Urban Wastewater Treatment Plants Research Articles

Environmental tradeoffs in municipal wastewater treatment plant upgrade: a life cycle perspective.

Municipal wastewater treatment plants (WWTPs) play an indispensable role in improving environmental water quality in urban areas. Existing WWTPs, however, are an important source of greenhouse gas (GHG) emissions and may not be able to treat increasingly complicated wastewater or meet stringent environmental standards. These WWTPs can be updated to address these challenges, and different technologies are available but with potentially different environmental implications. Life cycle assessment (LCA) is a widely used approach to identify alternatives with lower environmental footprint. In this study, LCA was applied to an actual urban WWTP, considering four scenarios involving upgrading and energy-resource recovery. The environmental performance with respect to life cycle GHG emissions and eutrophication impact was analyzed. The environmental benefits of reduced water pollution and energy and material displacement associated with energy-resource recovery process were also considered. The results showed tradeoffs among the four scenarios. Although upgrading the studied WWTP would meet discharge standard for total phosphorus and reduce total eutrophication impact by about 19%, it would increase GHG emissions by at least 16%. Besides, the energy-resource recovery mode for existing WWTP (S2) performs the best in terms of GHG emissions. For different biogas utilization methods, combined heat and power (CHP) system is superior to the existing method of delivering biogas to gas grid, in terms of energy recovery or reduction of GHG emissions and eutrophication impact. Our research results may provide a reference for plant managers to select the most environmentally friendly upgrade scheme and energy-resource recovery technique for future upgrade projects.

Antibiotic resistance: Global health crisis and metagenomics

Antibiotic resistance is a global problem which affects human health. The imprudent use of antibiotics (medicine, agriculture, aquaculture, and food industry) has resulted in the broader dissemination of resistance. Urban wastewater & sewage treatment plants act as the hotspot for the widespread of antimicrobial resistance. Natural environment also plays an important role in the dissemination of resistance. Mapping of antibiotic resistance genes (ARGS) in environment is essential for mitigating antimicrobial resistance (AMR) widespread. Therefore, the review article emphasizes on the application of metagenomics for the surveillance of antimicrobial resistance. Metagenomics is the next generation tool which is being used for cataloging the resistome of diverse environments. We summarize the different metagenomic tools that can be used for mining of ARGs and acquired AMR present in the metagenomic data. Also, we recommend application of targeted sequencing/ capture platform for mapping of resistome with higher specificity and selectivity.

Microplastic pollution in wastewater treatment plants in the city of Cádiz: Abundance, removal efficiency and presence in receiving water body

Wastewater treatment plants (WWTPs) have been appointed as one of the main sources of microplastics (MP) into marine ecosystems. The aim of this research work has been to study the influent and effluent of two WWTPs, both located in Cádiz, with different wastewater source (industrial and urban), as well as the receiving water bodies where the facilities discharge their sewage.MP were collected, extracted from wastewater matrixes and analysed according to the abundance, shape, size, and type of polymer, along with the removal rates of MPs in the plants.Subsequently, the data obtained on both WWTPs were compared, the main difference among the WWTPs was the amount of microplastics found in the wastewater, as well as the presence of polymers with resins from industrial activities.The results from this study established that the most representative form was fibers; about the size, 100–355 μm fraction was the most abundant, followed by 355–1000 μm and finally the size among 1000–5000 μm. Regarding to the type of polymers, 17 were identified using attenuated total refraction Fourier-transformed infrared spectroscopy (ATR-FTIR). Further, PVC, PE, EAA and HDPE were the largest found polymers.The presence of MPs in the influent varied from 645.03 ± 182.24 MPs/L to 1567.49 ± 413.18 MPs/L in the urban and industrial WWTP respectively; in the effluent, it varied from 16.40 ± 7.85 MPs/L to 131.35 ± 95.36 MPs/L. The removal rate overcome the 90% in all the samples.Receiving water bodies presented heterogeneous abundance of microplastics 6.64 ± 2.71 MPs/L and 0.83 ± 0.26 MPs/L in the zones close to IWWTP and UWWTP discharge point.The results obtained shows that despite the elimination efficiency in the WWTPs studied, these facilities act as a significant source of MPs into aquatic ecosystem due to large flow of water discharged.

Occurrence and removal of emerging pollutants in urban sewage treatment plants using LC-QToF-MS suspect screening and quantification

Urban wastewaters (WW) are a major vector of many emerging pollutants (EPs) to aquatic ecosystems, as urban wastewater treatment plants (WWTPs) are not designed to abate them. New methods are now critically necessary for a more comprehensive analysis of WW samples and for the assessment of the WWTP efficiency in EP removal. To this end, the present study aims to develop a methodology to identify and quantify EPs, especially pharmaceutical residues and pesticides, in the raw and treated wastewater of 10 heterogeneous WWTPs in a highly urbanized territory in France over three sampling campaigns, through the following steps: (1) development and implementation of a suspect screening of EPs in WW samples, based on a solid phase extraction followed by an LC-QToF-MS analysis; (2) confirmation of their identification by reinjection of WW samples spiked with authentic analytical standards; (3) quantification of previously identified compounds by targeted LC-QToF-MS analysis in raw and treated effluents and assessment of their removal efficiency by WWTPs. Forty-one EPs, including 37 pharmaceutical residues (such as anti-depressive, anti-hypertensive, or antipsychotic drugs) and 4 pesticides, were identified by suspect screening. Some of them (e.g. milnacipran) are reported for the first time in urban WWTPs in this study. High variability in detection frequency and concentrations were observed in function of the EP and WWTP. Nevertheless, median removal rates were considered negative or low for more than 50% of the EPs (respectively 4 and 17), leading to a quantification of significant concentrations in treated WW. Their release into receiving streams may thus lead to ecotoxicological risks that should be evaluated in order to prevent any degradation of the exposed ecosystems.

Levels of volatile methylsiloxanes in urban wastewater sludges at various steps of treatment

Volatile methylsiloxanes are wastewater organic pollutants originating from industrial and personal care products. They accumulate in sewage sludge and hamper biogas production through the formation of silicon dioxide on the surfaces of gas engines and turbines, yet there is few knowledge on their fate in sludge treatment systems. Here we studied the occurrence and removal of seven volatile methylsiloxanes along the solid treatment line of an urban wastewater treatment plant. We analyzed 75 sludge samples from seven locations using ultrasound-assisted solid–liquid extraction followed by gas chromatography-mass spectrometry. Results show that volatile methylsiloxanes occur in all samples with a predominance of cyclic homologues, particularly decamethylcyclopentasiloxane. Total siloxane levels reach 6087 ng/g dry weight in the secondary sludge, average at 3575 ng/g in digested sludge, and 5703 ng/g in the dewatered sludge, the latter being likely due to the addition of a polyelectrolyte. Overall, these levels call for measures to reduce methylsiloxane levels before the biogas production step.

Localized corrosion of (lean) duplex stainless steels in immersion units of urban wastewater treatment plants

AbstractWith lower alloying cost and higher mechanical properties, lean duplex stainless steels can be an alternative to the more commonly used austenitic stainless steels. However, these alloys are still not the preferred choice, probably due to a lack of field experience. A study was thus initiated in view of defining the limits of use of selected (lean) duplexes for urban wastewater treatment units. The present paper shows the localized corrosion performance of selected lean duplexes in chloride contaminated solutions. The results are compared with austenitic S30403 and S31603 and with the more standard duplexes S82441 and S32205. The effect of welding was also investigated. Exposures in field municipal wastewater plants were conducted for 1 year in low and high chloride content units. The results show that lean duplexes S32101 and S32202 can be used as alternatives to S30403 and S31603 in low chloride electrolytes. At 500 ppm of chloride content, duplex stainless steel S32304 showed better corrosion resistance than S30403 and S31603. For higher chloride contents (1000 ppm and above) the standard duplexes S82441 and S32205 shall be preferred.

Survey of rapid development of environmental surveillance methods for SARS-CoV-2 detection in wastewater

Environmental surveillance as a part of wastewater-based epidemiology (WBE) of SARS-CoV-2 can provide an early, cost-effective, unbiased community-level indicator of circulating COVID-19 in a population. The objective of this study was to determine how widely SARS-CoV-2 detection in wastewater is being investigated and what methods are used. A survey was developed and distributed, with results showing that methods were rapidly applied to conduct SARS-CoV-2 WBE, primarily to test wastewater influent from large urban wastewater treatment plants. Additionally, most methods utilized small wastewater volumes and the primary concentration methods used were polyethylene glycol precipitation, membrane filtration and centrifugal ultrafiltration followed by nucleic acid extraction and assay for primarily nucleocapsid gene targets (N1, N2, and/or N3). Since this survey was performed, many laboratories have continued to optimize and implement a variety of methods for SARS-CoV-2 WBE. Method comparison studies completed since this survey was conducted will assist in developing WBE as a supplemental tool to support public health and policy decision making responses.

Microplastic contamination in a conventional wastewater treatment plant in Thailand.

Plastic waste has become a global environmental concern. One type of plastic waste is microplastics (MPs), which can spread easily in the environment. Wastewater effluent is one of the land-based sources of MPs. This study investigates the amount of microplastic (MP) pollution in an urban wastewater treatment plant (WWTP) in Thailand. Water samples were collected and examined to find the types, morphology and sources of MPs. Wastewater was filtered through a set of sieves ranging from 5 mm to 0.05 mm. Sludge samples were also collected to find the potential risk from the application of dried sewage sludge. Fourier-transform infrared spectroscopy (FTIR) was used to confirm the types of MPs. The amount of MPs in the influent was 26.6 ± 11.8 MPs/L. More than one-third of MP particles were removed after a grit trap, followed by 14.24% removal in the secondary treatment. If the peak flow rate of the WWTP is reached, 2.32 × 109 MP particles can be released daily. The amount of MPs in a sludge sample was 8.12 ± 0.28 × 103 particles/kg dry weight. Dry sludge is one of the potential sources of MP contamination in agricultural soil. Most MPs in the liquid fraction and sludge sample were fibres. Results from FTIR analysis showed that the major types of MPs in the WWTP were polyester fibres, followed by polypropylene, polyethylene, silicone polymer and polystyrene. This finding indicates that a conventional WWTP may act as a path by which MPs enter the environment.

Emerging technologies for treatment of antibiotic residues from wastewater influent/effluent for sustainable environment: A case study with NFC-doped titania immobilized on polystyrene as an efficient technology

In this study, 5 urban and 2 industrial wastewater treatment plants (WWTPs) were investigated. Raw wastewaters and effluents of WWTPs were characterized in terms of both organic and inorganic pollutants and antibiotic residues. According to the analysis results; organic pollutants for raw wastewaters and influents in urban WWTP were measured between 412 and 921 ​mg ​L−1 for COD, 345–421 ​mg ​L−1 for TOC, 61–160 ​mg ​L−1 for COD, 48–83 ​mg ​L−1 for TOC, respectively. However, in industrial WWTPs, these values were determined in raw wastewaters between 1404 and 2367 ​mg ​L−1 for COD, 821–826 ​mg ​L−1 for TOC and in effluents between 272 and 408 ​mg ​L−1 for COD and 97–208 ​mg ​L−1 for TOC, respectively.In addition, in the characterization study of antibiotic residues by the results of HPLC/MS-MS measurements, the amounts of Ciprofloxacin (from the fluoroquinolones), Erythromycin (from the macrolides group) and Sulfamethoxasol (from the sulfonamide group), which are one of the three main groups of antibiotics in the waste water samples, were found in high amounts in both urban and industrial WWTPs despite the biological treatment process. More antibiotic residues (Erythromycin-ERY, Ciprofloxacin-CIP and Sulfamethoxasol-SMX) were detected in untreated raw wastewater compared to effluent wastewater. While CIP antibiotic was not found only one urban WWTP, the highest amounts in the effluents of 4 urban WWTPs were measured between 13,800 ​ng ​L−1 and 38,800 ​ng ​L−1. Moreover, ERY is only detected in high amount in one urban WWTP raw and effluent wastewater as 23,100 ​ng ​L−1 and 5430 ​ng ​L−1, respectively. The SMX was detected in 2 separates urban WWTPs at a value of 19,700 ​ng ​L−1 in the raw wastewater sample and at a value 10,100 ​ng ​L−1 in effluent sample of another urban WWTP. Antibiotic residue removal ratios after Advanced Oxidation Process using specially prepared NFC-doped TiO2 photocatalyst immobilized on polystyrene (PS) cup inner surface at amount 0.45 ​g were determined as 97%–~100% for CIP, 100% for ERY, 86%–~100% for SMX, 57%–64% for COD and 61,5%–72% for TOC, respectively.According to the above mentioned results, this study proved that photocatalytic oxidation processes performed under visible light with a specially prepared immobilized form (PS/Cup–NFC–0.45 ​g) photocatalyst provide higher antibiotic removal from both urban and industrial wastewater. Thus, these results showed us that if the application of NFC-doped Titania, immobilized on polystyrene, can be integrated with an appropriate reactor design on the real/pilot scale, this technology can be proposed as an efficient technology for sustainable environment.

DEVELOPMENT OF THE TECHNOLOGY FOR BIOCONVERSION OF WASTE ACTIVATED SLUDGE FROM AN URBAN WASTEWATER TREATMENT PLANT

Pilot tests of the composting of waste activated sludge in an urban wastewater treatment plant with a consortium of thermophilic and thermotolerant bacteria has been carried out. The most effective was the bioconversion of activated sludge together with pine sawdust in a ratio of 1:1 or 1:2 using forced aeration of the mixture (0.35 m3/min).

Occurrence of pharmaceutical active compounds in sewage sludge from two urban wastewater treatment plants and their potential behaviour in agricultural soils

The profile of pharmaceutical active compounds (PhACs) in two UWWTP was evaluated. The potential behaviour of PhACs on agriculture soils was evaluated based on their physicochemical properties and soil pH.

Environmental and Techno-Economic Analysis of the Integration of Biogas and Solar Power Systems to Urban Wastewater Treatment Plants

Environmental and Techno-Economic Analysis of the Integration of Biogas and Solar Power Systems to Urban Wastewater Treatment Plants

Fate of Household and Personal Care Chemicals (HPCCs) in Sewage and Sludge from Typical Urban Wastewater Treatment Plants

Fate of Household and Personal Care Chemicals (HPCCs) in Sewage and Sludge from Typical Urban Wastewater Treatment Plants

Efficiency and factors for agricultural use of sludge in circular Bulgarian economy

The issue of utilization of sludge from wastewater treatment in agriculture is an important socio-economic and environmental problem in the European Union and Bulgaria. Its significance is determined by the fact that the amount of sludge formed is constantly growing, as the annual amount of sludge produced in Europe is 8.7 million dry matter, and in Bulgaria reaches 53 thousand tons of dry matter. One of the main ways to utilize sludge from wastewater treatment is its use as fertilizer in agriculture. It is becoming a topical issue along with the growing interest into the effective “transformation of wastes into products” and their inclusion in supply chains and circular economy. In other countries, there are numerous studies on the effects, factors and efficiencies of sludge use in agriculture. Despite their relevance, in-depth studies of the diverse effects and critical factors of sludge utilization in Bulgarian agriculture are at an early stage. This paper presents the results of the first part of a large-scale study aimed at determining the socio-economic effects of sludge utilization in Bulgarian agriculture. First, an approach is presented to assess the multilateral effects, efficiencies and factors of sludge utilization in agriculture. Then the various factors stimulating and limiting the utilization of sludge in Bulgarian farms are identified. The results of a case study of a holding using sludge as fertilizer are then presented. Based on a qualitative analysis of regulations and institutional structure, and surveys with managers and experts of urban wastewater treatment plants, and farmers using and not-using sludge, the institutional, political, organizational, personal, educational, informational, social, economic, and environmental factors influencing the utilization of sludge in agriculture in two regions of the country (Sofia and Burgas) are identified. Impact factors are generally divided into two types: factors influencing the behavior of agents, and factors determining the type and extent of the effects of sludge use in agriculture. Research of this type is to continue and deepen to establish the economic, sectoral and regional specificities on the basis of more representative information from all participants and interested parties in the effective utilization of sludge in the country.

Life cycle assessment of urban wastewater treatment plants: a critical analysis and guideline proposal.

In its 30 years of existence, there are still many improvement possibilities in studies performing the life cycle assessment (LCA) of wastewater treatment plants (WWTPs). Hence, this paper aims to start a guideline development for LCA of urban WWTPs based on the information available in the scientific literature on the topic. The authors used the ProKnow-C systematic review methodology for paper selection and 111 studies were analyzed. The most significant points that can be improved are caused by missing essential information (e.g. functional unity and input data). Other important methodological aspects are covered: allocation process, functional unit choice, sensitivity analysis, and important fluxes to be considered. Many opportunities within the LCA of WWTPs were identified, such as optimization of WWTP operational aspects and resource recovery. Furthermore, LCA should be combined with other methodologies such as big data, data envelopment analysis, life cycle cost assessment, and social life cycle assessment. To achieve this potential, it is clear that the scientific and technical community needs to converge on a new protocol to ensure that LCA application becomes more reliable and transparent.

Effective dampening of temperature effects in an anammox reactor treating real mainstream wastewater

The aim of the present study was to evaluate the capability of an up-flow anammox sludge bed reactor (13 L) of dampening a 10 °C temperature drop at mainstream conditions while operating at constant nitrogen loading rates (0.11 ± 0.01 g N L−1 d−1). The up-flow anammox sludge bed reactor was fed with an aerobically pre-treated mainstream wastewater. The reactor temperature was controlled as to mimic a (realistic) summer-to-winter transition from 20 to 10 °C plus a three months period at 10 °C. During the 350 days of operation, the average nitrogen removal rate remained high (0.10 ± 0.01 g N L−1 d−1), indicating that the 10 °C drop did not affect the overall efficiency of the reactor. This can be explained as anammox activity differed among the different sludge bed sections. At 20 °C, anammox activity was mainly located at the bottom of the sludge bed. At 10 °C, the anammox activity decrease of the bottom sludge bed was compensated by an activity increase within the upper sludge bed sections. The contribution of heterotrophic denitrifying activity to the total nitrogen removal rate was assessed to be 3-to-5 times lower than that of anammox, even at 10 °C. Microbial community of 16S rRNA gene-targeted sequencing analyses resulted in the identification of an uncharacterized Planctomycetes in high numbers. This study demonstrated that the low temperatures should not be an obstacle for the feasibility of anammox bacteria in the main water line of an urban wastewater treatment plant.

Removal of Nitrogen and Phosphorus from Thickening Effluent of an Urban Wastewater Treatment Plant by an Isolated Green Microalga.

Microalgae are photosynthetic microorganisms and are considered excellent candidates for a wide range of biotechnological applications, including the removal of nutrients from urban wastewaters, which they can recover and convert into biomass. Microalgae-based systems can be integrated into conventional urban wastewater treatment plants (WW-TP) to improve the water depuration process. However, microalgal strain selection represents a crucial step for effective phytoremediation. In this work, a microalga isolated from the effluent derived from the thickening stage of waste sludge of an urban WW-TP was selected and tested to highlight its potential for nutrient removal. Ammonium and phosphate abatements by microalgae were evaluated using both the effluent and a synthetic medium in a comparative approach. Parallelly, the isolate was characterized in terms of growth capability, morphology, photosynthetic pigment content and photosystem II maximum quantum yield. The isolated microalga showed surprisingly high biomass yield and removal efficiency of both ammonium and phosphate ions from the effluent but not from the synthetic medium. This suggests its clear preference to grow in the effluent, linked to the overall characteristics of this matrix. Moreover, biomass from microalgae cultivated in wastewater was enriched in photosynthetic pigments, polyphosphates, proteins and starch, but not lipids, suggesting its possible use as a biofertilizer.

Novel Ti/RuO2IrO2 anode to reduce the dangerousness of antibiotic polluted urines by Fenton-based processes

The treatment of hospital wastewater is very complex, so treating polluted human urine is a significant challenge. Here, we tested a novel MMO-Ti/RuO2IrO2 electrode to reduce the ecotoxicity risk of hospital urines contaminated with antibiotics. This electrode was used as the anode in electro-Fenton (EF) and photoelectro-Fenton (PhEF) processes. The results were compared with those obtained using the boron-doped diamond (BDD) anode, as well as those obtained by a conventional Fenton oxidation. In order to analyze the performance of the processes, the treatments were evaluated on the subject of Penicilin G (PenG) removal, toxicity (using a standardized method with Vibrio Fisheri), and antibiotic activity (Enterococcus faecalis as the target bacterium). The results reveal that PenG degrades in the following order: Fenton < EF < PhEF. The best results are found for the MMO-PhEF, which completely removed PenG, decreased 96% of toxicity, and completely removed antibiotic activity. Besides, for comparison, tests were performed with BDD, and results point out the higher convenience of the new electrode in terms of acceptable use of energy because the effluents generated can be further degraded in an urban wastewater treatment plant. Because of that, MMO-RuO2-IrO2 emerges as a promising cost-effective material for the pre-treatment of hospital urine effluents.

Occurrence and seasonal distribution of five selected endocrine-disrupting compounds in wastewater treatment plants of the Metropolitan Area of Monterrey, Mexico: The role of water quality parameters.

Five endocrine-disrupting compounds (EDCs) were determined in four urban wastewater treatment plants (WWTPs) of the Metropolitan Area of Monterrey (MAM) in two seasonal periods (winter and summer). The MAM, one of the most urbanized areas in Mexico, is characterized by high industrial activity and population density, leading to extensive use of several EDCs. In the MAM, ∼90% of urban and industrial wastewater is treated in WWTPs, where EDCs can be partially eliminated. In this work, dissolved levels of 17β-estradiol (E2), 17α-ethinyl estradiol (EE2), bisphenol A (BPA), 4-nonylphenol (4NP), and 4-tert-octylphenol (4TOP) in wastewater were determined. The EDCs' determination was carried out through solid-phase extraction (SPE) and gas chromatography coupled to mass spectrometry (GC-MS). High EDCs levels (0.4-450ng/L) were found in the influents of WWTPs, while concentrations in the effluents ranged from 0.2 to 26.8ng/L, with E2, EE2, and 4TOP being the most persistent. The Spearman correlation analysis revealed the association between E2 and EE2 (r=0.4835, p<0.05), and between BPA and 4NP (r=0.5180, p<0.05), suggesting that these EDCs have similar sources. Also, E2, BPA, and 4TOP were positively correlated with the chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) (r=0.4080-0.5694, p<0.05), indicating the association of the EDCs with the organic matter in the wastewater. The factor analysis confirmed the significant correlation of COD, BOD, TSS, temperature, and pH with the high occurrence of 4TOP during the summer. It was also confirmed that summer warmer temperatures favored the removal of BPA and 4NP in the studied WWTPs. Finally, the studied sites were classified by cluster analysis in three groups, revealing the impact that seasonality has on the behavior of the selected EDCs.

Pollution by anthropogenic microfibers in North-West Mediterranean Sea and efficiency of microfiber removal by a wastewater treatment plant

The widespread pollution from the release of microfibers is an emerging concern as they are a potential threat to the environment. Their identification in samples in terms of quantity and pathways remain a challenge as contamination can be a major source of error. A systematic study of synthetic microfibers (MFs) has been carried out in different environmental compartments of an urban area and in the surface waters of the northwestern Mediterranean.The quantity, size and type of polymer of MFs were recorded in air, in waste water from a domestic washing machine, at the inlet and outlet of the Haliotis urban wastewater treatment plant (WWTP) in Nice (Provence Alpes Côte-d'Azur, France) and in a variety of coastal and offshore areas. The results showed that MFs released by clothes during washing (on average of 13 × 106 MFs per m3) are an important emitter of microplastics. Despite its high removal efficiency (87.5% to 98.5%) by Haliotis, a large number of MFs, estimated at 4.3 billion, enter the marine environment daily from the treatment plant. The attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterization of the raw materials showed that 14 to 50% of fibers are synthetic, mostly polyester and polyamide, the remaining 35 to 72% being natural polymers (cotton, wool) or manufactured by processing natural polymers (especially cellulose). MFs were found in all environmental compartments studied and appear to be widespread in coastal and offshore surface waters with concentrations varying from 2.6 × 103 to 3.70 × 104 m−3. The sources of MFs in the marine environment are multiple, with laundry fibers discharges from WWTP and the atmospheric transport of urban fibers are among the main pathways.