Algae-based Wastewater Treatment Research Articles

Algal-based membrane reactor for the remediation of emerging contaminants from wastewater: Mechanism, synthesis and technological advancement

With an increase in the world's economy and the human population, there's a growing need for drinking water suitable for consumption. Water management might inevitably become the top priority on a global scale. The rapidly evolving bioremediation landscape is a major driver for the development of sustainable solutions that can provide value beyond just environmental remediation. Phycoremediation or algae-mediated remediation is attracting the most attention because of its captivating sustainability characteristics, its ability to eliminate odors, fouling, and toxins, its ability to eliminate many common as well as emerging contaminants from the gaseous and aqueous environment, and its ability to produce biomass for a variety of value-added products. Algae-based wastewater treatment plants like bioreactors are gaining more attention than traditional membrane reactors as they are environmentally friendly and sustainable. Due to the non-function of traditional municipal wastewater treatment plants, emerging pollutants such as personal care products, pharmaceuticals, antibiotics, and mono- and polyaromatic hydrocarbons are discharged into the waterbody regularly causing harmful effects to aquatic lives. Algae-based membrane bioreactors (AMBRs), are the most advanced technology used to remove emerging contaminants (ECs) found in wastewater. Furthermore, mixed algae-MBRs become more popular than unialgal MBRs due to mutualistic synergism. Advancements in cylindrical and rectangular-shaped AMBRs were also found better for the bioremediation of ECs. In conclusion, various ECs and their remediation mechanisms by different algal strains and sustainable technologies are discussed in the present communication. Most importantly, modifications of AMBRs with microfiltration membrane or osmotic membrane or integrated with activated sludge have been considered in this research.

The role of algae-based wastewater treatment systems: A comprehensive review

Algae-based wastewater treatment systems have gained significant attention as sustainable and efficient solutions for nutrient removal, organic pollutant degradation, and biomass production. This comprehensive review explores the role of algae-based systems in wastewater treatment, covering key aspects such as nutrient uptake mechanisms, cultivation techniques, system design considerations, and environmental sustainability implications. Algae offer unique advantages for wastewater treatment, including high nutrient removal rates, CO2 sequestration, and the production of valuable biomass for biofuel production and nutrient recycling. Various cultivation methods, including open ponds, raceways, photobioreactors, and wastewater treatment wetlands, are evaluated for their suitability in different wastewater treatment scenarios. The integration of algae-based systems with conventional wastewater treatment processes, such as activated sludge and membrane bioreactors, is discussed to enhance treatment efficiency and resource recovery. Furthermore, the environmental sustainability of algae-based systems, including carbon footprint, water footprint, and ecosystem impacts, is assessed to identify opportunities for mitigating environmental impacts and promoting ecosystem resilience. Future research directions in algae-based wastewater treatment systems, such as optimization of cultivation conditions, development of novel algal strains, and techno-economic analysis of large-scale implementation, are proposed to address remaining challenges and accelerate the adoption of algae-based technologies in wastewater treatment practices. Overall, this review provides valuable insights into the role of algae-based systems as sustainable and versatile tools for wastewater treatment, highlighting their potential to address the growing challenges of nutrient pollution and water scarcity in the 21st century.

Fungi-assisted bio-flocculation of Picochlorum sp.: A novel bio-assisted treatment system for municipal wastewater

Integration of microalgal cultivation with wastewater reclamations are sustainable valorizations approach to nutrients removal and lipid-rich biomass production. Lower growth rates and higher harvesting costs are the major bottlenecks of algal-based wastewater treatment process. Therefore, this study was carried-out to investigate lipid-rich biomass production using wastewater and demonstrate the low-cost biomass harvesting method. Picochlorum sp. BDUG 100241 (PC) was explored in various combinations of untreated raw municipal wastewater (UTMWW) and secondary treated municipal wastewater (STMWW) with a conventional ASN-III medium. The day-night cycles, pH, and aeration were optimized to improve PC biomass production. For harvesting of PC biomass, different concentrations of filamentous fungi Aspergillus niger MTCC 281 (A. niger) and Stropharia sp. ITCC-8422 assisted bioflocculation approach was investigated. In the first phase of optimization, PC showed maximum nutrient removal efficiency and growth in 50 % STMWW +50 % ASN-III. The present results indicated that a 12:12 h day-night cycle and a pH of 7.0 with aeration resulted in the highest nutrient removal efficiency of COD (90.92 %), phosphate (92.26 %) and nitrate (87.20 %). This optimized conditions also improved the biomass production (2.66 g/L), lipid content (44.04 %), photosynthetic and carotenoids (astaxanthin and β-carotene) production. Further, 10 % Stropharia sp. and A. niger granulated pellets signified the bioharvesting of PC biomass with maximum bioflocculation efficiency of 90.15 % and 92.48 %, respectively. The incorporation of bioflocculants, namely Stropharia sp. and A. niger for the harvesting of microalga biomass facilitated the removal of nutrients, enhanced biomass production (4.21 and 4.01 g/L), and augmented lipid content (43.0 % and 47.33 %) respectively.

Exploring advanced phycoremediation strategies for resource recovery from secondary wastewater using a large scale photobioreactor

This study aimed to investigate the operation of a 1000L microalgae-based membrane photobioreactor system in a greenhouse for continuous secondary wastewater treatment using Desmodesmus sp., a green microalgae strain originally isolated from a German sewage plant. The research spanned both summer and winter seasons, seeking to comprehend key trends and optimization strategies. Maintaining low cell concentrations in the photobioreactor during periods of light inhibition proved advantageous for nutrient uptake rates. Effective strategies for enhancing algae-based wastewater treatment included cell mass recycling, particularly during periods of high light availability. In comparison to conventional continuous cultivation methods, employing cell recycling and high dilution rates during times of abundant light, alongside using low cell concentrations and dilution rates during light inhibition, resulted in an 80 % and 10 % increase in overall biomass productivity during summer and winter, respectively. Furthermore, nitrogen/phosphorus (N/P) removal rates exhibited a 23 % improvement during winter, while remaining unchanged in summer.

Reclamation Potential of Onsite Wastewater Post-Treatment with Microalgae: Chemical Elements Perspective

Algae-based wastewater treatment is a promising technology with various applications for excess biomass such as biofertilizer production or valuable elements extraction. The benefits of the technology have been discussed for larger wastewater treatment plants (WWTPs), but the use of microalgae in decentralized wastewater treatment has been barely reported. The current study screens the possible resource recovery potential of onsite technology, which adds algae-based post-treatment to the conventional biological treatment of domestic wastewater. The effluent from the onsite sequencing batch reactor (SBR) of a household was further processed in laboratory conditions using an SBR technology with two local monocultures of algae—Klebsormidium nitens (Kützing) Lokhorst and Tetradesmus obliquus (Turpin) M. J. Wynne. The decant and the generated algal biomass were analyzed in terms of their element content. The post-treated effluent has a slightly better quality for irrigation purposes than the effluent of the onsite treatment facility—up to 1.6 times increased concentration for macro-elements and up to 1.9 times for micro elements. However, the generated algal biomass shows promising potential for re-use as a fertilizing agent since it contains valuable macro- and micro-elements and the heavy (hazardous) metal content is considerably lower than the limiting values in the current European and national legislations. The K. nitens strain may attract interest since it accumulates valuable metals such as chromium (36 mg/kgDS), nickel (83 mg/kgDS), and silver (0.7 mg/kgDS) that can be derived from the biomass and turn the technology to a circular one.

Life cycle energy use and greenhouse gas emissions for a novel algal-osmosis membrane system versus conventional advanced potable water reuse processes: Part I

This study applied a life cycle assessment (LCA) methodology for a comparative environmental analysis between an innovative algae resource recovery and near zero-liquid discharge potable reuse system (i.e., the main system) versus a conventional potable reuse system (i.e., the benchmark system) through energy use and greenhouse gas (GHG) emissions. The objective of this study is to demonstrate that pilot-scale data coupled with LCA would provide valuable information for system optimization, integration, and improvements for the design of environmentally sustainable full-scale systems. This study also provides decision-makers valuable information regarding the energy demand and environmental impact of this innovative main system compared to a typical tried-and-true system for potable water reuse. The main system consists of a novel algal-based wastewater treatment coupled with a dual forward osmosis and seawater reverse osmosis (Algal FO-SWRO) membranes system for potable water recovery and hydrothermal liquefaction (HTL) to recover biofuels and valuable nutrients from the harvested algal biomass. The benchmark system refers to the current industry standard technologies for potable water reuse and waste management including a secondary biological treatment, microfiltration (MF), brackish water reverse osmosis (BWRO), ultraviolet/advanced oxidation process (UV-AOP), and granular activated carbon (GAC), as well as anaerobic digestion for sludge treatment. Respective energy and GHG emissions of both systems were normalized and compared considering 1 m3 of water recovered. Based on an overall water recovery of 76% designed for the benchmark system, the energy consumption totaled 4.83 kWh/m3, and the system was estimated to generate 2.42 kg of CO2 equivalent/m3 with most of the emissions coming from the biological treatment. The main system, based on an overall water recovery of 88%, was estimated to consume 4.76 kWh/m3 and emit 1.49 kg of CO2 eq/m3. The main system has high environmental resilience and can recover bioenergy and nutrients from wastewater with zero waste disposal. With the application of energy recovery devices for the HTL and the SWRO, increase in water recovery of the FO membrane, and replacement of the SWRO membrane with BWRO, the main system provides an energy-competitive and environmentally positive alternative with an energy demand of 2.57 kWh/m3 and low GHG emissions of 0.94 kg CO2 eq/m3.

Techno-economic assessment of a novel algal-membrane system versus conventional wastewater treatment and advanced potable reuse processes: Part II

This study developed a comprehensive techno-economic assessment (TEA) framework to evaluate an innovative algae resource recovery and near zero-liquid discharge potable reuse system (i.e., the main system) in comparison with a conventional potable water reuse system (i.e., the benchmark system). The TEA study aims to estimate the levelized costs of water of individual units and integrated processes including secondary wastewater treatment, advanced water purification for potable reuse, and sludge treatment. This would provide decision-makers valuable information regarding the capital and operational costs of the innovative main system versus a typical potable water reuse treatment train, along with possible routes of cost optimization and improvements for the design of full-scale facilities. The main system consists of (i) a novel algal-based wastewater treatment coupled with a dual forward osmosis and seawater reverse osmosis (Algal FO-SWRO) membranes system for potable water reuse and hydrothermal liquefaction (HTL) to produce bioenergy and subsequent nutrients extraction from the harvested algal biomass. The benchmark system includes (ii) an advanced water purification facility (AWPF) that consists of a conventional activated sludge biological treatment (CAS), microfiltration (MF), brackish water reverse osmosis (BWRO), ultraviolet/advanced oxidation process (UV-AOP), and granular activated carbon (GAC), with anaerobic digestion for sludge treatment. Capital expenditures (CAPEX) and operational expenditures (OPEX) were calculated for each unit of both systems (i.e., sub-systems). Based on a 76% overall water recovery designed for the benchmark system, the water cost was estimated at $2.03/m3. The highest costs in the benchmark system were found on the CAS and the anaerobic digester, with the UV-AOP combined with GAC for hydrogen peroxide (H2O2) quenching as the driving factor in the increased costs of the system. The cost of the main system, based on an overall 88% water recovery, was estimated to be $1.97/m3, with costs mostly driven by the FO and SWRO membranes. With further cost reduction and optimization for FO membranes such as membrane cost, water recovery, and flux, the main system can provide a much more economically viable alternative in its application than a typical benchmark system.

Free ammonia tolerance of cyanobacteria depends on intracellular pH

Algae-based wastewater treatment can remove nutrients from wastewater and simultaneously produce valuable products. However, inhibition of microalgae by NH3 in the wastewater poses a challenge to this process. It is desirable to understand the mechanism of inhibition by NH3 for physiological characterization of microalgae and their application. NH3 tolerance, which varies among species, is assumed to depend on intracellular pH. To verify the adequacy of the assumption, in this study, the 50% inhibitory concentration (EC50) of NH3 for four cyanobacterial species was evaluated as an indicator of NH3 tolerance and compared to intracellular pH. The EC50 of NH3 was 4.95, 5.05, 4.38, and 0.74 mM and the intracellular pH was 8.0, 8.4, 8.2, and 7.3 for Arthrospira platensis, Arthrospira fusiformis, Synechococcus leopoliensis, and Anabaena cylindrica, respectively. A significant correlation was obtained between intracellular pH and EC50. Analysis of the chlorophyll fluorescence of cells exposed to NH3 for 1.5 h showed that photochemical quenching was reduced rather than Fv'/Fm' under NH3 concentrations lower than EC50, suggesting that the electron transfer system downstream of photosystem II (PSII) was more sensitive than PSII itself. Because several sites downstream of PSII utilize H+, including ATP synthase, the inhibition may be caused as a result of H+ consumption by NH3 diffused inside the cells. As consumption of H+ in NH3 ionization is suppressed under high pH, species with higher intracellular pH probably have higher NH3 tolerance. These results should help understand the free NH3 tolerance of cyanobacteria.

The effect of the internal nutrient quota accumulation on algal-based wastewater treatment: Decoupling HRT and SRT to improve the process

The application of microalgae to wastewater treatment is an emerging technology following a circular economy approach. The optimization of such a process for large-scale applications in continuous reactors is not trivial, since both high nutrients removal and biomass productivity are desired. As microalgae are able to change their composition as a function of environmental variables, the accumulation of nutrients internal quota may have a role in the process. In this work, the kinetic parameters of microalgae growth and nutrients uptake/accumulation according to the Droop model were retrieved from experiments in continuous photobioreactors, and the model was used to investigate the behavior of the process. The analysis revealed that, by uncoupling hydraulic retention time (HRT) and solid retention time (SRT), both nutrients removal and biomass productivity could be optimized, which is not possible when operating a chemostat system. In wastewater with high nutrient concentration it was found that, by decoupling HRT and SRT, the same maximum biomass productivity of 470 g m−3 d−1 can be achieved as with a single chemostat reactor operating at SRT = 1.5 day, but reducing the outlet nutrient concentration by 15 %. In addition, by taking advantage of the Droop model's ability to predict the nutrient content in biomass, it is possible to work towards obtaining biomass with the desired internal amount of nutrients, varying, for example, the nitrogen quota from 11 % to 14 %, depending on the scope of the biomass produced.

Analysis on the Effects of 3D-Printed Bio-Propeller in Algal Nutrient Removal Efficiency and Biomass Production in a Laboratory-Scale Algal-Based Wastewater Treatment

Additive Manufacturing is an emerging technology used in wide applications including, wastewater treatment. This paper presents applied techniques of Additive Manufacturing in producing a 3D-printed prototype model of a laboratory-scale wastewater treatment process. This paper aims to show the efficiency of bioremediation of freshwater algae in reducing traces of phosphate and nitrates - both known pollutants responsible for eutrophication. The study also comparatively reviews two different set-ups: stagnant and aerated. 3D printed bio-propeller, a polylactic acid-based aerator, was applied to the latter aforementioned set-up and was designed to be durable, environmental oriented, and cost-efficient. Moreover, the features and details of the 3D-printed bio-propeller emphasized its ability to promote algae harvesting by acting as a sustainable biofilm for algal growth. It is found that both set-ups show significant algae bioremediation efficiency for the synthetic nutrients. Also, the aerated set-up indicated a favorable result with the highest efficiency of 92.857% for nitrates and 41.667% for phosphate. It is concluded that the potentials of 3D printed bio-propeller as a prime component of Rotating Biological Contractor (RBC) can promote sustainable wastewater treatment.

Cross-feeding among microalgae facilitates nitrogen recovery at low C/N

Although co-culture of microalgae has been found as a feasible strategy to improve biomass production, their interspecies relationships are not fully understood. Here, two algae taxa, Chlorella sp. and Phormidium sp., were mono-cultured and co-cultured in three photobioreactors for 70 days with periodically harvesting to investigate how dual-species interaction influence nitrogen recovery. Results showed that the co-culture system achieved a significantly higher protein production and nitrogen removal rate than those in the individual cultures at a C/N ratio of 3:1 (p < 0.05). Genome-Centered metagenomic analysis revealed their cooperative relationship exemplified by cross-feeding. Phormidium sp. had the ability to synthesize pseudo-cobalamin, and Chlorella sp. harbored the gene for remodeling the pseudo-cobalamin to bioavailable vitamin B12. Meanwhile, Chlorella sp. could contribute the costly amino acid and cofactors for Phormidium sp. Their symbiotic interaction facilitated extracellular polymeric substances (EPS) production and nitrogen recovery. The EPS concentration in co-culture was positively related to the settling efficiency (R2 = 0.774), which plays an essential role in nitrogen recovery. This study provides new insights into microbial interactions among the photoautotrophic community and emphasizes the importance of algal interspecies interaction in algae-based wastewater treatment.

A Review on the Reliability and the Readiness Level of Microalgae-Based Nutrient Recovery Technologies for Secondary Treated Effluent in Municipal Wastewater Treatment Plants

Algae-based wastewater treatment technologies are promising green technologies with huge economical potential and environmental co-benefits. However, despite the immense research, work, and achievement, no publications were found wherein these technologies have been successfully applied in an operational environment for nitrogen and phosphorus removal of secondary treated effluent in municipal wastewater treatment plants. Based on a literature review and targeted comprehensive analysis, the paper seeks to identify the main reasons for this. The reliability (considering inlet wastewater quality variations, operating conditions and process control, algae harvesting method, and produced biomass) as well as the technology readiness level for five types of reactors are discussed. The review shows that the reactors with a higher level of control over the technological parameters are more reliable but algal post-treatment harvesting and additional costs are barriers for their deployment. The least reliable systems continue to be attractive for research due to the non-complex operation and relieved expenditure costs. The rotating biofilm systems are currently undertaking serious development due to their promising features. Among the remaining research gaps and challenges for all the reactor types are the identification of the optimal algal strains, establishment of technological parameters, overcoming seasonal variations in the effluent’s quality, and biomass harvesting.

A Review of Microalgae- and Cyanobacteria-Based Biodegradation of Organic Pollutants.

This review proposes a new bioremediation method based on the diverse functionalities of algae. A greenway for cleansing wastewater is more ecologically friendly and environmentally sustainable than prior methods with other bacteria. New bioremediation technology employing algae and cyanobacteria for the removal of a wide range of organic contaminants is reasonable and has great potential. The prevalence of organic contaminants in aquatic habitats may endanger the health and well-being of several marine creatures. Agriculture, industry, and household trash are just a few of the human-caused sources of organic pollutants that contaminate waterways around the world. Before wastewater can be released into waterways, it must be cleaned. Algae-based wastewater treatment systems are becoming increasingly popular because of their environmental sustainability and lack of secondary pollutants. According to the kind of pollutant, the physicochemical properties of wastewater, and the algal species, algae and cyanobacteria can absorb and accumulate a wide spectrum of organic pollutants at different rates. In addition, phytoremediation is a cost-effective alternative to conventional treatments for degrading organic contaminants. Phycoremediationally produced algal biomass may also be an important part of the bioenergy value chain. This article focuses on microalgae and cyanobacteria species, which may remove many organic contaminants from water systems.

Application of Aspergillus niger F5 as an alternative technique to harvest microalgae and as a phosphorous removal treatment for cassava biogas effluent wastewater

Wastewater treatment using microalgae often produces effluents with unassimilated nutrients such as phosphorous with relatively high cost of harvesting process. The current study aims to develop a fungal pellet that solubilizes phosphate as a bio-adsorbent for enhancing microalgae harvesting process and additional removal of phosphorous to increase the harvestability of the algae and overcome the occurrence of unassimilated nutrients in the wastewater that often become problems in the algal-based wastewater treatment system. Isolated strains with phospate solubilizing activity, Aspergillus niger F5 and Aspergillus awamori F2, were found to show stable algal cells adsorption efficiency with less desoprtion as the increase of glucose concentration. Additional of A. niger F5 pellets after the total phosphorus (TP) concentration became stationary in cassava wastewater treatment using Chlorella vulgaris TISTR 8580 was found to significantly increase TP and chemical oxygen demand (COD) removals. Another approach by co-culturing the A. niger F5 and C. vulgaris TISTR 8580 also increased the removal efficiencies but less effective in trapping algal cells. However, total nitrogen removal decreased with both methods of application. With 70% adsorption efficiency, the addition of A. niger F5 pellets after reaching the stationary phase of TP removal in monoculture of C. vulgaris TISTR 8580 demonstrated a promising result for harvesting and enhancing the nutrient removal purposes algal-fungal pellet application.

Accumulation of Nutrients as Internal Quota Affects Algal-Based Wastewater Treatment: Decoupling Hrt and Srt to Improve the Process

Accumulation of Nutrients as Internal Quota Affects Algal-Based Wastewater Treatment: Decoupling Hrt and Srt to Improve the Process

Impacts of seasonality and operating conditions on water quality of algal versus conventional wastewater treatment: Part 1

Municipal wastewater is a reliable source from which water, renewable energy, and nutrients could be recovered for beneficial use. Our previous efforts have documented that an innovative algal-based wastewater treatment (WWT) system could recover energy and nutrients from wastewater while having a lower energy footprint than conventional WWT processes. As a biological treatment process, the algal WWT can be affected by algal species, operating conditions, and meteorological factors. This study aimed to identify suitable algal cultures to treat municipal wastewater during warm and cold weather. The algal system achieved the secondary effluent discharge standards for biochemical oxygen demand and nutrients within 2–3 days during warm weather (May to October, 25–55 °C) using an extremophilic algal strain Galdieria sulphuraria; and within 1–2 days in winter (November to April, 4–17 °C) using polyculture strains of algae with bacteria. The impact of seasonal variation and operating conditions on the water quality of pilot-scale algal bioreactors was compared with a full-scale conventional WWT system. The treatment performance of the algal system (NH4–N: 1.3 ± 1.25 mg/L in winter and not detected in summer and conventional system; PO4–P: 0.89 ± 0.6 mg/L in winter, 0.02 ± 0.03 mg/L in summer and, 5.93 ± 1.32 mg/L in conventional system) was comparable or better than that of the conventional WWT in nutrients removal and other contaminants were below the discharge standards. This study indicates that the algal system can be engineered for reliable wastewater treatment independent of seasonal variations.

Sunlight Intensity, Photosynthetically Active Radiation Modelling and Its Application in Algae-Based Wastewater Treatment and Its Cost Estimation

In algal pond used for treating wastewater, a part of the solar radiation (PAR) is used by algae for photosynthesis, and rest of the solar energy is wasted. To date, no studies have been conducted that optimize these aspects (wasted solar radiation for heat production) from an operational cost perspective. Therefore, a model is developed for the estimation of photosynthetically active radiation (PAR) from solar radiation. Subsequently, derived PAR was utilized in the optimization algorithm. Experimental data on PAR and solar radiation were used to obtain empirical parameters of the developed model. Using empirical parameters, diurnal PAR was estimated for other locations for which the diurnal variation of solar radiation was not available. Afterwards, the estimated solar radiation was used to obtain the cost of algal biomass production using wastewater. For this purpose, a cost function was minimized. The cost function contains various cost components of algae-based wastewater treatment. The major costs of the treatment were incurred by the sunlight harvesting, and distribution equipment, whereas the major income was registered through the conversion of sunlight to heat and biomass production. The yearly cost of treating 1m3 wastewater in the proposed wastewater treatment plant could be varied from 186 to −44 (Rs, INR). The capital cost of constructing a proposed treatment plant having a capacity of 1000 m3/day varied from 11–45 crores INR.

Advanced treatment of chicken farm flushing wastewater by integrating Fenton oxidation and algal cultivation process for algal growth and nutrients removal

Algae based wastewater treatment has been considered as the most promising win-win strategy for nutrients removal and biomass accumulation. However, the poor linking between traditional wastewater treatment and algal cultivation limits the achievement of this goal. In this study, a novel combination of Fenton oxidation and algal cultivation (CFOAC) system was investigated for the treatment of chicken farm flushing wastewater (CFFW). Fenton oxidation (FO) was adopted to reduce the excessive ammonia nitrogen, which might inhibit the algal growth. The results showed that single FO pretreatment removed 70.5 %, 96.7 %, 86.1 %, and 96.2 % of TN, TAN, TP, and COD, respectively. The highest biomass (235.8 mg/L/d) and lipid (77.3 mg/L/d) productivities were achieved on optimized CFOAC system after 7 days batch cultivation. Accordingly, the nutrients removal efficiencies increased to almost 100 %. Further fatty acid profile analysis showed that algae grown on optimal CFOAC system accumulated a high level of total lipids (32.8 %) with C16–C18 fatty acid as the most abundant compositions (accounting for over 60.6 %), which were propitious to biodiesel production. In addition, this CFOAC system was magnified from 1 L flask to 50 L horizontal pipe photobioreactor (HPPB) in semi-continuously culture under optimal conditions. The average biomass and lipid productivities were 995.7 mg/L/d and 320.6 mg/L/d, respectively, when cultured at 6 days hydraulic retention time with 1/3 substitution every two days. These findings proved that the novel CFOAC system is efficient in nutrients removal, algal cultivation, and biomass production for advanced treatment of CFFW.

Algal-based wastewater treatment: Evaluation of nitrogenous byproducts in chlorinated effluent

Water reuse is gaining traction as a means of balancing the water portfolio in the face of rapidly growing demand for potable water in water-stressed regions. While current guidelines for restricted reuse require final disinfection of the reclaimed water and residual free chlorine, the common practice of disinfection by chlorine can potentially form carcinogenic byproducts depending on certain precursors and the disinfectant demand. This study evaluated the formation of nitrogenous byproducts of chlorination in an algal-based wastewater treatment system (AWTS) capable of yielding discharge-ready effluent with non-detectable levels of pathogenic bacteria. Impacts of chlorination of the AWTS effluent were evaluated here in terms of selected nitrosamines to determine if a comprehensive DBP assessment would be justifiable. Optimal chlorine demand of the AWTS effluent to satisfy the reuse guidelines was found as 13.0 mg Cl2/L at pH of 6. Under this condition, none of the seven nitrosamines analyzed in this study were >50 ng/L. This finding is corroborated through non-targeted screening by liquid chromatography/high resolution mass spectrometry of the unchlorinated AWTS effluent revealing negligible levels of amines, which have been reported as key precursors of nitrosamines. Results of this study indicate that the AWTS holds promise in delivering safe reuse-quality effluent, warranting further comprehensive assessments.

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.