-term contradiction, while the contradictions may fall in the long term. It is more significant in southern regions and the cities with lower environmental regulation intensity. Also, there are significant differences in different wastewater treatment technology and scale. Significant improvements in effluent water quality are observed in WWTPs with 100,000 to 200,000 m3/day capacity and those using biofilm treatment technology. Through mechanism analysis, reasonable expansion of urban pipelines and WWTPs, promotion of biofilm treatment technology, reduction of energy consumption, and improvement of pollutant reduction efficiency are feasible paths to improve water quality and reduce carbon emissions. This research provides a perspective on solving water-carbon contradictions in WWTPs, holding critical significance for urban wastewater treatment and carbon emission management.

Evaluation of the Heavy Metals Content in Sewage Sludge from Selected Rural and Urban Wastewater Treatment Plants in Poland in Terms of Its Suitability for Agricultural Use

The amount of sewage sludge produced in Poland is increasing every year. Once stabilised and hygienised, sewage sludge is a valuable product, rich in biogenic elements such as nitrogen and phosphorus, which are essential for plant growth. However, in addition to the compounds that are beneficial to the soil, this sludge can also contain harmful substances such as heavy metals. The aim of this assessment is to analyse the content of seven heavy metals in sewage sludge from urban and rural wastewater treatment plants (WWTPs) located in Poland. This analysis allows for the suitability of sludge from the studied wastewater treatment plants for natural management to be assessed. The concentration ranges of Cd, Cu, Ni, Pb, Zn, Cr, and Hg in sludge samples from rural wastewater treatment plants were 0.6–9.5, 9.3–524, 4.8–90.0, 8.8–275.2, 575–1732, 7.5–170.0, and 0–3.8 mg/kg dry matter, respectively. In sludge samples from urban wastewater treatment plants, the concentration ranges of Cd, Cu, Ni, Pb, Zn, Cr, and Hg were 1.07–16.7, 32–195, 1.3–128.9, 21.2–322.4, 20–5351.1, 12.7–2759.8, and 0.1–1.55 mg/kg dry matter, respectively. Only one of the analysed wastewater treatment plants (Skarżysko-Kamienna) exceeded the limit values.

Possibility and Prospects for Using Combined Coagulants-flocculants in the Urban Wastewater Treatment System

A method is proposed for producing a powdered combined reagent, including an aluminum-silicon coagulant-flocculant, a sorption material and an acidity regulator of treated wastewater, as well as using this reagent in the treatment system of multi-component urban wastewater treatment plants. It has been shown that the use of powdered reagents of various compositions ensures purification efficiency for suspended solids in the range from 66.1 to 94.1 %, and for COD – from 70.1 to 78.0 %.

Selective microbial attachment to LDPE plastic beads during passage through the wastewater network

Urban wastewater treatment plants (WWTP) represent key point-source discharges of microplastics (MP) into the environment, however, little is known about the microbial carrying capacity of plastics travelling through them. The purpose of this study was to quantify the number of cells that become associated with MP at different locations within a WWTP, and to assess differences in microbiome communities. We conducted a field experiment incubating low density polyethylene (LDPE) MP beads in WWTP influent and effluent, as well as tracking free floating beads during passage in wastewater from a large municipal hospital to an urban WWTP, where they were subsequently recovered. Using two cell counting methods - automated flow cytometric true absolute cell counts and indirect cell quantification via protein content based on a model E. coli cell - we quantified cell attachment to LDPE beads. LDPE associated counts ranged from 350 × 103 cells cm−2 after incubation in wastewater effluent, and 990 × 103 cells cm−2 after incubation in wastewater influent. 16S rRNA gene amplicon sequencing was used to determine the bacterial community structure of the plastic-associated microbiomes. Our results showed that distinct bacterial communities developed on the LDPE MP following exposure to each wastewater type. Influent (untreated) wastewater LDPE-associated microbiomes were dominated by Bacillota whereas the microbes that attached in wastewater effluent (tertiary treated) were dominated by Pseudomonadota. In conclusion, this study provides clear evidence that microplastics migrating through the sewer network and WWTP rapidly accumulate microbiomes with unique microbial community structures varying from sewage influent to effluent. These findings demonstrate the differential microbiological risk from MP associated with routine wastewater discharges to those released from intermittent combined sewer overflows (CSOs) during storm events.

Enhancing Microplastics Recovery from Complex Sludge Samples Using COD-Guided Pretreatment

Given the society’s continuous reliance on plastic materials, large amounts of micron-sized plastic particles (i.e., microplastics, MPs) reach wastewater treatment plants (WWTPs) every day. Despite their effective removal from influent wastewater, over 90% of MPs in WWTPs are accumulated in sludge. Yet, there is no universally accepted method for quantifying and identifying MPs, obscuring our understanding of this pollution’s extent. Therefore, this study aims to develop a chemical oxygen demand (COD) based repeatable method for MPs analysis in sludge, which is a very complex, MPs-laden by product of WWTPs. The developed method is unique in that it removes the organic substances interfering with polymer analysis by monitoring the COD of sludge. Upon 90% of organic matter removal, MPs are extracted from the medium by a two-step density-based separation, sieved, stained with Nile Red, and counted using fluorescence microscopy. Moreover, quality assurance and quality control strategies including blank preparation and spike-and-recovery test procedures are followed. The protocol ensures a minimum 80% recovery rate of various MPs from both waste activated sludge (WAS) and wastewater samples, aligning with recommended standards. Crucially, the method preserves the chemical identity of MPs. Application of the protocol revealed that urban WWTP WAS had 475 MPs/g TS; industrial influent and effluents wastewater had 73 and 26 MPs/L; and industrial secondary and dewatered sludge had 114 and 132 MPs/g TS, consistent with the literature. This demonstrates the method’s robustness by revealing MPs reduction within the WWTP process and sludge accumulation as treatment progresses.Graphical

A novel membrane-based process to concentrate nutrients from sidestreams of an Urban Wastewater Treatment Plant through captured carbon dioxide from biogas

Among the challenges that wastewater treatment plants face in the path towards sustainability, reducing CO2 emissions and decrease the amount of waste highlight. Within these wastes, those that can cause eutrophication, such as nutrients (nitrogen and phosphorous) are of great concern. Herein we study a novel process to concentrate nutrients via membrane technology. In particular, we propose the use of forward osmosis, applying the carbonated solvent which contains the CO2 captured from the biogas stream as draw solution. This carbonated solvent has a high potential osmotic pressure, which can be used in forward osmosis to concentrate the nutrients stream. To this end, we present the results of an experimental plan specifically designed and performed to evaluate two main parameters: (1) nutrients concentration; and (2) water recovery. The process designed involves pH adjustment, membrane filtration to separate solids, pH reduction and forward osmosis concentration of nutrients. With this process, concentrations factor for nutrients in between 2 and 2.5 and water recovery of approximately 50 % with water flux of 7 to 8 L/(m2h) can be achieved.

Emerging Contaminants in the Effluent of Wastewater Should Be Regulated: Which and to What Extent?

Effluent discharged from urban wastewater treatment plants (WWTPs) is a major source of emerging contaminants (ECs) requiring effective regulation. To this end, we collected discharge datasets of pharmaceuticals (PHACs) and endocrine-disrupting chemicals (EDCs), representing two primary categories of ECs, from Chinese WWTP effluent from 2012 to 2022 to establish an exposure database. Moreover, high-risk ECs' long-term water quality criteria (LWQC) were derived using the species sensitivity distribution (SSD) method. A total of 140 ECs (124 PHACs and 16 EDCs) were identified, with concentrations ranging from N.D. (not detected) to 706 μg/L. Most data were concentrated in coastal regions and Gansu, with high ecological risk observed in Gansu, Hebei, Shandong, Guangdong, and Hong Kong. Using the assessment factor (AF) method, 18 high-risk ECs requiring regulation were identified. However, only three of them, namely carbamazepine, ibuprofen, and bisphenol-A, met the derivation requirements of the SSD method. The LWQC for these three ECs were determined as 96.4, 1010, and 288 ng/L, respectively. Exposure data for carbamazepine and bisphenol-A surpassed their derived LWQC, indicating a need for heightened attention to these contaminants. This study elucidates the occurrence and risks of ECs in Chinese WWTPs and provides theoretical and data foundations for EC management in urban sewage facilities.

The potential for water recovery from urban waste water - The perspective of urban waste water treatment plant operators in Poland

Water recovery from waste water has become an essential element of the circular economy in the Baltic Sea region. However, there is little data on the possibility of using water recovered from urban waste water. A survey was conducted to learn the opinions of Poland waste water treatment plant operators. They were asked whether they recovered water for internal or external needs. Respondents indicated opportunities and barriers in this activity. The opinions of 107 operators show that work is underway on closing internal circuits in urban WWTPs. These solutions are technically relatively easy to implement and show measurable benefits (i.e., saving drinking water). However, water recovery for external purposes is rare and is at a very early stage. Despite this, the potential is significant, although many financial, organizational, technical, and mental barriers exist. The most critical challenge is the safe use of reclaimed water and the cost-effectiveness of the solutions. The survey also shows a need for education and involvement of the public.

Economic–environmental trade-offs based support policy towards optimal planning of wastewater heat recovery

Wastewater heat, a promising alternative to traditional district heating and cooling sources, can be recovered using heat pumps and transmitted to surrounding buildings for winter heating and summer cooling. Despite its potential benefits, the policies to support wastewater heat recovery remain limited. This study provides support policies for local governments to encourage energy recovery in urban wastewater treatment plants, incorporating subsidies and renewable energy certificates. The local government aims to maximize the recovered energy, minimize the subsidy expenditure, and minimize the certificate price. Urban wastewater treatment plants seek to optimize producer profits under realistic planning constraints. This model was applied in Chengdu, China, which indicates that plants with a daily treatment scale exceeding 30,000 m3 can invest in heat recovery without support policies, achieving recovery ratios of only 27%–29%. As the calculated electricity charge accounts for about 90% of operating cost, the electricity price subsidy proves the most significant in improving the installed capacities, followed by renewable energy certificates, capital refunds, and tax reductions. Electricity prices and renewable energy certificates have combination and substitution effects. Further analysis shows that heat pump efficiencies have low sensitivity in project feasibility. Fluctuations in infrastructure costs have a minimal impact, while charges for heating and cooling services significantly influence feasibility. Lowering the available thermal energy ratio also affects project returns. The government can reduce risks in sensitive parameters by electricity price subsidies or renewable energy certificates.

The proliferation of antibiotic resistance genes (ARGs) and microbial communities in industrial wastewater treatment plant treating N,N-dimethylformamide (DMF) by AAO process.

The excessive use of antibiotics has resulted in the contamination of the environment with antibiotic resistance genes (ARGs), posing a significant threat to public health. Wastewater treatment plants (WWTPs) are known to be reservoirs of ARGs and considered to be hotspots for horizontal gene transfer (HGT) between bacterial communities. However, most studies focused on the distribution and dissemination of ARGs in hospital and urban WWTPs, and little is known about their fate in industrial WWTPs. In this study, collected the 15 wastewater samples containing N,N-dimethylformamide (DMF) from five stages of the anaerobic anoxic aerobic (AAO) process in an industrial WWTPs. The findings revealed a stepwise decrease in DMF and chemical oxygen demand (COD) content with the progression of treatment. However, the number and abundances of ARGs increase in the effluents of biological treatments. Furthermore, the residues of DMF and the treatment process altered the structure of the bacterial community. The correlation analysis indicated that the shift in bacterial community structures might be the main driver for the dynamics change of ARGs. Interestingly, observed that the AAO process may acted as a microbial source and increased the total abundance of ARGs instead of attenuating it. Additionally, found that non-pathogenic bacteria had higher ARGs abundance than pathogenic bacteria in effluents. The study provides insights into the microbial community structure and the mechanisms that drive the variation in ARGs abundance in industrial WWTPs.

Presence of Microplastic in Erzurum Urban Wastewater Treatment Plant

The rapid increase in the number of microplastics (MPs) in aquatic environments reveals the risk of increasing their harmful effects on living life. MPs, especially those with smaller particle sizes, are very difficult to detect and measure when they reach the aquatic environment. This study investigated the presence of microplastics at the entrance and exit points of the Erzurum Urban Wastewater Treatment Plant. The results showed that the average number of MPs in the influent and effluent was 36400 MP/m3 and 2875 MP/m3, respectively. Primary and secondary treatment processes cannot provide high removal efficiencies in removing MPs from wastewater. However, in WWTPs where tertiary treatment is carried out, as in the WWTP examined, the removal efficiency exceeds 90%.

Using the fish plasma model to evaluate potential effects of pharmaceuticals in effluent from a large urban wastewater treatment plant

Several pharmaceuticals and personal care products (PPCPs) were evaluated using the fish plasma model (FPM) for juvenile Chinook salmon exposed to effluent from a large urban wastewater treatment plant. The FPM compares fish plasma concentrations to therapeutic values determined in human plasma as an indication of potential adverse effects. We used human Cmax values, which are the maximum plasma concentration for a minimum therapeutic dose. Observed and predicted plasma concentrations from juvenile Chinook salmon exposed to a dilution series of whole wastewater effluent were compared to 1%Cmax values to determine Response Ratios (RR) ([plasma]/1%Cmax) for assessment of possible adverse effects. Several PPCPs were found to approach or exceed an RR of 1, indicating potential effects in fish. We also predicted plasma concentrations from measured water concentrations and determined that several of the values were close to or below the analytical reporting limit (RL) indicating potential plasma concentrations for a large number of PPCPs that were below detection. Additionally, the 1%Cmax was less than the RL for several analytes, which could impede predictions of possible effect concentrations. A comparison of observed and predicted plasma concentrations found that observed values were frequently much higher than values predicted with water concentrations, especially for low log10Dow compounds. The observed versus predicted values using the human volume of distribution (Vd), were generally much closer in agreement. These data appear to support the selection of whole-body concentrations to predict plasma values, which relies more on estimating simple partitioning within the fish instead of uptake via water. Overall, these observations highlight the frequently underestimated predicted plasma concentrations and potential to cause adverse effects in fish. Using measured plasma concentrations or predicted values from whole-body concentrations along with improved prediction models and reductions in analytical detection limits will foster more accurate risk assessments of pharmaceutical exposure for fish.

Defining Best Available Technique Performances for Urban Wastewater Plants: A French Application

The treatment of wastewater (WW) and the resulting sludge in urban WW treatment plants (UWWTPs) is accompanied by a significant consumption of resources as well as the concomitant emission of pollutants into the environment. One of the objectives of the NEXT (next generation of wastewater treatment plants) project is to identify sufficiently long-term optimization opportunities for processes to be selected as best available techniques (BATs) within the meaning of the industrial emissions directive (IED). The methodological framework used in this article is based on multi-criteria statistical tools, processing data from industrial plants to classify the sites studied and identify the reference plants in order to propose BAT references and associated emission levels that are reachable. Two public databases available on the internet were used, and 1,010 plants served as samples. The application and results demonstrated the applicability of the methodology and validated the mathematical approach used, as the thresholds comply with current French and European regulations. In the framework of the analysis conducted, five techniques (membrane bioreactor, bacterial bed, sand filter, and high-load or medium-load activated sludge) were identified as BAT according to the range of regulatory classification requirements for WW treatment plants (WWTPs). In addition, an example of reference values that may constitute a possible basis for the regulatory thresholds has been proposed. In parallel, a few discussion points were identified, including the choice of the metric for the reference values, the lack of data for the sludge line limiting identification of the BATs to the water line alone, the approximate characterization in the databases of certain parameters, as well as the problem of technique coupling due to the identification of one main technique.

Pilot plant approach combining photocatalysis and adsorption for antibiotics removal from slaughterhouse and urban wastewater treatment plant effluents

The main objective of this research is to perform a real case-study of antibiotic decontamination from real slaughterhouse and wastewater effluents by applying a sequential treatment of TiO2/UV–vis photocatalysis and adsorption. More precisely, the removal of five classes of antibiotics: enrofloxacin, sulfadiazine, trimethoprim, azithromycin, amoxicillin and amoxicillin degradation products was studied in an 80 L/h photocatalytic and adsorption pilot-scale plant over multiple cycles, operating in semi-continuous mode. The results exhibited significant removal rates, ranging from 77% to 100% for the slaughterhouse effluent, and 61–89% for the wastewater treatment plant effluent, thus demonstrating that the treatment is more effective when it is applied directly in the emission source, previous to antibiotic dilution in the municipal collector. Using the two processes sequentially results in greater efficiency than when they are used in isolation. After photocatalysis, antibiotic degradation products are easily adsorbed, since they have more affinity for the adsorbent, and the presence of competing compounds decreases considerably. After applying several cycles of treatment, the adsorption performance remains almost constant. By contrast, the photocatalysis performance decreased, which was attributed to catalyst agglomeration determined by Asymmetric Flow Field-Flow Fractionation (AF4) coupled with Dynamic Light Scattering (DLS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).