Papers by Veera Gnaneswar Gude
Water Environment Research, 2020
This article presents an update on the research and practical demonstration of wetland-based trea... more This article presents an update on the research and practical demonstration of wetland-based treatment technologies for protecting water resources and environment covering papers published in 2019. Wetland applications in wastewater treatment, stormwater management, and removal of nutrients, metals, and emerging pollutants including pathogens are highlighted. A summary of studies focusing on the effects of vegetation, wetland design and operation strategies, and process configurations and modeling, for efficient treatment of various municipal and industrial wastewaters, is included. In addition, hybrid and innovative processes with wetlands as a platform treatment technology are presented.
AQUA — Water Infrastructure, Ecosystems and Society, 2021
This article presents the evolving challenges and roles of our water resources in this contempora... more This article presents the evolving challenges and roles of our water resources in this contemporary world. First, water quality issues surrounding water supplies are discussed. Potential pathways to address the water quality challenges are presented, which include technological approaches for minimizing waste and enhancing resource recovery. Focused discussions on emerging global pollutants such as microplastics and PFAS (per-and poly-fluoro alkyl substances) and treatment alternatives are included. Next, the roles of used water (wastewater) in the wake of circular economy and recent outbreaks are discussed. The potential for energy and resource recovery possibilities and the critical role of wastewater treatment plants in controlling the spread of outbreaks are discussed in detail. Finally, perspectives on some of the key developments essential for transforming our water infrastructure, addressing water-centered socioeconomic issues and the critical needs of digitalization in water sector operations are presented.
ACS Omega, 2021
Aging infrastructure, increasing environmental regulations, and receiving water environment issue... more Aging infrastructure, increasing environmental regulations, and receiving water environment issues stem the need for advanced wastewater treatment processes across the world. Advanced wastewater treatment systems treat wastewater beyond organic carbon removal and aim to remove nutrients and recover valuable products. While the removal of major nutrients (carbon, nitrogen, and phosphorus) is essential for environmental protection, this can only be achieved through energy-, chemical-, and cost-intensive processes in the industry today, which is an unsustainable trend, considering the global population growth and rapid urbanization. Two major routes for developing more sustainable and circular-economy-based wastewater treatment systems would be to (a) innovate and integrate energy-and resource-efficient anaerobic wastewater treatment systems and (b) enhance carbon capture to be diverted to energy recovery schemes. This Mini-Review provides a critical evaluation and perspective of two potential process routes that enable this transition. These process routes include a bioelectrochemical energy recovery scheme and codigestion of organic sludge for biogas generation in anaerobic digesters. From the analysis, it is imperative that integrating both concepts may even result in more energy-and resource-efficient wastewater treatment systems.
Cleaner Engineering and Technology, 2021
Population growth, economic development, groundwater impairment due to salt water intrusion and l... more Population growth, economic development, groundwater impairment due to salt water intrusion and local vulnerabilities caused by rising sea levels prompt immediate necessity for customized adaptation strategies for the cities of Homestead and Miami in Florida. This paper presents a feasibility study of nuclear energy driven cogeneration plant for water and power production in Homestead, FL. Miami-Dade and Homestead, Florida is home to the Turkey Point Nuclear Generating Facility. The focus of this study is to investigate the economic feasibility of a seawater desalination facility on the site of an existing nuclear generating plant. While the cost of seawater desalination is often too great to overcome, it is hypothesized that sharing the infrastructure and processes with a power generating facility will lower the cost of producing freshwater. The analysis was completed with the aid of the desalination modeling software, DEEP. First, we estimate the population growth and water demands for Homestead, FL and then identify a suitable water desalination plant configuration based on freshwater and power production costs. We then compare cogeneration (water and power) schemes based on different energy sources and desalination technologies. The energy sources considered are nuclear energy, oil and natural gas for steam turbine and combined cycle power plants. In addition, we evaluate the water and power production costs for hybrid desalination configurations. Finally, the freshwater costs through nuclear desalination were assessed with other options and conventional ground water system costs. Environmental emissions saved through nuclear desalination and the need for considering this option despite the high costs are discussed in detail. The study concluded that reverse osmosis desalination plant powered by nuclear energy produced water at the lowest cost which is still three times the cost of current water rates in Homestead, Florida.
Water Environment Research, 2019
This article presents an update on the research and practical demonstration of wetland treatment ... more This article presents an update on the research and practical demonstration of wetland treatment technologies for wastewater treatment. Applications of wetlands in wastewater treatment (as an advanced treatment unit or a decentralized system) and stormwater management or treatment for nutrient and pollutant removal (met-als, industrial and emerging pollutants including pharmaceutical compounds and pathogens) are highlighted. A summary of studies involving the effects of vegetation , wetland design and operation, and configurations for efficient treatment of various municipal and industrial wastewaters is also included. © 2019 Water Environment Federation • Practitioner points • Provides an update on current research and development of wetland technologies for wastewater treatment. • Effects of vegetation, pathogens removal, heavy metals and emerging pollutants removal are included. • Wetland design and operation is a key factor to improve water quality of wetland effluent. Wetlands for Wastewater Treatment Constructed wetlands (CWs) mimic the simultaneous physical, chemical, and biological processes occurring in natural wetlands for wastewater treatment purposes (Wu et al., 2018). This section summarizes studies performed on the use of CWs for water and wastewater treatment to remove a variety of pollutants. For instance, Ali, Rousseau, and Ahmed (2018) monitored a full-scale hybrid CW system treating domestic wastewater under batch and continuous-flow conditions. Maximum removal efficiencies of 80 and 78%, 81 and 82%, 63 and 69%, and 79 and 89% were reported for chemical oxygen demand (COD), biological oxygen demand (BOD), total Kjeldahl nitrogen (TKN), and total suspended solids (TSS) for batch and continuous systems, respectively. Yadav, Chazarenc, and Mutnuri (2018) studied a two-stage VFCW system to treat single household raw wastewater under tropical climate. The removal efficiencies for COD, BOD, TKN, ammoniacal nitrogen (NH 3-N), total phosphorus (TP), total dissolved solid (TDS), and total volatile solids (TVS) in the 1st stage were 64%, 65%, 15%, 21%, 34%, and 54%, respectively, and those in the second stage reactor were 90%, 88%, 50%, 52%, 58%, and 71%, respectively. Moreover, a case-study (Riggio et al., 2018) has demonstrated that CWs can be a cost-effective option when compared to a traditional treatment process for wastewater reuse. The performance of CWs for wastewater treatment has been improved when combined with other technologies. For example, Corbella and Puigagut (2018) studied CWs as microbial fuel cells for improving treatment efficiency and energy generation. Gravel-based anode MFCs operated under closed-circuit mode produced ca. 18%, 15%, 31%, and 25% lower effluent concentrations of COD, TOC, PO 3− 4 , and
International Journal of Energy Research, 2019
Ballast water management is a national and international issue in the shipping industry because o... more Ballast water management is a national and international issue in the shipping industry because of potential ecological hazards caused by release of ballast water into the marine environment. Although many international standards have been implemented in recent years, technological and practical considerations make the ballast water treatment a major challenge for many shipping companies. In this paper, a novel concept of utilizing ballast water as source water for a multieffect desalination process driven by onboard waste heat to
meet the freshwater supply needs is proposed with theoretical analysis and practical considerations. A main engine capacity of 7500 kW in a cruise ship can serve as a potential waste heat source to be tapped for water desalination of 1000 m3/d, which can provide for freshwater needs of 2000 to 4000 ship occupants. This scenario presents as an attractive alternative to ballast water treatment as well as reducing the nonrenewable energy footprint of onboard water supplies in marine industry.
Scientific Reports, 2019
this study reports an investigation of the concept, application and performance of a novel bioele... more this study reports an investigation of the concept, application and performance of a novel bioelectrochemical nitritation-anammox microbial desalination cell (MDC) for resource-efficient wastewater treatment and desalination. Two configurations of anammox MDCs (anaerobic-anammox cathode MDC (AnA mox MDC) and nitration-anammox cathode MDC (NiA mox MDC)) were compared with an air cathode MDC (CMDC), operated in fed-batch mode. Results from this study showed that the maximum power density produced by NiA mox MDC (1,007 mW/m 3) was higher than that of AnA mox MDC (444 mW/m 3) and CMDC (952 mW/m 3). More than 92% of ammonium-nitrogen (NH 4 +-N) removal was achieved in NiA mox MDC, significantly higher than AnA mox MDC (84%) and CMDC (77%). The NiA mox MDC performed better than CMDC and AnA mox MDC in terms of power density, CoD removal and salt removal in desalination chamber. In addition, cyclic voltammetry analysis of anammox cathode showed a redox peak centered at −140 mV Vs Ag/AgCl confirming the catalytic activity of anammox bacteria towards the electron transfer process. Further, net energy balance of the NiA mox MDC was the highest (NiA mox MDC-0.022 kWh/m 3 >CMDC-0.019 kWh/m 3 >AnA mox MDC-0.021 kWh/m 3) among the three configurations. This study demonstrated, for the first time, a N-E-W synergy for resource-efficient wastewater treatment using nitritation-anammox process. Water and wastewater infrastructure accounts for approximately 3-4 percent of national energy demand in the United States 1. More than 50 percent of the supplied energy is used to meet the aeration demands for carbon and nitrogen oxidation processes in wastewater treatment 2. This particular energy demand is anticipated to increase significantly in the near future as many wastewater treatment plants aim to meet the USEPA's strict regulations for nitrogen discharge (1.0 mg/L ammonium nitrogen for discharge to surface water and 10 mg/L total nitrogen (TN) for discharge to soil 1). Current treatment schemes utilize autotrophic nitrification followed by heterotrophic denitrification techniques for nitrogen removal, adding significant demands for aeration energy and supplemental carbon. There is a growing interest to develop energy-positive and resource-efficient processes that minimize energy consumption in conventional processes and nitritation-anammox process is considered as one of the most promising alternatives to conventional biological nitrogen removal process 3. The scientific rationale for the proposed nitritation-anammox process stems from the anammox reaction sto-ichiometry shown in Reaction R1. Strous et al. 4 described the physical purification of anammox bacteria, which oxidize ammonium to nitrogen gas anaerobically, with nitrite (NO 2 −) as an electron acceptor and fixed carbon from CO 2 as a sole carbon source for the growth of anammox biomass (CH 2 O 0.5 N 0.15), making the organism an autotroph (see reaction R1). 1NH 132NO 0066HCO 0 13H 0 26 NO 0 06CH O N 203H O 1 02N (R1) 4 2 3 3 2 0 5 0 15 2 2 +. +. +. →. +. +. +. + − − + −. . This anaerobic oxidation reaction is thermodynamically more favorable than the aerobic ammonia oxidation reaction. The reported Gibb's free energy value for the anammox process is −358 kJ mol −1 NH 4 + 5 , which is higher than the aerobic ammonia oxidation process (ΔG = −235 kJ mol −1 NH 4 +) 6. The oxidation of ammonium
Engineering in Life Sciences, 2020
In this research, low strength synthetic wastewaters with chemical oxygen demand less than 300 mg... more In this research, low strength synthetic wastewaters with chemical oxygen demand less than 300 mg L −1 were treated at different concentrations in a bioelectrochemical desalination process. A process optimization model was utilized to study the performance of the photosynthetic bioelectrochemical desalination process. The variables include substrate (chemical oxygen demand) concentration, total dissolved solids, and microalgae biomass concentration in the cathode chamber. Relationships between the chemical oxygen demand concentration, microalgae, and salt concentrations were evaluated. Power densities and potential energy benefits from microalgal biomass growth were discussed. The results from this study demonstrated the reliability and reproducibility of the photosynthetic microbial desalination process performance followed by a response surface methodology optimization. This study also confirms the suitability of bioelectrochemical desalination process for treating low substrate wastewaters such as agricultural wastewaters, anaerobic digester effluents, and septic tank effluents for net energy production and water desalination.
Progress in Energy, 2020
Desalination technologies and industry have advanced significantly in the past two decades to mee... more Desalination technologies and industry have advanced significantly in the past two decades to meet the growing freshwater demands stimulated by the compounding issues of both water quality and quantity in many regions of the world. As desalination processes are energy demanding, there have been many efforts dedicated to improve energy-efficiency of the process units, enhance energy conservation and recovery, and increase renewable energy integration in desalination plants. This perspective article highlights recent key advances and discusses possible venues for further development in desalination energy portfolio to reduce specific energy consumption and, via integration with solar energy, to minimize the environmental footprint associated with freshwater production. First, an overview of current desalination technologies and their energy requirements are presented followed by a discussion on opportunities for improving energy efficiency and energy recovery in both membrane and thermal desalination technologies. Then, various combinations of renewable energy driven desalination plants are discussed with some recent highlights in solar energy driven membrane, thermal and hybrid desalination processes. Technological readiness levels for novel desalination processes, their perceived impact and expected near-future developments in renewable energy integrated desalination technologies are presented. Finally, the potential for solar driven desalination as a cost-competitive freshwater supply alternative is discussed.
International Journal of Environmental Research, 2020
Achieving energy self-sufficiency is critical for wastewater treatment plants (WWTPs) to comply w... more Achieving energy self-sufficiency is critical for wastewater treatment plants (WWTPs) to comply with rapidly changing
environmental regulatory standards in a sustainable manner. Currently, a small percentage of WWTPs around the world
produce energy for beneficial use and only a handful of these plants are energy self-sufficient. We propose three energypositive
wastewater treatment schemes and use quantitative analysis to assess their potentials for carbon and nitrogen
removal and energy generation from municipal wastewater. This research identifies potential challenges in the selection
and implementation of energy recovery process configurations and proposes practically feasible energy-positive wastewater
treatment process configurations. Energy self-sufficiency can be achieved through biogas production while simultaneously
minimizing the energy consumption for treatment. Furthermore, energy recovery can be enhanced in the near future (i) by
increasing the COD capture in primary treatment to enhance energy production; (ii) by replacing activated sludge process
with other less energy-intensive biological treatment technologies; and (iii) by increasing energy production from digesting
supplementary feedstock in anaerobic codigestion (AD) schemes. This paper presents a quantitative analysis of three process
schemes that progressively build upon the concept of transforming the conventional activated sludge wastewater treatment
plants (CAS-WWTP) into energy self-sufficient wastewater treatment facilities. These schemes also include a hypothetical
but practically feasible WWTP configuration, which represents an alternative energy self-sufficient wastewater process
scheme for future designs.
Photosynthetic microbial desalination cells (PMDCs) using microalgae biocathode (Chlorella vulgar... more Photosynthetic microbial desalination cells (PMDCs) using microalgae biocathode (Chlorella vulgaris species) were evaluated under three different process configurations. Static (fed-batch, SPMDC), continuous flow (CFPMDC) and a photo-bioreactor MDC (PBMDC), were developed to study the impact of process operation and design on wastewater treatment, water deionization, electricity generation, nutrient removal, and biomass production capacities. The effect of TDS concentration in desalination compartment on the overall performance of SPMDC was also studied. TDS and COD removal rates and power densities have increased with increase in TDS concentrations in the desalination compartment. TDS removal rates were 21.4%, 29%, and 32.2% with corresponding COD removal of 58%, 63%, and 64% at 5 g/L, 20 g/L and 35 g/L respectively. The power densities at these TDS concentrations were 285 mW/m 3 , 550 mW/m 3 and 675 mW/m 3 respectively in SPMDCs. Although the electricity production was lower, a higher biomass growth rate of 7 mg L À1 h À1 was recorded for CFPMDC. The COD removal and nutrient removal potentials were similar in all three experimental configurations. Experimental studies show that SPMDCs are more appropriate for bioelectricity production due to biofilm formation while the continuous flow or photobioreactor PMDCs are suitable for microalgae biomass production.
The act of ensuring freshwater is considered
the most essential and basic need for humanity.
Alth... more The act of ensuring freshwater is considered
the most essential and basic need for humanity.
Although the planet is water-rich in some terms, the
freshwater sources available for human consumption
and beneficial uses are very limited. Excess population
growth, industrial development coupled with improving
living standards have caused an unprecedented
need for freshwater all over the world. Regions once
rich in water resources are struggling to meet the ever
increasing demands in recent years. In addition,
climate change and unsustainable management practices
have led to a situation called ‘‘drought’’ in many
regions. Water supplies in drought conditions can be
addressed by taking two major approaches related to
management and technology development. The management
approaches include demand mitigation and
supply enhancement. Demand mitigation can be done
by implementing water conservation practices, and by
enforcing a mechanism to influence user-responsible
behavior through higher water fares and other billing
routes. Supply enhancement can be achieved by
utilizing the methods available for water reclamation,
reuse and recycle including rain harvesting. This paper
provides a critical insight of the causes for drought and
the issues caused by persistent drought conditions
followed by discussion of management and technological
approaches required to maintain adequate
water resources around the world. Challenges and
opportunities involved in implementation of desalination
and water reuse technologies in addressing global
water scarcity are discussed in detail with case studies
The synergistic effect of microwave and ultrasound irradiations was evaluated for biodiesel produ... more The synergistic effect of microwave and ultrasound irradiations was evaluated for biodiesel production from microalgae biomass (Nannochloropsis sp.) as raw material. A response surface methodology technique based on central composite design was used to understand the process parametric interdependence and optimize the process reaction variables. Reaction kinetics of algal fatty acid methyl ester (FAME) production was also studied. The optimum reaction conditions were determined as wet algal biomass to methanol ratio of 20 g to 30 mL, 1 wt% catalyst concentration, and 7‐minute reaction time at 140 W of microwave power and 140 W of ultrasound power. The estimated activation energy was 17,298 J/mol −1 K −1 for a first‐order reaction kinetics. This study revealed that microwave energy dissipation at a low rate of 140 W combined with 140 W of ultrasound intensity is adequate to produce FAMEs at a maximum yield of 48.2%. Results from this optimization study suggest that a more detailed and mechanistic energy optimization study is critical to increase the FAME yield and maximize energy benefits.
This research investigates a novel platform for an energy-yielding wastewater treatment and desal... more This research investigates a novel platform for an energy-yielding wastewater treatment and desalination scheme in which the organic matter present in wastewater is purposely fed to the exoelectrogenic bacteria to produce bioelectricity in a three-compartment bioelectrochemical system called photosynthetic microbial desalination cell (PMDC). The role of an inorganic carbon source in the microalgae biocathode was studied. Addition of sodium bicarbonate (NaHCO 3) increased power production, microalgae growth and desalination rate. A power density of 660 mW/m 3 was measured which is about 7.5 times higher than the PMDCs without NaHCO 3. Desalination rate was more than 40% after 72 h. Overall, the process could be energy-positive while producing 4.21 kWh per m 3 of wastewater treated including desalination energy savings and microalgae biomass energy potential.
Current wastewater treatment processes such as activated sludge process and other aeration techno... more Current wastewater treatment processes such as activated sludge process and other aeration technologies are resource-consuming and are unsustainable. Novel and integrated processes are crucial to the development of sustainable wastewater treatment systems. In this context, anaerobic treatment technologies provide numerous opportunities for minimization of energy and resource consumption and maximization of beneficial products. Further, integration of anaerobic digestion augmented by co-digestion, fermentation, dark fermentation or photo-fermentation and other bioelectrochemical systems may result in resource-efficient waste management and environmental protection. This mini-review discusses various possibilities and highlights recent developments of integrated aerobic and anaerobic technologies with bioelectrochemical systems for sustainable wastewater treatment.
This study presents the use of an autotrophic microorganism, Anammox bacteria, as a sustainable b... more This study presents the use of an autotrophic microorganism, Anammox bacteria, as a sustainable biocatalyst/
biocathode in microbial desalination cells (MDCs) for energy-positive wastewater treatment. We report the first
proof of concept study to prove that anammox mechanism can be beneficial in MDCs to provide simultaneous
removal of carbon and nitrogen compounds from wastewater while producing bioelectricity. A series of experiments
were conducted to enrich and evaluate the anammox mechanism and the process performance in
continuous, fed-batch mode conditions. Coulombic efficiency of MDCs and nitrite and ammonium removal of
wastewater increased in successive batch studies. A maximum power density of 0.092Wm−3 (or a maximum
current density of 0.814 Am−3) with more than 90% of ammonium removal was achieved in this system. We
calculated the Nernst potential for the nitrite reduction in the anammox biocathode chamber and compared with
experimental values. Sequential removal of carbon and nitrogen compounds in anode and cathode chambers
respectively, was also evaluated. Further, the inhibition effect of high nitrogen concentrations and the variations
in microbial community profiles, especially, anammox presence was studied at different carbon and ammonia
concentrations. Experimental studies and microbial community analysis are presented in detail.
• First study of anammox biocathode in
microbial desalination and wastewater
treatment.
• Maximum power and current densities
of 0.092 W/m3 and 0.8143 A/m3 were
obtained.
• Nitrogen removal of more than 90%
was achieved in anammox biocathode
compartment.
Algae biomass is the most promising feedstock for biofuel production since it can provide a
susta... more Algae biomass is the most promising feedstock for biofuel production since it can provide a
sustainable route to achieve independence from fossil fuel sources. Energy-positive biofuel
production from algal biomass has been the major goal for many researchers in recent years.
The search for efficient extraction and chemical conversion methods that produce high energy
ratios has become an important endeavor in this field. In this regard, microwaves and
ultrasound have been utilized as convenient mechanisms in algal biodiesel production.
However, none of the studies reported on the energy analysis of the extraction and
transesterification methods. Energy analysis of the extractive-transesterification processes using
microwave (with ethanol and with ethanol and hexane as co-solvent) and ultrasound
irradiations to produce biocrude from microalgae (Chlorella sp.) is presented in this paper.
Power input and reaction volumes were varied to study the effects of power density and
intensity on the biocrude yields. Results from this analysis show that a biocrude yield higher
than 90% could be obtained with an energy input to output ratio of less than one when
microwave irradiation is used as the heating mechanism.
A B S T R A C T This study presents the first report on the performance of Photosynthetic microbi... more A B S T R A C T This study presents the first report on the performance of Photosynthetic microbial desalination cells under different flow configurations. Three different photosynthetic MDCs (using Chlorella vulgaris) were evaluated for their performance and energy generation potentials. Static (fed-batch, SPMDC), continuous flow (CFPMDC) and a photobioreactor MDC (PBMDC, resembling lagoon type PMDCs) were developed to study the impact of process operation and design on wastewater treatment, electricity generation, nutrient removal, and biomass production capacities. A maximum power density of 753.75 mW m À3 was produced in a SPMDC while a higher biomass growth rate of 7 mg L À1 h À1 was recorded for CFPMDC. In addition, PMDCs showed high removal rates of organic carbon and nutrient compounds. Experimental studies revealed that PMDCs can be configured to maximize energy recovery through either biomass or bioelectricity production. Finally, microbial composition analysis on different biosolids samples in the PMDCs revealed very diverse groups of microbial communities.
Biodiesel as a renewable fuel has the potential to replace non-renewable fossil fuels and associa... more Biodiesel as a renewable fuel has the potential to replace non-renewable fossil fuels and associated environmental pollution. The most commonly used method in biodiesel production is transesterification of virgin and used oil feedstock. However, the chemical reaction (transesterification) does not proceed spontaneously, which means excess reactants are required to move the reaction to completion. The biodiesel reaction efficiency can be improved by incorporating green chemistry principles and process intensification effects. Green chemistry principles can be used to design chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Microwave-and ultrasound-enhanced biodiesel synthesis can improve the reaction efficiency due to higher product recovery, low by-product formation, and reduced energy consumption. In addition, utilization of green metrics such as E-factor, atom economy (utilization), mass intensity or mass productivity, and reaction mass efficiency can help design safer and highly efficient biodiesel synthesis. Green chemistry principles have been analyzed for other processes in greater details, but they are rarely discussed in the context of biodiesel production. Process intensification by microwave-and ultrasound-mediated biodiesel production was never discussed from the perspective of green chemistry and sustainable process development. This research review article discusses the role of green chemistry and process intensification in biodiesel production followed by specific examples and illustrations on green metrics of microwave-and ultrasound-enhanced biodiesel synthesis and the effect of catalysts and solvents including discussions on reaction kinetics and activation energy in detail for the first time in the literature. Keywords Green chemistry · Biodiesel · Microwaves · Ultrasound · Atom economy · E-factor · Process intensification
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Papers by Veera Gnaneswar Gude
meet the freshwater supply needs is proposed with theoretical analysis and practical considerations. A main engine capacity of 7500 kW in a cruise ship can serve as a potential waste heat source to be tapped for water desalination of 1000 m3/d, which can provide for freshwater needs of 2000 to 4000 ship occupants. This scenario presents as an attractive alternative to ballast water treatment as well as reducing the nonrenewable energy footprint of onboard water supplies in marine industry.
environmental regulatory standards in a sustainable manner. Currently, a small percentage of WWTPs around the world
produce energy for beneficial use and only a handful of these plants are energy self-sufficient. We propose three energypositive
wastewater treatment schemes and use quantitative analysis to assess their potentials for carbon and nitrogen
removal and energy generation from municipal wastewater. This research identifies potential challenges in the selection
and implementation of energy recovery process configurations and proposes practically feasible energy-positive wastewater
treatment process configurations. Energy self-sufficiency can be achieved through biogas production while simultaneously
minimizing the energy consumption for treatment. Furthermore, energy recovery can be enhanced in the near future (i) by
increasing the COD capture in primary treatment to enhance energy production; (ii) by replacing activated sludge process
with other less energy-intensive biological treatment technologies; and (iii) by increasing energy production from digesting
supplementary feedstock in anaerobic codigestion (AD) schemes. This paper presents a quantitative analysis of three process
schemes that progressively build upon the concept of transforming the conventional activated sludge wastewater treatment
plants (CAS-WWTP) into energy self-sufficient wastewater treatment facilities. These schemes also include a hypothetical
but practically feasible WWTP configuration, which represents an alternative energy self-sufficient wastewater process
scheme for future designs.
the most essential and basic need for humanity.
Although the planet is water-rich in some terms, the
freshwater sources available for human consumption
and beneficial uses are very limited. Excess population
growth, industrial development coupled with improving
living standards have caused an unprecedented
need for freshwater all over the world. Regions once
rich in water resources are struggling to meet the ever
increasing demands in recent years. In addition,
climate change and unsustainable management practices
have led to a situation called ‘‘drought’’ in many
regions. Water supplies in drought conditions can be
addressed by taking two major approaches related to
management and technology development. The management
approaches include demand mitigation and
supply enhancement. Demand mitigation can be done
by implementing water conservation practices, and by
enforcing a mechanism to influence user-responsible
behavior through higher water fares and other billing
routes. Supply enhancement can be achieved by
utilizing the methods available for water reclamation,
reuse and recycle including rain harvesting. This paper
provides a critical insight of the causes for drought and
the issues caused by persistent drought conditions
followed by discussion of management and technological
approaches required to maintain adequate
water resources around the world. Challenges and
opportunities involved in implementation of desalination
and water reuse technologies in addressing global
water scarcity are discussed in detail with case studies
biocathode in microbial desalination cells (MDCs) for energy-positive wastewater treatment. We report the first
proof of concept study to prove that anammox mechanism can be beneficial in MDCs to provide simultaneous
removal of carbon and nitrogen compounds from wastewater while producing bioelectricity. A series of experiments
were conducted to enrich and evaluate the anammox mechanism and the process performance in
continuous, fed-batch mode conditions. Coulombic efficiency of MDCs and nitrite and ammonium removal of
wastewater increased in successive batch studies. A maximum power density of 0.092Wm−3 (or a maximum
current density of 0.814 Am−3) with more than 90% of ammonium removal was achieved in this system. We
calculated the Nernst potential for the nitrite reduction in the anammox biocathode chamber and compared with
experimental values. Sequential removal of carbon and nitrogen compounds in anode and cathode chambers
respectively, was also evaluated. Further, the inhibition effect of high nitrogen concentrations and the variations
in microbial community profiles, especially, anammox presence was studied at different carbon and ammonia
concentrations. Experimental studies and microbial community analysis are presented in detail.
• First study of anammox biocathode in
microbial desalination and wastewater
treatment.
• Maximum power and current densities
of 0.092 W/m3 and 0.8143 A/m3 were
obtained.
• Nitrogen removal of more than 90%
was achieved in anammox biocathode
compartment.
sustainable route to achieve independence from fossil fuel sources. Energy-positive biofuel
production from algal biomass has been the major goal for many researchers in recent years.
The search for efficient extraction and chemical conversion methods that produce high energy
ratios has become an important endeavor in this field. In this regard, microwaves and
ultrasound have been utilized as convenient mechanisms in algal biodiesel production.
However, none of the studies reported on the energy analysis of the extraction and
transesterification methods. Energy analysis of the extractive-transesterification processes using
microwave (with ethanol and with ethanol and hexane as co-solvent) and ultrasound
irradiations to produce biocrude from microalgae (Chlorella sp.) is presented in this paper.
Power input and reaction volumes were varied to study the effects of power density and
intensity on the biocrude yields. Results from this analysis show that a biocrude yield higher
than 90% could be obtained with an energy input to output ratio of less than one when
microwave irradiation is used as the heating mechanism.