Algae-based Wastewater Treatment Research Articles

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.

Pollution prevention and waste phycoremediation by algal-based wastewater treatment technologies: The applications of high-rate algal ponds (HRAPs) and algal turf scrubber (ATS)

Following the escalating human population growth and rapid urbanization, the tremendous amount of urban and industrial waste released leads to a series of critical issues such as health issues, climate change, water crisis, and pollution problems. With the advantages of a favorable carbon life cycle, high photosynthetic efficiencies, and being adaptive to harsh environments, algae have attracted attention as an excellent agent for pollution prevention and waste phycoremediation. Following the concept of circular economy and biorefinery for sustainable production and waste minimization, this review discusses the role of four different algal-based wastewater treatment technologies, including high-rate algal ponds (HRAPs), HRAP-absorption column (HRAP-AC), hybrid algal biofilm-enhanced raceway pond (HABERP) and algal turf scrubber (ATS) in waste management and resource recovery. In addition to the nutrient removal mechanisms and operation parameters, recent advances and developments have been discussed for each technology, including (1) Innovative operation strategies and treatment of emerging contaminants (ECs) employing HRAPs, (2) Biogas upgrading utilizing HRAP-AC system and approaches of O2 minimization in biomethane, (3) Operation of different HABERP systems, (4) Life-cycle and cost analysis of HRAPs-based wastewater treatment system, and (5) Value-upgrading for harvested algal biomass and life-cycle cost analysis of ATS system.

Integration of Algal Biofuel Production with Municipal Wastewater Treatment: a Review

The integration of algae-based wastewater treatment and biofuel production has been of growing research interest in recent years. This article reviewed recent researches in algae biofuel production and the integration of algal wastewater treatment and biofuel production. The methods to algal biofuel production, biofuel productivity, and removal rate of treated municipal wastewater were summarized in this review. Chlorella is largely used, especially in biodiesel and bioethanol production. Spirulina is more often used to produce biogas. The removal rate of NH4+-N can be high in this integration. The most common biofuel products in this integration are biomethane and lipid. Traces of the integration are numerous on laboratory basis and limited in commercial use for now. The barrier to apply it from lab to commercial use may include a high cost during algae harvesting as well as land use and availability. Possible solutions and research gaps are outlined in this article.

Photo-sequencing batch reactor with Klebsormidium nitens: a promising microalgal biotechnology for sustainable phosphorus management in wastewater treatment plants.

This study aims at improving the existing algal-based wastewater treatment technologies by overcoming some of the major drawbacks of these systems such as large required land area, culture contamination, and energy-intensive algal harvesting. The experiments were carried out in an open photo-sequencing batch reactor at a laboratory-scale for nearly 2 months. A specific strain ACUS00207 of the aeroterrestrial green microalga Klebsormidium nitens (Kützing) Lokhorst was used. The strain is native to Bulgaria and belongs to a species that has never been used before in suspended growth systems for wastewater treatment for phosphorus removal. The culture of K. nitens showed promising results: phosphorus removal rates ranging from 0.4 to 1 mg total phosphorus L-1 d-1, efficient settling properties, and resistance to culture contamination with native microalgae. On the basis of the observed phosphorus removal mechanism of biologically mediated chemical precipitation/phosphorus precipitation, an innovative working mode of the sequencing batch reactor is suggested for reducing the hydraulic retention time and the required land area.

Review of Challenges for Algae-Based Wastewater Treatment: Strain Selection, Wastewater Characteristics, Abiotic, and Biotic Factors

Abstract This paper will focus on the challenges associated with algae-based wastewater treatment (ABWWT). To elucidate the issue, this review will investigate the following: (1) microalgal strain ...

Assessment of algae-based wastewater treatment in hot climate region: Treatment performance and kinetics

This study evaluated the use of microalgae for wastewater treatment in hot climate regions. The growth rates of C. vulgaris (C.v.) and N. oleoabundans (N.o.) at 36 °C were studied in primary effluent (PE), secondary effluent (SE) and centrate (CEN) and their performance in removing soluble chemical oxygen demand (CODs), inorganic nitrogen and total dissolved phosphorus were determined. A comprehensive kinetics model was developed to predict algae growth and treatment efficiencies under the studied conditions. Significant differences between the growth patterns and rates of C.v. and N.o. were observed in different wastewater samples. C.v. showed the highest growth rate in CEN followed by PE and SE. N.o. showed the highest growth rate in PE followed by SE and CEN. The percentage CODs removals (%CODs) for C.v. were 51%, 55% and 80%, and for N.o. were 63%, 47% and 72% in PE, SE, and CEN, respectively. Ammonia removal efficiencies (70%–84%) were very similar for C.v. and N.o. in different wastewaters. Phosphorus removal by C.v. and N.o. was high in PE (> 84%), moderate in CEN (>22%) and limited in SE (<15%). Growth rates of C.v. and N.o and percent removals of CODs, ammonia, nitrate and total dissolved phosphorus at 36 °C were compared to those at 20 °C.The kinetics of algal strains, validated using experimental data, accurately reproduced the growth profile and evolution of organic matter and nutrients, permitting process optimization and scale-up. The results of the study showed that microalgae can be successfully cultivated in a wide range of wastewaters at 36 °C and can achieve natural treatment of wastewaters in hot climate regions by removing organic carbon, nitrogen, and phosphorus.

Algal pathway towards meeting United Nation’s sustainable development goal 6

ABSTRACT Recent reports have pointed out that, at the current rate of development, the world will fail to meet Goal 6 of the United Nation’s 17 Sustainable Development Goals (SDGs) to ensure the availability of sanitation and water for all. Over half the world’s population in the middle- and low-income countries will not have sanitation and water with sufficient quality and quantity due to limited financial and freshwater resources. An algal-based wastewater treatment (A-WWT) system is proposed here as an appropriate and affordable pathway to support SDG 6 as well as 11 other related SDGs. Our previous reports on this A-WWT system have documented its ability to produce discharge-ready water, comparable in quality to that of the conventional activated sludge-based (CAS) system, but at lower initial cost and lower energy needs. In the current study, we demonstrate that activated carbon adsorption and ozonation are potential follow-up processes to reclaim high-quality water for beneficial reuse. The quality of water reclaimed by the A-WWT system is shown to be superior to what is currently possible with the CAS system. Microbial assessments and Microtox toxicity assays confirm that the reclaimed water from the A-WWT system is safe for agricultural reuse. The A-WWT system holds promise as a greener alternative to meet the four targets under SDG 6: improving water quality, wastewater treatment, and safe reuse; increasing water-use efficiency and ensuring freshwater supplies; implementing water reuse management; and protecting and restoring water-related ecosystems.

Environmental life cycle comparisons of pig farming integrated with anaerobic digestion and algae-based wastewater treatment

This article shows environmental life cycle comparisons of four scenarios of manure management systems (MMS) for the intensive pig farming systems in terms of materials, transport, energy, and emissions. The MMS scenarios are categorized by different combinations of outside storage, anaerobic mono-/co-digester, and algae-based wastewater treatment (AWWT), where the conventional MMS scenario merely uses the outside storage (Scenario 1) or adopts an integrated anaerobic mono-digester and the outside storage (Scenario 2). The nonconventional MMS scenario uses an integrated anaerobic mono-digester and AWWT process (Scenario 3), notably the harvested algae biomass is used to fully substitute a few ingredients of swine diets. Using life cycle assessment (LCA) methodology, it is validated that Scenario 3 reduces the total environmental impact by 35.5%–40% as compared to Scenarios 1 and 2 and increases the nutrient recovery of nitrogen ratio from 58% (Scenario 1) to 81%. Scenario 4 uses an integrated anaerobic co-digester and AWWT process, where the harvested algae biomass is partially recycled to substitute the partial ingredients of swine diets and the remaining part is fed into the anaerobic co-digester for improving the biogas yield, to increase the algae biomass yield by 49% and also enhance the cogeneration of heat and power by 26.6% and 7%, respectively, as compared to Scenario 3.

Metagenomic insights into virus removal performance of an algal-based wastewater treatment system utilizing Galdieria sulphuraria

An algal wastewater treatment system capable of reducing dissolved organics, nutrients, and pathogenic bacteria to secondary discharge standards in a single step has been reported on previously. The current study evaluates pathogenic virus reduction in this algal wastewater treatment system and compares it with that in conventional wastewater treatment systems using culture- and nucleic acid-based quantitative methods and shotgun metagenomic sequencing technique. Log removal of somatic coliphages (3.13 ± 0.34), F-specific coliphages (1.23 ± 0.34), Enterovirus (1.05 ± 0.32), and Norovirus GI (1.49 ± 0.16) in the algal wastewater treatment system without any chlorination were comparable to those in the conventional wastewater treatment system with chlorination. While the virus community in the chlorinated effluent of the conventional system was diverse with ~250 species, only 14 discrete virus species were found in the unchlorinated effluent of the algal-based system, none of them pathogenic to humans. This study demonstrated the feasibility of the A-WWT system in delivering pathogenically-safe, high-quality effluent for disposal or beneficial reuse with minimal post-disinfectant demand.

Microalgae wastewater treatment: Biological and technological approaches.

Current global environmental issues raise unavoidable challenges for our use of natural resources. Supplying the human population with clean water is becoming a global problem. Numerous organic and inorganic impurities in municipal, industrial, and agricultural waters, ranging from microplastics to high nutrient loads and heavy metals, endanger our nutrition and health. The development of efficient wastewater treatment technologies and circular economic approaches is thus becoming increasingly important. The biomass production of microalgae using industrial wastewater offers the possibility of recycling industrial residues to create new sources of raw materials for energy and material use. This review discusses algae‐based wastewater treatment technologies with a special focus on industrial wastewater sources, the potential of non‐conventional extremophilic (thermophilic, acidophilic, and psychrophilic) microalgae, and industrial algae‐wastewater treatment concepts that have already been put into practice.

Removal of antibiotic resistance genes in an algal-based wastewater treatment system employing Galdieria sulphuraria: A comparative study

In this study, we compared removal of antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) in two wastewater treatment systems fed with the same primary effluent: a conventional wastewater treatment system (consisting of a trickling filter followed by an activated sludge process) versus an algal-based system, employing an extremophilic alga, Galdieria sulphuraria. Our results demonstrated that the algal system can reduce concentrations of erythromycin- and sulfamethoxazole-resistant bacteria in the effluent more effectively than the conventional treatment system. A decreasing trend of total bacteria and ARGs was observed in both the treatment systems. However, the relative ratio of most ARGs (qnrA, qnrB, qnrS, sul1) and intI1 in the surviving bacteria increased in the conventional system; whereas, the algal system reduced more of the relative abundance of qnrA, qnrS, tetW and intⅠ1 in the surviving bacteria. The role of bacteriophages in horizontal gene transfer (HGT) of ARGs in the two systems was indicated by a positive correlation between ARG absolute abundance in bacteriophage and ARG relative abundance in the bacteria. Four of the five detectable genes (qnrS, tetW, sul1 and intI1) were significantly reduced in the algal system in bacteriophage phase which signified a decrease in phage-mediated ARG transfer in the algal system. Results of this study demonstrate the feasibility of the algal-based wastewater treatment system in decreasing ARGs and ARB and in minimizing the spread of antibiotic resistance to the environment.

Mechanisms of pharmaceutical and personal care product removal in algae-based wastewater treatment systems

The widespread distribution of pharmaceuticals and personal care products (PPCPs), particularly in the built environment, has led to increased concern about their effects on both human and ecosystem health. In this research, we investigated the role of algae species Scenedesmus obliquus and Chlorella vulgaris in governing PPCP transfer and transformation mechanisms in algae-containing environments. Lab-scale algal bioreactors were created under various conditions of light, water matrix, and sterilization method to isolate and elucidate reaction mechanisms affecting carbamazepine, ibuprofen, gemfibrozil, and triclosan. The parent compounds and their potential transformation products were analyzed in both the water and algae phases. The results showed that ibuprofen was primarily biotransformed due to synergistic relationships between the algae and the bacteria. Ibuprofen biotransformation products tentatively identified as hydroxy-ibuprofen, carboxy-ibuprofen, and 4-isobutylcatechol were detected in several samples. In all the reactors exposed to light, triclosan underwent both phototransformation and biotransformation. Triclosan biotransformation took place in Scenedesmus obliquus, as demonstrated by the presence of triclosan-O-sulfate in the algae extracts. No evidence of significant carbamazepine and gemfibrozil transfer or transformation was observed under the experimental conditions tested. These results suggest that microalgal–bacterial consortia can facilitate PPCP transformation in algae-based passive water treatment systems.

Effects of seeding density on photogranulation and the start-up of the oxygenic photogranule process for aeration-free wastewater treatment

The oxygenic photogranule (OPG) process is a new algae-based wastewater treatment method, relying on light-driven granulation of filamentous cyanobacteria, microalgae, and non-phototrophic microorganisms (i.e., photogranulation). Seeding the OPG reactor with hydrostatically formed photogranules has been shown as a new start-up approach, which is reproducible and can significantly decrease the start-up period. However, due to early research stage for the OPG process, this seeding approach has not yet been investigated at good depth and its protocol is yet to be established. The objective of this study is to investigate the impact of seeding density on photogranulation and the start-up of the OPG process. Three sequencing-batch reactors (R1-R3) were seeded with a different number of hydrostatically formed photogranules (thus, started with different seeding densities) and operated to treat primary effluent wastewater. The three reactors showed significantly different photogranulation rates and physicochemical characteristics of the produced biomass. Reactor R2, seeded at 900 mg/L dry solids, produced photogranules showing compact, spherical structures with increased hydrophobicity. R2 exhibited the highest yield of biomass, which was also found to be more enriched with proteins, carbohydrates and lipids than biomass from other reactors. R2 also showed better settleability of biomass than others, while all three reactors enabled effective organic matter and dissolved nitrogen removal without external aeration. These results suggest that seeding density is important for the OPG process and optimized seeding density can promote effective start-up as well as bioenergy recovery with increased biomass yield and biorefinery/bioenergy potential.

Pathogen reduction in an algal-based wastewater treatment system employing Galdieria sulphuraria

The feasibility of an algal-based wastewater treatment system employing an extremophilic alga, Galdieria sulphuraria, in removing dissolved organic carbon and nutrients from primary-settled wastewater has been demonstrated at pilot scale. Here, pathogen-reduction capability of this system was assessed and compared against that of an existing traditional wastewater treatment system (WWTS). While total coliform in the influent (2.3 × 107 CFU/100 mL) was reduced by 3.3 log units in the WWTS, no total or fecal coliform were detected in the algal effluent. Results of qPCR analysis confirmed 98% removal of total bacteria and complete removal of Enterococcus faecalis and Escherichia coli in the algal system. Illumina MiSeq sequencing showed diverse bacteria phyla (>10 classifications) in the WWTS-effluent; but, only two classifications in the algal effluent. Bacteria kingdom relative to the entire microbial population declined from 99% to 83% in the WWTS; and to 17% in the algal system. Proteobacteria phylum (which includes mostly putative pathogenic bacterial genera) dominated the WWTS-effluent (abundance = 35%). Substantial alteration of the bacterial profile was observed in the algal system: Acidobacteria phylum being the most dominant (98%), and Proteobacteria, the least (2%). At the genus level, enteritis-causing Arcobacter species were detected only in the WWTS-effluent with a relative abundance of 0.9%.

Assessment of membrane photobioreactor (MPBR) performance parameters and operating conditions

Membrane photobioreactor (MPBR) technology is an emerging algae-based wastewater treatment system. Given the limitations due to the general use of conventional analytical approaches in previous research, this study aims to provide a more comprehensive assessment of MPBR performance through advanced characterisation techniques. New performance parameters are also proposed, encompassing five important aspects of MPBR system efficiency (i.e. biomass concentration, composition, production, nutrient uptake and harvesting potential). Under initial standard operating conditions, performance parameters, such as cell count/MLSS ratio, cell viability, proportion of bacteria and biomass yield coefficient, were found to offer new insights into the operation of MPBR. These parameters were then used, for the first time, to systematically investigate MPBRs operated under different hydraulic retention times (HRTs) and solids retention times (SRTs). Applying shorter HRT and SRT was observed to increase cell viability and productivity (up to 0.25 × 107 cells/mL·d), as anticipated due to the higher nutrient loading. It was noted that the faster growing algal cells featured lower requirement for nutrients. On the other hand, extending HRT and SRT resulted in a more heterogeneous culture (lower cell count/MLSS ratio and higher proportion of bacteria), achieving a higher degree of autoflocculation and greater NO3-N and PO4-P removals of up to 79% and 78% respectively. The results demonstrate the trade-off between applying different HRTs and SRTs and the importance of fully characterising system performance to critically assess the advantages and limitations of chosen operating conditions.

The fate of nitrogen through algal treatment of landfill leachate

Nitrogen was tracked though an algae-based landfill leachate remediation system. This system was designed to remove nutrients from the liquid waste via nitrogen assimilation into new algae biomass. While the nitrogen removal pathway of bio-assimilation was present, it was not the only nitrogen removal pathway in the treatment system. Weekly measurements of the dissolved inorganic nitrogen (ammonia-N, nitrate-N, and nitrite-N) and the nitrogen content of the biomass were used to track nitrogen transformation pathways during this yearlong study. During a major part of the study (83.4% of the observed weeks), all nitrogen could not be accounted for in the dissolved inorganic nitrogen or biomass portions of the system. It is hypothesized that some of the unaccounted-for nitrogen was lost due to volatilization of gaseous nitrogen species. Based upon characteristic distribution of measured dissolved inorganic nitrogen and the nitrogen content of the biomass for each week and prior metagenomic analysis of the microbial community in the treatment system, we have postulated potential scenarios of the fate of nitrogen in this algae-based wastewater treatment system. Further research is needed to identify all pathways of nitrogen conversion in algae-based wastewater remediation systems and verify our proposed scenarios.

Nutrient removal and community structure of wastewater-borne algal-bacterial consortia grown in raw wastewater with various wavelengths of light

The use of microalgae-bacteria co-culture systems is attractive for wastewater treatment. On the other hand, naturally developed wastewater-borne algal-bacterial consortia growing in real wastewater has rarely been studied and characterized. In this study, wastewater-borne algal-bacterial consortia was grown for photosynthetic oxygen production, nutrient removal, and biodiversity in real wastewater using light-emitting diodes (LEDs) with various wavelengths (blue, green, red, and white light) and intensities (250, 500, 1,000, and 2000 μmol m−2s−1). Among the four wavelengths, green light showed the highest tolerance to photoinhibition but the energy efficiency for oxygen production was the lowest. In addition, illumination with red and white lights at 500 μmol m−2s− onto 500 mg TSS L−1 appeared to be practical and efficient. In PSBRs operation, the illumination of red and white light resulted in removal ratios of 88.3% and 79.0% for TN, 96.8% and 97.0% for TP, 92.4% and 91.9% for TSS, and an algal biomass productivity of 1.03 and 1.01 g L−1 d−1, respectively. The diversity of bacteria was changed by the different wavelength of light, but the dominant species of algae was not changed. These results are expected to provide valuable technical information on algae-based wastewater treatment systems.

Review on Challenges and Limitations for Algae-Based Wastewater Treatment

Review on Challenges and Limitations for Algae-Based Wastewater Treatment

Effect of CO2 addition on biomass energy yield in wastewater treatment high rate algal mesocosms

Carbon limitation in algal-based wastewater treatment ponds typically constrains microalgae growth and consequently biomass energy yield, particularly in summer. This study investigates the effect of CO2 addition on algal biomass energy yield in wastewater treatment high rate algal mesocosms (WWT HRAM). Two experiments (summer and winter) were conducted using 15 replicate HRAMs under outdoor conditions while the cultures were bubbled continuously with different air:CO2 mixtures including: air (control mesocosm), 0.5%, 2%, 5% and 10% CO2. The effects of CO2 addition were evaluated by determining the productivity, algal proportion, chemical composition, energy content, and settleability of the biomass. Under summer conditions there was a direct relationship between biomass productivity and CO2 concentration with the maximum productivity increase (50% higher than control) occurring in the 10% CO2-HRAMs. Under winter conditions there was no significant difference in biomass productivity between treatments. In both experiments, the biomass energy content varied slightly (19.3–22.8kJ·g−1) with %CO2 addition, with a slight trend of increasing at higher %CO2 level and where the biomass lipid content was higher. CO2 augmentation led to a change in the HRAM algal composition and consequently changed the biomass settleability. The total biomass energy yield and its gravity harvestable proportion (calculated by multiplying biomass concentration, energy content and harvest efficiency) were highest for the 5% CO2-HRAMs in summer and for the 0.5% CO2-HRAMs in winter. These results show that CO2 addition (indicated by maintaining a culture pH of 6–7 in summer and 7–8 in winter) not only improves biomass productivity and energy content but selects for easily harvestable colonial algal species which are less susceptible to zooplankton grazing.

A comparison of feasible methods for microalgal biomass determinations during tertiary wastewater treatment

One of the most important parameters for monitoring, designing and optimizing the algae-based wastewater treatment system is the biomass concentration. The determination method of microalgal biomass concentration in the culture medium by Volatile Suspended Solids (VSS), as a conventional method, was found inconvenient because it takes long time to obtain the results. In this study, the performance of five feasible methods for microalgal biomass determinations was evaluated and compared. The coefficient of determination (R2) of Optical Density (OD), Total Suspended Solids (TSS), turbidity and wet weight was 0.9903, 0.9698, 0.975, 0.9794 and 0.9922, 0.9686, 0.9649, 0.9694 for C. vulgaris and Phormidium sp., respectively. After comparing with the VSS method during wastewater treatment process, OD is recommended as a reliable method for biomass determinations for green (C. vulgaris) and blue-green (Phormidium sp.) algae.