The Role of Coagulation-flocculation in the Pretreatment of Reverse Osmosis in Power Plant

Abstract

The objective of this work is to simulate pretreatment steps on a laboratory scale with the purpose of producing a higher quality permeate for feed reverse osmosis process. Pretreatment steps involved in this work are a combination of physical and chemical processes, such as coagulation-flocculation, sand filtration, and microfiltration. Samples of seawater next to Itaqui thermoelectric power plant in Maranhão, State of Brazil, powered by coal, were collected and characterized. The characterization indicated high levels of turbidity, which is unusual for seawater, indicating the need of pretreatment to reverse osmosis. The combination of polyaluminum chloride dosages of 30 mg/L and 0.3 mg/L of Nalclear 8,173 anionic polymer allowed the reduction of turbidity values to below 1 Nephelometric Turbidity Unit (NTU). The use of coagulation and microfiltration membranes provided values of silt density index next to 3, while with sand filter, the silt density index values were higher than 4.

The Role of Coagulation and Microfiltration in Seawater Pre-treatment

“…Due to aluminium-based coagulants having a strong charge opposite to that of the membrane surface and the relatively high solubility of Al, it can be concentrated, producing aluminium hydroxide and aluminium silicate solids, causing precipitate scaling for the membrane in the following desalination step. Consequently, FeCl 3 is the most preferable for coagulation in the case of salty water treatment [15,16]. Yang and Kim had evaluated the effect of coagulation on the performance of MF for the removal of particles under various coagulant dosages and pH.…”

Electrospinning on 3D Printed Polymers for Mechanically Stabilized Filter Composites

“…Filters are used to separate water from oil, biological and inorganic material from water or gas fluids, etc. Several technologies are used, depending on the exact application, such as granular filtration with quartz sand [1], superhydrophobic meshes for water/oil separation [2], reactive superhydrophobic paper for water filtration [3], molecular sieves from graphene oxide for nanofiltration [4] or reverse osmosis for water cleaning in power plants [5].…”