Harmful algal bloom removal and eutrophic water remediation by commercial nontoxic polyamine-co-polymeric ferric sulfate-modified soils

Abstract

Harmful algal bloom has posed great threat to drinking water safety worldwide. In this study, soils were combined with commercial nontoxic polyamine poly(epichlorohydrin-dimethylamine) (PN) and polymeric ferric sulfate (PFS) to obtain PN-PFS soils for Microcystis removal and eutrophic water remediation under static laboratory conditions. High pH and temperature in water could enhance the function of PN-PFS soil. Algal removal efficiency increased as soil particle size decreased or modified soil dose increased. Other pollutants or chemicals (such as C, P, and organic matter) in eutrophic water could participate and promote algal removal by PN-PFS soil; these pollutants were also flocculated. During PN-PFS soil application in blooming field samples, the removal efficiency of blooming Microcystis cells exceeded 99 %, the cyanotoxin microcystins reduced by 57 %. Water parameters (as TP, TN, SS, and SPC) decreased by about 90 %. COD Mn , PO 4 -P, and NH 4 -N also sharply decreased by >45 %. DO and ORP in water improved. Netting and bridging effects through electrostatic attraction and complexation reaction could be the two key mechanisms of Microcystis flocculation and pollutant purification. Considering the low cost of PN-PFS soil and its nontoxic effect on the environment, we proposed that this soil combination could be applied to remove cyanobacterial bloom and remediate eutrophic water in fields.

A critical review on control methods for harmful algal blooms

“…In China, its implementation in the natural environment at mesocosm scale showed a change in microplankton community, with an increase in diversity (multi‐algae coexistence) together with a decrease of nutrients in the water column and diminished release of nutrients from the sediments (Dai et al . ). At larger scale in the same lake, the impact was similar, showing restoration of submerged vegetation (Macrophyte) suggesting that nutrient limitation can be manipulated using the MLS technology and secondarily that ecological recovery can be promoted (Wang et al .…”

“…(), acid treatment and later addition of cationic polymers (poly(epichlorohydrin–dimethylamine) and polymeric ferric sulphate) to natural soils were shown to be effective against Microcystis cells in laboratory assays (Dai et al . ). A different approach, consisting in fabrication of a new flocculant based on clays, was followed by Gu et al .…”

Study of Adsorption and Flocculation Properties of Natural Clays to Remove Prorocentrum lima

“…For instance microcystis cells were negatively charged in natural water with pH of 6–10 then bound with organic cations and ions, resulting in aggregation. However, the aggregation effect would not lead to flocculation without a proper gravity function [ 21 ]. In our experiments the addition of clay addresses this problem triggering Prorocentrum lima sedimentation.…”

“…Several strategies have been studied for removing HABs such as the biological and microbial algaecides [ 15 , 16 , 17 ], chemical [ 18 ], mechanical [ 19 ], and genetic measures [ 20 ]. However, these methods have drawbacks, such as the introduction of new species to control the algae population, the use of agents that could be harmful to other organisms and environmentally damaging or the inapplicability to large scale [ 21 ]. So far few technologies can be applied successfully at large scales in natural waters in an ecologically safe and cost-effective way [ 22 ].…”

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

“…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).…”