Removal of Microcystis aeruginosa using cationic starch modified soils

Abstract

a b s t r a c tA cheap and biodegradable modifier, cationic starch (CS), was used to turn local soils into effective flocculants for Microcystis aeruginosa (M. aeruginosa) removal. The isoelectric point of soil particles was remarkably increased from pH 0.5 to 11.8 after modification with CS, which made CS modified soil particles positively charged and obtain algal flocculation ability. At the soil concentration of 100 mg/L, when the CS modifier was 10 mg/L, 86% of M. aeruginosa cells were removed within 30 min. Lower or higher CS dosage led to limited algal removal. About 71% and 45% of M. aeruginosa cells were removed within 30 min when CS was 5 mg/L and 80 mg/L, respectively. This is because only part of algal cells combined with CS modified soil particles through charge neutralization at low dosage, while flocs formed at high CS dosage were positively charged which prevents further aggregation among the flocs. The floc stability was quantified by a floc breakage index under applied shear force. Algal flocs formed at acid and alkaline conditions were more prone to be broken than those at the neutral condition. The cost and biodegradability concerns may be largely reduced through the use of CS modified local soils. For field applications, other practical issues (e.g., re-suspension) should be further studied by jointly using other methods.

Manipulating nutrient limitation using modified local soils: A case study at Lake Taihu (China)

“…Most of geo-engineering materials so far only focus on the P reduction. The MLS materials (Li and Pan, 2013;Shi et al, 2016;Zou et al, 2006) can simultaneously manipulate N and P by removing algal blooms in short term, affecting redox environment in the sediment, and restoring submerged vegetation in long term in shallow waters (Pan et al 2011(Pan et al , 2012a. High water clarity and the low nutrient concentrations can be quickly obtained by MLS flocculation.…”

Effect of algal flocculation on dissolved organic matters using cationic starch modified soils

“…Once positive charges were overdosed, the removal efficiency decreased, since the reversal of cell surface charge (Fig. 2b) potentially reintroduced the electrostatic repulsion and prevented aggregation between CS-MS and algae particles (Jangkorn et al, 2011;Mosse et al, 2012;Shi et al, 2015). Hence, to achieve effective algal removal using MSs, the modifier loading mainly depended on the charge density.…”

“…Modified soils (MSs) have triggered great interest as geo-engineering materials for cyanobacterial bloom control in recent years (Lürling and van Oosterhout, 2013;Mackay et al, 2014;Spears et al, 2014;Tian et al, 2014). Although many studies on algal removal using MSs have been reported (Li and Pan, 2013;Pan et al, 2011a;Shi et al, 2015;Zou et al, 2005), little is known about its potential impacts on the receiving waters.…”

“…Several chemical coagulants (e.g., aluminum and ferric salts) and organic macromolecular flocculants (e.g., cationic starch, chitosan and Moringa oleifera) have been tested as soil modifiers for algal removal (Dai et al, 2015;Li and Pan, 2013;Pan et al, 2006;Shi et al, 2015). Compared with chemical coagulants, organic macromolecular flocculants are often easily biodegradable, eco-friendly and are well accepted by the public (Mukherjee et al, 2014;Ndabigengesere and Narasiah, 1998;Renault et al, 2009).…”

“…Charge neutralization is a main mechanism operating algal flocculation using MSs, which can reduce the electrostatic repulsion and promote aggregation between MSs and algae particles (Li and Pan, 2013;Shi et al, 2015). To achieve the effective algal removal, desired amount of positive charges are needed to neutralize negative charges on algal cell surface .…”