Urban Wastewater Treatment Research Articles

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.

Design of an improved process optimization model for enhancing the efficiency of the wastewater treatment process

ABSTRACT Efficient wastewater treatment is crucial for environmental protection and ensuring the availability of potable water. However, existing optimization models often fall short in effectively analyzing historical data, optimizing dosages, or predicting optimal process parameters. This paper aims to address these challenges by proposing an advanced process optimization model that enhances the efficacy of wastewater treatment processes. Our objectives include the development of a novel method for optimizing various aspects of the treatment procedure using Auto Encoders (AE), Genetic Algorithm (GA), and Vector Autoregressive Moving Average (VARMA) models. Extensive experimentation with multiple datasets and samples, including the Melbourne Wastewater Treatment Dataset, Urban Wastewater Treatment, and Global Wastewater Treatment, was conducted to validate our model. The results demonstrate significant improvements in our proposed model, with an average improvement of 8.5% in treatment quality, a 4.9% reduction in delay, and a 9.5% increase in water purity compared to recently proposed models. We conclude that our model provides a valuable framework for optimizing wastewater treatment in a variety of settings due to its adaptability and effectiveness. Future research could explore the integration of additional advanced techniques and real-time monitoring systems to further enhance the model's precision, efficiency, and robustness.

Nutrient Removal and Recovery from Municipal Wastewater

With the ongoing amendment of the EU legislation on the treatment of urban wastewater, stricter requirements for the removal of pollutants are expected, which calls for the need for innovative wastewater treatment technologies. Biological systems are still the first choice. A survey of typical bioreactors applied in wastewater treatment is presented. The wastewater treatment objective, biochemical environment, and microbial growth are selected as the main criteria for the classification of these bioreactors. Hydraulic and kinetic aspects are considered, along with the advantages and drawbacks of these bioreactors regarding the selection of the appropriate type of reactor; as well, details regarding the operation of reactors are mentioned. The aim of this paper is to provide operators and designers with a brief overview of the selected traditional and advanced processes, reactors, and technologies for nutrient removal from municipal wastewater. The possibilities and limitations in complying with more strict effluent standards are also discussed. Methods of nutrient recovery are added value. From the evaluation of the published papers, we determine that the currently applied traditional methods for nutrient removal have the potential to also convey the expected stricter limits.

Ultraviolet technology application in urban water supply and wastewater treatment in China: Issues, challenges and future directions

This study thoroughly explores the application of Ultraviolet (UV) water treatment technology in urban wastewater treatment and water supply in China, highlighting its crucial role in enhancing water quality safety. UV technology, with its environmentally friendly and low-carbon characteristics, is deemed more in line with the demands of sustainable development compared to traditional chemical disinfection methods. The widespread application of UV technology in urban wastewater treatment in China, particularly in the context of urban sewage treatment, is examined. However, to better promote and apply UV technology, there is a need to deepen the understanding of this technology and its application among a broad base of users and design units. The importance of gaining in-depth knowledge about the performance of UV water treatment equipment, the design calculation basis, and operational considerations, as well as the ongoing development of relevant standards, is underscored to ensure that the equipment used in projects complies with engineering design and production requirements. Furthermore, the positive trend of UV technology in the field of advanced oxidation, indicating a promising trajectory for engineering applications, is pointed out. Regarding the prospects of industrial development, a thorough analysis is conducted in the article, emphasizing the necessity for all stakeholders to collaborate and adopt a multi-level approach to promote the sustainable development and application of UV water treatment technology. This collaborative effort is crucial for providing effective safeguards for China's environment, ecology, and human health.

Effectiveness of a natural coagulant based on common mallow (Malva sylvestris) in urban wastewater treatment

ABSTRACT This study evaluated the effectiveness of a natural coagulant based on common mallow (Malva sylvestris) to remove turbidity in urban wastewater. A 22 factorial design was selected to determine the optimal dose and the working pH of the natural coagulant. Its potential was studied in 50.0–450 mg/L and 4.00–10.0 ranges of doses and pH, respectively. A simplex lattice mixture evaluated its effectiveness as a coagulant aid combined with aluminum sulfate (conventional coagulant). Mixture proportions 0.000–1.00 were studied for each component, finding the proportion more effective. Results showed that the coagulation treatment could be feasible since a turbidity removal efficiency of 73.7% can be achieved under optimal conditions (50.0 mg/L and pH of 10.0). Likewise, a turbidity removal of 58.9% is obtained using 250 mg/L and maintaining wastewater pH (7.45). This efficiency can be increased using 31.0% natural coagulant mixed with 69.0% aluminum sulfate at 250 mg/L without modifying the wastewater pH. This improvement was associated with the natural coagulant’s high molecular weight and long-chained structure since these properties enhance settling time, floc size and strength, and low sludge production. These results support using common mallow as a natural coagulant, making its use more feasible in alkaline water pH or as a coagulant aid combined with aluminum sulfate for urban wastewater treatment. A cost of USD 370/Kg of natural coagulant was estimated, which is higher than conventional coagulants. However, a cost-effectiveness analysis of its implementation should be performed since process scaling costs could significantly reduce its price.

Walnut shells as a promising sorbent for treatment of urban surface wastewater

Food industry is one of the most stable sectors of the global market demonstrating the annual growth of the production output, including in the walnut kernel production, with subsequent generation of waste as a result of its processing. The use of walnut shells as a material for production of sorbents is a promising method of waste disposal. The goal of this research is to evaluate the sorption capacity of walnut shells to clean surface wastewater from urban territories. The object of research was the surface wastewater from urban territories. OPTIMA 2100DV spectrometer (Perkin Elmer), pH-150MI microprocessor pH meter, and JEOL JSM-6460 LV scanning electron microscope were used during the research. The obtained experiment data have shown that walnut shells are a promising material for production of sorbents.

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.

Life cycle assessment of anaerobic-anoxic-oxic and extended aeration of the activated sludge treatment system for urban wastewater treatment: a case study in Iran

Life cycle assessment of anaerobic-anoxic-oxic and extended aeration of the activated sludge treatment system for urban wastewater treatment: a case study in Iran

Enhancing pollutant removal efficiency in urban domestic wastewater treatment through the hybrid multi-soil-layering (MSL) system: A case study in Morocco.

This paper evaluates the performance and potential of a full-scale hybrid multi-soil-layering (MSL) system for the treatment of domestic wastewater for landscape irrigation reuse. The system integrates a solar septic tank and sequential vertical flow MSL and horizontal flow MSL components with alternating layers of gravel and soil-based material. It operates at a hydraulic loading rate of 250 L/m2/day. Results show significant removal of pollutants and pathogens, including total suspended solids (TSS) (97%), chemical oxygen demand (COD) (88.57%), total phosphorus (TP) (79.93%), and total nitrogen (TN) (88.49%), along with significant reductions in fecal bacteria indicators (4.21 log for fecal coliforms and 3.90 log for fecal streptococci) and the pathogen Staphylococcus sp. (2.43 log). The principal component analysis confirms the effectiveness of the system in reducing the concentrations of NH4, COD, TP, PO4, fecal coliforms, fecal streptococci, and fecal staphylococci, thus supporting the reliability of the study. This work highlights the promising potential of the hybrid MSL technology for the treatment of domestic wastewater, especially in arid regions such as North Africa and the Middle East, to support efforts to protect the environment and facilitate the reuse of wastewater for landscape irrigation and agriculture.

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.

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.

Evaluation of the role of urban domestic wastewater treatment systems for greenhouse gases emissions in China

Rapid urbanization has exacerbated the dual challenge of mitigating water pollution and reducing greenhouse gas (GHG) emissions. The present study offers insights into the actual role of urban domestic wastewater treatment systems by shedding light on their capacity to act as GHG emitters. We introduce a modelling framework to calculate GHG emissions from wastewater treatment systems in China over the past two decades. Our analysis showed that treated wastewater volume increased by over 4.5 times, but GHG emissions also increased by 2.9 times. The annual emissions from wastewater treatment were -on average- nearly 60 Tg CO2-eq over the past two decades, accounting for <1% of the total national emissions. We also found a significant spatial variability with thirteen developed areas contributing >70% of the GHG emissions. Constructions and operations of wastewater treatment systems approximately accounted for 17% and 83% of the GHG emissions, respectively. Our study also proposes a hierarchical governance framework based on ten major regions that could maximize the efficiency in mitigating water pollution and GHG emissions in China.

Enhancing urban wastewater treatment: Chlorella vulgaris performance in tertiary treatment and the impact of anaerobic digestate addition

The rising urban wastewater discharge into waterways resulted in harmful environmental effects. Microalgae can bioremediate wastewaters by removing contaminants such as nitrogen and phosphorus and can be rather tolerant to toxic compounds. Managing the anaerobic digestate resulting from sludge treatment in wastewater treatment plants faces some obstacles related to its high contaminant content. This work aims to study the ability of the microalga Chlorella vulgaris to perform the tertiary treatment of urban wastewater, assessing its growth, nutrient removal and the effect of the addition of digestate at different concentrations in this treatment phase. A secondary effluent was supplied with 1% (M1), 5% (M5) and 10% (M10) (v/v) of anaerobic digestate and used to culture microalgae. An assay using only secondary effluent was also performed (S). C. vulgaris grew successfully in all effluents except for the M10, and the highest specific growth rate was obtained in the M1 assay, 0.35 ± 0.01 d−1. Ammonium-nitrogen was completely removed in the S, M1 and M5 assays (>99.9%). Microalgae successfully removed phosphate-phosphorus from the tested effluents, achieving a negligible concentration in the M1 assay and a removal efficiency of 96.2 ± 0.2%, 51 ± 2%, and 43 ± 3% in S, M5 and M10, respectively. These results showed that microalgal cultures could efficiently remediate the secondary effluent and its mixture with 1% (v/v) of anaerobic digestate, achieving nutrient concentrations below the current legislation limits and the more restrictive limits predicted for future legislation.

Metagenomic insights into the wastewater resistome before and after purification at large‑scale wastewater treatment plants in the Moscow city

Wastewater treatment plants (WWTPs) are considered to be hotspots for the spread of antibiotic resistance genes (ARGs). We performed a metagenomic analysis of the raw wastewater, activated sludge and treated wastewater from two large WWTPs responsible for the treatment of urban wastewater in Moscow, Russia. In untreated wastewater, several hundred ARGs that could confer resistance to most commonly used classes of antibiotics were found. WWTPs employed a nitrification/denitrification or an anaerobic/anoxic/oxic process and enabled efficient removal of organic matter, nitrogen and phosphorus, as well as fecal microbiota. The resistome constituted about 0.05% of the whole metagenome, and after water treatment its share decreased by 3–4 times. The resistomes were dominated by ARGs encoding resistance to beta-lactams, macrolides, aminoglycosides, tetracyclines, quaternary ammonium compounds, and sulfonamides. ARGs for macrolides and tetracyclines were removed more efficiently than beta-lactamases, especially ampC, the most abundant ARG in the treated effluent. The removal efficiency of particular ARGs was impacted by the treatment technology. Metagenome-assembled genomes of multidrug-resistant strains were assembled both for the influent and the treated effluent. Ccomparison of resistomes from WWTPs in Moscow and around the world suggested that the abundance and content of ARGs depend on social, economic, medical, and environmental factors.

Comprehensive carbon footprint analysis of wastewater treatment: A case study of modified cyclic activated sludge technology for low carbon source urban wastewater treatment

To reduce pollution and carbon emissions, a quantitative evaluation of the carbon footprint of the wastewater treatment processes is crucial. However, micro carbon element flow analysis is rarely focused considering treatment efficiency of different technology. In this research, a comprehensive carbon footprint analysis is established under the micro carbon element flow analysis and macro carbon footprint analysis based on life cycle assessment (LCA). Three wastewater treatment processes (i.e., anaerobic anoxic oxic, A2O; cyclic activated sludge technology, CAST; modified cyclic activated sludge technology, M-CAST) for low carbon source urban wastewater are selected. The micro key element flow analysis illustrated that carbon source mainly flows to the assimilation function to promote microorganism growth. The carbon footprint analysis illustrated that M-CAST as the optimal wastewater treatment process had the lowest global warming potential (GWP). The key to reduce carbon emissions is to limit electricity consumption in wastewater treatment processes. Under the comprehensive carbon footprint analysis, M-CAST has the lowest environmental impact with low carbon emissions. The sensitivity analysis results revealed that biotreatment section variables considerably reduced the environmental impact on the LCA and the GWP, followed by the sludge disposal section. With this research, the optimization scheme can guide wastewater treatment plants to optimize relevant treatment sections and reduce pollution and carbon emissions.

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).

Treatment of greywater with nanofiltration for nutrient removal – 2-year experience from Helsingborg

Abstract Source-separated sanitation and greywater treatment have become an increasingly attractive alternative to traditional wastewater management systems in recent years due to their potential to combat water scarcity, ease resource recovery, and meet tightening effluent demands. In Helsingborg, Sweden, source-separated wastewater from the new city district of Oceanhamnen is being collected and treated in a new treatment plant (RecoLab) to test, among other issues, how efficient greywater treatment can be in achieving low discharge limits for pollutants. The greywater treatment consists of activated sludge treatment, drum filter micro-sieving, and nanofiltration. In the first two years of operation, the robustness of the treatment system during periods with extreme conditions, e.g., very low and very high organic matter concentrations, was tested. The combination of biological treatment and nanofiltration has achieved stable effluent concentrations below 10 mg/L chemical oxygen demand, 2 mg/L total nitrogen, and 0.2 mg/L total phosphorus as average values for 22 months of operation with an average flow of 43 m3/day. The treatment system for greywater treatment thus shows the possibility to achieve low discharge limits and meet the new proposed effluent demands of the EU Urban Wastewater Treatment Directive.

A Critical Review on Methodologies for the Energy Benchmarking of Wastewater Treatment Plants

The main priority at wastewater treatment plants (WWTPs) is the attainment of a high quality of treated effluent ensuring the highly effective removal of pollutants and protecting the environment and public health. However, WWTPs are made of energy-intensive processes and consequently, they are considered major energy consumers in the public sector. The need to move towards energy neutrality in the wastewater sector was recently pointed out by the proposal of a recast Urban Wastewater Treatment Directive. To date, a comprehensive methodology for energy audits at WWTPs is still missing. The present review aims at discussing the state of the art on energy consumption at WWTPs and at surveying the energy benchmarking methodologies currently available highlighting the main advantages and limitations. It was pointed out that aeration represents the highest energy-intensive compartment in WWTPs (40–75% of total energy). The wide overview provided by key performance indicators (KPIs) might be overcome by applying benchmarking methodologies based on data envelopment analysis (DEA). The latest is properly designed for WWTPs and able to manage multiple inputs and outputs. However, the obtained findings are often limited and fragmented, making the standardization of the methodology difficult. Consequently, future investigations are advised on the development of standard procedures related to data acquisition and collection and on the implementation of online and real-time monitoring. Considering the lack of standardized methodology for the energy benchmarking of WWTPs, the present article will provide essential information to guide future research, helping WWTP utilities to reach the energy audit goals in the accomplishment of incoming EU directives.