Potential of biogenic and non-biogenic waste materials as flocculant for algal biomass harvesting: Mechanism, parameters, challenges and future prospects.

In this review article, waste materials (biogenic/non-biogenic) are focused as the flocculants for harvesting of algal biomass. Chemical flocculants are widely utilized for the effective harvesting of algal biomass at a commercial scale while the high cost is a major drawback. The waste materials-based flocculants (WMBF) are started to utilize as one of the cost-effective performance for dual benefits of waste minimization and reuse for sustainable recovery of biomass. The novelty of the article is articulated with the objective that presents an insight of WMBF, classification of WMBF, preparation methods of WMBF, mechanisms of flocculation, factors affecting flocculation-mechanism, challenges and future recommendations that are required for harvesting of algae. The WMBF are shown similar flocculation mechanisms and flocculation efficiencies as chemical flocculants. Thus, the utilization of waste material for the flocculation process of algal cells minimizes the waste load into the environment and transforms the waste materials into valuable resources.

Impact of Pollutant Load from Textile Dyeing Industry Wastewater on Biometric Growth Profile of Vigna radiata.

The phytoremediation of wastewater has certain advantages, but the interactions of soil and crop properties have not been systematically studied. This study aimed to analyze how different concentrations of textile dyeing industry wastewater (25%, 50%, 75%, and 100%) affected soil qualities, growth, and yield attributes (Vigna radiata). In reaction to dyeing effluent at varying concentrations, the seed germination percentage, growth metrics such as tolerance index, phytotoxicity percentage, relative toxicity, extreme and plumule length were calculated. With increasing effluent concentrations, a gradual decrease in the germination of seed and seedling growth was observed. The maximal relative toxicity and percentage of phytotoxicity was 100%. Interaction of biometric growth profile relative seed germination, relative root growth, relative shoot growth, growth index, and seedling vigor index of V. radiata and physicochemical parameter of textile dyeing industry wastewater were also investigated by using the Pearson correlation co-efficient. Principal component analysis (PCA) is helped to obtain and recognize the factors/sources accountability of different concentrations of textile dyeing industry wastewater. The results of the PCA revealed that four components (PC1 to PC4) out of total principal components retained PC1, PC2, with values of 69.25% and 28.85%, respectively.

A critical overview of upstream cultivation and downstream processing of algae-based biofuels: Opportunity, technological barriers and future perspective.

Fossil fuels are sharing a large portion of energy demand. Conventional energy sources emit a huge amount of greenhouse gas into the atmosphere, which creates energy and environmental challenges for the ecosystem. To fulfill the world energy demand and to support environmental as well as economic development in a sustainable way, with the utilization of technological advancement of renewable energy resources, algae are presently believed as most adaptable feedstock materials for bioenergy production. Algae has a high fixation rate of atmospheric carbon dioxide which supports to fast growth rate with high productivity per unit area in the form of renewable algal biomass. The present article aims to elaborate on the three generations of biofuels, sustainable microalgae biomass production, cultivation systems, and a wide range of growth parameters. The microalgae harvesting methods and their challenges are also discussed, with a special focus on lipid extraction methods and future r recommendations. The upstream and downstream processes of microalgae could help to harness the microalgae energy in an eco-friendly manner and will help in achieving overall sustainable development.

Impact of pH on Pollutional Parameters of Textile Industry Wastewater with Use of Chlorella pyrenoidosa at Lab-Scale: A Green Approach.

The current study focused on the pollution remediation of textile industry wastewater by using Chlorella pyrenoidosa in two different physical forms: free algal biomass and immobilized algal biomass. The hypothesis behind the present study was to analyze the pollution reduction efficiency of immobilized algal biomass and free algal biomass on comparative scale on the basis of the adsorption process which is directly proportional with the surface area of the adsorbate. So, in this context the immobilized form of algae could enhance the pollution reduction efficiency due to availability of more surface area. So, the textile industry wastewater was treated by both free algal biomass and immobilized algal biomass and the major wastewater contributors like nitrate, phosphate, Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were assessed before and after the treatment process. To conclude the optimum comparative results, the pH of wastewater was maintained constant, as it can capitalize or moderate the adsorption process (initial pH of was 8.2 ± 0.1, but it was maintained to 8). The contamination remediation was found to be effective with immobilized algal biomass (46.7% of nitrate, 59.4% of phosphate, 83.1% BOD and 83.0% of COD) than free algal biomass (43.2% of nitrate, 56.7% of phosphate, 71.4% of BOD and 78.0% COD).

Impact assessment on water quality in the polluted stretch using a cluster analysis during pre- and COVID-19 lockdown of Tawi river basin, Jammu, North India: an environment resiliency.

Pollution-free rivers give indication of a healthy ecosystem. The stretch of Tawi river particularly in the Jammu city is experiencing pollution load and the quality is degraded. The present study highlights the impact of COVID-19 lockdown on the water quality of Tawi river in Jammu, J&K Union Territory. Water quality data based upon the real-time water monitoring for four locations (Below Tawi Bridge, Bhagwati Nagar, Belicharana and Surajpur) have been obtained from the web link of Jammu and Kashmir Pollution Control Board. The important parameters used in the present study include pH, alkalinity, hardness, conductivity, BOD and COD. The river was designated fit for bathing in all the monitoring locations except Bhagwati Nagar which recorded a BOD value >5 mg/L because of domestic sewage and municipal waste dumping. The overall water quality in the river during lockdown was good and falls in Class B with pH (7.0-8.5), alkalinity (23.25-185.0 mg/L), hardness (84.25-177.5 mg/L), conductivity (117-268 ms/cm). The improved water quality obtained during lockdown is never long-lasting as evident from the BOD and COD values observed during Unlock 1.0 due to accelerated anthropogenic activities in response to overcoming the economic loss, bringing the river water quality back to the degraded state. The statistical analysis known as cluster analysis has also been performed to evaluate the homogeneity of various monitoring sites based on the physicochemical variables. The need of the hour is to address the gaps of rejuvenation strategies and work over them for effective river resiliency and for sustainable river basin management.

Utilization of Chlorella pyrenoidosa for Remediation of Common Effluent Treatment Plant Wastewater in Coupling with Co-relational Study: An Experimental Approach.

Earlier investigations on biological methods of wastewater treatment have revealed that algal based wastewater treatment could be a green, cost effective and efficient approach for the removal of heavy metals. So, this study aimed to assess the potential of microalga Chlorella pyrenoidosa for remediation of heavy metals (Cr, Cu, Pb, Zn, Cd, Mn, and Ni) from varying concentration (25%, 50%, 75 and 100%) of wastewater collected from Common Effluent Treatment Plant. Heavy metals such as Cr, Cu, Pb, Zn, Cd, Mn, and Ni have been removed significantly from the wastewater, with percentage removal ranging from 73%, 60%, 75%, 66%, 87%, 83%, and 74% with 50% test solution, 57%, 59%, 70%, 56%, 72%, 66%, and 62% with 75% test solution, and 47%, 55%, 56%, 71%, 61%, 77%, and 72% with 100% test solution respectively. Studies on biochemical assay (protein, carbohydrate, and pigment) of Chlorella pyrenoidosa were also an important part of the present investigation to understand the interaction of heavy metals with algal biochemical compounds using Pearson correlation co-efficient. Biomass grown in CETP wastewater can be used for synthesis of various fruitful value-added end products like bio-diesel, pharmaceutical products, cosmetic products, bio-adsorbent etc.

Cultivation of two Chlorella species in Open sewage contaminated channel wastewater for biomass and biochemical profiles: Comparative lab-scale approach.

Open sewage contaminated channel wastewater (OSCCW) has high pollutant loads, responsible for eutrophication, when mixed with various channels of urban communities. But, these pollutants can be converted and recovered into useful end products with the help of algal species. In this study, two species of Chlorella (C. vulgaris and C. pyrenoidosa) were selected and investigated for the production of algal biomass and nutrient removal efficiencies with 50% concentration of OSCCW, in a comparative way at lab-scale. Chlorella sp. cultivated in OSCCW have removed nitrate (76.9-78.8%) and phosphate (67.6-79.7%) whereas COD (72.4-76.2%) and BOD (62.3-72.4%) respectively. Correlation analysis was investigated between physico-chemical parameters and biochemical profile of both species to analyze the positive and negative correlation between two variables. The bio-chemical profile and biomass productivity of both species of Chlorella were observed well on the basis of productivity of biomass (60.1, 56.5 mg/l/d), carbohydrate (15.71, 8.82 mg/l/d), protein (11.21, 15.82 mg/l/d), lipid (20.8, 17.5 mg/l/d) and chlorophyll (0.78, 0.67 mg/l/d) in OSCCW. The maximum lipid content (34.6%) was obtained with C. pyrenoidosa as compared to C. vulgaris. Findings also support that OSCCW is well-off with nutrient resources, which can be suitable alternative for algal biomass production and remediated wastewater can be used for animal and fish farming type activities.

Technological advancements in jaggery-making processes and emission reduction potential via clean combustion for sustainable jaggery production: An overview.

Jaggery is a kind of unrefined non-centrifugal sugar (NCS) used mainly in Asia, Africa, Latin America, and the Caribbean. Traditionally, jaggery is produced by concentrating sugarcane juice in open pans with the help of bagasse combustion. However, due to thermal energy loss with flue gases and an unscientific approach in plant construction, jaggery plants have a poor thermal efficiency of less than 25%, poor emission characteristics, and a high bagasse consumption rate. Advanced jaggery-making techniques use solar energy and heat pumps for jaggery production. However, these techniques are in the early stage of development, and the literature indicates that these techniques should be used in conjuction with traditional ones to improve the performance of jaggery making plants. This literature review describes advances in jaggery-making methods, critically analyzed them, and provides a qualitative comparison of these methods. Further, gaps in the existing literature are identified and reported for future research direction. In addition, efforts have been made to quantify and estimate the emissions reduction and bagasse consumption potentials from the traditional jaggery industry to make this rural industry a sustainable and profitable business for rural entrepreneurs. The comparison with the recently developed clean combustion device exhibits that the harmful emissions from the jaggery industry could be reduced drastically viz. 95%-98% of PM2.5; 92%-95% of CO, and 52-60% of CO2, while saving more than 35% of bagasse consumption. Implemented at a national scale, it may reduce nearly 3% of all harmful emissions in the country, which is equally applicable elsewhere.

Novel approach for harvesting of microalgal biomass using electric geyser waste material deposit as flocculant in coupling with poultry excreta leachate.

The aim of this work was to study the flocculation efficiency of algal biomass (Chlorella pyrenoidosa) in coupling with waste materials i.e. poultry excreta leachate by using other waste material which was obtained from deposition of scaling in electric geyser. Utilization of electric geyser waste material deposit (EGWMD) for flocculation is a novel approach because of various elements which are replica of chemical flocculants responsible for flocculation mechanism in culture medium. Flocculation process was optimized by response surface methodology and 98.21% flocculation efficiency was achieved with designed process parameters as temperature 32.5 °C, flocculant dose 275 mgL-1, pH 5 and time 30 min. The reusability of spent medium was also analyzed at 70.2% and 32.5% flocculation efficiency with two successive steps. The cellular morphology of pre-harvested and post-harvested Chlorella pyrenoidosa was also observed. EGWMD is abundant and freely available that has no application till now and can alternate of chemical flocculants.

Utilization of solar energy for wastewater treatment: Challenges and progressive research trends.

This article offers a trend of inventions and implementations of photocatalysis process, desalination technologies and solar disinfection techniques adapted particularly for treatment of industrial and domestic wastewater. Photocatalysis treatment of wastewater using solar energy is a promising renewable solution to reduce stresses on global water crisis. Rendering to the United Nation Environment Programme, 1/3 of world population live in water-stressed countries, while by 2025 about 2/3 of world population will face water scarcity. Major pollutants exhibited from numerous sources are critically discussed with focus on potential environmental impacts & hazards. Treatment of wastewater by photocatalysis technique, solar thermal electrochemical process, solar desalination of brackish water and solar advanced oxidation process have been presented and systematically analysed with challenges. Both heterogenous and homogenous photocatalysis techniques employed for wastewater treatment are critically reviewed. For treating domestic wastewater, solar desalination technologies adopted for purifying brackish water into potable water is presented along with key challenges and remedies. Advanced oxidation process using solar energy for degradation of organic pollutant is an important technique to be reviewed due to their effectiveness in wastewater treatment process. Present article focused on three key issues i.e. major pollutants, wastewater treatment techniques and environmental benefits of using solar power for removal of pollutants. The review also provides close ideas on further research needs and major concerns. Drawbacks associated with conventional wastewater treatment options and direct solar energy-based wastewater treatment with energy storage systems to make it convenient during day and night both listed. Although, energy storage systems increase the overall cost of the wastewater treatment plant it also increases the overall efficiency of the system on environmental cost. Cost-efficient wastewater treatment methods using solar power would significantly ensure effective water source utilization, thereby contributing towards sustainable development goals.

Fungal bioleaching of metals from refinery spent catalysts: A critical review of current research, challenges, and future directions.

Petroleum refining operations such as hydroprocessing and fluid catalytic cracking (FCC) generate huge quantities of spent catalysts containing toxic and valuable metals (Ni, V, Mo, Co, W, Al, etc.), the management of which is a serious environmental issue. Besides environmental concerns, the different metals present in the spent catalysts are also a valuable commodity to modern industries. Therefore, these spent catalysts also provide an opportunity to use it as a source of value to the refiners. In recent years, a biotechnological based leaching process 'bioleaching' has emerged as a promising eco-friendly technique for the extraction of metals from these refinery spent catalysts. Among various bioleaching agents such as archean, bacterial, or fungi, the process mediated by the fungi (Aspergillus niger, Penicillium simplicissimum, and many others) is gaining attention owing to the high metal extraction ability of the various fungal produced metabolites (organic acids) under moderately acidic conditions. Furthermore, the ability of these fungi to withstand wide process conditions (pH, spent catalyst concentration, substrate types, etc.), high metal toxicity and use of low-cost organic substrate make them an ideal candidate for bioleaching. In this review article, we shed light on the role and mechanisms of fungi involved in extracting different metals from spent hydroprocessing and FCC catalysts. Key process parameters that affect the efficiency of fungal based bioleaching are discussed. The techno-economic challenges associated with the process are elaborated, and the needed future research directions to promote its commercial applications are highlighted. Based on our analysis, it can be argued that the fungi bioleaching has potential, however, some challenges (slower kinetics, and health and safety) should be addressed before the process can be scaled up for the commercial application.

Bioprocessing of cultivated Chlorella pyrenoidosa on poultry excreta leachate to enhance algal biomolecule profile for resource recovery.

The aim of this work was to study the cultivation of Chlorella pyrenoidosa on poultry excreta leachate to enhance the biochemical composition of algal biomass. The growth of microalgae was analyzed with different concentrations of poultry excreta leachate in BG-11 and distilled water. The biomolecules observed have high value in the form of carbohydrates (0.64 gL-1), protein (1.02 gL-1), chlorophyll (20 µg mL-1) and lipid amount (0.49 gL-1) with PEL BG -25%. Biomass produced in PEL BG -25% was also found to be 60% (2.5 gL-1) higher than the BG-11 medium as a control (1.5gL-1). Recovery of nutrients was observed with leachate wastewater concentration in terms of nitrate (84.2%), ammonium nitrogen (53.1%), and inorganic phosphate (96.2%). Hence, sustainability of microalgae cultivation in wastewater provides a new insight for resource utilization.

Production of algal biomass for its biochemical profile using slaughterhouse wastewater for treatment under axenic conditions.

Slaughterhouse produce large amount of wastewater, containing high pollutant load in terms of protein, fats and meat pieces, might lead to source of non-point contamination. Various concentrations (25%, 50%, 75%, and 100%) of slaughterhouse wastewater were used to increase the algal biomass production, pollutants removal and biochemical profile analysis under controlled conditions of C. pyrenoidosa. Results showed that the maximum biomass yield 430 mg L-1 was achieved at 50% concentration of wastewater to other concentration of wastewater. Direct relation was observed in between pollution load and nutrient load of SHWW with biochemical profile of C. pyrenoidosa. The COD/BOD ratio (1.9) was found to be significant on the scale of degradability by algal biomass. Sufficient nutrient removal efficiencies (23-42%, 18-48%) and pollutant load efficiencies (17-31%, 7-29%) were observed. Findings showed that slaughterhouse wastewater is rich in nutrients, which can be utilized for algal biomass production and wastewater remediation for future endeavors.

Evaluation of carbonized waste tire for development of novel shape stabilized composite phase change material for thermal energy storage.

This work is focused on the preparation of an activated charcoal by carbonization of waste tire rubbers (WTRs) and its evaluation for shape-stabilization of dodecyl alcohol (DDA) as an organic phase change material (PCM) used for thermal energy storage (TES). In the composite, DDA had TES function as carbonized waste tire (CWT) acted as supporting and thermal conductive frameworks. CWT prevented leakage of melted DDA during phase change due to its good adsorption ability until the weight ratio of DDA reached 78%. The shape-stabilized composite PCM was characterized by FT-IR, XRD, SEM, DSC and TGA techniques. The DSC results revealed that the composite PCM had very appropriate melting point of 21.68 ± 0.12 °C and considerable high latent heat capacity of 181.6 ± 1.2 J/g for thermoregulation of buildings. Compared to DDA, thermal degradation temperature of the composite PCM was extended as about 50 °C. The 500-cycled composite PCM had still showed reliable TES properties. Additionally, thermal conductivity (0.431 ± 0.010 W/m·K) of the composite PCM was measured as about 2.3 times higher than that of DDA. The heating and cooling periods of the composite PCM were reduced by 17.2 and 20.0%, respectively compared to that of DDA due to its enhanced thermal conductivity. All results suggested that the produced CWT as low-cost and environmental friendly supporting material can be evaluated for absorbing PCMs used for passive solar TES utilization in buildings.

Temperature dependent morphological changes on algal growth and cell surface with dairy industry wastewater: an experimental investigation.

In the present study, influence of temperature and dairy industry waste water (DIWW) concentration on the growth of Chlorella pyrenoidosa has been done along with the thermodynamic analysis of different functions viz. change in enthalpy (∆H), change in entropy (∆S), free energy change (∆G), and activation energy (E a) to study the impact on cell size distribution and morphological changes. Among the studied temperatures, higher biomass productivity was observed at 35 °C at 75% of DIWW. Thermodynamic analysis showed the spontaneous and exothermic nature of growth of C. pyrenoidosa. Experimental data have significantly proven the kinetic and thermodynamics functions with 35 °C temperature, ∆H (- 46.78 kJ mol-1), ∆S (- 0.10 kJ mol-1), ∆G (- 14.8 kJ mol-1), and E a (49.28 kJ mol-1). At this temperature, size distribution showed maximum percentage (48%) cells were of 6540 nm, whereas the minimum percentage (3%) cells were of 2750 nm. SEM-EDX study revealed that increase in temperature leads to increase in roughness and elemental deposition of metal on cell surface.

Bio-fixation of flue gas from thermal power plants with algal biomass: Overview and research perspectives.

Rate of energy production is reflecting growth of nations and most of energy produced from the coal and natural gas-based thermal power plants (TPPs). Flue gas (point sources of emission) are main exhaustible form of gases that come from thermal power plants and are continuously promoting climate change and various environmental problems in global scenario. The present available technologies of flue gas treatment are energy and cost-intensive process. Among the available techniques for fixation of flue-gases at sustainable part, microalgal bio-fixation of flue gas is an alternative promising and competent technology with assurance of eco-friendly path of low energy and low-cost solution for pollution abetment with production of value added products. According to mechanism involves during photosynthetic process of microalgae, it utilizes atmospheric CO2 and CO2 from flue gases for their growth. Past, present and future treatment technologies for flue gas with their challenges are discussed. Recent experimental studies and commercially available bioreactors are very particular for bio-fixation of flue gas from thermal power plants are also reviewed with their future perspectives. The commercial viability of process with specific microalgal strains and utilized biomass for further value-added products are suggested with future limitations.

Experimental studies on zeta potential of flocculants for harvesting of algae.

An experimental study was performed to evaluate the comparative efficiency of bio-flocculant (waste egg shell), laboratory available calcium carbonate (LACC) and alum (Al2 (SO4)3) for harvesting of unicellular microalga, Chlorella pyrenoidosa. The influence of pH on zeta potential (ζ) was also studied to explain the chemistry of flocculation process. The maximum harvesting efficiency (99%) was obtained with alum with deformities in algal cell surfaces. Waste egg-shell material is developed as a low-cost bio-flocculant for harvesting of Chlorella pyrenoidosa using 100 mg egg-shell bio-flocculant/L and 100 mg LACC/L, zeta potential analysis was completed to further understand the chemistry of harvesting efficiency over the different ranges of pH (2.0, 4.0, 6.0, 8.0, and 10.0). The optimized range for harvesting efficiency (HE) of pH is 4.0-8.0 for both flocculants. Maximal harvesting efficiency was achieved at pH 4.0 (99%) and pH 8.0 (95%) with bio-flocculant and LACC respectively. Hence, bio-flocculant based harvesting method is found as the best way to dewatering the algal biomass from aqueous medium with entire and intact algal cell surface with environment friendly and cost-effective approach.

Experiment-based thermodynamic feasibility with co-digestion of nutrient-rich biowaste materials for biogas production.

Wild strains of algal biomass, a major contributor for eutrophication in freshwater bodies, can be used as a potential substrate in association with other nutrient-rich biowaste materials like animal excreta and industrial wastewater, for biogas production. This novel concept was experimentally evaluated and analyzed by the modified Gompertz equation for maximum biogas production (µm), lag phase (λ), and biogas yield (P). The value of correlation coefficient (R2) was 0.99 at varying temperature ranges (30, 40, and 50 °C). Thermodynamic functions like enthalpy (∆H), entropy (∆S), and Gibb's free energy (∆G) were evaluated for the chemical oxygen demand removal efficiency. Thermodynamic functions such as ∆G (-), ∆H (+), and ∆S (+) showed the spontaneous and endothermic nature of substrate degradation and biogas production was found to be increased with increasing temperature. So, this novel co-digestion approach using nutrient-rich biowaste materials provides a new insight into biogas production with the aim of waste-to-energy generation.

Microalgal cultivation for value-added products: a critical enviro-economical assessment.

The present review focuses on the cultivation of algal biomass for generating value-added products (VAP) and to assess their economic benefits and harmful environmental impact. Additionally, the impact of bioreactor designs on the yield of microalgal biomass for VAP is also considered. All these factors are discussed in relation to the impact of microalgae production on the bio-economy sector of commercial biotechnology.

A critical review on factors influencing fermentative hydrogen production.

Biohydrogen production by dark fermentation of different waste materials is a promising approach to produce bio-energy in terms of renewable energy exploration. This communication has reviewed various influencing factors of dark fermentation process with detailed account of determinants in biohydrogen production. It has also focused on different factors such as improved bacterial strain, reactor design, metabolic engineering and two stage processes to enhance the bioenergy productivity from substrate. The study also suggest that complete utilization of substrates for biological hydrogen production requires the concentrated research and development for efficient functioning of microorganism with integrated application for energy production and bioremediation. Various studies have been taken into account here, to show the comparative efficiency of different substrates and operating conditions with inhibitory factors and pretreatment option for biohydrogen production. The study reveals that an extensive research is needed to observe field efficiency of process using low cost substrates and integration of dark and photo fermentation process. Integrated approach of fermentation process will surely compete with conventional hydrogen process and replace it completely in future.