Centrifugation is the most commonly used method for harvesting autotrophically produced microalgae, but it is expensive due to high energy demands. With the aim of reducing these costs, we tested electrocoagulation with iron electrodes for harvesting Chlorella vulgaris. During extensive lab-scale experiments, the following factors were studied to achieve a high harvesting efficiency and a low iron content in the harvested biomass: electric charge, initial biomass concentration, pH, temperature, agitation intensity, residual salt content and electrolysis time. A harvesting efficiency greater than 95% was achieved over a broad range of conditions and the residual iron content in the biomass complied with legislative requirements for food. Using electrocoagulation as the pre-concentration step prior to centrifugation, total energy costs were reduced to 0.136 kWh/kg of dry biomass, which is less than 14% of that for centrifugation alone. Our data show that electrocoagulation is a suitable and cost-effective method for harvesting microalgae.
- MeSH
- biomasa MeSH
- Chlorella vulgaris * MeSH
- elektrokoagulace MeSH
- elektrolýza MeSH
- flokulace MeSH
- mikrořasy * MeSH
- Publikační typ
- časopisecké články MeSH
In this study, a novel harvesting emulsion (HEM) consisting of cooking oil in an aqueous solution of cetyltrimethylammonium bromide (CTAB) was tested for the harvesting of a technologically important microalga, Chlorella vulgaris. The influence of HEM dose, biomass and bovine serum albumin (BSA) (model interferer compound) on harvesting efficiency (E) were studied. The HEM E was over 90% at pH 10 (0.33% (v/v) cooking oil, 6.7 mg/L of CTAB) and 12 (0.13% (v/v) cooking oil, 2.7 mg/L of CTAB). Harvesting efficiencies at pH 4 and 7 were < 73.5% due to the absence of precipitate formation. Bovine serum albumin (10 mg/L) increased the HEM dose necessary to achieve E ˃ 90% by 1.2 (pH 10), and 3 fold (pH 12). By manipulating the dose of HEM and pH, the method of harvesting (flocculation/sedimentation or flotation) was adjustable depending on the technological requirements.
- MeSH
- biomasa MeSH
- Chlorella vulgaris * MeSH
- flokulace MeSH
- mikrořasy * MeSH
- povrchově aktivní látky MeSH
- vaření MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
Coagulation followed by floc separation is a key process for the removal of algal organic matter (AOM) in water treatment. Besides optimizing coagulation parameters, knowledge of the properties of AOM-flocs is essential to maximizing AOM removal. However, the impact of AOM on the floc properties remains unclear. This study investigated how peptides/proteins derived from the cellular organic matter (COM) of the cyanobacterium Microcystis aeruginosa influenced the size, structure, and shape of flocs formed at different shear rates (G). Flocs formed by kaolinite, COM-peptides/proteins and a mixture of the same were studied, and the effect of intermolecular interactions between floc components on floc properties was assessed. The coagulation experiments were performed in a Taylor-Couette reactor, with aluminum (Al) or ferric sulphate (Fe) utilized as coagulants. Image analysis was performed to gauge floc size and obtain data on fractal dimension. It was found that floc properties were affected by the presence of the COM-peptides/proteins and the coagulant used. COM-peptides/proteins increased floc size and porosity and widened floc size distributions. The Fe coagulant produced larger and less compact flocs than Al coagulant. Moreover, the decrease in floc size that occurred in parallel with increase in shear rate was not smooth in progress. A rapid change for the kaolinite-coagulant suspension and two rapid changes for the suspensions containing COM were observed. These were attributed to various intermolecular interactions between floc components participating in coagulation at different G. Based on the results obtained, shear rates suitable for efficient separation of flocs containing COM were suggested.
- MeSH
- bakteriální proteiny MeSH
- čištění vody metody MeSH
- flokulace MeSH
- Microcystis * MeSH
- mikrobiologie vody * MeSH
- peptidy MeSH
- Publikační typ
- časopisecké články MeSH
The removal of algal organic matter (AOM) is a growing concern for the water treatment industry worldwide. The current study investigates coagulation of non-proteinaceous AOM (AOM after protein separation), which has been minimally explored compared with proteinaceous fractions. Jar tests with either aluminum sulphate (alum) or polyaluminium chloride (PACl) were performed at doses of 0.2-3.0 mg Al per 1 mg of dissolved organic carbon in the pH range 3.0-10.5. Additionally, non-proteinaceous matter was characterized in terms of charge, molecular weight and carbohydrate content to assess the treatability of its different fractions. Results showed that only up to 25% of non-proteinaceous AOM can be removed by coagulation under optimized conditions. The optimal coagulation pH (6.6-8.0 for alum and 7.5-9.0 for PACl) and low surface charge of the removed fraction indicated that the prevailing coagulation mechanism was adsorption of non-proteinaceous matter onto aluminum hydroxide precipitates. The lowest residual Al concentrations were achieved in very narrow pH ranges, especially in the case of PACl. High-molecular weight saccharide-like organics were amenable to coagulation compared to low-molecular weight (<3 kDa) substances. Their high content in non-proteinaceous matter (about 67%) was the reason for its low removal. Comparison with our previous studies implies that proteinaceous and non-proteinaceous matter is coagulated under different conditions due to the employment of diverse coagulation mechanisms. The study suggests that further research should focus on the removal of low-molecular weight AOM, reluctant to coagulate, with other treatment processes to minimize its detrimental effect on water safety.
Physical floc properties were systematically investigated by analysing the structure of algal and cyanobacterial flocs produced by five species (green algae (Chlorella vulgaris) and cyanobacteria (Microcystis aeruginosa (strain CS-564), Microcystis aeruginosa (strain CS-555/01), Dolichospermum circinale and Cylindrospermopsis raciborskii) using aluminium sulphate (alum) at different doses and pH values. The properties of spherical, compact flocs were determined using a laser diffraction instrument and a new in situ image analysis technique was validated to analyse the structure of more complex flocs. The incorporation of algal-derived organic matter (AOM) into the flocs was inferred by evaluating the dissolved organic matter concentration character before and after flocculation using liquid chromatography with organic carbon detection (LC-OCD). D. circinale, C. raciborskii, and M. aeruginosa (CS-564) produced large flocs (2-9 mm), while M. aeruginosa (CS-555) and C. vulgaris produced smaller flocs (<2 mm). While differences in physical floc properties were observed to result from changes in coagulation mechanism, the cell morphology and the AOM composition were the most influential factors. Examination of floc properties can give a rapid insight at the plant for trouble shooting, particularly through the use of the in situ techniques and provide a mechanism by which floc properties can be tailored to downstream processes.
- MeSH
- Chlorella vulgaris * MeSH
- čištění vody * MeSH
- flokulace MeSH
- Microcystis * MeSH
- sinice * MeSH
- Publikační typ
- časopisecké články MeSH
Amongst harvesting processes, alkaline flocculation stands out as a technically feasible and low cost method. The interference of model wastewater components with alkaline flocculation of Chlorella sorokiniana (pH 8-12), induced by calcium phosphate (CaP) precipitates, was evaluated. Between the compounds tested, inorganic nitrogen, sodium alginate, salinity and algal organic matter had no effect on flocculation efficiency (FE). The negative effect of humic acids, sodium dodecyl sulphate and alkalinity on FE was partial. Bovine serum albumin and bacterial organic matter (BOM) of Escherichia coli showed the strongest disruption of FE. The impact of BOM can be explained by the high protein content (65% of total organic carbon). Proteins, negatively charged at alkaline pH, interrupt microalgae flocculation by preferentially interacting with positively charged CaP precipitates. The simultaneous effects of multiple substances were tested to simulate real wastewater. The results confirm the need to investigate the composition of wastewater prior to alkaline flocculation.
- MeSH
- biomasa MeSH
- Chlorella * MeSH
- flokulace MeSH
- fosforečnany vápenaté MeSH
- mikrořasy * MeSH
- odpadní voda MeSH
- Publikační typ
- časopisecké články MeSH
Poly(ethylene imine)s (PEIs) have been widely studied for biomedical applications, including antimicrobial agents against potential human pathogens. The interactions of branched PEIs (B-PEIs) with environmentally relevant microorganisms whose uncontrolled growth in natural or engineered environments causes health, economic, and technical issues in many sectors of water management are studied. B-PEIs are shown to be potent antimicrobials effective in controlling the growth of environmentally relevant algae and cyanobacteria with dual-functionality and selectivity. Not only did they effectively inhibit growth of both algae and cyanobacteria, mostly without causing cell death (static activity), but they also selectively flocculated cyanobacteria over algae. Thus, unmodified B-PEIs provide a cost-effective and chemically facile framework for the further development of effective and selective antimicrobial agents useful for control of growth and separation of algae and cyanobacteria in natural or engineered environments.
- MeSH
- antiinfekční látky chemie farmakologie MeSH
- Chlamydomonas reinhardtii růst a vývoj MeSH
- flokulace MeSH
- iminy * chemie farmakologie MeSH
- Microcystis růst a vývoj MeSH
- polyethyleny * chemie farmakologie MeSH
- Synechococcus růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Algae affect the performance of drinking water treatment significantly when they decay and release considerable amounts of cellular organic matter (COM). The study describes the cyanobacterium Merismopedia tenuissima and its COM and investigates the effect of their simultaneous coagulation. As COM is highly complex mixture, we characterised it in terms of hydrophobicity, protein content and molecular weights (MWs). To describe the coagulation mechanisms and molecular interactions in the system, we determined both COM and cell surface charge by means of potentiometric titration and zeta potential analysis, respectively, and performed the jar tests with single components and their mixtures with and without a coagulant (ferric sulphate). The coagulation tests performed with the individual components or with their mixtures proved efficient cell removals (up to 99%) but relatively low COM removals (37 ÷ 57%). This disproportion can be attributed to the prevalence of hydrophilic compounds and to the high portion of low-MW organics in COM. Coagulation of COM/cell mixtures achieved comparable efficacy with single component tests, using even lower coagulant doses. Furthermore, COM presence substantially deviated the pH optimum for cell removal and thus altered coagulation mechanisms. While single cells interacted prevailingly through adsorption onto Fe-oxide-hydroxides at about neutral pH (6.0-7.7), the COM/cell mixtures succumbed to charge neutralisation by Fe-hydroxopolymers within moderately acidic pH range (5.0-6.5). Moreover, COM initiated cell flocculation also at acidic pH in both the presence (pH 3.4-3.9) and the absence of a coagulant (pH 3.6-4.6). This supportive effect is ascribed to relatively high-MW COM (>10 kDa), serving as a natural flocculant through inter-particle bridging mechanism and exhibiting nearly the same COM/cell removals as ferric sulphate.
- MeSH
- adsorpce MeSH
- čištění vody * MeSH
- flokulace MeSH
- pitná voda * MeSH
- proteiny MeSH
- sinice * MeSH
- Publikační typ
- časopisecké články MeSH
Chemical treatment processes have mostly been considered as an efficient way for biosolid minimization. The improvement of sludge dewatering was more a welcome side-effect of these sequential processes. In this study, heat-activated sodium peroxydisulphate (PDS) and potassium peroxymonosulphate (MPS) were applied in order to disintegrate waste activated sludge (WAS). PDS and MPS treatment of WAS results in the polymer transfer of organic matter from the solid phase to the liquid phase. Our research work was done for chemical disintegration of WAS by PDS and MPS in doses of 0.2%, 0.4%, 0.6%, 0.8% and 1% (169.5, 339.0, 508.5, 678.0 and 847.5 mg [Formula: see text]) activated at temperatures of 60°C and 90°C for 30 min. The application of these methods causes the soluble chemical oxygen demand value to increase in the supernatant. In addition, there was a positive influence on the sludge volume index which decreased for the highest doses of PDS of over 63% and 77% and MPS of over 78% and 82% through heat activation at temperatures of 60°C and 90°C, respectively. Furthermore, MPS was more successful in the floc particle destruction, therefore it caused a higher sludge settlement acceleration (sedimentation/compaction speed) than PDS. The experimental results demonstrated that the application of heat-activated PDS and MPS may become a novel effective way of processing sewage sludge.
One of the key bottlenecks of the economically viable production of low added value microalgal products (food supplements, feed, biofuels) is the harvesting of cells from diluted culture medium. The main goals of this work were to prepare a novel flocculation agent based on spent brewer's yeast, a brewery by-product, and to test its harvesting efficiency on freshwater Chlorella vulgaris in different environments. The yeast was first autolyzed/hydrolyzed and subsequently chemically modified with 2-chloro-N,N-diethylethylamine hydrochloride (DEAE). Second, optimal dosage of modified spent yeast (MSY) flocculant for harvesting C. vulgaris was determined in culture media of various compositions. It was found that the absence of phosphorus ions decreased (0.4 mg MSY/g biomass), while the presence of algogenic organic matter (AOM) increased (51 mg MSY/g biomass) the required dosage of flocculant as compared to complete mineral medium with phosphorus and without AOM (12 mg MSY/g biomass).
- MeSH
- biomasa MeSH
- Chlorella vulgaris růst a vývoj MeSH
- flokulace MeSH
- fotoelektronová spektroskopie MeSH
- koncentrace vodíkových iontů MeSH
- kultivační média chemie MeSH
- organické látky chemie MeSH
- Saccharomyces cerevisiae metabolismus MeSH
- sladká voda * MeSH
- statická elektřina MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
