Improved virus removal by high-basicity polyaluminum coagulants compared to commercially available aluminum-based coagulants

Abstract

We investigated the effects of basicity, sulfate content, and aluminum hydrolyte species on the ability of polyaluminum chloride (PACl) coagulants to remove F-specific RNA bacteriophages from river water at a pH range of 6-8. An increase in PACl basicity from 1.5 to 2.1 and the absence of sulfate led to a reduction of the amount of monomeric aluminum species (i.e., an increase of the total amount of polymeric aluminum and colloidal aluminum species) in the PACl, to an increase in the colloid charge density of the PACl, or to both and, as a result, to high virus removal efficiency.The efficiency of virus removal at around pH 8 observed with PACl-2.1c, a nonsulfated 2 high-basicity PACl (basicity 2.1-2.2) with a high colloidal aluminum content, was larger than that observed with PACl-2.1b, a nonsulfated high-basicity PACl (basicity 2.1-2.2) with a high polymeric aluminum content. In contrast, although extremely high basicity PACls (e.g., PACl-2.7ns, basicity 2.7) effectively removed turbidity and UV260-absorbing natural organic matter and resulted in a very low residual aluminum concentration, the virus removal ratio with PACl-2.7ns was smaller than the ratio with PACl-2.1c at around pH 8, possibly as a result of a reduction of the colloid charge density of the PACl as the basicity was increased from 2.1 to 2.7. Liquid 27 Al NMR analysis revealed that PACl-2.1c contained Al 30 species, which was not the case for PACl-2.1b or PACl-2.7ns. This result suggests that Al 30 species probably played a major role in virus removal during the coagulation process. In summary, PACl-2.1c, which has high colloidal aluminum content, contains Al 30 species, and has a high colloid charge density, removed viruses more efficiently (>4 log 10 for infectious viruses) than the other aluminum-based coagulants-including commercially available PACls (basicity 1.5-1.8), alum, and PACl-2.7ns-over the entire tested pH (6-8) and coagulant dosage (0.54-5.4 mg-Al/L) ranges.

An alternative method for preparation of polyaluminum chloride coagulant using fresh aluminum hydroxide gels: Characterization and coagulation performance

“…PAC G2.0 possesses the highest Al b content of 70.04% in the research, and the value is far larger than that in the similar research (Li Liu and Li, 2010). It has been reported that high Al b content resulted in the excellent coagulation performance in the water treatment (Shirasaki et al, 2014;Shu-xuan et al, 2014;Xu and Gao, 2012). The distributions of Al 13 and Al m in PAC G with different basicity values possess the similar tendency (Table 1 and Fig.…”

“…Aluminum species distribution is presented by calculating the contents of Al a , Al b and Al c , and it profoundly influences the coagulation efficiency of PAC (Shirasaki et al, 2014;Shu-xuan et al, 2014). The aluminum species in PAC G were measured via the application of Al-Ferron timed spectrophotometric method based on the different reaction time of hydroxyl-aluminum with the Ferron reagent (8-hydroxy-7-iodoquinoline-5-sulfonic acid) (Sinopharm Chemical Reagent Co., Ltd., China) (Feng et al, 2007).…”

“…Aluminum species were mainly divided into three categories as follows: Al a which reacted with Ferron within 60 s, Al b which reacted with Ferron within 120 min and Al c which needed much more time to react with Ferron or did not react with Ferron at all. Al c was obtained by subtracting Al a and Al b from the total aluminum (Ng et al, 2012;Shirasaki et al, 2014). The absorbance at 370 nm was measured by a UV-vis spectrophotometer (Beijing Purkinje General Instrument Co., Ltd., China) (Zouboulis and Tzoupanos, 2010).…”

“…It aggregates the small suspended and colloidal particles in the water to become bigger ones after coagulant is added, and the aggregated particles are easily removed by gravity settlement or filtration (Alexander et al, 2012;Verma et al, 2012). In recent years, some research efforts have been devoted to aluminum-based coagulants, a kind of efficient and widespread inorganic coagulant (Shirasaki et al, 2014;Bi et al, 2004). Polyaluminum chloride (PAC) as the prehydrolyzed aluminum coagulant attracts increasing attention for wider scope of application, lower alkalinity consumption, less sludge production and lower residual aluminum concentration in the treated water compared with conventional aluminum coagulant (Ghafari et al, 2009;Wu et al, 2007;Yang et al, 2010).…”

“…It is generally accepted that the coagulation efficiency of PAC with high basicity value is better than that of one with low basicity value for the large amount of preformed middle/high polymeric aluminum and high charge density (McCurdy et al, 2004;Shirasaki et al, 2014). However, it is reported that PAC with low basicity value perform better in some cases (Yan et al, 2008;Yang et al, 2011).…”