Abstract
Coagulation and sedimentation performances of aluminum sulphate and ferric chloride were comparatively investigated in presence of Grewia spp. biopolymer for the treatment of concentrated laterite suspensions. Jar tests experiments were carried out at different laterite suspension concentrations (10, 20, and 30 g/L) and pH values (5 and 7). The performances of these coagulants were assessed in terms of interfacial settling velocities and sediment concentration factors. Results showed that after addition of Grewia spp. biopolymer, sedimentation velocities were greater when ferric chloride and aluminum sulphate were used alone. When hydrolyzing salts were used alone, the highest settling velocities were obtained with 10 g/L of laterite suspension at pH 5 and settling speeds were 0.22 and 0.28 cm/min for aluminum sulphate and ferric chloride, correspondingly. Addition of Grewia spp. biopolymer led to an increase of settling velocities to 0.56 and 0.57 cm/min, respectively. The sediment concentration factor was also found to be high when Grewia spp. was added. With 30 g/L of laterite suspension, sediment concentration factors at pH 5 were 1.47 and 2.12 for aluminum sulphate and ferric chloride separately. Addition of Grewia spp. biopolymer with aluminum sulphate and ferric chloride produced more compact sludge with sediment concentration factors of 4 and 3.13, respectively. Flocs structures could successfully explain the obtained results.
Highlights
Rivers are one of the main sources of raw water for the production of drinking water in the tropical region. us, during the rainy season, river water contains extremely high concentration of suspended matter especially laterite clay particles which are the major component of soil. ese particles confer to the brown color of raw water and may act as adsorbent of pollutants [1, 2]; they need to be removed from raw water
We have shown during our previous work that biopolymer extracted from Grewia spp. bark has flocculating properties [20]. ere are several studies on the sedimentation of kaolin suspension with salts alone and in combination with some coagulant aids [21,22,23]
To our knowledge, nothing is known about the sedimentation behavior of laterite suspension when Grewia spp. biopolymer is used in combination with hydrolyzing salts. is study is aimed at examining the effects of hydrolyzing salts as coagulants in conjunction with Grewia spp. biopolymer as natural coagulants aid on the sedimentation behavior of concentrated laterite suspension
Summary
Rivers are one of the main sources of raw water for the production of drinking water in the tropical region. us, during the rainy season, river water contains extremely high concentration of suspended matter especially laterite clay particles which are the major component of soil. ese particles confer to the brown color of raw water and may act as adsorbent of pollutants [1, 2]; they need to be removed from raw water. Many coagulants are widely used in water treatment processes and can be classified as natural organic (extract of Moringa seed and Opuntia), inorganic (e.g., aluminum sulphate, iron sulphate, and iron chloride), and synthetic organic polymers (e.g., polyacrylamides). Ese natural coagulants/flocculants, in contrast to synthetic ones, are more accessible and nontoxic [17, 18]. To our knowledge, nothing is known about the sedimentation behavior of laterite suspension when Grewia spp. biopolymer is used in combination with hydrolyzing salts. Is study is aimed at examining the effects of hydrolyzing salts as coagulants in conjunction with Grewia spp. biopolymer as natural coagulants aid on the sedimentation behavior of concentrated laterite suspension To our knowledge, nothing is known about the sedimentation behavior of laterite suspension when Grewia spp. biopolymer is used in combination with hydrolyzing salts. is study is aimed at examining the effects of hydrolyzing salts as coagulants in conjunction with Grewia spp. biopolymer as natural coagulants aid on the sedimentation behavior of concentrated laterite suspension
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