Operation Of Wastewater Treatment Plants Research Articles

Are adding carbon sources and activated sludge helpful to the full-scale packing-reinforced multistage biological contact oxidation process?

The performance of wastewater treatment plants (WWTPs) is closely related to the structure and function of microbial communities which are frequently regulated by inoculating carbon source or new microbes. However, the status of microbial communities may be determined by the homeostasis of the bioreactors or properties of the influent especially in full-scale wastewater treatment plants. In this study, a full-scale packing-reinforced multistage biological contact oxidation process (PMBCOP) was used for investigating the durative impacts of carbon source addition and new sludge inoculation on the structure, stability and metabolic pathways of microbial communities. The results showed that inoculation of carbon sources or new sludge significantly increased the diversity (Chao1 and Shannon index) and reciprocal cooperations among microorganisms which further improved the stability of microbial communities and the COD (by 15%) and NH3-N (by 3%) removal efficiencies. Proteobacteria and Bacteroidota were two dominant phyla in the system and were responsible for the main metabolic pathway, i.e. amino acid metabolism. Nevertheless, the modifications of key genera, stability, up-regulated metabolites and enriched metabolic pathways as well as the improved removal efficiencies were not able to persist. The resistant ability of microbial community declined after stopping adding carbon source and new sludge which resulted in the instability and low removal efficiencies of the PMBCOP and aroused the requirements on exploring deep homeostatic mechanism of microbial communities and new promoting strategies. This study provided new insights on the durative effects on the succession and metabolism of microbial communities combing with the performances of the full-scale wastewater treatment plant which is helpful for the management of full-scale WWTPs.

Re-granulation and performance of anaerobically digested bacterial and algal-bacterial aerobic granular sludge.

Effective treatment and sustainable waste sludge management are critical challenges for future biorefinery wastewater treatment plants (WWTPs). This study investigated the feasibility of re-granulating anaerobically digested bacterial and algal-bacterial aerobic granular sludge (AGS) for sustaining the continuous operation of the AGS-based WWTPs due to the requirement of long-term operation for granulation of flocculent activated sludge. Rapid re-granulation was achieved within 12 and 6 days respectively from digested bacterial AGS and algal-bacterial AGS, demonstrating their high stability and settleability even after anaerobic digestion (AD). The re-granulated bacterial AGS system exhibited >90% dissolved organic carbon (DOC) removal, probably attributed to its greater microbial diversity and richness and elevated extracellular polymeric substances (EPS) secretion. The re-granulated algal-bacterial AGS system featured enhanced functional adaptability. It showed a lower average effluent dissolved total carbon concentration (∼100mg/L) and high total inorganic nitrogen removal (>89%) in addition to>56% maximum total phosphorus removal. Morphological observations revealed that some granules retained their compact structure and cores after AD, providing a niche for their re-granulation. Aromatic proteins and fulvic acid-like organics were the critical promoters for AGS regranulation. Notable shifts in microbial community structure, particularly the increase in abundance of photosynthetic bacteria such as Erythromicrobium, Leptolyngbya, and Rhodobacter, played an essential role in enhancing the overall performance of the re-granulated algal-bacterial AGS. By validating the system's effectiveness and exploring the factors governing re-granulation, this study proposes a viable strategy for advancing the sustainability of AGS-based WWTPs and promoting circular bioeconomy practices.

Analysis and Optimization of Hydraulic Calibration for Maximum Performance of Wastewater Treatment Plants

The hydraulic calibration of treatment units in wastewater treatment plants is a crucial task. It involves demonstrating the relative placement of these various units in relation to the water line that traverses the plant, and helps indicate the ground surface for establishing the optimal elevations of the plant's structures and hydraulic controls. This process is meticulous, complex, and prone to errors. Special attention must be given to the issue of varying hydraulic loads that the plant will receive, particularly at the inlet. Such variations can disrupt hydraulic operation and negatively impact the plant's performance. For these reasons, the hydraulic calibration of treatment units must always be verified and analyzed for most of the common hydraulic constraints encountered in practice. This article focuses on the different types of flow and their regimes commonly found in wastewater treatment plants, and aims to guide users on how to optimize the hydraulic profile. It highlights the impact of head losses and integrates a range of potential alternatives for achieving hydraulic efficiency in a wastewater treatment plant.

Machine learning application in municipal wastewater treatment to enhance the performance of a sequencing batch reactor wastewater treatment plant

An ML model optimized the performance of an SBR WWTP when applied to OSL scenarios, ensuring regulatory compliance.

Assessment of Wastewater Treatment Plants (WWTPs) Performance in El-Sharkia, Egypt

Assessment of Wastewater Treatment Plants (WWTPs) Performance in El-Sharkia, Egypt

Real-Time Determination of Total Suspended Solids in Activated Sludge’s Carousel Using a Single Emitter Ultrasonic Sensor

Sludge management is a very relevant aspect in the operation of Wastewater Treatment Plants (WWTPs). In activated sludge systems, it is common to have daily (or continuous) monitoring of total suspended solids in the aeration tank (MLSS). If such control is not properly performed, it can cause solids to wash out in the secondary sedimentation tank or significantly impact BOD (Biochemical Oxygen Demand) and nitrogen removal. There are many commercially available systems which can provide real-time monitoring of solids (mainly optical or ultrasound sensors). Even though commercially available (usually with a high cost), there are still issues related to the use of such sensors. The most important one is the progressive accumulation of solids, which cause measurement errors. In this work, the authors investigated the application of a low-cost US sensor for MLSS (mixed-liquor suspended solids) monitoring in two full-scale activated sludge WWTPs. The tested sensor was similar to a previously described device, which had been previously employed in a pilot-scale UASB reactor in Brazil. The main differences were related to an integrated treatment and acquisition system which allowed real-time treatment of the US wave as well as data acquisition at a predefined time. The values generated by the sensor were compared with a commercial optical sensor installed in the same WWTP and double-checked with periodic gravimetric tests. The results at a Leeuwarden WWTP showed that the measurements of the US sensor, the optical sensor, and gravimetric test did not present significant differences during the test period at a significance level of 5%. Absolute errors were on average 0.04% (US sensor) and 0.03% (optic sensor) of MLSS compared to the gravimetric test. Although the use of the tested US sensor for monitoring solids in WWTP is promising, there are still several improvements that need to be made to the sensor. These include implementing a more precise calibration frequency, establishing a cleaning routine, and preventing sensor fouling. Furthermore, the sensor still needs a more thorough cost–benefit analysis, which would help assess the practicality of implementing this technology in various WWTPs.

The Impact of Seasonal Variations in Rainfall and Temperature on the Performance of Wastewater Treatment Plant in the Context of Environmental Protection of Lake Como, a Tourist Region in Italy

This study investigates the impact of extreme weather conditions on the performance of a wastewater treatment plant (WWTP) in Como, Italy, in terms of influent (inf) and effluent (eff) quality parameters. During winter (October–December), the average temperature was 8.76 °C ± 11.43 °C, with 7.01 mm rainfall, while summer (May–September) averaged 23.24 °C ± 6.2 °C with 5.2 mm rainfall. Despite seasonal variations, the pH levels remained consistent. Phosphorus removal by the WWTP was efficient, with the winter influent averaging 4.16 ± 5.53 mg/L, the winter effluent averaging 0.33 ± 1.06 mg/L, the summer influent averaging 3.53 ± 2.9 mg/L, and the summer effluent averaging 0.31 ± 0.75 mg/L. The COD and BOD5 levels showed seasonal trends, with a higher winter-influent COD (450.43 ± 560.56 mg/L) than in summer (410.96 ± 302 mg/L). These higher winter values of effluent may be due to lower biological activity at cooler temperatures, affecting the efficiency of organic matter breakdown and treatment. The winter influent BOD averaged 249.57 ± 220.42 mg/L, with the winter effluent being 2.95 ± 2.04 mg/L, while the summer influent BOD was 214.44 ± 345.5 mg/L and the summer effluent was 3.01 ± 7.5 mg/L. The TSSs and Total-N showed similar seasonal patterns, with there being slight decreases in the TSSs removal efficiency during warmer months. Although microplastic pollution was not directly analyzed in this study, wastewater treatment plants play a crucial role in mitigating microplastic contamination. Despite rainfall influencing the phosphorus and organic load concentrations, the studied plant maintained over 90% pollutant removal efficiency, demonstrating resilience and compliance with regulatory standards. The WWTP’s consistent COD and BOD5 reductions highlight its robust performance amid climate variations

Identification of Barriers and Driving Forces for Circular Economy (CE) Implementation in Water and Wastewater Companies

ABSTRACTWater and wastewater management sector is one of the basic areas of implementing a circular economy (CE). Enterprises operating in this sector are mainly wastewater treatment plants (WWTPs) managed by municipalities or private companies. They encounter various barriers and facilitators to implement CE, in the area of technology development and management. However, a limited number of works in the available literature focus on nontechnological aspects of implementing CE in WWTPs. Therefore, this paper presents a comprehensive analysis of challenges (including driving forces and barriers) for WWTPs in the process of implementing CE policy goals. The PESTEL strategic analysis method was used, taking into account the identification of political, economic, social, technological, environmental, and legal factors. It was confirmed that there are more incentives than barriers to actively implementing CE model in analyzed enterprises. The most important driving forces include: (i) favorable European CE policy, as recommendations and law regulations in the area of water, raw materials, and energy recovery; (ii) society's pressure on resource protection; (iii) possible revenues from the sale of recovered water, energy or CE‐fertilizers; (iv) financial support for CE solutions. Among defined barriers that could slow down the circular transformation, the most important are: (i) lack of clearly stated regulations regarding water, energy, and raw materials recovery, as well as transparency and regulatory risk; (ii) limited own financial resources of WWTPs operators; (iii) high cost of investments and maintaining recovery/recycling technologies. Those results may be of key importance to practitioners in strategic decision making for the improved application of circularity in the operating process. Because the implementation of CE solutions should have an integrated approach throughout the enterprise, it is recommended to develop circular business models for these companies, that would take into account both the core business (water and wastewater management) as well as possibilities of further CE implementation, such as recovery of water, energy, and raw materials. In the coming years, such solutions could be financially supported by the national and European sources, which may have a positive impact on the acceleration to the CE model.

Effect of Differentially Charged Polystyrene Nanoplastics on the Performance of Biological Denitrification in Wastewater Treatment

Nanoplastics are widely distributed in the environment and can accumulate in organisms. Increasing attention has been paid to the toxic effects of nanoplastics in wastewater biological treatment processes. In this study, polystyrene nanoplastics with different charges were synthesized and used in sequencing batch activated sludge reactors for short-term nanoplastic exposure experiments. Both positively and negatively charged nanoplastics inhibited the nitrogen removal efficiency and gene expressions of nitrification and denitrification-related genes of activated sludge. The inhibiting effect on nitrification of both nanoplastics was enhanced with increasing concentration. The study further evaluated the molecular mechanisms by which differently charged nanoplastics affect denitrification efficiency using the model denitrifying bacterium Pseudomonas stutzeri （P. stutzeri）. The results showed that both positively and negatively charged nanoplastics affected the efficiency of biological denitrification by P. stutzeri, mainly including the promotion of NO3- to NO2- conversion and the significant acceleration of N2O production. Meanwhile, negatively charged nanoplastics inhibited the growth of P. stutzeri and disrupted the cell membrane of the bacterium； however, no change was observed in the expression of denitrification-related functional genes and the nanoplastics might have affected the enzymatic activities of Nir and Nos, which in turn affected the bioprocessing efficiency. This study can provide a certain reference for the evaluation of the biosafety of nanoplastics and provide a certain support for the stable operation of wastewater treatment plants.

Hybrid data driven approach based on ANNs-PCA for wastewater treatment plant performance assessment

Hybrid data driven approach based on ANNs-PCA for wastewater treatment plant performance assessment

A Multivariable Probability Density-Based Auto-Reconstruction Bi-LSTM Soft Sensor for Predicting Effluent BOD in Wastewater Treatment Plants.

The precise detection of effluent biological oxygen demand (BOD) is crucial for the stable operation of wastewater treatment plants (WWTPs). However, existing detection methods struggle to meet the evolving drainage standards and management requirements. To address this issue, this paper proposed a multivariable probability density-based auto-reconstruction bidirectional long short-term memory (MPDAR-Bi-LSTM) soft sensor for predicting effluent BOD, enhancing the prediction accuracy and efficiency. Firstly, the selection of appropriate auxiliary variables for soft-sensor modeling is determined through the calculation of k-nearest-neighbor mutual information (KNN-MI) values between the global process variables and effluent BOD. Subsequently, considering the existence of strong interactions among different reaction tanks, a Bi-LSTM neural network prediction model is constructed with historical data. Then, a multivariate probability density-based auto-reconstruction (MPDAR) strategy is developed for adaptive updating of the prediction model, thereby enhancing its robustness. Finally, the effectiveness of the proposed soft sensor is demonstrated through experiments using the dataset from Benchmark Simulation Model No.1 (BSM1). The experimental results indicate that the proposed soft sensor not only outperforms some traditional models in terms of prediction performance but also excels in avoiding ineffective model reconstructions in scenarios involving complex dynamic wastewater treatment conditions.

Application of Recycled Plastic Specimens to Enhance Waste Water Treatment Plant Operation for Subterranean Flow Constructed Wetlands

Application of Recycled Plastic Specimens to Enhance Waste Water Treatment Plant Operation for Subterranean Flow Constructed Wetlands

Resilience Adaptation Through Risk Analysis for Wastewater Treatment Plant Operators in the Context of the European Union Resilience Directive

To combat new threats to critical infrastructure, the European Union enacted new regulations for their member states. With the directive on measures for a high common level of cybersecurity (NIS2) and the directive on critical infrastructure resilience (EU RCE), EU member states must identify critical infrastructure (CIs) and enable measures to reduce the risk of default in stress situations. The topic of resilience in urban water systems has already been of interest in previous research. However, there are still open questions. As it is a multidisciplinary term, understanding resilience and its adaptation into management systems is not an easy task for practitioners. This study will provide an overview of resilience within the framework of municipal wastewater treatment plants (WWTP) and show the current situation of existing implementation of safety and security regulations, taking Germany as an example. One of the main requirements of the EU RCE is a risk assessment (RA) for CIs. Until now, risk analysis for WWTP in research was mostly carried out for individual WWTP. By applying guidelines from the drinking water sector, this paper shows a possible methodology for a risk analysis. This paper aims to support practitioners by forming a common understanding of resilience and risk as well as providing an example for a risk analysis.

Practical implications of adding powdered activated carbon in advanced wastewater treatment for process and plant design

ABSTRACT The addition of powdered activated carbon (PAC) in advanced wastewater treatment is increasingly recognized for its effectiveness in removing micropollutants from secondary effluents. This study investigates the implications of PAC dosing on treatment performance, particularly in terms of natural and effluent organic matter (OM) removal, turbidity reduction, and sludge characteristics. Results indicate that while PAC incorporation significantly enhances the adsorption of OM, it necessitates higher coagulant dosages to achieve comparable or improved turbidity levels. The study also reveals that lower pH levels facilitate the removal of OM, thereby increasing the availability of adsorption sites on PAC for micropollutants. Moreover, PAC addition results in the formation of larger, denser flocs that settle faster, leading to a reduction in sludge volume by approximately 20%. However, the increased coagulant demand and the subsequent rise in sludge volume highlight the need for the optimized process design to balance treatment efficiency with operational costs. This research provides valuable insights for the design and operation of wastewater treatment plants, emphasizing the importance of tailored coagulant dosing and process adjustments when integrating PAC into existing treatment frameworks.

Assessment of carbon efficiency in wastewater treatment plants through Stochastic non-parametric data envelopment analysis (StoNED): Insights from Spanish facilities

Assessment of carbon efficiency in wastewater treatment plants through Stochastic non-parametric data envelopment analysis (StoNED): Insights from Spanish facilities

Generic and site-specific social life cycle assessment of municipal wastewater treatment systems in Spain: challenges and limitations of the method when applied to resource recovery systems

Abstract Purpose This work aims to provide insights on the application of social life cycle assessment (S-LCA) in evaluating the social impacts associated with municipal wastewater treatment (WWT). The study assesses the social risks and social performance of two municipal WWT systems in Catalonia, Spain: a conventional wastewater treatment plant (WWTP) (Reference System) and a novel system that recovers water and other valuable resources (Novel System). Methods S-LCA was conducted at Generic and Site-Specific levels using 1 m3 of wastewater treatment as the functional unit (FU). The Generic assessment was conducted via the Product Social Impact Life Cycle Assessment (PSILCA) database, while the Site-Specific assessment employed the Subcategory Assessment Method (SAM) with four-level reference scales to assess the social performance of the WWTP operator and its first-tier suppliers. Furthermore, activity variables were calculated based on organizations’ shares in the total costs per FU, and the Novel System’s multifunctionality was solved through economic allocation. Results were aggregated by (i) assigning equal weights to organizations and (ii) factoring in organizations’ weights and the allocation factor, leading to results per FU. Results and discussion The Generic analysis results indicated that the Novel System entailed fewer social risks than the Reference System. Most social risks in both systems occurred in the subcategories “Access to material resources,” “Fair salary,” “Freedom of association and collective bargaining,” “Contribution to economic development,” and “Corruption.” In the Site-Specific assessment, the Novel System presented better social performance than the Reference System per 1 m3 of wastewater treatment. The latter’s performance per FU did not meet the basic requirement in four out of eleven subcategories, mainly due to the performance and weight of a chemical supplier. Allocation greatly benefitted the Novel System’s results per FU compared to the results obtained when equal weights were applied. Conclusions Activity variables were used to connect organizations’ conduct with particular WWT systems, and multifunctionality was solved. This approach allowed for obtaining results per FU at both assessment levels. However, social performance was also evaluated by calculating the average social performance of each system without considering activity variables and the FU, leading to different results. The social performance of the Novel System per FU was satisfactory across all subcategories but required improvement in four subcategories based on the average results. Given the limitations of using activity variables and allocation in S-LCA, further research is necessary to appropriately evaluate and compare the social effects of novel resource recovery systems.

Energy efficiency evaluation of wastewater treatment plants: A methodological proposal for its benchmarking

Energy efficiency evaluation of wastewater treatment plants: A methodological proposal for its benchmarking

Nanostructured materials as hazardous wastewater micropullutants: Sources, behavior, and impact on functional bacterial community of activated sludge

Unique properties of nanoscale materials make them attractive for industrial, medical, agricultural, and environmental applications. Nevertheless, the release of nanoparticles into the environment is a major concern due to the lack of knowledge about their behavior in the environment and potential widespread environmental impacts. On the one hand, nanomaterials are perceived as pollutants that may affect activated sludge microorganisms and, consequently, the efficiency of wastewater treatment processes. On the other hand, some nanomaterials can be intentionally added to activated sludge systems to improve their performance in terms of, e.g., sludge settling and removing heavy metals or organic pollutants. As a result, nanoparticles are frequently accumulated in wastewater, which is considered to be a major source of nanoparticle release to the surrounding environment. Processes that involve the action of activated sludge are used worldwide in wastewater treatment plants due to their excellent capacity of removing nutrients, degrading toxins, and retaining biomass. High concentrations of nanoparticles entering activated sludge systems can affect their growth and metabolism. The research studies, which are reviewed in the present article, show that nanoparticles significantly reduce the relative abundance of the activated sludge microbial community associated with nitrification, denitrification, and phosphorus removal. The knowledge about the structure of the activated sludge microbial community with an assessment of nanomaterial toxicity can contribute to optimizing the sludge population and improving the performance of wastewater treatment plants.

Deep insights into the assembly mechanisms, co-occurrence patterns, and functional roles of microbial community in wastewater treatment plants

The understanding of activated sludge microbial status and roles is imperative for improving and enhancing the performance of wastewater treatment plants (WWTPs). In this study, we conducted a deep analysis of activated sludge microbial communities across five compartments (inflow, effluent, and aerobic, anoxic, anaerobic tanks) over temporal scales, employing high-throughput sequencing of 16S rRNA amplicons and metagenome data. Clearly discernible seasonal patterns, exhibiting cyclic variations, were observed in microbial diversity, assembly, co-occurrence network, and metabolic functions. Notably, summer samples exhibited higher α-diversity and were distinctly separated from winter samples. Our analysis revealed that microbial community assembly is influenced by both stochastic processes (66%) and deterministic processes (34%), with winter samples demonstrating more random assembly compared to summer. Co-occurrence patterns were predominantly mutualistic, with over 96% positive correlations, and summer networks were more organized than those in winter. These variations were significantly correlated with temperature, total phosphorus and sludge volume index. However, no significant differences were found among microbial community across five compartments in terms of β diversity. A core community of keystone taxa was identified, playing key roles in eight nitrogen and eleven phosphorus cycling pathways. Understanding the assembly mechanisms, co-occurrence patterns, and functional roles of microbial communities is essential for the design and optimization of biotechnological treatment processes in WWTPs.

Some Possible Process Configurations for Modern Wastewater Treatment Plants for Per- and Polyfluoroalkyl Substances (PFASs) Removal

Per- and polyfluoroalkyl substances (PFASs) have been detected in the influent, effluent, and sludge/biosolids of wastewater treatment plants (WWTPs) globally. Due to their potential to bioaccumulate in humans, wildlife, and the environment over time owing to their seriously persistent nature and/or strong C-F bonds, PFASs can cause public health concerns. Conventional processes in full-scale WWTPs are usually inefficient in PFASs removal from wastewater and sludge, and advanced treatment technologies are needed for PFASs removal. This study intends to briefly (i) summarize the technologies for PFASs remediation in wastewater and sludge; (ii) review PFASs removal in full-scale WWTPs; (iii) discuss some possible theoretical configurations for the wastewater processing train of modern WWTPs for PFASs remediation; and finally (iv) provide future directions. Further research regarding the techno-economic assessment and optimization of treatment technologies in removing PFASs (especially short-chain PFASs) from real wastewater as well as the performance of full-scale WWTPs consisting of advanced innovative efficient treatment technologies for PFASs removal and associated costs (i.e., construction, operation, maintenance, chemical, energy, and amortization) is still required.