Coagulant derived from waste biogenic material for sustainable algae biomass harvesting

doi:10.1016/j.algal.2020.101982

Algal Research

Volume 50, September 2020, 101982

https://doi.org/10.1016/j.algal.2020.101982 Get rights and content

Highlights

•
Gastropod shell coagulant produced sustainable algae harvesting procedure.
•
Gastropod shell coagulant improved the biomass harvesting rate, volume and filterability.
•
Sweep coagulation was the mechanism of biomass harvesting using Gastropod shell coagulant.
•
Gastropod shell coagulant enhanced the breakage and recovery factors of harvested flocs.
•
Gastropod shell coagulant is non-toxic to the culture medium and harvested biomass.

Abstract

Highly efficient and sustainable algae harvesting that produced biomass with enhanced characteristics and reusable culture medium were developed from the use of coagulant derived from the waste shell of Gastropod. Thermally treated Gastropod shell samples were screened for the algal cell harvesting efficiency (%) and the underlying mechanism was elucidated from the hydrodynamic equilibrium data and scanning electron microscopic analysis. The floc strength, settling rate parameters, settleability, and filterability were determined and compared with the flocs obtained from the pH induced autocoagulation system. The values of floc settling rate and the sludge volume index (mL/g) showed that the flocs obtained from the Gastropod shell system (rate constant = 1.945 L·mol⁻¹·s⁻¹) settled faster and more compacted than those from the pH induced system (rate constant = 0.2155 (L·mol⁻¹·s⁻¹). Both the growing and harvested flocs from the Gastropod shell system had better strength and breakage factors (>90%) than the pH induced system. The proximate and elemental compositions of the biomass from the Gastropod shell system were comparable with those from centrifugation and pH induced systems. Both the separated culture medium and the harvested algae biomass were successfully reused, in separate systems, to cultivate fresh algae. This indicated the non-toxic effects of the coagulants on both the culture medium and the algae harvested biomass.

Graphical abstract

Introduction

The coagulation-flocculation (CF) procedure is attractive for algae harvesting because it is simple, fast, and little or no energy is required for the operation. The snag with the procedure is the coagulant's high cost, toxicity to the algal biomass and the generation of large volume of contaminated and non-recyclable culture medium. Thus, it was postulated that a sustainable harvesting procedure should have broad applications, high biomass harvesting, low process economy, minimal energy requirement and operational simplicity [1]. Since the success of the downstream industrial applications hinges on the sustainability of the initial harvesting stage, a sustainable harvesting procedure is crucial to the overall process economy and efficiency. It has been reported that harvesting through the use of metal salt coagulants or chitosan is just a tad cheaper than through centrifugation, which is currently the most popular method [2]. The cost of algae biomass harvesting using ultrasound waves, centrifugation, and CF using biopolymers has been reported to be too expensive for such applications as biofuel production [3,4].

Inorganic multivalent metal salts (e.g. FeCl₃, Al₂(SO₄)₃ and Fe₂(SO₄)₃) are considered highly efficient coagulants for microalgal harvesting, but they are bedecked with myriads of challenges that limit the application in real-life. For example, ferric salts impart a brown-yellow coloration on the harvested flocs, which hindered the use of biomass for pigment extraction purposes [20]. Aluminum salts induce cell lysis, to a value that ranged between 10 and 25% in the harvested flocs [5]. It is noteworthy that despite the effectiveness of these metal salts, large dosages are required for effective and optimal harvesting efficiency, making it an expensive and unsustainable option [6]. Additionally, the harvested flocs are often contaminated by the metal ions, thereby, hampering the application as biofuel or animal feed stock [7]. Since it has been identified that the cost of coagulant represents an appreciable amount in the overall process economy (i.e. between 4% and 7%), exploring the naturally available coagulant options (e.g. phosphates, carbonates, calcium and magnesium ions) in wastewater, brackish or sea water is now a focus [8,9].

In order to leverage on the benefits of the CF as an auspicious algal harvesting procedure and to obviate some of the identified challenges, the present study aimed at a systematic evaluation of a waste biogenic material, the shell of a Gastropod (African land snail), for marine algae, (Chlorella vulgaris) harvesting. The ability of the alkali earth metals (i.e. Ca²⁺ and Mg²⁺) to induce algae coagulation in pH induced autoflocculation has been highlighted [6,[8], [9], [10],21,22]. It was posited that the autocoagulation of algal cell at high pH is induced more by the inorganic precipitate formation and not just by pH value alteration [6]. Herein, the thesis for the choice of the GS as a coagulant is predicated on the mineralogical and elemental profiles and the rifeness. The elemental and mineralogical assays of the GS showed that it is rich in calcium and the calcium carbonate polymorphs (i.e. aragonite, calcite and vaterite) were identified [11,12]. Since GS is globally distributed, large tons are discharged as waste from food processing industries, which made it an abundant low-cost material that could be harnessed for microalgae harvesting.

Herein, the influence of the thermal treatment of the GS on the algae harvesting efficiency was studied, at different calcination temperature that ranged between 100 °C and 1000 °C. The optimum dosage of the GS sample with the highest harvesting efficiency was determined and the rate parameters of the harvested floc sedimentation were also evaluated. The harvested floc characteristics (proximate and elemental analysis, surface architecture, settleability, filterability, size, strength and breakage factors) were determined. The reuse potential of the separated culture medium and the viability of the harvested flocs were evaluated to assess the process economy, sustainability and the toxicity of the coagulant to the culture medium and the harvested biomass.

Section snippets

Preparation of Gastropod Shell

The raw GS was prepared as previously reported [[11], [12], [13], [14]] before it was subjected to thermal treatment, in the furnace, at varying temperatures (100, 250, 500, 750 and 1000 °C) for 2 h. The products were labeled GS₁₀₀, GS₂₅₀, GS₅₀₀, GS₇₅₀ and GS₁₀₀₀, according to the respective thermal treatment temperature. The characteristics (i.e. elemental and mineralogical composition, BET surface areas, and the surface functional groups) of these materials have been reported in our previous

Harvesting efficiency and optimum coagulant dose

The HE (%) values of the different GS samples showed that only GS₁₀₀₀exhibited proclivity for algae cell harvesting (Fig. 1). The OD value of the raw algal solution was reduced from 0.230 to 0.044 (i.e. 80.87% of OD attenuated) with the addition of the GS₁₀₀₀. The OD values of the supernatants obtained from the algal solutions treated with the other GS samples showed the occurrence of hyperchromic shift in the OD value. This manifested as a negative OD attenuation (Fig. 1), with the OD values

Perspectives on field application and sustainability

Amongst the major shortcomings identified with the use of chemical coagulants for algae biomass harvesting are the high coagulant cost and contamination of the harvested biomass and the culture medium by the chemical coagulant. The HE (%) of the algae flocs derived from the GS₁₀₀₀ showed that it is a promising and sustainable material that is comparable with other calcium rich materials that have been investigated for algae harvesting (Table 4). Considering the fact that GS is a waste material,

Conclusion

A sustainable coagulant derived from the GS was highly efficient in the harvesting of algae biomass. The flocs obtained from the GS system settled faster with much lower values of the SVI (mL/g), when compared with the flocs derived from the pH induced system. The filterability of the flocs derived from both the GS and the pH induced systems were analogous. Sweep coagulation was confirmed as the underlying mechanism of algae harvesting from the hydrodynamic equilibrium data and the surficial

CRediT authorship contribution statement

Oladoja N. Abiola:Conceptualization, Writing - original draft, Investigation, Formal analysis.Jafar Ali:Investigation, Formal analysis.Wang Lei:Validation, Writing - review & editing.Nie Yudong:Investigation, Formal analysis.Gang Pan:Supervision, Validation, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The Authors are grateful to the Chinese Academy of Sciences President's Fellowship Initiative (CAS-PIFI), 2019, for the award of Visiting Scientist Fellowship to OLADOJA Nurudeen Abiola to undertake this research.

Declaration of conflict of interest

The authors report no commercial or proprietary interest in any product or concept discussed in this article.

Statement of informed consent, human/animal rights

No conflicts, informed consent, or human or animal rights are applicable to this study.

References (30)

M.K. Danquah et al.
Microalgal growth characteristics and subsequent influence on dewatering efficiency
Chem. Eng. J.
(2009)
L. Christenson et al.
Production and harvesting of microalgae for wastewater treatment, biofuels, and bioproducts
Biotechnol. Adv.
(2011)
C.A. Laamanen et al.
Flotation harvesting of microalgae
Renew. Sust. Energ. Rev.
(2016)
D. Vandamme et al.
Flocculation of Chlorella vulgaris induced by high pH: role of magnesium and calcium and practical implications
Bioresour. Technol.
(2012)
A.K. Lee et al.
Energy requirements and economic analysis of a full-scale microbial flocculation system for microalgal harvesting
Chem. Eng. Res. Des.
(2010)
A. Schlesinger et al.
Inexpensive non-toxic flocculation of microalgae contradicts theories; overcoming a major hurdle to bulk algal production
Biotechnol. Adv.
(2012)
B.T. Smith et al.
Sedimentation of algae flocculated using naturally available, magnesium-based flocculants
Algal Res.
(2012)
I. Branyikova et al.
Physicochemical approach to alkaline flocculation of Chlorella vulgaris induced by calcium phosphate precipitates
Colloids Surf. B: Biointerfaces
(2018)
N.A. Oladoja et al.
Green reactive material for phosphorus capture and remediation of aquaculture wastewater
Process. Saf. Environ. Prot.
(2017)
N.A. Oladoja et al.
Phosphorus recovery from aquaculture wastewater using thermally treated gastropod shell
Process. Saf. Environ. Prot.
(2015)

N.A. Oladoja et al.

Low-cost biogenic waste for phosphate capture from aqueous system

Chem. Eng. J.

(2012)

N.A. Oladoja et al.

Towards the development of a reactive filter from green resource for groundwater defluoridation

Chem. Eng. J.

(2016)

J. Gasperi et al.

Treatment of combined sewer overflows by ballasted flocculation: removal study of a large broad spectrum of pollutants

Chem. Eng. J.

(2012)

K.-Y. Show et al.

Algal biomass dehydration

Bioresour. Technol.

(2013)

J. Phasey et al.

Harvesting of algae in municipal wastewater treatment by calcium phosphate precipitation mediated by photosynthesis, sodium hydroxide and lime

Algal Res.

(2017)

Cited by (11)

Potential of biogenic and non-biogenic waste materials as flocculant for algal biomass harvesting: Mechanism, parameters, challenges and future prospects
2023, Journal of Environmental Management
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.
Potential of microalgae cultivation using nutrient-rich wastewater and harvesting performance by biocoagulants/bioflocculants: Mechanism, multi-conversion of biomass into valuable products, and future challenges
2022, Journal of Cleaner Production
Citation Excerpt :
Further discussion focused on the harvesting of microalgae from the suspended culture system. Microalgae harvesting in suspended growth system is mostly carried out using coagulation–flocculation and sedimentation methods, which are mentioned as the most feasible methods (Oladoja et al., 2020; Phasey et al., 2017). Coagulation consists of destabilizing the negative charge of colloidal particles (such as microalgae), whereas flocculation is the aggregation of neutralized particles into flocs (Gutiérrez et al., 2015).
Microalgae have been identified as one of the new feedstocks for renewable energy production. The conversion of microalgae into various valuable products has also been increasing in the last decade. Microalgae harvesting, one of the most important stages in microalgae production, has been studied and reviewed by many researchers. However, most harvesting methods still utilize chemicals during the process, which make harvested biomass not directly ready for food/feed production and pharmaceutical-related processes. Biocoagulants/bioflocculants are emerging compounds that can be used during the harvesting of microalgae because their existence does not introduce toxicity in the harvested biomass. Considering its potential to produce ready-to-use biomass, biocoagulants/bioflocculants have a bright future in microalgal biomass production processes. This review article highlights simultaneous wastewater treatment and microalgal biomass production as an emerging method in accommodating a circular economy paradigm. This paper juxtaposes the utilization of chemical-based coagulants/flocculants and biocoagulants/bioflocculants in harvesting microalgae. Biodegradability, effectiveness, harvested biomass characteristics, and potential of medium reuse are emphasized in the discussion. The agglomeration mechanisms of microalgae during harvesting, recent advances in the microalgal biomass conversions, and future challenges related to the utilization of biocoagulants/bioflocculants are also described in detail. Microalgae harvesting by using biocoagulants/bioflocculants is a feasible and promising environmentally friendly technology for microalgal biomass production.
Control strategies against algal fouling in membrane processes applied for microalgae biomass harvesting
2022, Journal of Water Process Engineering
Citation Excerpt :
The most used harvesting solutions for concentrating algae biomass are: (i) coagulation, (ii) dissolved air flotation, (iii) centrifugation, and (iv) membrane filtration. Briefly, (i) Coagulation consists of adding coagulants in the feed solution in order to reduce the electrostatic repulsion between the microalgae cells, thus causing their settling [14]. ( ii) Dissolved air flotation (DAF) relies on air micro-bubble generation to promote microalgae flocs rising to the interface where the biomass is accumulated [15]. (
Microalgae biomass is increasingly applied in a variety of high-end applications, such as biofuel production, CO₂ fixation, food, and cosmetics. As the demand for microalgae increases, improvements in biomass harvesting techniques are required since dewatering represents a significant fraction of the total algae production cost. While membrane technology is growing as a means to achieve effective biomass harvesting, fouling from microalgae suspensions is a major drawback, since these streams are rich in organic compounds, nutrients, and biological materials. The aim of this paper is to present the state-of-the-art of the control strategies to manage algal fouling. The control strategies are divided into: (i) mitigation strategies, including pre-treatment options, modified membrane surfaces, and hydrodynamic approaches; and (ii) adaptation strategies, which include physical, mechanical, and chemical cleaning. Fouling mitigation strategies are implemented in membrane separation processes seeking to maintain high productivity without compromising biomass quality, while minimizing the energy cost related to fouling control. Adaptation techniques include optimization of the cleaning time and effective removal of the irreversible foulants. Further, minimization in the use of chemicals and of the backflush permeate must be achieved to ensure an efficient performance in chemical cleaning and backwash approaches, respectively. Finally, the article discusses future research perspectives in membrane-based microalgae harvesting with a focus on zero liquid discharge and effective fouling control strategies within the water-energy nexus.
Calcium ions-effect on performance, growth and extracellular nature of microalgal-bacterial symbiosis system treating wastewater
2022, Environmental Research
Citation Excerpt :
Recently, many efforts have been done to promote the sedimentation performance of microalgae cells in MABS system, as well as the biomass harvesting efficiency (Iasimone et al., 2021; Sun et al., 2019; Kumar et al., 2017). In terms of biological methods, the sedimentation enhancement of microalgae biomass can be realized by the adhesion function contributed by extracellular polymeric substances of bacteria (Sun et al., 2019; Oladoja et al., 2020). In terms of physical methods, the negative charge on the surface of microalgae cells is employed to promote directional movements and aggregations of microalgae cells under the action of electric force by introducing external electric fields (Khatib et al., 2021; Kumar et al., 2017).
Microalgal-bacterial symbiosis (MABS) system treating wastewater has attracted great concern because of its advantages of carbon dioxide reduction and biomass energy production. However, due to the low density and negative surface charge of microalgae cells, the sedimentation and harvesting performance of microalgae biomass has been one limitation for the application of MABS system on wastewater treatment. This study investigated the performance enhancement of microalgae harvesting and wastewater treatment contributed by calcium ions (i.e., Ca²⁺) in the MABS system. Results showed that a low Ca²⁺ loading (i.e., 0.1 mM) promoted both COD and nutrients removal, with growth rates of 11.95, 6.53 and 1.21% for COD, TN and TP compared to control, and chlorophyll a was increased by 64.15%. Differently, a high Ca²⁺ loading (i.e., 10 mM) caused removal reductions by improving the aggregation of microalgae, with reduction rates of 34.82, 3.50 and 10.30% for COD, NH₄⁺-N and TP. Mechanism analysis indicated that redundant Ca²⁺ adsorbed on MABS aggregates and dissolved in wastewater decreased the dispersibility of microalgae cells by electrical neutralization and compressed double electric layer. Moreover, the presence of Ca²⁺ could improve extracellular secretions and promoted flocculation performance, with particle size increasing by 336.22%. The findings of this study may provide some solutions for the enhanced microalgae biomass harvest and nutrients removal from wastewater.
Advanced wastewater treatment process using algal photo-bioreactor associated with dissolved-air flotation system: A pilot-scale demonstration
2022, Journal of Water Process Engineering
Citation Excerpt :
A standout amongst the most vital parameter for photo-bioreactor is the proportion of surface lit up to the volume of the reactor (S/V) [39]. One of the drawbacks of WWT with algae is harvesting the algae from the effluents [40]. A comparative study of various flocculation methods is presented [41].
This research explores the feasibility of using an algal photo-bioreactor as an integrated algal-bacterial treatment system combined with a dissolved air flotation (DAF) system for the deduction of COD, BOD₅, TSS, TN and TP from primary treated wastewater (PTW). Isolated algae species of Anomoeoneis, Scenedesmus, Anabaena and Spirulina at fixed hydraulic retention time (HRT) of 16 h were used to conduct batch experiments to determine optimum conditions of pH, temperature, light intensity and mixing rate on the removal rates of contaminants. The optimum removal rates were studied at neutral pH, 25 °C, light intensity of 90 μmol m⁻²S⁻¹ and 100 rpm mixing rate. A scaled-up pilot plant treatment system was designed, constructed and operated to evaluate the system performance to treat (0.1 L/min) of primary treated wastewater disposed of ZENIN WWTP-Giza, Egypt. The design criteria of the algal photo-bioreactor were acquired from the batch investigations. The plant was operated for 10 continuous days and the analytical analysis was performed twice a day at a fixed time. The DAF system was used to isolate the infiltrated algae from the system for cultivation and reuse purposes. The achieved results revealed the superior COD, BOD₅, TSS, TN and TP removal percent reached in average 56.4%, 61%, 59.2%, 48.3% and 51.7% at 12 pm and 49.7%, 54.9%, 52.4%, 39% and 40.57% at 12 am, respectively. All data gained from experimental studies demonstrated the efficiency of using algal photo-bioreactor combined with DAF system as an effective wastewater treatment technique.
Diatoms recovery from wastewater: Overview from an ecological and economic perspective
2021, Journal of Water Process Engineering
Citation Excerpt :
The speed and time of centrifugation vary depending upon the target microalgal species. Even though reasonably successful, however, it might harm delicate cells through sheer pressure [79]. This method involves the use of enrichment media.
Alarming water pollution is toxic to the aquatic ecosystem leading to a sharp decline in species diversity. Diatoms have great potency to survive in contaminated water bodies, hence they can be compelling bioindicators to monitor the change in the environmental matrices effectively. Around the globe, researchers are intended to evaluate the impact of pollution on the diatoms recovery and techniques used for the assessment. The diatoms are precious for futuristic need viz. value-added products, energy generation, pharmaceuticals, and aquaculture feedstocks. All these applications led to a significant rise in diatoms research among the scientific community. This review presents different isolation practices, cultivation, and other challenges associated with the diatoms. A precise focus is given to diatoms isolation techniques from highly polluted water bodies with the main thrust towards obtaining an axenic culture to elucidate the significance of pure diatom cultures. Recovery of “jewels of the sea” from polluted water signifies the prospective ecological and economic aspects.

View all citing articles on Scopus

View full text

Coagulant derived from waste biogenic material for sustainable algae biomass harvesting

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Preparation of Gastropod Shell

Harvesting efficiency and optimum coagulant dose

Perspectives on field application and sustainability

Conclusion

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgement

Declaration of conflict of interest

Statement of informed consent, human/animal rights

Chem. Eng. J.

Biotechnol. Adv.

Renew. Sust. Energ. Rev.

Bioresour. Technol.

Chem. Eng. Res. Des.

Biotechnol. Adv.

Algal Res.

Colloids Surf. B: Biointerfaces

Process. Saf. Environ. Prot.

Process. Saf. Environ. Prot.

Chem. Eng. J.

Chem. Eng. J.

Chem. Eng. J.

Bioresour. Technol.

Algal Res.