Abstract
The increasing demand for water resources (primarily for human consumption and industrial and agricultural activity) is driven by socio-economic development, and population growth. Recent research has been focusing on alternative coagulants based on natural elements, as opposed to the commonly used iron and aluminum salts, for use in water and wastewater treatment processes. In this context, a thorough literature review on alternative coagulants and their application to water treatment processes has been conducted in this work. In addition, three experiments have been conducted with a widely used natural organic coagulant (Moringa oleifera). The alternative clarification system used is the helically coiled tube flocculator (HCTF), with high turbidity removal efficiency and low processing times. A comparative analysis of the turbidity reduction over time was performed with samples collected after 600, 900, 1200, 1500, 1800, 2100, 2400, and 2700 s from the hydraulic circuit. The process efficiency using the proposed alternative coagulant reached 95.3% (after 1800 s). The turbidity removal efficiency remained almost constant after 1800 s, with variations below 1%. These results prove that natural alternative agents can be powerful tools in the water treatment process, with efficiency values exceeding those obtained using chemicals (e.g., aluminum sulphate) as coagulant/ flocculant agents.
Highlights
IntroductionCoagulation and flocculation are very important steps in water treatment processes
Based on the results encountered in the literature, Moringa oleifera was chosen as the alternative coagulant to be studied, due to its high potential for the removal of impurities (Muniz et al, 2015), and its availability in Brazil
This paper analyzed alternative coagulants studied in the literature and their application to water treatment processes
Summary
Coagulation and flocculation are very important steps in water treatment processes. Chemicals are commonly added to water in a rapid mixing stage, thereby enhancing particles destabilization and, flocs formation. The flocs formed are removed from water in the flotation/ sedimentation step. The quality of the treated water should satisfy established governmental regulations, to avoid causing damages to the environment and human health (Santos, Pereira, Santana, & Silva, 2011). In this context, the development of new techniques and products to improve process efficiency becomes necessary
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