Existing Wastewater Treatment Plants Research Articles

Shortcut nitrification and denitrification shed light on simultaneous removal of conventional contaminants and antibiotic resistance genes (ARGs)

The threats of emerging pollutants like antibiotic resistance genes (ARGs) in wastewater utilities are gaining growing attention. Based on the existing wastewater treatment process (WWTPs), especially in the biological treatment units, how to remove conventional pollutants and ARGs simultaneously and efficiently is very important. We noted that driving factors of ARGs reduction highly overlaps with that controlling shortcut nitrification and denitrification (e.g., pH, free ammonia (FA), and free nitrous acid (FNA)). This was statistically confirmed by a lab-scale and pilot-scale test. On this basis, we then propose shortcut nitrification and denitrification can be a potential approach, reducing ARGs and conventional contaminants efficiently and economically. This innovative concept may provide new opportunities for ARGs reduction, and possibly renovate the present tech-map of existing wastewater treatment plants (WWTPs).

Challenges and Recent Advances in Enzyme-Mediated Wastewater Remediation-A Review.

Different classes of artificial pollutants, collectively called emerging pollutants, are detected in various water bodies, including lakes, rivers, and seas. Multiple studies have shown the devastating effects these emerging pollutants can have on human and aquatic life. The main reason for these emerging pollutants in the aquatic environment is their incomplete removal in the existing wastewater treatment plants (WWTPs). Several additional treatments that could potentially supplement existing WWTPs to eliminate these pollutants include a range of physicochemical and biological methods. The use of enzymes, specifically, oxidoreductases, are increasingly being studied for their ability to degrade different classes of organic compounds. These enzymes have been immobilized on different supports to promote their adoption as a cost-effective and recyclable remediation approach. Unfortunately, some of these techniques have shown a negative effect on the enzyme, including denaturation and loss of catalytic activity. This review focuses on the major challenges facing researchers working on the immobilization of peroxidases and the recent progress that has been made in this area. It focuses on four major areas: (1) stability of enzymes upon immobilization, enzyme engineering, and evolution; (2) recyclability and reusability, including immobilization on membranes and solid supports; (3) cost associated with enzyme-based remediation; and (4) scaling-up and bioreactors.

Urban Wastewater Treatment in African Countries: Evidence from the Hydroaid Initiative

This study is based on the evidence collected during the “Technical e-Learning Course on Wastewater Treatment”, an international training project developed in 2020 in Italy by the Hydroaid Association, in collaboration with Turin Polytechnic. This work intended to address the sustainability of urban sanitation in various African countries, which the world of international cooperation has been looking at in recent years with growing interest. A comparative analysis of the current strategies and technological solutions was conducted. Data and information reported by the project participants were elaborated and verified. Four African countries—Benin, Egypt, Ethiopia, and Malawi—were considered and two relevant case studies among those proposed by the participants were presented. Starting from this analysis, significant elements about the status and coverage of wastewater management were extracted and reported. The analysis of existing wastewater treatment plants (WWTPs) allowed evaluating their design features and current status of operation. Considerations about the environmental, economic, social, and technical sustainability of wastewater treatment and management were finally reported. Conducting such an analysis provided support in identifying the best practices and the most recurrent problems linked to the various African contexts, which need to be considered for a complete definition of the planning strategy for accessible, efficient, and sustainable sanitation infrastructures.

Organic, nitrogen, and phosphorus removal in hospital wastewater treatment using activated sludge and constructed wetlands

Due to COVID-19 pandemic, hospital becomes the main and critical facility in any countries. This has also negatively affected the environment, as the wastewater discharged was also increased. Wastewater treatment plant in the hospital will also be affected as there will be fluctuations in volume and quality of wastewater. Hence there is an urgency to choose the appropriate technology as main solution and to improve existing wastewater treatment plant. We will report the performance of integrated system of activated sludge and constructed wetlands applied in a hospital wastewater treatment plant. Both technologies were chosen because they are simple, cheap, and highly effective technologies for wastewater treatment. Activated sludge was able to reduce organic, ammonia, and phosphat content significantly. However, the quality of effluent was still not able to meet the regulation. Application of constructed wetlands as finishing treatment was able to improve the quality of effluent to meet the standard and resulted in BOD, COD, ammonia, and phosphate of 25 mg/L, 24.18 mg/L, <0.01 mg/L, and 0.46 mg/L, respectively. Hence it can be concluded that the integration of activated sludge and constructed wetlands can be an appropriate and effortless treatment system for low-strength wastewater to meet a strict quality standard.

Ferrate (VI) as efficient oxidant for elimination of sulfamethazine in aqueous wastes: Real matrix implications

The presence of antibiotics in aquatic environments has become a serious concern since they develop the antibiotic/multi-drug-resistant bacteria which further affect to living beings. The study intended to assess the freshly synthesized ferrate (VI) in the degradation of an important emerging micro-pollutant i.e., sulfamethazine (SMZ). Moreover, the real matrix implications are extensively conducted for implication of ferrate (VI) technology as safer and viable options. Batch reactor studies enabled the molar ratio of ferrate (VI) to sulfamethazine is 2:1 with overall rate constant 6,128 mM-2.min-1. Percentage elimination of sulfamethazine was observed Ca. 80% at initial sulfamethazine concentration 0.02 mM and ferrate (VI) dose 0.1 mM. Presence of several co-ions NaCl, Na2HPO4, NaNO3, oxalic acid and NaNO2 showed insignificant effect on elimination of sulfamethazine; whereas the efficiency of ferrate (VI) was lowered due to glycine and EDTA. Mineralization of sulfamethazine is significantly increased at lower pH value (pH 5.0). Further, the removal of sulfamethazine in the real water matrix showed that the elimination efficiency of sulfamethazine is almost unaffected as compared to the distilled water treatment. This implied that ferrate (VI) is a viable and greener option for treatment of emerging water pollutants to enhance the efficiency of existing wastewater treatment plants.

Assessing socio-economic value of innovative materials recovery solutions validated in existing wastewater treatment plants

Cost benefit analysis (CBA) and social impact assessment are well established methodologies to systematically estimate the viability of investments on technologies as well as the benefits for the society. However, there is a limited application of these assessment methods in the wastewater sector especially for resource recovery to deliver circularity objectives within urban water cycle management. In this regard, the Horizon 2020 SMART-Plant Innovation Action aimed to evaluate holistic impacts of wastewater-based resource recovery by applying and adapting cost benefit and social analysis on innovative technologies (SMARTechs). The SMARTechs were implemented and validated in real wastewater treatment plants (WWTPs) across Europe and Mediterranean basin where potential impacts in terms of carbon, material and energy efficiency, recovery and safe reuse were defined. Sixteen bottom-up SMARTech scenarios were analysed for the estimation of technical, economic and social impacts using CBA, social life cycle assessment (S-LCA) and social readiness level (SRL) methods. Overall, the SMARTechs created benefits both from an environmental and social point of view, with a maximum relative total economic value up to +23% compared to baseline scenario (without any SMARTech implementation). In terms of social benefits, the S-LCA highlighted a global positive impact of all the SMARTechs in terms of technical characteristics and social acceptance. Specifically, SMARTech 1 (cellulose recovery) was the most socially accepted solution thanks to its high performance and simplicity. Finally, based on the SRL assessment, most of the SMARTechs were positioned within the SRL range of 6–7, which implies a good societal acceptance and adaptation potential.

Identifying wastewater management tradeoffs: Costs, nearshore water quality, and implications for marine coastal ecosystems in Kona, Hawai'i.

Untreated and minimally treated wastewater discharged into the environment have the potential to adversely affect groundwater dependent ecosystems and nearshore marine health. Addressing this issue requires a systems approach that links land use and wastewater management decisions to potential impacts on the nearshore marine environment via changes in water quality and quantity. To that end, a framework was developed to assess decisions that have cascading effects across multiple elements of the ridge-to-reef system. In an application to Kona (Hawai'i, USA), eight land use and wastewater management scenarios were evaluated in terms of wastewater system upgrade costs and wastewater related nutrient loads in groundwater, which eventually discharge to nearshore waters, resulting in potential impacts to marine habitat quality. Without any upgrades of cesspools or the existing wastewater treatment plant (WWTP), discharges of nutrients are expected to increase substantially with permitted development, with potential detrimental impacts to the marine environment. Results suggest that converting all of the existing cesspools to aerobic treatment units (ATU) and upgrading the existing WWTP to R-1 quality provide the highest protection to nearshore marine habitat at a cost of $569 million in present value terms. Other wastewater management options were less effective but also less costly. For example, targeted cesspool conversion (a combination of septic and ATU installation) in conjunction with the WWTP upgrade still provided a substantial reduction in nutrients and potential impacts to marine habitat quality relative to the present situation at a price point roughly $100 million less than the entirely ATU option. Of note, results were more sensitive to the inclusion of the WWTP upgrade option than they were to assumptions regarding the efficiency of the cesspool conversion technologies. The model outputs also suggest that the spatial distribution of potential impacts should be carefully considered when comparing different wastewater management scenarios. When evaluated separately, the WWTP option reduced total nutrients by more than the targeted cesspool conversion option at a fraction of the cost. However, potential improvements in marine habitat quality only occurred in the immediate vicinity of the WWTP, whereas the benefits under targeted cesspool conversion were more evenly distributed along the coast.

From wastewater treatment to water resource recovery: Environmental and economic impacts of full-scale implementation

To reduce greenhouse gas emissions and promote resource recovery, many wastewater treatment operators are retrofitting existing plants to implement new technologies for energy, nutrient and carbon recovery.In literature, there is a lack of studies that can unfold the potential environmental and economic impacts of the transition that wastewater utilities are undertaking to transform their treatment plants to water resource recovery facilities (WRRFs). When existing, literature studies are mostly based on simulations rather than real plant data and pilot-scale results. This study combines life cycle assessment and economic evaluations to quantify the environmental and economic impacts of retrofitting an existing wastewater treatment plant (WWTP), which already implements energy recovery, into a full-scale WRRF with a series of novel technologies, the majority of which are already implemented full-scale or tested through pilot-scales. We evaluate five technology alternatives against the current performance of the WWTP: real-time N2O control, biological biogas upgrading coupled with power-to-hydrogen, phosphorus recovery, pre-filtration carbon harvest and enhanced nitrogen removal. Our results show that real-time N2O control, biological biogas upgrading and pre-filtration lead to a decrease in climate change and fossil resource depletion impacts. The implementation of the real-time measurement and control of N2O achieved the highest reduction in direct CO2-eq emissions (-35%), with no significant impacts in other environmental categories. Biological biogas upgrading contributed to counterbalancing direct and indirect climate change impacts by substituting natural gas consumption and production. Pre-filtration increased climate change reduction by 13%, while it increased impacts in other categories. Enhanced sidestream nitrogen removal increased climate change impacts by 12%, but decreased marine eutrophication impacts by 14%. The reserve base resource depletion impacts, however, were the highest in the plant configurations implementing biological biogas upgrading coupled with power-to-hydrogen. Environmental improvements generated economic costs for all alternatives except for real-time N2O control. The results expose possible environmental and economic trade-offs and hotspots of the journey that large wastewater treatment plants will undertake in transitioning into resource recovery facilities in the coming years.

Application of Biological and Chemical Processes to Wastewater Treatment

Existing wastewater treatment plants (WWTPs) face huge challenges that can impede the achievement of sustainable development goals for clean water and sanitation (SDG 6) and clean energy (SDG 7), amongst others [...]

Microbial Fuel Cell Technology—A Critical Review on Scale-Up Issues

Microbial fuel cell (MFC) technology has attracted a great amount of attention due to its potential for organic and inorganic waste treatment concomitant with power generation. It is thus seen as a clean energy alternative. Modifications and innovations have been conducted on standalone and hybrid/coupled MFC systems to improve the power output to meet the end goal, namely, commercialization and implementation into existing wastewater treatment plants. As the energy generated is inversely proportional to the size of the reactor, the stacking method has been proven to boost the power output from MFC. In recent years, stacked or scale-up MFCs have also been used as a power source to provide off-grid energy, as well as for in situ assessments. These scale-up studies, however, encountered various challenges, such as cell voltage reversal. This review paper explores recent scale-up studies, identifies trends and challenges, and provides a framework for current and future research.

Enhancement of biological nutrient removal process with advanced process control tools in full-scale wastewater treatment plant

One of the major challenges in existing WasteWater Treatment Plants (WWTPs) is to comply with the increasingly stringent nutrient discharge limits established by the competent authorities to enhance environmental protection, while keeping operation costs as low as possible. This paper describes the results obtained from upgrading a full-scale WWTP during seven years (2013–2020) applying five different Advanced Process Control (APC) strategies. Results show that implementation of APC and the development of ammonia-based aeration control, aeration/non-aeration cycles, improved internal/external recirculation and chemical dosage controls resulted in an improvement in nutrients removal rates (+25.48% and +9.25%, for nitrogen and phosphorus, respectively) and in a reduction (-21.79%) of the specific energy ratio. In addition, the promotion of an Enhanced Biological Phosphorous Removal (EBPR) process by APC resulted in an improvement in biological phosphorous removal (+43.90%), chemical savings (-20.00%) and nutrient recovery in the dewatered sludge. Molecular biology tools and laboratory batch tests confirmed the Polyphosphate Accumulating Organisms (PAOs) activity, specifically Tetrasphaera genera. Finally, an economic analysis was conducted, showing a rate of return for the incurred capital expenses with the implemented APC systems of about five years, being an affordable alternative to the upgrading existing WWTPs.

Investigation of operational parameters for retaining properties of micro-plastics for typical aerobic wastewater treatment unit

Given the large number of existing wastewater treatment plants (WWTPs), this paper investigates the effects of routine operational factors on retaining the properties of the microplastics (MPs) of a typical aerobic bioreactor, which is widely adopted in both municipal and industrial WWTPs. The three most detected plastics, namely, polyethylene, polypropylene, and polyvinyl chloride, are pulverized and injected into an anoxic–oxic configured laboratory facility to explore the size distribution and removal efficiency of the MPs in the effluent. A laser particle analyzer is used for the continuous particle size distribution testing, which indicates that nearly all the particles whose diameters exceed 35 μm are retained. This phenomenon poses a threat to mammal health for particles less than 20 μm in diameter that dominate the effluent’s abundance. Comprehensive discussions and comparisons with existing works in terms of how the three operational factors affect the bioreactor’s retaining properties significantly are presented. The moderate mixed liquor suspended solids and short hydraulic retention time of the bioreactor are beneficial to the MPs removal based on the in-depth analysis of variance of the limited experiment runs. Furthermore, the sludge in the bioreactor renders an adsorption–desorption pathway in retaining the MPs.

Current status of textile wastewater management practices and effluent characteristics in Tanzania.

Textile wastewater from wet processing units is a major environmental problem. Most chemicals, including dyes, are only partly consumed, resulting in highly colored wastewater containing a variety of chemicals released into the environment. This paper gives information on the current management of textile wastewater in Tanzania. A semiquantitative analysis was done to identify the main types of chemicals used in wet processing units, wastewater characteristics and existing wastewater treatment methods in the textile industry. The performance evaluation of the existing wastewater treatment plants is also discussed. The advantages of integrating constructed wetlands with the existing treatment facilities for textile wastewater are explained. It has been observed that pretreatment and dying/printing of the fabrics are the main two processes that produce wastewater in many textile companies. Main pollutants are chemicals used from pretreatment and materials removed from de-sizing, bleaching and scouring processes. Dyes, printing pigments and dye auxiliaries are the main pollutants from the dyeing/printing process. Most of the textile companies in Tanzania are equipped with effluent treatment plants. Wastewater treatment plants have basically similar units, which are coagulation-flocculation, sedimentation through clarifiers and aerobic reactor. However, their effluents do not meet discharge limits stipulated by the Tanzania Bureau of Standards (TBS).

Magnetic poly(acrylic acid)-based hydrogels for rapid ammonium sorption and efficient sorbent separation from sewage

Ammonium sorption and recovery processes typically take place in conventional packed columns, with a configuration that enables maximum sorption by the sorbents. However, batch or semi-continuous operations in packed columns have associated issues such as scaling and frequent backwashing requirements, which are economically prohibitive. As an alternative, ammonium sorption could occur in well-mixed continuously stirred tanks, which would allow for the ammonium sorption process to be retrofitted in existing wastewater treatment plants, provided that efficient sorbent separation can be achieved. This study demonstrates, for the first time, the preparation of magnetic poly(acrylic acid)-based (PAA) ammonium sorbents through the incorporation of magnetic (Fe3O4) nanoparticles (MNP) produced via scalable and cost-effective electrochemical synthesis. The MNP and PAA hydrogels were synthesized independently and the MNPs subsequently integrated into the PAA hydrogel network by particle diffusion and physical entrapment. No adverse effects on swelling and ammonium sorption following immersion in either synthetic or real sewage were observed after MNPs were incorporated into the hydrogels. Importantly, PAA-MNP hydrogels demonstrated high ammonium sorption efficiencies (80–93%) in real sewage and achieved rapid ammonium recovery of 73 ± 1.1% within 15 min of mild acid washing (pH 4) 15 min at a maximum recovery.

Direct membrane filtration (DMF) for recovery of organic matter in municipal wastewater using small amounts of chemicals and energy

The recovery and utilization of organic matter in municipal wastewater are essential for the establishment of a sustainable society, such that these factors have drawn significant recent attention. The up-concentration of organic matter via direct membrane filtration (DMF), followed by anaerobic digestion, is advantageous over the treatment of the entire wastewater by an anaerobic process, such as an anaerobic membrane bioreactor (AnMBR). However, the occurrence of severe membrane fouling in the DMF is a problem. In this study, DMF was carried out at an existing wastewater treatment plant to attempt long-term operation. A combination of vibration of membrane modules, short-term aeration, and chemically enhanced backwash (CEB), with multiple chemicals (i.e., the alternative use of citric acid and NaClO), was found to be effective for the mitigation of membrane fouling in DMF. Furthermore, switching the feed from influents to effluents in the primary sedimentation basin significantly mitigated membrane fouling. In this study, in which microfiltration membrane, with a nominal pore size of 0.1 μm, was used, ∼75% of the organic matter in raw wastewater was recovered, with the volumetric concentration of wastewater by 50- or 150-fold. Organic matter recovered by DMF had significantly higher potentials for biogas production than the excess sludge generated from the same wastewater treatment plant. An analysis of the energy balance (i.e., the energy used for DMF and recovered by DMF) suggests that the proposed DMF can produce a net-positive amount of electricity of ∼0.3 kWh from 1 m3 of raw wastewater with a typical strength (chemical oxygen demand of 500 mg/L).

Bio-Hydrogen Production from Wastewater: A Comparative Study of Low Energy Intensive Production Processes

Billions of litres of wastewater are produced daily from domestic and industrial areas, and whilst wastewater is often perceived as a problem, it has the potential to be viewed as a rich source for resources and energy. Wastewater contains between four and five times more energy than is required to treat it, and is a potential source of bio-hydrogen—a clean energy vector, a feedstock chemical and a fuel, widely recognised to have a role in the decarbonisation of the future energy system. This paper investigates sustainable, low-energy intensive routes for hydrogen production from wastewater, critically analysing five technologies, namely photo-fermentation, dark fermentation, photocatalysis, microbial photo electrochemical processes and microbial electrolysis cells (MECs). The paper compares key parameters influencing H2 production yield, such as pH, temperature and reactor design, summarises the state of the art in each area, and highlights the scale-up technical challenges. In addition to H2 production, these processes can be used for partial wastewater remediation, providing at least 45% reduction in chemical oxygen demand (COD), and are suitable for integration into existing wastewater treatment plants. Key advancements in lab-based research are included, highlighting the potential for each technology to contribute to the development of clean energy. Whilst there have been efforts to scale dark fermentation, electro and photo chemical technologies are still at the early stages of development (Technology Readiness Levels below 4); therefore, pilot plants and demonstrators sited at wastewater treatment facilities are needed to assess commercial viability. As such, a multidisciplinary approach is needed to overcome the current barriers to implementation, integrating expertise in engineering, chemistry and microbiology with the commercial experience of both water and energy sectors. The review concludes by highlighting MECs as a promising technology, due to excellent system modularity, good hydrogen yield (3.6–7.9 L/L/d from synthetic wastewater) and the potential to remove up to 80% COD from influent streams.

Evaluation of the available strategies to control the emission of microplastics into the aquatic environment.

No effective strategy has been found so far to control the emission of microplastics. The purpose of this article is to review the available control strategies, as well as barriers to developing them. Based on the estimations in the available literature, decomposition of larger plastics, clothes washing and tire abrasion play an essential part in the total emission rate of microplastics into the ocean. Nonetheless, there is no corresponding information regarding the soil, and more information is needed to prioritize the emission sources of microplastics more preciously. Generally, there have been two approaches for the management of the microplastic issues, including the substitution of non-plastic materials for plastic ones in products such as personal care products, and microplastic removal from wastewater. The former is in its infancy and has commenced only in a few developed countries. Existing wastewater treatment plants (WWTPs) as the other approach can transfer a significant portion of the microplastics into the sludge. The result is that the final destination of these microplastics can be the soil. Since there is little information on how serious the impact of microplastics is on the soil as compared with water, the currently used WWTPs cannot be considered as a final remedy. Furthermore, there has been not been any specifically designed techniques to remove microplastics from wastewater efficiently and economically.

Sludge reduction by an anaerobic side-stream reactor process: A full-scale application

In the present paper, a new process, whose acronym is UTN (University of Trento) system, is proposed and tested at full scale for reducing the amount of sludge of the wastewater treatment plant. The UTN system allows sludge reduction in conventional activated sludge (CAS) due to the cell lysis, the sludge decay and, above all, to the selection of slow growing microorganism. In this study, the first full-scale UTN system was tested by retrofitting an existing wastewater treatment plant located in Marmirolo (Lombardia, Italy) having a treatment capacity of 6,000 population equivalent (PE). Performances of the UTN system were evaluated in terms of sludge reduction, together with organic carbon and nutrients removal efficiencies. Results obtained over 10 month of monitoring period, divided in period I (7 months) and period II (3 months), characterized by different operative conditions, have reported a specific sludge production of 0.37 and 0.23 kg TSS per kg of COD removed, respectively; which is 50% and 69% lower than that observed in the reference period when the plant worked under conventional activated sludge process. Furthermore, results revealed that the UTN system allows a high removal of wastewater typical pollutants, without causing negative effects on the effluent quality, always ensuring compliance with the regulatory discharge limits.

Resource Recovery Potential of Wastewater Treatment Plants in Yogyakarta

Wastewater contains water, nutrients, and energy resources, which can be recovered for human activities. Product from wastewater is one of the solutions to provide energy and food security amidst the looming energy and fertilizer crisis. Unfortunately, wastewater treatment plants in developing countries are often designed not to accommodate the concept of resource recovery. Currently, there is a real lack of feasibility analysis of upgrading existing wastewater treatment plants to accommodate the concept of resource recovery. Therefore, this study aims to determine the resource recovery potential in existing wastewater treatment plants in Yogyakarta and identify their limitations for resource recovery. Two wastewater treatment plants in Yogyakarta were assessed, one with anaerobic treatment, the other with stabilization ponds. The feasibility is assessed by the parameter of wastewater flow, organics, nutrients, and microbiology compounds. The findings of this study will be beneficial for a regional management standpoint to consider the most suitable strategy for wastewater management in Yogyakarta.

Iron-enhanced primary sedimentation and acidogenic sludge fermentation to achieve self-sufficient organic carbon supply for enhanced nutrient removal in wastewater treatment✰

To treat municipal wastewater with a low carbon to nitrogen ratio, the addition of an external carbon source is often needed to achieve enhanced nutrient (nitrogen and phosphorus) removal. To meet this need, this research developed an innovative strategy for reserving and utilizing organic pollutants to achieve a self-sufficient organic carbon supply for wastewater treatment. In the new system, before biological treatment by a sequencing batch reactor (SBR), Fe-based chemically enhanced primary sedimentation (CEPS) was used to reserve part of the organics from the wastewater in the CEPS sludge. By acidogenic fermentation in the side-stream, the settled organics in the CEPS sludge were converted into volatile fatty acids and other soluble organics to provide a suitable carbon source for denitrification in the anoxic phase of the SBR. The experimental results showed that the new SBR system integrated with CEPS and acidogenic sludge fermentation removed up to 89% of the total phosphorus (TP) and 83% of the total nitrogen (TN) from the wastewater. Compared with the conventional SBR system, TP and TN removal was increased by more than 65% and 50%, respectively. As well as increasing nutrient removal efficiency without the need for external carbon addition, the Fe-based CEPS greatly reduced the organic load on the SBR biological treatment process, reducing the aeration cost. Overall, a cost-effective wastewater treatment process is developed that can be used to upgrade existing wastewater treatment plants to improve the nutrient removal performance and meet more stringent discharge standards.