Reuse of Aluminum‐based Water Treatment Sludge to Immobilize a Wide Range of Phosphorus Contamination: Equilibrium Study with Different Isotherm Models

Abstract

The adsorption equilibrium of a wide range of phosphorus species by an aluminium-based water treatment sludge (Al-WTS) was examined in this study. Four kinds of adsorption-isotherm models, namely Langmuir, Freundlich, Temkin and Dubinin-Radushkevich, were used to fit the adsorption equilibrium data. In order to optimise the adsorption-isotherm model, correlation coefficient (R 2 ) and four error functions were employed to facilitate the evaluation of fitting accuracy. Experiments have demonstrated that the Al-WTS may be an excellent raw material to adsorb P in polluted aqueous environment with adsorption ability in the order of KH 2 PO 4 (ortho-P) > Na(PO 3 ) 6 (poly-P) > C 10 H 14 N 5 O 7 P· H 2 O (organic-P). More importantly, this study provides an entire comparison of the four isotherms in describing the P adsorption behaviour. By considering both the standard leastsquare based R 2 and the results of four error functions analysis, this study reveals that the Freundlich isotherm appears to be the best model to fit the experimental equilibrium data. Langmuir and Temkin isotherms are also good models in current experimental conditions while DubininRadushkevich isotherm poorly described the adsorption behaviour. The error analysis in this study provides vital evidence to reflect its role in facilitating the optimisation in adsorption isotherm study.Obviously, R 2 seems inadequate in optimising multi-isotherm models due to its inherent bias resulting from the least-squares linearisation.

Application of waterworks sludge in wastewater treatment plants

“…Increasing interest in the usage of WWS for the removal of phosphate at the WWTP is seen in the past two decades in the form of many laboratory studies (e.g. Babatunde and Zhao 2010;Ippolito et al 2003;Yang et al 2009;Zhao et al 2007); however, the reuse of WWS at WWTP is rarely seen in practice. The reported studies on phosphate removals with WWS show that the sorption of phosphate is a two-stage process: a quick sorption followed by slow sorption (cited in Ippolito et al 2011).…”

“…Hence the majority of studies on WWS reuse have been performed with aluminium-rich WWS (e.g. Babatunde and Zhao 2010;Ippolito et al 2003;Makris et al 2004;Yang et al 2009;Zhao et al 2007) and very few were based on ironrich WWS (e.g. Makris et al 2004;Leader et al 2008).…”

Two strategies for phosphorus removal from reject water of municipal wastewater treatment plant using alum sludge

“…It is clear that, compared with the raw anaerobically digested sludge, the addition of alum sludge into anaerobically digested sludge could lead to the improvement of the sludge dewaterability as gauged by CST and SRF. More significantly, the P concentration in the supernatant of the mixed sludge is tremendously reduced due to the adsorption by alum sludge (Yang et al, 2006;Zhao et al, 2007). It is noted that the TOC and pH of the supernatant of the mixed sludge are increased, and this may be caused by the release of TOC from the alum sludge during P adsorption (Yang et al, 2006).…”

Adsorption behaviors of acetaminophen onto sediment in the Weihe River, Shaanxi, China

“…However, it cannot be the only standard due to the inherent deviation of linear regression. In order to quantitatively comparing the applicability of the Langmuir and Freundlich adsorption isotherms in the data fitting, the following four error functions were employed for error analysis (Zhao et al, 2007) The sum of the squares of the errors (SSE)…”