Municipal Wastewater Treatment Processes Research Articles

Sustainability Strategies in Municipal Wastewater Treatment

The European Parliament adopted a legislative resolution of 10 April 2024 on the proposal for a directive of the European Parliament and of the Council concerning urban wastewater treatment. The reduction in pollution in discharged treated wastewater in the parameters of BOD5, total nitrogen, and total phosphorus was emphasized. Based on these results, it stated that the impacts on the quality of lakes, rivers, and seas in the EU are visible and tangible. At the same time, it was emphasized that the sector of urban wastewater removal and treatment is responsible for 0.8% of total electricity consumption and about 0.86% of all greenhouse gas emissions in the entire EU. Almost a third of these emissions could be prevented by improving the treatment process, better use of sewage sludge, and increasing energy efficiency, as well as a higher rate of use of renewable resource technologies. It is also necessary to integrate treatment processes into the circular economy. Sludge management and water reuse are suboptimal as too many valuable resources are still being wasted. This article focuses on sustainable municipal wastewater treatment, innovative and new wastewater treatment processes and technologies (combined and hybrid processes, ANAMMOX, etc.) and their use in practice with the aim of increasing environmental and energy efficiency and reducing the carbon footprint. The research is focused on the possibilities of increasing the efficiency of energy processing of sludge, reuse of nitrogen and phosphorus, sludge, and reuse of treated wastewater.

New approach to multivariate statistical process control and its application to wastewater treatment process monitoring

This paper presents a new process monitoring and fault diagnosis approach based on a modified Multivariate StatisticalProcess Control (MSPC) and evaluates its applicability to municipal wastewater treatment process monitoring. Firstly,a conventional MSPC, based on Principal Component Analysis (PCA), is adjusted to provide an easy-to-understand userinterface and then a new yet simplified reconfigurable diagnostic model is introduced. The user interface that has beendeveloped is designed to integrate MSPC seamlessly with existing process monitoring systems that use the so-called trendgraphs. The proposed diagnostic model is constructed by aggregating small models with either one or two inputs, whichenhances the tractability of the diagnostic model. The effectiveness of the modified MSPC is demonstrated through a series of offline and online experiments, using a set of real multivariate process data from a municipal wastewater treatment.plant.

Fabrication of heterogeneous catalyst for production of biodiesel form municipal sludge

Sewage sludge, a semi-solid byproducts of municipal wastewater treatment processes, offers a sustainable and cost-effective feedstock for biodiesel production through the synthesis of catalytic heterogeneous catalysts. In this study, we developed a novel heterogeneous catalyst by impregnating aluminum nitrate and calcite, obtained from carbon dioxide-sequestering bacteria, onto DigSBiochar (Biochar derived from digested sewage sludge). The produced catalyst was subsequently immobilized with the lipase enzyme isolated from Bacillus sp., creating a bioactive material for the transesterification of lipids in sewage sludge. Comprehensive characterization of the biocatalysts was conducted using Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FE-SEM). Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the resulting fatty acid methyl esters (FAMEs) demonstrated that the highest yield was achieved with the enzyme immobilized on the activated heterogeneous catalyst using methanol (99 %), followed by the activated heterogeneous catalyst with methanol (96 %), and methanol with Sulfuric acid (82 %). This study underscores the potential of utilizing municipal sewage sludge as a valuable resource for producing efficient heterogeneous catalysts, thereby advancing sustainable waste management practices and promoting renewable energy production.

Recovery of organic matters by activated sludge from municipal wastewater: Performance and characterization

Municipal wastewater treatment processes consume a significant amount of energy and generate substantial carbon emissions. However, organic matters existing in municipal wastewater hold the potential as a valuable carbon source. Activated sludge has the potential to capture and recover the organic matters, thereby enriching carbon sources and facilitating subsequent sludge anaerobic digestion as well as in line with the concept of sustainable development. Based on above, this study investigated the enrichment and recovery characteristics and mechanisms of activated sludge adsorption on carbon sources in municipal wastewater, while optimizing the recovery conditions. The results indicated that insoluble organic matters, as well as a fraction of dissolved organic matters, can be effective recovered within approximately 40 min. Specifically, 74.1% of insoluble organic matters and 25.8% of soluble organic matters were successfully captured by the activated sludge, resulting in a 5.0% increase in sludge organic matter content. Moreover, activated sludge demonstrated remarkable recovery of particulate organic matters across various particle sizes, particularly larger particles (>5 μm) with high protein content. Notably, the dissolved biodegradable organics such as tryptophan and tyrosine protein-like substances according to 3D-EEM and lipids, proteins/amino sugars, and carbohydrates according to FT-ICR MS can be effectively recovered. Finally, the study revealed that the recovery of organic matters from the wastewater by activated sludge followed the pseudo-second-order kinetics model, with surface binding, hydrogen bonding and interparticle diffusion in sludge flocs as the primary adsorption mechanisms. This approach had abroad application prospects for improving the profitability of wastewater treatment plants.

Novel three-sludge municipal wastewater treatment process coupling denitrifying phosphorus removal with anaerobic ammonium oxidation

The two-sludge anoxic dephosphation (DEPHANOX) process frequently encounters the challenge of elevated effluent ammonia levels in practical applications. In this study, the anaerobic ammonium oxidation (anammox) biofilm was introduced into the DEPHANOX system, transforming it into a three-sludge system, enabling synchronous nitrogen and phosphorus elimination, particularly targeting ammonia. Despite a chemical oxygen demand/total nitrogen ratio of 4.3 ± 0.8 in the actual municipal wastewater and 4.5 h of aeration, the effluent total nitrogen was 13.7 mg/L, lower than the parallel wastewater treatment plant. Additionally, the effluent ammonia reduced to 5.1 ± 2.5 mg/L. Notably, denitrifying phosphorus removal and anammox were coupled in the anoxic zone, yielding 74.5 % nitrogen and 87.8 % phosphorus removal. 16S rRNA gene sequencing identified denitrifying phosphorus-accumulating organisms primarily in floc sludge (Saprospiraceae 7.07 %, Anaerolineaceae 1.95 %, Tetrasphaera 1.57 %), while anammox bacteria inhabited the biofilm (Candidatus Brocadia 4.00 %). This study presents a novel process for efficiently treating municipal wastewater.

Soft Sensor of the Key Effluent Index in the Municipal Wastewater Treatment Process Based on Transformer

Soft Sensor of the Key Effluent Index in the Municipal Wastewater Treatment Process Based on Transformer

Alteration of antimicrobial phenotypic resistance of E. coli in municipal wastewater treatment process and receiving canal water in Bangkok, Thailand

Alteration of antimicrobial phenotypic resistance of E. coli in municipal wastewater treatment process and receiving canal water in Bangkok, Thailand

Primena vodenih eutektičkih rastvarača za hemijsku valorizaciju otpadnog mulja - određivanje mineralnog sadržaja

Sewage sludge is a by-product of municipal wastewater treatment processes with significant soil-forming and fertilizing characteristics. However, if sewage sludge contains heavy metals, it can negatively affect the soil environment. The accumulation of heavy elements in the soil can negatively affect the circulation of elements in the natural environment, regarding plants, animals, and humans. The primary sources of heavy metals in human and animal food are plants, which are also the primary consumers of mineral nutrients from soil and water. Even a very small amount of heavy metals in the body can create metabolic problems, reduced body functions, and compromised immune and enzymatic processes, all of which contribute to various diseases and may even cause death. The aim of this study was to find a suitable system for mineral extraction from the municipal sewage sludge after water purification, collected from the wastewater treatment plant in Vlasotince, so the real composition of sewage sludge could be obtained. For that purpose, different aqueous deep eutectic solvents were applied: choline chloride:lactic acid (ChCl:LA), choline chloride:urea (ChCl:U), choline chloride:glycerol (ChCl:G), choline chloride:propylene glycol (ChCl:PEG), choline chloride:citric acid (ChCl:CA), and choline chloride:ethylene glycol (ChCl:EG).The concentrations of minerals after wet digestion were determined by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). The results showed that the highest amounts of minerals, especially Ca, P, and Fe, were extracted using aqueous acidic deep eutectic solvent systems (ChCl:LA and ChCl:CA). Also, the mineral composition of sewage sludge indicates the possibility of its use as a significant soil fertilizer supplement.

Biodegradable Microplastics in Municipal Wastewater and Sludge Treatment Processes: A Review on Occurrence, Fate, and Effects

Biodegradable Microplastics in Municipal Wastewater and Sludge Treatment Processes: A Review on Occurrence, Fate, and Effects

Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment, Sewage Sludge Digestion and Biogas Upgrading: A Review

Anaerobic membrane bioreactors (AnMBRs) are formed through the combination of anaerobic digestion and membrane technology. The upgraded technology separates SRT from HRT in the anaerobic digester, shortening the treatment period, reducing the digester’s volume and improving effluent quality. Furthermore, AnMBRs have a strong tolerance for the existing forms of objects and can handle liquids, high-solid materials and gases. Up to now, AnMBRs have been utilized in the treatment of various types of industrial and municipal wastewater, organic solid waste and also biogas upgrading, and they have achieved excellent performance. However, there are few studies which have discussed their multiple utilization, especially following the flow of wastewater treatment. This study summarizes the application of AnMBRs in their diverse roles in the municipal wastewater treatment process. The discussion revolves around energy generation and the fouling issue of AnMBRs in the treatment of municipal wastewater, the digestion of sewage sludge generated in conventional municipal wastewater treatment and the upgrading of biogas after anaerobic digestion. In addition to controlling operating parameters, strategies used to improve the treatment effectiveness are also introduced. Lastly, online methods for preventing membrane fouling, which is the main operational obstacle to AnMBRs’ wider spread, are also discussed. This review aims to provide a fresh perspective on how AnMBRs are utilized in waste treatment.

Effectiveness of monochloramine for inactivation of coronavirus in reclaimed water

Fecal shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by infected persons into wastewater was documented early during the COVID-19 pandemic, thereby stimulating inquiries into the effectiveness of municipal wastewater treatment processes for the reduction of infectious viruses. In wastewater treatment plants, free chlorine has traditionally been the disinfectant utilized due to its low cost and high efficacy. However, regulations limiting disinfection by-products have prompted a shift to chloramination in many areas of the United States. While studies regarding the effectiveness of free chlorine against many viral agents are abundant, the efficacy of monochloramine (NH2Cl) has been less well researched. This study aimed to determine the effectiveness of pre-formed monochloramine for disinfection of human coronavirus 229E (HCoV-229E) in both phosphate-buffered saline (PBS) and reclaimed water from a water reclamation plant in Tucson, Arizona. Reclaimed water was sampled over the course of six months (August 2020 to November 2020), and dosed with monochloramine at 3 mg/L. An additional 1 mg/L free ammonia was added to simulate the operational conditions of the treatment plant. Viability was determined using MRC-5 host cell monolayers, using the TCID50 assay method. An average Ct99.9 (concentration of disinfectant multiplied by the contact time to achieve a 99.9 % reduction of the target organism) of 176 mg*min/L monochloramine was determined. No significant difference in inactivation rate was observed between the dosed reclaimed water and phosphate buffered saline (PBS). These data indicate that monochloramine is an effective disinfectant for coronaviruses. They also indicate that the water matrix type did not significantly impact the disinfection efficacy of monochloramine against HCoV-229E in reclaimed wastewater compared to PBS.

New approach to multivariate statistical process control and its application to wastewater treatment process monitoring

This paper presents a new process monitoring and fault diagnosis approach based on a modified Multivariate Statistical Process Control (MSPC) and evaluates its applicability to municipal wastewater treatment process monitoring. A conventional MSPC based on Principal Component Analysis (PCA) is firstly adjusted to have an easy-to-understand user interface and then a new yet simplified decomposable diagnostic model is introduced. The developed user interface is designed to seamlessly connect MSPC to existing process monitoring system adopting the so-called trend graphs. The proposed diagnostic model is derived in a constructive way by aggregating small size models with one input or two inputs to improve tractability of the diagnostic model. The effectiveness of the modified MSPC is illustrated through some offline and on-line experiments by using a set of real multivariate process data at a municipal wastewater treatment plant.

Suppression of nitrite oxidizing bacteria by hydrogen peroxide for energy reduction in municipal wastewater treatment

This paper investigated the application of hydrogen peroxide (H2O2) for achieving partial nitrification in mainstream municipal wastewater treatment process. The investigation was carried out in both bench-scale and pilot-scale sequencing batch reactor systems using primary effluent as feed from municipal wastewater treatment plant. H2O2 played a dual role of: (1) inhibitor for nitrifying microorganisms, and (2) supplemental oxygen source. Bench scale studies were carried out at various doses of initial hydrogen peroxide concentrations (10,25,50,100 mg/L). It was found that at a concentration of 50 mg/L and above ammonia removal reduced by more than 80% implying significant impact on both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). After an acclimatization period of 18 days at a dose of 50 mg/L H2O2, complete nitrification was observed with about 30% nitrite accumulation in the effluent which showed NOBs were impacted more significantly than AOBs. It was also observed from the long-term pilot-scale study that the inhibitory impact on NOBs is almost double the impact of on AOBs which facilitated partial nitrification resulting a nitrite accumulation ratio up to 60% in the effluent at 2 mg/L DO and 15 days SRT.Peroxide dosing resulted in an energy savings of 12–15% compared to a control reactor. It was also shown that by reducing the DO from 2 to 1 mg/L, additional power saving of 15% is achievable. Therefore, the proposed approach is an efficient method for aeration energy savings and can be easily implemented in existing wastewater treatment plants.

Metabolic implications for predatory and parasitic bacterial lineages in activated sludge wastewater treatment systems

Deciphering unclear microbial interactions is key to improving biological wastewater treatment processes. Microbial predation and parasitism in wastewater treatment ecosystems are unexplored survival strategies that have long been known and have recently attracted attention because these interspecies interactions may contribute to the reduction of excess sludge. Here, microbial community profiling of 600 activated sludge samples taken from six industrial and one municipal wastewater treatment processes (WWTPs) was conducted. To identify the shared lineages in the WWTPs, the shared microbial constituents were defined as the family level taxa that had ≥ 0.1% average relative abundance and detected in all processes. The microbial community analysis assigned 106 families as the shared microbial constituents in the WWTPs. Correlation analysis showed that 98 of the 106 shared families were significantly correlated with total carbon (TC) and/or total nitrogen (TN) concentrations, suggesting that they may contribute to wastewater remediation. Most possible predatory or parasitic bacteria belonging to the phyla Bdellovibrionota, Myxococcota, and Candidatus Patescibacteria were found to be the shared families and negatively correlated with TC/TN; thus, they were frequently present in the WWTPs and could be involved in the removal of carbon/nitrogen derived from cell components. Shotgun metagenome-resolved metabolic reconstructions indicated that gene homologs associated with predation or parasitism are conserved in the Bdellovibrionota, Myxococcota, and Ca. Patescibacteria genomes (e.g., host interaction (hit) locus, Tad-like secretion complexes, and type IV pilus assembly proteins). This study provides insights into the complex microbial interactions potentially linked to the reduction of excess sludge biomass in these processes.

An Overview of Municipal Wastewater and Sludge Treatment Process

An Overview of Municipal Wastewater and Sludge Treatment Process

Converting sludge to slag through a high temperature slagging co-gasification process: An evaluation based on a demonstration trial and life cycle assessment

A variety of sludge-based waste materials with distinctive physical and chemical characteristics are co-treated with municipal solid waste (MSW) in a demonstration-scale high-temperature slagging gasifier. The waste materials tested include dewatered sewage sludge (originated from industrial and municipal wastewater treatment processes, respectively), dried sewage sludge, sludge incineration ashes, and waterworks sludge (originated from freshwater treatment process). Up to 49.5% by mass of dried sewage sludge is successfully co-gasified with MSW and up to 89.5% of the solid residues from the gasification process is recovered as reusable slag and recyclable metals. Despite feeding of various waste mixtures, stable operation of the slagging gasifier is achieved with the proper control of the temperature profiles inside the gasifier, the melting of inorganic residues, smooth discharge of the molten slag, and effective flue gas emissions control. Various types of waste-derived slag are characterized to evaluate their potentials to be applied as sustainable construction materials. Toxicity characteristic leaching procedure (TCLP) and compliance batch leaching test results indicate that the sludge-derived slag is environmentally safe with very low pollution potential. In addition, life cycle assessment (LCA) is performed to comprehensively evaluate the treatment of sludge-based waste materials via slagging co-gasification technology. These findings reveal the promising potentials of converting sludge to slag through the high temperature slagging gasification process based on both engineering and environmental aspects, as well as the possible areas for further advancement in the future.

Self-organizing modeling and control of activated sludge process based on fuzzy neural network

The wastewater treatment process contains multiple complex biochemical reactions featured by strong nonlinear and time-varying dynamics due to the built-in discontinuity and uncertainty. Herein, a self-organizing fuzzy neural network with an efficient scheme for parsimonious (SOFNN-ESP) was orchestrated to improve the self-organizing modeling of municipal wastewater treatment process by combing predictive algorithms to deal with the complex water treatment procedure. The SOFNN-ESP algorithm could identify sewage treatment plants by a high-throughput parameter screening system and recursive least square method in real-time, which provided dynamic setting feedback and promoted water quality. The integration of the SOFNN-ESP algorithm and a model predictive control (MPC) further improved the accuracy in water quality controlling via immediately adjusting weight parameters of the network. This gradient algorithm also realized the online dynamic tracking of dissolved oxygen and nitrate nitrogen level by simultaneous tracking of multiple performance indicators and optimizing setting values of the control variable. SOFNN-ESP-MPC gave an error of <5 % when the peak error of proportional integral differential controller was >10 %. Concerning the benchmark simulation model No.1 of municipal wastewater treatment, the SOFNN-ESP-MPC method exhibited a compact network structure and outstanding generalization performance. The self-organizing modeling and predictive control strategy proposed in this study could effectively improve the prediction accuracy and control efficiency of the activated sludge process model, which is of great significance for the efficiency improvement of sewage treatment process.

Co-Occurrence and Cooperation between Comammox and Anammox Bacteria in a Full-Scale Attached Growth Municipal Wastewater Treatment Process.

Cooperation between comammox and anammox bacteria for nitrogen removal has been recently reported in laboratory-scale systems, including synthetic community constructs; however, there are no reports of full-scale municipal wastewater treatment systems with such cooperation. Here, we report intrinsic and extant kinetics as well as genome-resolved community characterization of a full-scale integrated fixed film activated sludge (IFAS) system where comammox and anammox bacteria co-occur and appear to drive nitrogen loss. Intrinsic batch kinetic assays indicated that majority of the aerobic ammonia oxidation was driven by comammox bacteria (1.75 ± 0.08 mg-N/g TS-h) in the attached growth phase, with minimal contribution by ammonia-oxidizing bacteria. Interestingly, a portion of total inorganic nitrogen (∼8%) was consistently lost during these aerobic assays. Aerobic nitrite oxidation assays eliminated the possibility of denitrification as a cause of nitrogen loss, while anaerobic ammonia oxidation assays resulted in rates consistent with anammox stoichiometry. Full-scale experiments at different dissolved oxygen (DO = 2 - 6 mg/L) setpoints indicated persistent nitrogen loss that was partly sensitive to DO concentrations. Genome-resolved metagenomics confirmed the high abundance (relative abundance 6.53 ± 0.34%) of two Brocadia-like anammox populations, while comammox bacteria within the Ca. Nitrospira nitrosa cluster were lower in abundance (0.37 ± 0.03%) and Nitrosomonas-like ammonia oxidizers were even lower (0.12 ± 0.02%). Collectively, our study reports for the first time the co-occurrence and cooperation of comammox and anammox bacteria in a full-scale municipal wastewater treatment system.

Mechanical Properties and Water Resistance of Magnesium Oxychloride Cement–Solidified Residual Sludge

As a solid waste, the amount of residual sludge produced by the municipal wastewater treatment process is escalating. How to dispose it properly is attracting much attention in society. Herein, solidifying residual sludge using magnesium oxychloride cement (MOC) is promising for converting it into building materials. Various factors of mass ratio (RW/S) of liquid to solid, molar ratio (Rn) of MgO to MgCl2 in MOC, mass ratio (Rm) of residual sludge to MOC, the mass concentration of Na2SiO3 (DNa2SiO3), and dosage of fly ash (DF) influenced the unconfined compression strength (RC) of the as–obtained MOC–solidified residual sludge, and it was characterized using SEM and XRD analysis. The results show that the value of RC for MOC–residual sludge solidified blocks increased initially and then decreased as Rn and Rm increased, respectively, for 60–day curing. At 10–day curing, equilibrium RC was reached at all RW/S values except 1.38, and at 60–day curing, RC decreased with RW/S increasing. The maximum RC of 60 days of 20.90 MPa was obtained at RW/S = 0.90, Rn = 5.0, and Rm = 1.00. Furthermore, adding Na2SiO3 or fly ash in the solidifying process could improve RC. The water resistance test showed that SM13 and NF5 samples exhibited good alkaline resistance after immersion for 7 and 14 days in an aqueous solution with pH = 7.0–11.0. The water resistance of MOC–residual sludge solidified blocks decreased with increase in immersion duration in aqueous solutions. The fly ash could also help improve water resistance of MOC–solidified residual sludge in neutral and basic aqueous solutions. This work provides an important theoretical basis and possibility for the efficient disposal and comprehensive utilization of residual sludge through solidification/stabilization technology using MOC from the perspective of mechanics and water resistance.

The different units’ performance and bed length effect of constructed wetland on the removal of organic substances, solids and nutrients from municipal wastewater: a case study, Iran

This study investigated the overall performance and bed length effect of the horizontal subsurface flow constructed wetland (CW) process for full-scale municipal wastewater treatment. 168 samples were collected, including 84 samples in the hot and 84 in the cold season. Seven sampling points were selected as follows: (1) inlet raw wastewater, (2) effluent from an anaerobic pond, (3) from the first 5 m of the selected reed bed, (4) 5 m second, (5) 5 m third, (6) 5 m fourth, and (7) 5 m fifth from the reed bed. The evaluation parameters included biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP). The results showed that the removal efficiency for the BOD5, COD, TSS, TN, and TP was equal to 90.6%, 90.1%, 94%, 50.2%, and 35.4%, respectively. In the final treated effluent, the concentration of all studied parameters was less than the maximum allowable amount for discharge to the receiving water. The results showed that although the treatment plant’s pollution load for BOD5 and COD parameters in winter was significantly higher than in summer, the treatment plant efficiency in winter was not significantly different from summer. The results also showed that a 15-m bed in the CW system is suitable for achieving the standard of the environmental protection organization of Iran for municipal wastewater treatment in the hot season; however, it seems not to be enough in the cold season. So, 25 m of reed bed length will be required in practice. Finally, it can be concluded that the Qasr-e-Shirin wastewater treatment plant has the proper capability to remove municipal wastewater pollutants in different temperature conditions and the quality of the final effluent indicates the accuracy of the design criteria for this system.