Deciphering carbon dioxide fluxes and interactions in the Ganga river Basin of South Asia.

Anthropogenic influences significantly modify the hydrochemical properties and material flow in riverine ecosystems across Asia, potentially accounting for 40-50% of global emissions. Despite the pervasive impact on Asian rivers, there is a paucity of studies investigating their correlation with carbon dioxide (CO2) emissions. In this study, we computed the partial pressure of CO2 (pCO2) using the carbonate equilibria-based model (pCO2SYS) and examined its correlation with hydrochemical parameters from historical records at 91 stations spanning 2013-2021 in the Ganga River. The investigation unveiled substantial spatial heterogeneity in the pCO2 across the Ganga River. The pCO2 concentration varied from 1321.76 µatm, 1130.98 µatm, and 1174.33 µatm in the upper, middle, and lower stretch, respectively, with a mean of 1185.29 µatm. Interestingly, the upper stretch exhibited elevated mean pCO2 and FCO2 levels (fugacity of CO2: 3.63 gm2d-1) compared to the middle and lower stretch, underscoring the intricate interplay between hydrochemistry and CO2 dynamics. In the context of pCO2 fluctuations, nitrate concentrations in the upper segment and levels of biological oxygen demand (BOD) and dissolved oxygen (DO) in the middle and lower segments are emerging as crucial explanatory factors. Furthermore, regression tree (RT) and importance analyses pinpointed biochemical oxygen demand (BOD) as the paramount factor influencing pCO2 variations across the Ganga River (n = 91). A robust negative correlation between BOD and FCO2 was also observed. The distinct longitudinal patterns of both parameters may induce a negative correlation between BOD and pCO2. Therefore, comprehensive studies are necessitated to decipher the underlying mechanisms governing this relationship. The present insights are instrumental in comprehending the potential of CO2 emissions in the Ganga River and facilitating riverine restoration and management. Our findings underscore the significance of incorporating South Asian rivers in the evaluation of the global carbon budget.

Assessing sustainability of microalgae-based wastewater treatment: Environmental considerations and impacts on human health.

An integrated life cycle assessment (LCA) and quantitative microbial risk assessment (QMRA) were conducted to assess microalgae-mediated wastewater disinfection (M-WWD). M-WWD was achieved by replacing ultraviolet disinfection with a microalgal open raceway pond in an existing sewage treatment plant (STP) in India. Regarding impacts on human health, both M-WWD and STP yielded comparable life cycle impacts, around 0.01 disability-adjusted life years (DALYs) per person per year. However, QMRA impacts for M-WWD (0.053 DALYs per person per year) were slightly lower than that for STP while considering exposure to E. coli O157:H7 and adenovirus. Additionally, a comparative LCA resolved the dilemma about the appropriate utilization of microalgal biomass. Among biodiesel, biocrude, and biogas production, the lowest impacts of 0.015 DALYs per person per year were obtained for biocrude for 1 m3 water treated by M-WWD. Electricity consumption in microalgae cultivation was a major environmental hotspot. Overall, M-WWD, followed by production of microalgal biocrude, emerged as a sustainable alternative from environmental and public health perspectives. These findings set the foundation for pilot-scale M-WWD system development, testing, and economic evaluation. Such comprehensive investigations, encompassing LCA, QMRA, and resource recovery scenarios, offer crucial insights for stakeholders and decision-makers in wastewater treatment and environmental management.

A comparative analysis of growth kinetics, image analysis, and biofuel potential of different algal strains.

Due to the global population growth and economic development, energy demand has increased worldwide. Countries take steps to improve their alternative and renewable energy sources. Algae is one of the alternative energy sources and can be used to produce renewable biofuel. In this study, nondestructive, practical, and rapid image processing techniques were applied to determine the algal growth kinetics and biomass potential of four algal strains, including C. minutum, Chlorella sorokiniana, C. vulgaris, and S. obliquus. Laboratory experiments were conducted to determine different aspects of biomass and chlorophyll production of those algal strains. Suitable non-linear growth models, including Logistic, modified Logistic, Gompertz, and modified Gompertz models, were employed to determine the growth pattern of algae. Moreover, the methane potential of harvested biomass was calculated. The algal strains were incubated for 18 days, and the growth kinetics were determined. After the incubation, the biomass was harvested and assessed for its chemical oxygen demand content and biomethane potential. Among the tested strains, C. sorokiniana was the best in biomass productivity (111.97 ± 0.9 mg L-1d-1). The calculated vegetation indices, namely; colorimetric difference, color index vegetation, vegetative, excess green, excess green minus excess red, combination, and brown index values showed a significant correlation with biomass and chlorophyll content. Among the tested growth models, the modified Gompertz shows the best growth pattern. Further, the estimated theoretical CH4 yield was highest for C. minutum (0.98 mL g-1) compared to other tested strains. The present findings suggest that image analysis can be used as an alternative method to study the growth kinetics and biomass production potential of different algae during cultivation in wastewater.

An integration of algae-mediated wastewater treatment and resource recovery through anaerobic digestion.

Eutrophication is one of the major emerging challenges in aquatic environment. Industrial facilities, including food, textile, leather, and paper, generate a significant amount of wastewater during their manufacturing process. Discharge of nutrient-rich industrial effluent into aquatic systems causes eutrophication, eventually disturbs the aquatic system. On the other hand, algae provide a sustainable approach to treat wastewater, while the resultant biomass may be used to produce biofuel and other valuable products such as biofertilizers. This review aims to provide new insight into the application of algal bloom biomass for biogas and biofertilizer production. The literature review suggests that algae can treat all types of wastewater (high strength, low strength, and industrial). However, algal growth and remediation potential mainly depend on growth media composition and operation conditions such as light intensity, wavelength, light/dark cycle, temperature, pH, and mixing. Further, the open pond raceways are cost-effective compared to closed photobioreactors, thus commercially applied for biomass generation. Additionally, converting wastewater-grown algal biomass into methane-rich biogas through anaerobic digestion seems appealing. Environmental factors such as substrate, inoculum-to-substrate ratio, pH, temperature, organic loading rate, hydraulic retention time, and carbon/nitrogen ratio significantly impact the anaerobic digestion process and biogas production. Overall, further pilot-scale studies are required to warrant the real-world applicability of the closed-loop phycoremediation coupled biofuel production technology.

Integrating life cycle assessment with quantitative microbial risk assessment for a holistic evaluation of sewage treatment plant.

An integrated approach was employed in the present study to combine life cycle assessment (LCA) with quantitative microbial risk assessment (QMRA) to assess an existing sewage treatment plant (STP) at Roorkee, India. The midpoint LCA modeling revealed that high electricity consumption (≈ 576 kWh.day-1) contributed to the maximum environmental burdens. The LCA endpoint result of 0.01 disability-adjusted life years per person per year (DALYs pppy) was obtained in terms of the impacts on human health. Further, a QMRA model was developed based on representative sewage pathogens, including E. coli O157:H7, Giardia sp., adenovirus, norovirus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The public health risk associated with intake of pathogen-laden aerosols during treated water reuse in sprinkler irrigation was determined. A cumulative health risk of 0.07 DALYs pppy was obtained, where QMRA risks contributed 86 % of the total health impacts. The annual probability of illness per person was highest for adenovirus and norovirus, followed by SARS-CoV-2, E. coli O157:H7 and Giardia sp. Overall, the study provides a methodological framework for an integrated LCA-QMRA assessment which can be applied across any treatment process to identify the hotspots contributing maximum environmental burdens and microbial health risks. Furthermore, the integrated LCA-QMRA approach could support stakeholders in the water industry to select the most suitable wastewater treatment system and establish regulations regarding the safe reuse of treated water.

Anaerobic digestion as a tool to manage eutrophication and associated greenhouse gas emission.

Eutrophicated inland water bodies are noticed to be one of the contributing factors to greenhouse gas (GHGs) emissions. Direct discharge of untreated or partially treated water is a major concern. Microalgae-based technology and management are regarded as one of the potential nature-based approaches to combat eutrophication. In turn, the microalgae facilitate the recovery of GHGs contributing compounds in the form of organic biomass. The recovered algal biomass can be harnessed for the production of biofuels and other bio-products, like biofertilizer, using anaerobic digestion. By virtue, circular bio-economy can be achieved alongside mitigating GHGs emissions. Before implementing, it is vital to thoroughly explore the links between the process and potential alternatives for wastewater treatment, waste valorization, biofuel production, and land usage. Thus, the present review discusses the impact of eutrophication on ecology and environment, current technologies for mitigating eutrophication and GHGs, and energy recovery through the anaerobic digestion of algal biomass. Further, the processes at the intercept of wastewater treatment and biogas production were reviewed to leverage the potential of anaerobic digestion for making a circular bioeconomy framework.

Allelopathic effect of benzoic acid (hydroponics root exudate) on microalgae growth.

Hydroponic effluent (HE) contains a reasonable amount of residual nutrients. Therefore, HE could be used as a low-cost growth media for microalgae mediated resource recovery and water recycling. However, the presence of root exudates (particularly, benzoic acid) may lead to toxicity in microalgae.In the present study, the allelopathic effects of benzoic acid on microalgal growth was tested. During 96 h batch growth, Chlorella pyrenoidosa showed the highest biomass concentration (0.064-0.037 g.L-1) compared to Chlorella sorokiniana (0.09-0.26 g.L-1) at the tested benzoic acid doses. Moreover, both the species showed growth stimulation and growth inhibition up to certain benzoic acid doses. Hence, both the microalgal species showed allelopathic behaviour at different doses of benzoic acid. Further, the observed half effective concentration (96 h EC50) were 65.10 mg.L-1 and 105.27 mg.L-1, respectively, for Chlorella pyrenoidosa and C. sorokiniana with 95% confidence limits. Further, Haldane's model best fitted with experimental data of both the microalgae (r âˆ¼ 0.99). Overall, the study reveals that the HE with low benzoic acid dose may serve as a suitable growth media for microalgae. However, further in-depth research interventions using real HE are desirable to determine its real-world applicability.

Impact of microplastics on riverine greenhouse gas emissions: a view point.

In recent decades, microplastics (MPs < 5 mm) are ubiquitous and considered a serious emerging environmental problem. However, due to the limited recovery and long-lasting durability MPs, debris is frequently accumulating in riverine ecosystems, thereby impacting microbial activity and its communities. The presence of MPs may alter the microbial richness, variety, and population, thereby impacting the transformation of biogeochemical cycles. The occurrence, fate, and transport of MPs in marine and terrestrial ecosystems and their impact on biogeochemical or nutrient cycling are reported in the scientific fraternity. Yet, the global scientific community is conspicuously devoid of research on impact of MPs on riverine greenhouse gas (GHG) emissions. The presented view point provides a novel idea about the fate of MPs in the riverine system and its impact on GHG emissions potential. Literature reveals that DO and nutrients (organic carbon, NH4+, NO3-) concentrations play an important role in potential of GHG emission in riverine ecosystems. The proposed mechanism and research gaps provided will be highly helpful to the hydrologist, environmentalist, biotechnologist, and policymakers to think about the strategic mitigation measure to resolve the future climatic risk.

Mixotrophic microalgal-biofilm reactor augmenting biomass and biofuel productivity.

The present work aimed to evaluate the mixotrophic growth of Chlorella pyrenoidosa in a microalgal-biofilm reactor (MBR) using waste glycerol as an organic carbon source. The biomass productivity of C. pyrenoidosa (10.14 g m-2 d-1) under the mixotrophic mode was remarkably higher than that observed during the phototrophic mode (4.16 g m-2 d-1), under similar incubation conditions. The hydraulic retention time (HRT) of 6 d was found optimal for the higher productivity of microalgae in the MBR. Notably, based on biofuel quality, mixotrophically grown microalgal biomass was noted to have better suitability for biomethane production compared to biodiesel. Besides, up to 98.09, 75.74, and 55.86% removal of phosphate, nitrate, and COD, respectively, was recorded within 6 d under mixotrophic growth. Overall, the present findings magnificently demonstrate the efficient recycling of waste glycerol for higher biomass production coupled with phycoremediation using mixotrophic MBR.

Use of reverse osmosis reject from drinking water plant for microalgal biomass production.

The present study evaluates the use of reverse osmosis (RO) reject, termed as ROR, for microalgal biomass production. The supplementation of ROR from two different sources, namely domestic RO unit (ROR1) and commercial-scale RO plant (ROR2), showed a synergistic effect on the growth and biochemical composition of Chlorella pyrenoidosa. Among the tested ROR1 doses, the highest biomass production (1.27±0.06 g L-1) was observed with 25% ROR1 supplemented growth media. In contrast, the lipid content (28.85±3.13% of TS) in C. pyrenoidosa at 50% ROR1 dose was almost twice that in BG11 (positive control). Interestingly, the microalgae showed relatively higher biomass production (1.37±0.07 g L-1) and higher lipid content (33.23±3.92% of TS) when 50% ROR2 was used in growth media. At the same time, the estimated carbohydrate and protein contents were 28.41±0.73 and 29.75±0.31% of TS, respectively. Furthermore, the lipid productivity (28.98±2.79 mg L-1 d-1) was relatively higher than the nutrient media (12.35±1.34 mg L-1 d-1). The present findings revealed that the RO reject from drinking water purifiers can efficiently be utilized for lipid-rich microalgal biomass production. Hence, the dependency on freshwater resources for mass scale microalgae cultivation through recycling of RO reject can be reduced.

Enzymatic pretreatment of algal biomass has different optimal conditions for biogas and bioethanol routes.

Enzymatic pretreatment is emerging as an efficient tool for the extraction of biofuel precursors from algal biomass. However, yardsticks for end-use directed selection of optimal pretreatment conditions are not yet identified. The present study, for the first time, reveals different optimal conditions for algal biomass solubilization and sugar release. Algal biomass pretreatment optimization was carried out using the Taguchi method. Crude enzyme from Aspergillus fischeri was found effective for pretreatment of Chlorella pyrenoidosa. Maximum sugar yield (190 mg g-1 biomass) from algal biomass was observed at a substrate concentration of 4 g L-1, with a 5% enzyme load at temperature 60°C, pH 5.5, and shaking speed of 80 rpm. In contrast, maximum sCOD (1350 mg g-1 biomass) was obtained at 2 g L-1 substrate concentration with enzyme load of 20% v/v, at 60°C, pH 4, and shaking speed of 100 rpm. Hence, the first set of conditions would be more beneficial for bioethanol production. Whereas another set of conditions would improve the biofuel production that requires maximum solubilization of algal biomass, such as fermentative methane production. Overall, the present observations established that process conditions required for enzymatic pretreatment of algal biomass should be selected according to the desired biofuel type.

Utilization of starch effluent from a textile industry as a fungal growth supplement for enhanced α-amylase production for industrial application.

Desizing process in textile industry produces large volume of starch effluent. This carbon-rich waste can be used for resource recovery, such as the production of industrially useful enzymes. The present work assesses the usability of starch effluent from textile industry as an additional carbon source for enhanced production of α-amylase during solid-state fermentation (SSF) of agro-wastes by Trichoderma reesei. A significant increase (p ≤ 0.05) in α-amylase activity (25.48 ± 1.12 U mL-1) was observed with supplementation of starch effluent in SSF. Partial purification of α-amylase by 80% ammonium sulphate precipitation produced a yield of 58.39% enzyme with purification fold of 1.89. The enzyme was thermally stable at 40 °C with 90% residual activity after 5 h and 70% residual activity at 50 °C after 3 h. Using Michaelis-Menten kinetics analysis, the estimated Km and Vmax values for the partially purified α-amylase were found to be 2.55 mg mL-1 and 53.47 U mg-1, respectively. For the rapid assessment of the industrial application, desizing of the fabric was attempted. The cotton fabric was efficiently desized using α-amylase (at a concentration of 1% on the weight of fabric basis) at 80 °C. The present work demonstrates starch effluent from desizing process as a resource for the production of amylase. The amylase can further be used in the desizing process. With in-depth research, the work may lead to the development of a closed-loop, waste-recycling process for the textile industry.

An eco-friendly strategy for dairy wastewater remediation with high lipid microalgae-bacterial biomass production.

The present study attempts to integrate phyco-remediation and enhanced lipid productivity using microalgae-bacterial consortium enriched from wastewater fed aquaculture pond. Metagenomic analyses and microscopic images of the consortium revealed the presence of Chlorella variabilis, Parachlorella kessleri, Thermosynechococcus elongatus, Chlamydomonas, Phaeodactylum tricornutum, Oscillatoriales, Synechocystis sp., Microcystis aeruginosa, Nostocales, Naviculales, Stramenopiles, other members of Chlorophyceae, Trebouxiophyceae, and Chroococcales along with potential bacterial bioremediants. During a 30 days trial run (15 days stabilization and 14 days remediation studies) for phyco-remediation drastic reduction in the nutrient and COD content from the tested wastewater samples was seen. There was up to 93% and 87.2% reduction in chemical oxygen demand (COD) and ammonium concentration, respectively. Further, almost 100% removal of nitrates and phosphates from the dairy wastewater upon 48 h of treatment with polyculture under ambient temperature (25 ± 2 °C) with 6309 lux illumination and mild aeration, was observed for all the seven cycles. Interestingly, the nutrient and COD concentrations in the treated water were below the discharge standards as per Central Pollution Control Board (CPCB) norms. In additions, biomass (reported as dry cell weight) was enhanced by 67% upon treatment with ammonia-rich dairy wastewater exhibiting 42% lipid, 55% carbohydrate, and 18.6% protein content enhancement. The polyculture mainly grown as attached biofilm to the surface, offered an easy harvesting and separation of grown biomass from the treated wastewater. Overall, dairy wastewater was found to be a potential nutrient source for microalgae-bacteria cultivation thereby making the treatment process sustainable and eco-friendly.

Occurrence, fates and potential treatment approaches for removal of viruses from wastewater: A review with emphasis on SARS-CoV-2.

The world is combating the emergence of Coronavirus disease 2019 (COVID-19) caused by novel coronavirus; severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Further, due to the presence of SARS-CoV-2 in sewage and stool samples, its transmission through water routes cannot be neglected. Thus, the efficient treatment of wastewater is a matter of utmost importance. The conventional wastewater treatment processes demonstrate a wide variability in absolute removal of viruses from wastewater, thereby posing a severe threat to human health and environment. The fate of SARS-CoV-2 in the wastewater treatment plants and its removal during various treatment stages remains unexplored and demands immediate attention; particularly, where treated effluent is utilised as reclaimed water. Consequently, understanding the prevalence of pathogenic viruses in untreated/treated waters and their removal techniques has become the topical issue of the scientific community. The key objective of the present study is to provide an insight into the distribution of viruses in wastewater, as well as the prevalence of SARS-CoV-2, and its possible transmission by the faecal-oral route. The review also gives a detailed account of the major waterborne and non-waterborne viruses, and environmental factors governing the survival of viruses. Furthermore, a comprehensive description of the potential methods (physical, chemical, and biological) for removal of viruses from wastewater has been presented. The present study also intends to analyse the research trends in microalgae-mediated virus removal and, inactivation. The review also addresses the UN SDG 'Clean Water and Sanitation' as it is aimed at providing pathogenically safe water for recycling purposes.

New insights on improved growth and biogas production potential of Chlorella pyrenoidosa through intermittent iron oxide nanoparticle supplementation.

In the present work, the effect of α-Fe2O3-nanoparticles (IONPs) supplementation at varying doses (0, 10, 20 and, 30 mg L-1) at the intermittent stage (after 12th day of growth period) was studied on the growth and biogas production potential of Chlorella pyrenoidosa. Significant enhancements in microalgae growth were observed with all the tested IONPs doses, the highest (2.94 ± 0.01 g L-1) being at 20 mg L-1. Consequently, the composition of the biomass was also improved. Based on the precedent determinations, theoretical chemical oxygen demand (CODth) as well as theoretical and stoichiometric methane potential (TMP, and SMP) were also estimated. The CODth, TMP, SMP values indicated IONPs efficacy for improving biogas productivity. Further, the biochemical methane potential (BMP) test was done for IONPs supplemented biomass. The BMP test revealed up to a 25.14% rise in biogas yield (605 mL g-1 VSfed) with 22.4% enhanced methane content for 30 mg L-1 IONPs supplemented biomass over control. Overall, at 30 mg L-1 IONPs supplementation, the cumulative enhancements in biomass, biogas, and methane content proffered a net rise of 98.63% in biomethane potential (≈ 2.86 × 104 m3 ha-1 year-1) compared to control. These findings reveal the potential of IONPs in improving microalgal biogas production.

Bacteremia by Chryseobacterium indologenes in a Patient with Lung Cancer: A Clinical and Microbiological Investigation.

We present a case of bacteremia by an unsual, instrinsically multidrug resistant organism, Chryseobacterium indologenes in a 59 year old gentleman with squamous cell carcinoma of lung with multiple metastasis. Despite of treating as per sensitivity report after isolatingChryseobacterium indologenes, patient could not be survived. The pathogenicity and predictability of the organism towards antibiotics, bothin vivo and in vitro needs further research. HOW TO CITE THIS ARTICLE: Bhagawati G, Bhardwaj A et al. Bacteremia by Chryseobacterium Indologenes in a Patient with Lung Cancer: A Clinical and Microbiological Investigation. Indian J Crit Care Med 2019;23(3):157-159.

Improved methane yield from wastewater grown algal biomass.

Methane production from the algal biomass cultivated in a laboratory scale continuous photobioreactor (PBR) using sewage was evaluated in the present work. During the preliminary experiments, algal biomass reached up to 1.69 ± 0.35 g L-1 in 12 days' growth period. Besides, 65 to 100% removal in concentrations of total dissolved phosphorus (TDP), nitrate nitrogen (NO3-N), total ammoniacal nitrogen (TAN) and soluble chemical oxygen demand (sCOD) was also recorded. The sCOD removal in the reactor was 100%, whereas removal of TDP, NO3-N and TAN were up to 75, 40 and 92%, respectively. Upon anaerobic digestion, the fresh algal biomass showed methane yield of 180 mL g-1 VSfed. Further, algal biomass was stored under natural conditions in open containers (aerobic conditions) in darkness at room temperature (27-30 °C) for 72 h. Interestingly, >48% COD solubilization from algal biomass was observed during storage. Pretreatment through natural storage was further confirmed with qualitative observations including scanning electron and fluorescence microscopic analysis. Moreover, higher methane yield (284.38 mL g-1 VSfed) was observed from the samples stored for 60 h. Thus, natural storage for a designated period may be recommended as a prerequisite stage in the process of methane production from wastewater-grown algal biomass.

Development and performance evaluation of an algal biofilm reactor for treatment of multiple wastewaters and characterization of biomass for diverse applications.

A modified algal biofilm reactor (ABR) was developed and assessed for high biomass productivity and treatment potential using variable strength wastewaters with accumulation of specialized bio-products. The nonwoven spun bond fabric (70GSM) was selected as suitable biofilm support on the basis of attachment efficiency, durability and ease of harvesting. The biomass productivity achieved by ABR biofilms were 4gm-2d-1, 3.64gm-2d-1 and 3.10gm-2d-1 when grown in livestock wastewater (LSW), domestic grey water (DGW) and anaerobically digested slurry (ADS), respectively. Detailed characterization of wastewater grown biomass showed specific distribution of biomolecules into high lipid (38%) containing biomass (DGW grown) and high protein (44%) biomass (LSW and ADS grown). The feasibility assessment of ABR in terms of net energy return (>1) favored its application in an integrated system for treatment and recycling of rural wastewaters with simultaneous production of biomethane, livestock feed supplement and bio fertilizers.

Algae mediated treatment and bioenergy generation process for handling liquid and solid waste from dairy cattle farm.

In the present work four algae were tested for their biomass production potential in neat livestock wastewater. Chroococcus sp.1 was found to be the best for biomass production under controlled (2.13 g L(-1)) and outdoor conditions (4.44 g L(-1)) with >80% of nutrients removal. The produced biomass was then digested with cattle dung as cosubstrate. Interestingly, up to 291.83 ± 3.904 mL CH4 g(-1) VS fed was produced during codigestion studies (C/N ≈ 13.0/1). In contrast to this, only 202.49 ± 11.19 and 141.70 ± 2.57 mL CH4 g(-1) VS fed was recorded with algae (C/N ≈ 9.26/1) and cattle dung (C/N ≈ 31.56/1) alone, respectively. The estimated renewable power generation potential of the investigated coupled process was around 333.79-576.57 kW h d(-1) for a dairy farm with 100 adult cattle. However, further scale-up and testing is needed to make this process a reality.