Fouling comparisons of the organic fractions in surface and algae-laden waters make it possible to determine the main compounds responsible for the fouling of ultrafiltration (UF) membranes. This study examined the fouling of UF membranes and its relationship to the characteristics of the organic fractions found in drinking-water supply. Four types of water were prepared by combining natural organic matter (NOM) from lake water with algal organic matter (AOM) from four algae species commonly found in freshwater. Liquid chromatography-organic carbon detection (LC-OCD) and a fluorescence excitation-emission matrix (FEEM) were used to analyze the feed water and permeate to assess the interactions between and fouling behavior of the organic fractions. The results showed that the interaction of large-molecular-weight AOMs on the membrane surfaces and their transport through the membrane pores were the main fouling mechanisms. Polysaccharides followed by protein-like substances were the organic compounds responsible for the fouling of the UF membranes. The fouling affinity of these substances was attributed to two processes, the adsorption of their carboxyl, hydroxyl and cationic groups on the membrane surfaces, and the molecular complexation of their organic groups. The humic substances\' retention was marginal and attributed to the synergetic effects of the polysaccharides and proteins.

The rapid development of coastal aquaculture in recent decades has led to excessive discharge of organic matter and nutrients into surrounding waters, which could result in eutrophication and potentially affect metal cycling. In our study, the influence of algal organic matter on metal accumulation was examined in three coastal sediment cores taken from a tropical region, Hainan Island, China. Overall, metal pollution adjacent to aquaculture ponds remained at low levels on the coast, except Zn, Cd, and Sn were moderately to highly enriched in the Dongjiao sediments. The δ13C values and the atomic C/N ratios indicated a major contribution of phytoplankton to sedimentary organic matter at the Dongjiao site. Moreover, both the algae-derived organic matter and effluent nitrogen were significantly associated with the enriched Zn, Cd, and Sn, suggesting that nutrient-induced phytoplankton growth and its organic matter may act as a \"biological pump\" to enhance the accumulation of metals. Wastewater treatment for aquaculture ponds should include the control of algal organic matter.

The increasing occurrence of algal and cyanobacterial blooms and the related formation of algal organic matter (AOM) is a worldwide issue that endangers the quality of freshwater sources and affects water treatment processes. The associated problems involve the production of toxins or taste and odor compounds, increasing coagulant demand, inhibition of removal of other polluting compounds, and in many cases, AOM acts as a precursor of disinfection by-products. Previous research has shown that for sufficient AOM removal, the conventional drinking water treatment based on coagulation/flocculation must be often accompanied by additional polishing technologies such as adsorption onto activated carbon (AC). This state-of-the-art review is intended to serve as a summary of the most current research on the adsorption of AOM onto AC concerning drinking water treatment. It summarizes emerging trends in this field with an emphasis on the type of AOM compounds removed and on the adsorption mechanisms and influencing factors involved. Additionally, also the principles of competitive adsorption of AOM and other organic pollutants are elaborated. Further, this paper also synthesizes previous knowledge on combining AC adsorption with other treatment techniques for enhanced AOM removal in order to provide a practical resource for researchers, water treatment plant operators and engineers. Finally, research gaps regarding the AOM adsorption onto AC are identified, including, e.g., adsorption of AOM residuals recalcitrant to coagulation/flocculation, suitability of pre-oxidation of AOM prior to the AC adsorption, relationships between the solution properties and AOM adsorption behaviour, or AOM as a cause of competitive adsorption. Also, focus should be laid on continuous flow column experiments using water with multi-component composition, because these would greatly contribute to transferring the theoretical knowledge to practice.

Algal organic matter (AOM) is an important source for the dissolved organic matter (DOM) pool in aquatic systems, particularly in eutrophic waters. In this study, we reported the dynamic pattern of AOM hydrophobicity during the growth cycle of Microcystis aeruginosa using the partition coefficients of AOM in the aqueous two-phase system (KATPS) as a simple quantitative measure. AOM hydrophobicity had significant and non-monotonic changes during the growth cycle. It increased in the lag and early exponential phases, then decreased in the late exponential and stationary phases, and rebounded in the decline phase. AOM hydrophobicity determined using the resin fractionation, SUVA254, and nuclear magnetic resonance methods shared similar non-monotonic pattern. Nevertheless, the correlations among these indicators were poor. The partition behavior of polycyclic aromatic hydrocarbons and chlorobenzenes to AOM was assessed based the KATPS dataset and the two-phase system (TPS) model. The TPS model showed good prediction power for the partition behavior of AOM with an RMSE of 0.23, suggesting that it was applicable to AOM from Microcystis aeruginosa. Our results indicate that algae activity will influence the overall hydrophobicity of the DOM pool depending on the growth phase, resulting in changes in the bioavailability of hydrophobic organic compounds in aquatic systems.

Ultrasound-enhanced coagulation is capable of effectively removing algal cells in algae-laden water. However, study differences in ultrasound settings, algal cell conditions and coagulant properties complicate the accurate evaluation of this technique for practical applications. No study has yet compared algae (and algal organic matters) removal among different frequencies of ultrasound in the ultrasound-coagulation process. In this study, the ultrasound at three typical frequencies, 29.4, 470 and 780 kHz, were applied for this purpose. The results showed that high-frequency ultrasound at 470 and 780 kHz had substantially greater improvement of coagulation than low-frequency ultrasound at 29.4 kHz (For example, the turbidity removal at 1 mg-Al/L of polymeric aluminum chloride increased by 204.2%, 571.9% and 563.2% under 29.4, 470 and 780 kHz ultrasound-coagulation, respectively, at 3.42 J/mL). Algal cells exhibited irreversible physical damage and the release of intracellular organic matters (such as odorous compounds) under low-frequency ultrasound with energy densities ≥ 3.42 J/mL, whereas high-frequency ultrasound was characterized by nonviolent impairment, including oxidative degradation and gas vacuole destruction (particularly reversible) resulting from ultrasound-induced radicals and cell resonance, respectively. Avoiding the severe destruction of algal cells is crucial for minimizing the toxicity and secondary pollution of the treated water. To achieve satisfactory removal, protected safety and better economy, the optimal energy density for each frequency was also determined. The findings from the analyses of the laboratory-cultured sample were confirmed via real eutrophic surface water. This study provides new insights and guidance for the ongoing study of harmful algal removal by ultrasound-enhanced coagulation.

Membrane distillation (MD) frequently deals with membrane biofouling caused by deposition of algal organic matter (AOM) from algal blooms, hampering the treatment efficiency. In this study, AOMs, which are soluble extracellular polymeric substance (sEPS), bounded EPS (bEPS), and internal organic matter (IOM) from three benthic species (Amphora coffeaeformis, Cylindrotheca fusiformis, and Navicula incerta) were exposed to a temperature range to resemble the MD process. Results showed that EPS had higher polysaccharide fraction than protein with 85.71%, 68.26%, and 71.91% for A. coffeaeformis, N. incerta, and C. fusiformis, respectively. Both the EPS polysaccharide and protein concentration linearly increase with temperature, but the opposite was true for IOM and high-molecular-weight (HMW) polysaccharide. At 80°C, 5812.94 μg/g out of 6304.28 μg/g polysaccharide in A. coffeaeformis was of low molecular weight (LMW); hence, these findings suggested that they were the major foulants to clog the narrow pores within virgin hydrophobic membrane, forming a conditioning layer followed by deposition of HMW and hydrophilic polysaccharides onto the macropores to cause irreversible fouling. Cell lysis occurring at higher temperature increases the total protein content about 25% within the EPS matrix, inducing membrane plugging via hydrophobic-hydrophobic interactions. Overall, the AOM composition at different temperatures will likely dictate the fouling severity in MD. PRACTITIONER POINTS: EPS production of three benthic diatoms was the highest at 80°C. EPS from diatoms consists of at least 75.29% of polysaccharides. Small molecular weight carbohydrates (<12 kDa) were potential foulants. Proteins of internal organic matter (>56%) give irreversible attachment towards membranes. A. coffeaeformis was considered as the most fouling diatoms with highest EPS amount of 6304.28 μg/g.

Algal organic matter (AOM) and natural organic matter (NOM) from a typical eutrophic lake were comprehensively investigated in terms of their physico-chemical property, components and disinfection byproduct formation potentials (DBPFPs). The relationships between specific chemical properties of AOM and NOM with their corresponding DBPFPs were further evaluated during chlorination. Results indicated that AOM had lower specific UV absorbance (SUVA) but richer organic nitrogen contents than NOM. Fluorescence excitation emission matrix spectroscopy further demonstrated that AOM were chiefly composed of aromatic protein-like and soluble microbial byproduct-like matters, while NOM were mainly contributed from humic acid-like and soluble microbial byproduct-like substances. Although the molecular weight (MW) distribution of AOM and NOM showed no significant difference, size-exclusion chromatography with organic carbon as well as organic nitrogen detection (LC-OCD-OND) revealed that AOM were concentrated with the fraction of building blocks and NOM had higher concentrations of biopolymers and humics (HS). Moreover, AOM displayed higher DBPFPs than NOM, especially for nitrogenous DBPFP (N-DBPFP). MW < 1 kDa fractions both in AOM and NOM contributed the largest proportion to the formation of carbonaceous disinfection byproducts (C-DBPs). In addition, Pearson correlation analysis showed that bulk parameter SUVA was significantly relevant to the formation potentials of trihalomethane both in AOM and NOM, but was ineffective for carbonaceous DBPFP (C-DBPFP) prediction. Dissolved organic nitrogen contents in biopolymer and HS characterized by LC-OCD-OND had strong correlations with N-DBPFPs from AOM and NOM, indicating that LC-OCD-OND quantitative analysis could improve the prediction accuracy of the DBP formation than bulk parameters during NOM and AOM chlorination.

Ozonation pretreatment is typically implemented to improve algal cell coagulation. However, knowledge on the effect of ozonation on the characteristics and coagulation of associated algal organic matter, particularly cellular organic matter (COM), which is extensively released during algal bloom decay, is limited. Hence, this study aimed to elucidate the impact of ozonation applied before the coagulation of dissolved COM from the cyanobacteria Microcystis aeruginosa. Additionally, the degradation of microcystins (MCs) naturally present in the COM matrix was investigated. A range of ozone doses (0.1-1.0 mg O3/mg of dissolved organic carbon - DOC) and ozonation pH values (pH 5, 7 and 9) were tested, while aluminium and ferric sulphate coagulants were used for subsequent coagulation. Despite negligible COM removal, ozonation itself eliminated MCs, and a lower ozone dose was required when performing ozonation at acidic or neutral pH (0.4 mg O3/mg DOC at pH 5 and 7 compared to 0.8 mg O3/mg DOC at pH 9). Enhanced MC degradation and a similar pattern of pH dependence were observed after preozonation-coagulation, whereas coagulation alone did not sufficiently remove MCs. In contrast to the benefits of MC depletion, preozonation using ≥ 0.4 mg O3/mg DOC decreased the coagulation efficiency (from 42%/48% to 28%-38%/41%-44% using Al/Fe-based coagulants), which was more severe with increasing ozone dosage. Coagulation was also influenced by the preozonation pH, where pH 9 caused the lowest reduction in COM removal. The results indicate that ozonation efficiently removes MCs, but its employment before COM coagulation is disputable due to the deterioration of coagulation.

Algae cells and algal organic matter (AOM) present in algae impacted source water pose a serious threat to the safety of drinking water. Conventional water treatment processes poorly remove AOM that can transform to harmful disinfection byproducts (DBPs) during ensuing disinfection. This article offers a comprehensive review on the impacts of pre-oxidation on the formation of DBPs from AOM in subsequent chlor(am)ination. Various characterization techniques for algal cells and AOM are first overviewed with an effort to better understanding of correlation between the AOM properties and downstream DBP formation. Then, the present work reviews recent studies on application of different pre-oxidation technologies, such as chlor(am) ination, UV irradiation, ozonation, ferrate (VI), permanganate oxidation and UV-based advanced oxidation processes (AOPs), to remove algal cells and degrade AOM. Pre-oxidation can reduce the stability of algal cells and inactivate algal cells for promoting cell aggregation and thus favoring coagulation. Meanwhile, pre-oxidation can mitigate and degrade AOM into small molecular weight organic compounds to reduce DBP formation potential during subsequent chlor(am)ination. Finally, this review provides an overall evaluation on the applicability of different pre-oxidation processes, and identifies future research demands.

Low molecular weight algal organic matter (AOM), as a frequent water contaminant with poor coagulation efficiency, adversely affects the quality of produced water and serves as a source of potentially carcinogenic disinfection by-products. AOM removal from water is inevitable to eliminate the negative health and environmental impacts. This research evaluates the removal of arginine, phenylalanine and aspartic acid, which are amino acids abundant in AOM. Adsorption experiments were performed at 10, 18 and 25 °C and pH 5, 7 and 9 using two different activated carbons (FTL, PIC). Amino acids showed endothermic adsorption behaviour, with a higher removal at higher temperature. Higher temperature increased the diffusion of amino acid molecules, reduced the solution viscosity, or enhanced the hydrophobic interactions contributing to adsorption. The effect of temperature manifested differently during experiments depending on the chemical nature of the amino acids, the pH value and the surface properties of the carbon. Phenylalanine isotherms showed specific waves (Langmuir type 4). pH had a greater effect on arginine adsorption than did temperature. Aspartic acid isotherms exhibited a decrease in adsorption at higher pH values and higher temperatures. The principal mechanisms involved in amino acid adsorption were hydrophobic interactions, electrostatic interactions or hydrogen bonds.