Release Of Intracellular Organic Matter Research Articles

Removal of Anabaena by ultrasonic pretreatment enhancing-coagulation and water treatment processes

Cyanobacteria bloom brings great challenges to the safety of the drinking water process. Ultrasonic pretreatment can effectively enhance coagulation to remove algae cells from algae-laden water. However, due to the special chain-like structure of Anabaena, the removal characteristics of Anabaena in water treatment process are quite different from those of unicellular cyanobacteria. No study has yet systematic studied on the enhancement effect of ultrasonic enhanced water treatment process on Anabaena. Therefore, this paper studied the characteristics and mechanism of ultrasonic pretreatment to enhance the removal of Anabaena, and carried out pilot experiments. The results showed that ultrasound irradiation at 740 kHz and 1.12 MHz had a great effect on the destruction of the chain-like structure and cell structure of Anabaena. After 15 min, the removal rate of Anabaena cells reached 16.0% and 30.4%, respectively, and the release of intracellular organic matter (IOM) reached 4.3 and 6.0 mg/L, in which phycocyanin released more. The damage of dynamic ultrasound irradiation on algae cells is weak, which can avoid the influence of uneven ultrasound irradiation on algae cells. The enhanced coagulation effect was better after 740 kHz ultrasonic pretreatment for 1 min, and the removal rates of algal cells, turbidity and dissolved organic carbon (DOC) increased by 7%, 9.4% and 12.6%, respectively. Pilot scale experiments demonstrate that ultrasonic pretreatment leads to a notable enhancement in the removal efficiency during the coagulation and sedimentation stages. After 4 h of operation, the turbidity and algal cell removal in the sedimentation stage increased by 6.1% and 14.0%, respectively. In addition, the removal of DOC in the final treated water increased by 6.7%. Furthermore, the disinfection by-products (DBPs) concentration experiences a reduction exceeding 200 μg per liter. Together, these results show a substantial improvement in filtration efficiency and effluent quality. This study provides guidance for the ongoing study of ultrasonic pretreatment to remove chain-like cyanobacteria.

Two wastes into one resource: Carbide slag-driven anaerobic fermentation of excess sludge towards short-chain fatty acids recovery

The anaerobic fermentation has been regarded as promising technology for short-chain fatty acids (SCFAs) recovery from excess sludge. Despite that various treatment approaches have been developed, the sustainable waste utilization of carbide slag in enhancing anaerobic fermentation has rarely been reported. It demonstrated that the carbide slag-derived alkaline condition dominantly contributed to triggering extracellular polymeric substance disruption and microbial cell lysis by protein molecule deconstruction. Considerable sludge hydrolysis was facilitated owing to extracellular and intracellular organic matter release, solubilizing 14.73 % of total solid organic matters in 4-h treatment. Correspondingly, massive SCFAs of 2219.70 mg COD/L (mainly acetate) were produced through 8-day anaerobic fermentation, with the improved acidification and the inhibited methanogenesis. Approximately 83.03–96.21 % of the recoverable SCFAs were extracted after sludge conditioning and solid–liquid separation, providing remarkable economic benefit of 196.23 CNY/ton VSS and carbon-emission reduction of 0.069–0.347 ton CO2/ton VSS. The findings proposed an innovative and sustainable carbide slag-driven anaerobic fermentation strategy for SCFAs recovery and waste stabilization, with low heavy metal residual and negligible environmental risks in “two wastes into one resource” pattern.

Biological effects of hydroxyl radical inactivation for typical red tide algae Alexandrium tamarense

Dinoflagellates are responsible for harmful algal blooms (HABs) worldwide and cause serious ecological security crises and economic losses to the aquaculture industry. In this study, hydroxyl radicals (•OH) were generated by the synergistic effect of strong ionization discharge and hydrodynamic cavitation and were injected into cells to inactivate Alexandrium tamarense within 9 s at a total reactive oxidant (TRO) concentration of 1.0 mg/L. The concentration and time (CT) value of •OH inactivating A. tamarense was 0.153 mg•min/L, which is 1/100 that of ClO2 inactivation. Scanning electron microscopy results demonstrated that the integrity of the algal cells remained without any leakage of intracellular organic matter post •OH inactivation. Furthermore, the chromosomes in the nucleus unwound and broke into fragments under a transmission electron microscope, indicating that the DNA was damaged. In comparison, ClO2 contributed to the severe destruction of cell membranes and walls, resulting in massive intracellular organic matter (IOM) leakage. Based on the single cell gel electrophoresis results, DNA comet length increased 329 % post •OH inactivation, demonstrating that •OH induced DNA fragmentation. Additionally, based on the transcriptomic analysis of A. tamarense, •OH induced a DNA repair response, indicating that DNA strand breakage occurred. In summary, DNA strand breakage and fragmentation were the major reasons for •OH rapidly inactivating A. tamarense with cell integrity retained, which provided critical advancements in controlling HAB safely and efficiently. This method avoids the risk of A. tamarense lysis and IOM release, while guaranteeing marine water security.

The apoptosis of Chlorella vulgaris and the release of intracellular organic matter under metalimnetic oxygen minimum conditions

Metalimnetic oxygen minimum (MOM) is a frequent occurrence in lakes and reservoirs, and its formation is related to the blooming and apoptosis of algae. In this study, the apoptosis mechanism of Chlorella vulgaris (C. vulgaris) and the release of intracellular organic matter (IOM) under different MOM conditions were analyzed by changing the dissolved oxygen (DO) (7.0 mg/L, 3.0 mg/L, and 0.3 mg/L) and water pressure (0.3 MPa and normal pressure). The integrity and auto-fluorescence of algae cells decreased rapidly in the first 8 days, and then stabilized gradually during the development of MOM. Compared with that of water pressures, DO had a significant effect on the activity of algal cells, and higher initial DO levels (3.0 mg/L and 7.0 mg/L) accelerated the lysis of algal cells. The integrity of algae cells decreased to 28.8 %, 31.8 % and 56.6 % at the initial DO of 7 mg/L, 3 mg/L and 0.3 mg/L under 0.3 MPa, respectively. Meanwhile, the concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) continued to increase and reached their maximum at 8 or 12 days, respectively, due to the IOM release caused by algal cell rupture, and then gradually decreased due to microbial degradation. Consistent with the results of membrane integrity, the highest DOC and DON concentrations were found at higher initial DO conditions. By parallel factor analysis, the change in total organic matter fluorescence intensity was consistent with DOC, once again increasing in the first 8 days and then gradually decreasing. The increased humic-like component, which is related to higher aromaticity, led to the monotonic increase of HAAFPs and THMFPs. However, the released IOM of C. vulgaris had lower N-DBPFPs, with TCNMFP predominating primarily. In summary, these results shed new lights on exploring the apoptosis of algae and the release of IOM during the development of MOM.

Moderate pre-photocatalysis-enhanced coagulation alleviates ultrafiltration membrane fouling of algae-laden water

Moderate chemical pre-oxidation of coagulation to remove algae without breakage of the algae cells and release of algal organic matter has been well reported, while little was known about moderate pre-photocatalysis followed by coagulation on the ultrafiltration performance and membrane fouling control during algae-laden water treatment. Herein, three pretreatment methods (photocatalysis, coagulation and moderate pre-photocatalysis-enhanced coagulation (PC)) were investigated to reduce membrane fouling during ultrafiltration of algae-laden water. Moderate photocatalysis by a composite of Bi2O3-TiO2/PAC (Bi-doped TiO2 nano-composites supported by powdered activated carbon) not only avoided algae cell breakage and controlled the release of intracellular organic matter, but also halved the aluminum sulphate (AS) coagulant dosage, since Bi2O3-TiO2/PAC acted as both a photocatalyst and flocculation core. Under optimal conditions (1.2 g/L Bi2O3-TiO2/PAC irradiated under visible light for 20 min and 0.1 mM AS), the removal of OD680, DOC and UV254 were 83.8 %, 60.3 % and 77.3 % respectively. Moderate photocatalysis degraded medium and high molecular weight organics (biopolymers, humic substances and building blocks) to low MW acidic and neutral organics, resulting in effective removals of humic substances and microbial metabolites typically present in algal-derived pollutant. Following PC pre-treatment with ultrafiltration, 87.5 % increase in the final specific flux, 96.1 % reduction in irreversible resistance, and a change in the fouling mechanism from cake layer blockage to intermediate blockage. In addition, the zeta potential was reduced and the interaction force between pollutant-pollutant/membrane became a repulsive force. This work demonstrates the potential benefits of moderate pre-photocatalysis-enhanced coagulation to remove algal contaminants and mitigate ultrafiltration membrane fouling.

Excess Sludge Disintegration by Discharge Plasma Coupled with Thiosulfate

Surplus sludge disposal and treatment are major issues in wastewater treatment plants. Discharge plasma oxidation is an effective approach for sludge dewatering and digestion. In this study, excess sludge disintegration by non-thermal discharge plasma coupled with thiosulfate (TSA) was investigated. After 20 min of the single discharge plasma treatment, the soluble chemical oxygen demand (SCOD) increased to 404.93 mg L−1, and it climbed even more to 549.08 mg L−1 after adding 15 mmol L−1 of TSA. The water content of the filter cake also reduced even more in the presence of TSA. There was an appropriate dosage of TSA available. In the discharge plasma coupled with TSA system, reactive oxygen species (·OH and O2−) were generated and had significant involvement in the disintegration of the sludge. The addition of TSA enhanced the production of OH. These reactive oxygen species decomposed the floc structures and facilitated the transformation of organic compounds, resulting in a decrease in the average size of the sludge aggregates. The ratio of soluble extracellular polymer substances (S-EPS) was enhanced, while the ratio of the tightly bound fraction was reduced after the treatment. Thus, discharge plasma coupled with TSA promoted microbial cell lysis and facilitated the release of intracellular organic matter and bound water, ultimately enhancing the sludge’s dewaterability.

Effect of exogenous CaO addition on H2S production from waste activated sludge and its influence mechanism.

Hydrogen sulfide (H2S) production from waste activated sludge (WAS) is the main reason for odor emission during anaerobic fermentation system. CaO has been reported to effectively improve the resources recovery of WAS, but its potential effect on H2S production in anaerobic fermentation process remains unrecognized. In present study, it was found that the addition of 60mg/g VSS CaO greatly inhibited H2S production and the maximum yield of H2S was 60.1±1.8% lower than the control. Mechanism investigation demonstrated that CaO destroyed sludge structure and increased the release of intracellular organic matter with hydrogen bonding networks destroying, but had a mild effect on the transformation of sulfur containing organic matters and inorganic sulfate reduction. Additionally, the enhancement in H+ and S2- consumption by alkaline condition and metal ions release was another reason for the inhibition of H2S production in CaO addition reactors. Furthermore, microbial analysis showed that CaO addition importantly reduced the hydrolysis microorganism, particularly denitrification hydrolytic bacterias (e.g.,unclassified_f_Chitinophagaceaeand Dechloromonas), sulfate reducing bacterias (SRBs) (e.g., unclassified_c_Deltaproteobacteria and Desulfosarcina) and genes (e.g.,PepD, cysN/D, CysH/C and Sir) involved in organic sulfur hydrolysis and sulfate reduction. Results from this study provides theoretical insights into the practical applications of CaO.

Evaluation of efficiency of disruption methods for Coelastrella sp. in order to obtain high yields of biochemical compounds release

Downstream processes in microalgae, such as the extraction of high value-added compounds, are often hampered by the intrinsic rigidity of the cell wall. The toughness of this structure makes the intracellular compounds less available for extraction, which means that cell disruption methods are necessary to apply. Coelastrella sp. is a terrestrial microalga that reveals to be a promising source of bioactive compounds; however, due to its extremely resistant wall, few extraction and determination studies of these compounds have been performed. In order to maximize the extraction efficiency and be as energy-efficient as possible, five different cell disruption methods have been optimized: Freeze-Thaw cycles – ten freezing cycles at −80 °C and thawing at 40 °C; Bead Milling – 32 % (in volume) of beads (0.5 mm) and treatment time of 6 min; High-speed homogenization - 25,000 rpm for 80 min; Microwave – 800 W for 12 min; and Sonication – 40 kHz for 60 min.Sonication and bead milling proved to be the most efficient processes in cell disruption and intracellular organic matter release, with a value of 9.6 and 5.4, respectively. In addition to these two methods, which yielded rupture efficiencies above 90 % after the application of the treatment, High-speed homogenization also showed a disruption efficiency of around 90 %. On the other hand, microwave and freeze-thaw cycles had a low impact on Coelastrella sp. cells, allowing the surviving of about 39 % and 66 % of the initial sample, respectively. Sonication showed the highest efficiency in the release of proteins, carbohydrates and lipids, always followed by bead milling as the most efficient. Freeze-thaw cycles have shown to be the most efficient in releasing phenolic compounds, whereas microwave was the most inefficient in releasing biochemical compounds overall.Considering the results obtained and the energy consumption in each treatment, bead milling can be considered the most efficient method.

Algal organic matter impact on 2-methylisopropanol and geosmin adsorption by activated carbon: Variation with algae growth and decay, prediction by fluorescence surrogates

Algae-producing odorants have negative effects on the aesthetic quality of drinking water, and activated carbon adsorption is commonly used to abate the odorants. However, in eutrophic waters, algal organic matter (AOM) produced by the dominant cyanobacteria (e.g., Microcystis aeruginosa) strongly interferes with the activated carbon adsorption of trace odorants from source waters. In this study, the applicability of using spectrometric surrogates to evaluate the effect of AOM from Microcystis aeruginosa on odorant adsorption by activated carbon was investigated. During the stationary phase, the DOC concentration of extracellular organic matter (EOM) increased due to algal metabolism (from 3.52 mg/L to 7.81 mg/L) and further accumulated (to 12.40 mg/L) during the decline phase due to the release of intracellular organic matter (IOM), resulting in increased competition against odorants. The adsorption of chromogenic organics in AOM was first evaluated to screen possible spectrometric surrogates for predicting odorant adsorption. The fluorescence component (Ex: 260 nm/Em: 400–460 nm) was the best candidate for predicting odorant adsorption in both AOM solutions and reservoir water. In contrast, poor performance was found for the commonly used UV absorbance at 254 nm and protein-like fluorescence components, due to the weak adsorbability of corresponding chromogenic materials. Our results indicate that fluorescence spectroscopy is promising in predicting odorant adsorption with AOM interference in source waters.

Fluorescence and molecular weight dependence of disinfection by-products formation from extracellular organic matter after ultrasound irradiation

Algal blooms have a negative impact on the safety of drinking water. Ultrasonic radiation technology is an “environment-friendly” technology that is widely used in algae removal. However, this technology leads to the release of intracellular organic matter (IOM), which is an important precursor of disinfection by-products (DBPs). This study investigated the relationship between the release of IOM in Microcystis aeruginosa and the generation of DBPs after ultrasonic radiation as well as analyzed the generation mechanism of DBPs. Results showed that the content of extracellular organic matter (EOM) in M. aeruginosa increased in the order of 740 kHz >1120 kHz >20 kHz after 2 min of ultrasonic radiation. Organic matter with a molecular weight (MW) greater than 30 kDa increased the most, including protein-like, phycocyanin (PC) and chlorophyll a, followed by small-molecule organic matter less than 3 kDa, mainly humic-like substances and protein-like. DBPs with an organic MW range of less than 30 kDa were dominated by trichloroacetic acid (TCAA), while those with an MW greater than 30 kDa had the highest trichloromethane (TCM) content. Ultrasonic irradiation changed the organic structure of EOM, affected the amount and type of DBPs, and tended to generate TCM.

Studies on DNA fragmentation and cell integrity of rapidly hydroxyl radical inactivated Microcystis aeruginosa

Microcystis aeruginosa (M. aeruginosa) blooms occur frequently in freshwater lakes and reservoirs, posing a great threaten to drinking water safety. When using conventional oxidants remedy toxic algae, there is an unavoidable shortage leading to cell rupture and release of intracellular organic matter (IOM), thus causing more serious hazard to water safety. In this study, with the synergistic effect of strong ionisation discharge and hydrodynamic cavitation, hydroxyl radical (•OH) were generated and injected into cells to inactivate M. aeruginosa within 3 s. •OH-inactivated M. aeruginosa was intact without rupture and exhibited a 39 % increase in dissolved organic carbon (DOC) due to the degradation of the components of the cell wall and extracellular matrix. For comparison, ClO2 inactivated M. aeruginosa after 10 min of exposure, which induced cell rupture and a 113 % increase in DOC due to the release of IOM. Meanwhile, in •OH-inactivated M. aeruginosa, intracellular •OH was increased to 2 times according to the detection by fluorescence probe and the DNA oxidative damage biomarker 8-hydroxy-2′-deoxyguanosine increased to 1.4 times according to the enzyme-linked immunosorbent assay, confirming the direct action of •OH on the DNA. And •OH induced DNA fragmentation in cells of M. aeruginosa was identified by comet assay and TUNEL assay, finding a 4636 % increase in the DNA tail length, and 96.71 % of the cells showed DNA phosphatediester bond cleavage. In summary, the main reason for the rapid •OH-inactivation of M. aeruginosa is DNA fragmentation, which may represent a new method for the safely and efficient control of harmful algal blooms.

A moderate activated sulfite pre-oxidation on ultrafiltration treatment of algae-laden water: Fouling mitigation, organic rejection, cell integrity and cake layer property

In this study, a moderate oxidation strategy, in-situ pretreatment with ferrous activated sulfite (Fe(II)/S(IV)), was employed to mitigate membrane fouling during the filtration of algae-laden water and to improve the rejection of organic matter. It was worth noting that the moderate oxidant can avoid serious cells breakage and control the release of intracellular organic matter. Besides, sulfite-based pretreatment had an excellent removal effect DBPs, including chloroform (TCM), dichloroacetonirile (DCAN) and trichloronitromethane (TCNM). Fe(II)/S(IV) pretreatment also improved the removal of DOC and UV254 and the proportion of hydrophilic substances was increased to 91.4% which was conductive to membrane fouling alleviation. With the increase in Fe(II) dosage, both the Rr and Rir were declined since the macromolecular organic transforming to micromolecular organic and the coagulation effect by the in-situ generation of Fe(III). Meanwhile, permeable channels formed on the loose and porous cake layer due to the in-situ Fe(III) could enhance the specific flux. When the ratio of Fe(II)/S(IV) was 2:1, the fouling mechanism was inferred to cake filtration which showed a great discrepancy with other condition.

Effects and behaviors of Microcystis aeruginosa in defluorination by two Al-based coagulants, AlCl3 and Al13

The complexity of natural water made it difficult to remove fluoride. Based on the environmental problems found in the investigation, the fluoride removal research in the water containing algal cells was carried out. In this study, AlCl3 and [AlO4Al12(OH)24(H2O)12]7+ (Al13) were used to remove fluoride. Additionally, the role of aluminum speciation in fluoride removal and the effect of Microcystis aeruginosa on the fluoride removal by different aluminum species coagulants were elucidated. The results showed that AlCl3 mainly removed fluoride by physical interactions, surface adsorption and enmeshment. When algal cells were added to the system, the fluoride removal rate increased from 22.75 % to 72.99 % at a dosage of 40.0 mg/L. This was because algal cells greatly increased the distribution of Al(OH)3 in the flocs. In particular, the specific surface area of the flocs containing algal cells reached 160.77 m2/g, which allowed more fluoride to be adsorbed. However, excessive Al3+ led to serious damage to algal cells and release of intracellular organic matter (IOM), worsening the effect of defluoridation. F− and Al3+ formed AlF2+ and AlF2+ via complexation in water. These compounds were not conducive to defluoridation. Al13 removed fluorine mainly through ion exchange, substitution and hydrogen bonding. Algal cells had an inhibitory effect on defluorination, which was observed in the process of coagulation by different Al dosages. Al13 achieved agglomeration of algal cells and generated small and dense flocs through charge neutralization and electrostatic patch mechanism. Once Al13 combined with algal cells and algae organic matter (AOM), the reaction between Al13 and fluoride would be weakened. Al13 not only maintained the defluoridation performance, but also did not damage the integrity of algal cells, even at high dosages.

Pre-oxidation enhanced cyanobacteria removal in drinking water treatment: A review

Cyanobacterial bloom has many adverse effects on source water quality and drinking water production. The traditional water treatment process can hardly achieve satisfactory removal of algae cells. This review examines the impact of pre-oxidation on the removal of cyanobacteria by solid-liquid separation processes. It was reported that the introduction of chemical oxidants such as chlorine, potassium permanganate, and ozone in algae-laden water pretreatment could improve algae removal by the subsequent solid-liquid separation processes. However, over dosed oxidants can result in more serious water quality risks due to significant algae cell lysis and undesirable intracellular organic matter release. It was suggested that moderate pre-oxidation may enhance the removal of cyanobacteria without damaging algae cells. In this article, effects of moderate pretreatment on the solid-liquid separation processes (sedimentation, dissolved air flotation, and membrane filtration) are reviewed.

Fe2+ activating sodium percarbonate (SPC) to enhance removal of Microcystis aeruginosa and microcystins with pre-oxidation and in situ coagulation

The frequent occurrence of cyanobacterial blooms has become a concern for drinking water safety. Common pre-oxidation, which was widely considered to enhance the followed coagulation, can cause the rupture of algae cell, leading to the undesirable release of intracellular organic matter. In this study, the Fe2+ activating sodium percarbonate (SPC/Fe2+) process for pre-oxidation and in situ coagulation was proved to effectively remove Microcystis aeruginosa without damaging cell integrity at optimal combined doses of SPC (0.2 mM) and Fe2+ (0.2 mM). Moreover, the SPC/Fe2+ process can not only control the release of MCs, but also reduce extracellular MCs from 5.22 μg/L to 1.50 μg/L, due to their moderate oxidation. Meanwhile, the SPC/Fe2+ treatment produces low levels of residual Fe after settling. During sludge ageing, owing to oxidation damage on cells arising from the SPC/Fe2+ treatment, cells continually suffered severe damage and lysed on day 4, leading to large release of intracellular organic matter and MCs, correspondingly. As a result, it is worth noting that the M. aeruginosa cells in stored sludge should be treated or disposed of early. These findings support the development of a green and cost-effective technology to handle cyanobacteria-containing water based on SPC/Fe2+ for ensuring water quality.

Enhanced Dewaterability of Waste-Activated Sludge in Presence of Fe(Ⅱ)-Activated Calcium Peroxide

Ferrous iron-activated calcium peroxide (Fe2+/CaO2) was innovatively put forward to improve the dewaterability of waste-activated sludge. The effects of initial pH, Fe2+, and CaO2dosages on sludge dewatering performance were investigated and its internal mechanism for achieving deep sludge dewatering was thoroughly explored. The results indicated that the best dewatering performance was obtained by dosing 3.31 mmol·g-1 Fe2+ and 3.68 mmol·g-1 CaO2 under neutral pH, in which specific resistance to filtration (SRF) and water content (WC) reduced from 20.99×1012 m·kg-1 and 86.61% to 3.91×1012 m·kg-1 and 76.15%, respectively. Fe2+/CaO2 oxidation caused sludge microbial cell lysis, release of intracellular organic matter, and degradation of extracellular polymeric substances (EPS). Meanwhile, the generated Fe3+ facilitated re-flocculation of sludge particles into rigid and porous structure flocs, which was beneficial to the release of EPS-bound water to achieve deep sludge dewatering. From the perspective of technology and economy, the Fe2+/CaO2 process is economical and practical, and has a promising application prospect in improving the dewatering performance of waste-activated sludge.

Inactivation of harmful Anabaena flos-aquae by ultrasound irradiation: Cell disruption mechanism and enhanced coagulation

Harmful algal blooms pose a potential threat to the safety of drinking water sources. Ultrasound is an effective method for algae removal. However, this method can lead to the release of algal organic matter and the effects and toxic mechanisms of ultrasound on Anabaena are still poorly understood. The destruction mechanism of Anabaena flos-aquae cells under different ultrasonic conditions, the safety of intracellular organic matter (IOM) release to water and the enhanced coagulation efficiency of ultrasound were studied. Results showed that high-frequency ultrasound was effective in breaking down algae cells. After 10 min ultrasonication at 20 kHz, 5 min at 740 kHz and 1 min at 1120 kHz, the algae cells were inactivated and algae growth was halted. Ultrasound radiation can lead to the release of IOM, primarily chlorophyll a and phycocyanin, followed by some tryptophan and humic substances, polysaccharides, and proteins. The sonicated ribosomes were considerably reduced, and the antioxidant system of cells was also damaged to some extent. The coagulation effect of algae cells was substantially improved after ultrasonication. Thus, the safety of algae cell removal could be improved by controlling the changes in physiological structure and IOM release of algae cells by adjusting the ultrasound parameters.

Effective removal of Microcystis aeruginosa and microcystins by integrated pre-oxidation and coagulation: an environmental and economical way

The frequent occurrence of cyanobacteria blooms has gained worldwide concern. The conventional pre-oxidation methods are not only less effective in removing Microcystis aeruginosa cells, but also tend to trigger secondary pollution with an inevitable release of intracellular organic matter. In this study, Fe2+/persulfate process was applied to generate sulfate radicals and simultaneously form in situ Fe (III) for integrated oxidation–coagulation, leading to a notable enhancement in M. aeruginosa removal without cell breakage and better control of microcystins. Results showed that the Fe2+/persulfate mass ratio of 1:1 and the FeSO4 dosage of 0.1 mmol/L were efficient in M. aeruginosa removal. With the optimal FeSO4 dosage, up to 90.1% of M. aeruginosa were removed intact with the cell zeta potential of − 0.814. After settling down of M. aeruginosa within 30 min, the chlorophyll-a removal efficiency reached 98.9% and microcystins decreased remarkably. Furthermore, the degradation of algal organic matters was significantly enhanced with a relatively lower residual Fe. Protein-like substances and dissolved microbial metabolites were preferentially oxidized. The cell lysis only occurred to a small number of M. aeruginosa during the Fe2+/persulfate process, preventing from the environmental risk posed. This work demonstrates that an appropriate Fe2+/persulfate ratio and FeSO4 addition is a feasible and promising method for removing M. aeruginosa in an environmental-friendly and cost-effective way.

Assessing disinfection byproduct risks for algal impacted surface waters and the effects of peracetic acid pre-oxidation

Peracetic acid pre-oxidation of algal impacted waters can reduce formation of trihalomethanes but promote formation of haloacetonitriles, due to the degradation of dissolved organic matter and coincident release of intracellular organic matter.

Eliminating Cyanobacteria and Controlling Algal Organic Matter—Short Notes

Coagulation and flocculation processes could reduce particulate algal cells efficiently, but they are not so performant in dealing with solubilized algal organic matter in potable water factories. This work reviews the main findings found in recent publications. Many techniques used in the water treatment industry encounter the problem of microalgae lysis, toxin release, and degradation. Indeed, chemical coagulants such as alum and pre-oxidation injecting chlorine can trigger demolition to algal cell integrity leading to the release of intracellular organic matter. As suggestion, chlorination could be decreased to the disinfection (i.e., before sand filtration) averting pre-disinfection and keeping the post-disinfection. Moreover, algae recuperation instead of its removal in drinking water treatment plants remains an encouraging outlook especially if the surface water arrives from dams where algae blooms happen usually. Algae remain a sustainable energy resource with a huge capacity for CO2 fixation. The micro-algae could be developed in photo-bioreactors or in open ponds. A fresh attracting domain of investigation would be fast and simultaneous algal biodiesel production with drinking water treatment in the biodiesel production/water treatment plant without chemicals use.