Abstract

Abstract
The objective of this study is to evaluate the coagulation-flocculation process in clarification of leachate from the landfill Technical Center of Souk-Ahras city. In the first step, three coagulants based on iron: ferrous sulfate FeSO4.7H2O ; ferrous chloride FeCl2.4H2O and ferric chloride FeCl3 have been tested. The influence of some parameters namely pH leachate, dose and nature of the coagulant and adding a flocculant was studied. The best treatment efficiency is obtained at 20% of FeCl3 by giving turbidity of 4.09 NTU with adjusting pH of raw leachate at acidic pH (3.5 ± 0.2) prior to coagulant addition and at a basic pH (7.5 ± 0.2) after addition of coagulant.
The iron valence and the nature of anion at which is linked, play a determinant role in the clarification of leachate. The treatments made with ferric chloride in the presence of a flocculant have proved that the starch is more efficient than lime giving an abatement rate of 99.4% for COD and 85.7% for BOD5.
In the second step the treatment of leachate has been optimized in presence of three coagulants (ferric chloride, aluminum sulphate and ordinary alum) where two types of agitation (mechanical and ultrasound) have been implemented. The parametric study revealed that pH adjustment of lixiviate was crucial for the success of treatment. The stronger reduction of turbidity was obtained with a coagulant dose of 15%, a stirring speed of 250 rpm and a stirring time of about 5 min for both aluminium sulphate and ordinary alum and 15 min for ferric chloride. An optimum coagulant-to-leachate volume ratio of one was found for the three coagulants, resulting in a turbidity reduction of 99.4%, 98.9% and 98.6% with ferric chloride, aluminium sulphate and ordinary alum, respectively. Bacteriological analyses highlighted the absence of total germs, fecal coliforms and streptococci for leachates treated with ferric chloride or aluminium sulphate. In contrast, coliforms including 9 total germs, 4 fecal germs and 3 faecal streptococci per 100 mL were detected for leachates treated with ordinary alum. The treatment of leachate was improved by using ultrasound waves with a frequency of 37 kHz and a power of 30 W. Indeed, a significant decrease in the turbidity of supernatants was observed as compared with the use of mechanical agitation, and a value of 0.19 NTU (instead of 0.61 NTU with mechanical agitation) was obtained for a treatment carried out with ferric chloride. The clarification of leachates was optimal at 20 °C providing a BOD5 of 100 mg O2/L for both ferric chloride and aluminium sulphate, and 200 mg O2 /L for ordinary alum.


Keywords: Coagulation, Flocculation, Leachate, Iron, Starch, Lime, Bacteriological analysis; Jar test, Physicochemical analysis, Ultrasound agitation.

Information

Item Type:	Thesis
Divisions:	» Laboratory sciences and technical water and environment » Faculty of Science and Technology
ePrint ID:	2476
Date Deposited:	2020-12-21
Further Information:	Google Scholar
URI:	https://www.univ-soukahras.dz/en/publication/article/2476

BibTex