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For the in-situ treatment process of landscape waters, ponds, reservoirs and other water bodies, there is a significant deviation between the experiment results and the actual treatment effect due to volume amplification effect. Therefore, this study systematically explored the influence of hydraulic conditions, dosing frequency, dosing intervals of coagulant, and coagulant dilution multiples on the removal efficiency of particulate and organic matter on a large scale to precisely simulate the practical treatment situation. Results showed that dosing intervals and dosing frequency played an important role in the aggregation and settling process of particulate matter by influencing the energy barrier between particles, while hydraulic conditions affected the structure and settling characteristics of flocs. The overall trend of the total organic matter was consistent with that of particulate matter. However, only the freshly formed aluminum hydroxide precipitates had adsorption activity to humic substances. The adsorption could be completed rapidly so that hydraulic conditions had no influence on the aggregation process of humic substances. While during stirring and aging process, humic substances was found to be released due to the polymerization and crystallization of aluminum precipitates. From the results of pilot tests, a treatment strategy was implemented for a reservoir in southern China and the ideal treatment effect was achieved. This study provided theoretical foundation and design guidance for the in-situ coagulation treatment of landscape waters, ponds and reservoirs. [Display omitted] [ABSTRACT FROM AUTHOR]

Membrane filtration combined with pre-coagulation has advantages in advanced wastewater treatment. As a model of a microbial polysaccharide, research on the effect of sodium alginate (SA) on alum hydrolysis has been rare; therefore, it is necessary to gain insight into the interface interaction between SA molecules and Al species, and the role SA plays during floc formation. In this study, the interaction mechanism between SA and Al species has been investigated, by evaluating the effect of SA on floc characteristics and membrane fouling during coagulation–ultrafiltration with different Al species coagulants (AlCl 3 and preformed Al 13). Al 2p X-ray photoelectron spectroscopy (XPS) confirmed that the complexation of ligands and Al species strongly affects the reaction pathways for Al hydrolysis and the final nature of the flocs, as Al 13 can be decomposed into octahedral precipitates when SA is added. The presence of SA can affect floc properties, which have important impacts on the characteristics of the cake layer and membrane fouling. Due to the bridging ability of SA, the floc strength increased by about 50% using Al a , which was much better than preformed Al 13 , with a percentage increase of only about 6%. Moreover, the recovery factor of HA-flocs was decreased from 96% to 43% with SA addition of 0.5 mg/L. It was concluded that SA can affect the characteristics of the cake layer and membrane fouling through participating in the formation of primary flocs and altering the Al hydrolysis pathway. Unlabelled Image [ABSTRACT FROM AUTHOR]

[Display omitted] • Stirring condition did not significantly affect the HA removal performance. • The HA decreased the aggregation rate and D f of floc. • Prolonged fast stirring was disadvantage of larger floc size at equilibrium. • Stirring condition affected the elemental proportions and structure of flocs. Number of studies have explored the mechanism of humic acid (HA) removal by coagulation, while studies on the formation and growth mechanism of HA-floc are still limited. In this study, a series of dynamically monitored experiments were carried out and floc characterization techniques were applied to investigate HA-floc growth mechanisms and properties under different stirring conditions. First, HA was removed in the early stages and varied insignificantly during floc growth, and the stirring condition did not affect the removal of HA. Moreover, HA hindered the effective collision, resulting in a slower floc growth rate and a lower fractal dimension. Although stirring condition did not markedly affect the HA removal performance, it had a remarkable effect on floc growth and structure. For example, gentle stirring resulted in larger floc d 50 and pore size. Intense stirring accelerated the breakage or aging of flocs, resulting in a reduction in the final floc size at equilibrium. In particular, fast stirring in the early stage of coagulation advanced floc growth, but decreased the zeta potential and active sites of flocs, and reduced the capacity of the primary aggregates to grow into larger flocs. This study provides information on the floc formation and growth mechanism and the properties of flocs formed under different stirring conditions, which are helpful for optimizing the coagulation process on organic matter removal and guide the processes utilizing flocs. [ABSTRACT FROM AUTHOR]

• Flocs would absorb and release NOM during aging, aquatic humics is the primary releasing organic matter. • The flocs generated form Al 13 and AlCl 3 have the same organic release pattern during aging, but the release intensity of Al 13 is lower. • The flocs generated form nanoparticles and microparticles have different release and absorption pattern of NOM during aging. • The flocs will further generate Al hydrolysates with higher polymerization during aging. Most studies on the interaction between coagulation and NOM (natural organic matter) currently focus on pollutant removal and coagulant species distribution, while studies on floc aging are lacking. Investigation onto the effects of floc aging could guide further processes that utilize flocs, such as densadeg sludge recirculation, floc predeposition for ultrafiltration, sludge condensation, and other traditional sludge reflux processes. In this study, flocs generated by Al 13 and AlCl 3 in microparticle- and nanoparticle-containing water were investigated, and the effect of floc aging on NOM was quantified based on several organic matter characterization techniques. Flocs absorb and release organics during aging. The flocs generated from micro-SiO 2 have a significant absorbing effect for LWM-N (low-molecular-weight neutral substances) and protein-like substances, while the absorption of NOM by flocs generated from nano-SiO 2 is insignificant. HS (humic substances) with high aromaticity are released during floc aging. From the molecular perspective, the molecules released during floc aging are those with higher double bond equivalents and higher aromaticity, while the absorbed molecules are those with lower double bond equivalents and lower aromaticity. 2D-COS (two-dimensional correlation spectroscopy) demonstrated that the flocs generated by Al 13 and AlCl 3 had the same organic release patterns but different intensities, while the flocs generated in the micro-SiO 2 and nano-SiO 2 systems had different organics release patterns. Abundant aluminum hydrolysates with low polymerization and amorphous Al(OH) 3 would be produced from AlCl 3 during the coagulation process and then undergo hydroxyl‑bridging reaction and crystallization during floc aging, thus releasing more HS with high aromaticity into the supernatant; in comparison, prehydrolyzed Al 13 produces a more stable floc and releases less HS during aging. The flocs produced by nano-SiO 2 and Al-based coagulants release higher aromaticity HS into the water than those produced by micro-SiO 2 , which may be related to the formation of more highly polymerized degree hydrolysates and nanocrystalline Al(OH) 3 in the nano-SiO 2 system. The flocs generated in water with micro-SiO 2 may contain a large amount of Al-OH and have a loose structure, thus further absorbing NOM, such as protein-like substances and LWM-N. In contrast, the flocs generated from nano-SiO 2 possess abundant adsorbed water and a denser structure; thus, organic matter cannot be absorbed stably. [Display omitted] [ABSTRACT FROM AUTHOR]