The use of alum as coagulant for removing cyanobacterial cells in drinking water

A variety of problems can occur due to the presence of cyanobacteria in water resources used for drinking, agricultural, industrial, commercial, and recreational purposes. In addition, certain cyanobacteria genera are producers of several potent toxins, which endanger the human and animal health. Coagulation is the key step in water treatment process for algae and cyanobacteria, and their associated metabolites removal. The objective of this study was to examine the coagulation processes to optimize the removal of cyanobacterial cells from drinking water under various aluminum sulfate dose and pH values. The influence of cationic polyelectrolyte as a coagulant aid on the cells in accompany with aluminum sulfate was also studied. A set of jar test experiments at 200rpm of rapid mixing, and 30rpm of slow mixing and 30min settling time were conducted to find the optimum chemical dose and pH. From the results of the tests, the optimum dose and pH for aluminum sulfate coagulant and polyelectrolyte were obtained corresponding to the lowest concentrations of cyanobacterial cells and turbidity

Removal of intra- and extracellular microcystin by submerged ultrafiltration (UF) membrane combined with coagulation/flocculation and powdered activated carbon (PAC) adsorption

In this study, we investigated the performance of conventional (coagulation/flocculation -> powdered activated carbon [PAC] adsorption) and advanced treatment (coagulation/flocculation -> PAC adsorption -> submerged ultrafiltration [UF] membrane) processes separately and sequentially for the removal of total (intra- and extracellular) microcystin. Results of the conventional treatment process demonstrated that coagulation/flocculation alone was not effective (up to 70%) for the removal of total microcystin, while the uptake of total microcystin was achieved up to 84% by PAC adsorption (PAC dose of 20 mg/L). In addition, the adsorption kinetic mechanism of PAC was also examined using several kinetic models. Results showed that the pseudo-second order (PSOM) and Weber-Morris intraparticle diffusion model (IPDM) are the most suitable models for this study (r(2)>0.98 and p-values <= 0.05). On the other hand, up to 94% of microcystin was effectively removed when the coagulation/flocculation and PAC systems were combined with UF membranes. Also, the permeate concentration was found to be 0.3 mg/L, which is below the World Health Organization (WHO) guideline value of 1 mu g/L. Overall results indicated that higher removal of microcystin occurred using the advanced treatment process. Therefore, this combined system appears to be a promising treatment technique for the removal of total microcystin. (C) 2017 Elsevier B.V. All rights reserved