Abstract
The goal of this study was to characterize and then optimize the treatment process of effluent generated from couscous and pasta industry. The crude effluent is characterized by a high level of organic concentration (from 2269 to 4383 mg/l). The optimization of coagulation-flocculation process was then performed to minimize chemical oxygen demand (COD). The experiments were carried out using the response surface methodology (RSM). A central composite design (CCD) was used to evaluate the effects and the interactions of three factors; coagulant dosage, flocculant dosage and pH on the wastewater treatment efficiency. Quadratic models was developed for the response variables and it successfully describes the experimental data (R2= 0.728). Analysis of variance (ANOVA) showed that only the coefficients corresponding to the flocculant dosage were significant (p < 0.0001). In order to take into account the variability of the initial organic concentration of the effluent, the CCD was repeated thrice by using a wastewater having initially different organic charges (530, 1775 and 2722 mg/l). Whatever was the initial organic charge of the wastewater, the optimal coagulant dosage was found constant (about 50 mg/l) and the optimal pH value was about 11.0. On the contrary, the optimal flocculant dosage varied linearly (from 24 to 50 mg/l) with the initial COD (from 529 to 2722 mg/l). These optimal conditions allow a COD removal varying from 78 to 93%. Irrigation and germination tests were carried out with treated and untreated wastewater and they showed that these effluents could be adequately recycled in culture irrigation. Key words: Couscous and pasta industry effluent, COD removal, central composite design, response surface methodology (RSM), irrigation tests.
Highlights
Several wastewater treatment methods are available as on date in order to ensure good quality effluent before disposal into the municipal sewer systems (Drogui et al, 2008)
The experiments were carried out using the response surface methodology (RSM)
The pH values varied from 5.57 to 8.45 in the upstream tank. This could be attributed to the variability of chemical composition of the water discharged by this industrial activity, whereas the treated wastewater collected after the decantation tank presents a pH value ranging from 4.65 to 7.00. pH values are sometimes out of the ranges fixed by standards and this variability could be attributed to the alkalinization step which is arbitrarily realized
Summary
Several wastewater treatment methods are available as on date in order to ensure good quality effluent before disposal into the municipal sewer systems (Drogui et al, 2008). The wastewaters vary in terms of the pollutant composition depending on the origin of the industry. The disposal of such effluents in the environment will lead to surface and groundwater contamination: increase in chemical oxygen demand, eutrophisation, ecosystem imbalance and human health risks (Bektas et al, 2004). The pasta industry produces wastewater with high concentrations of organic compounds that are not completely removed by preliminary treatments or biological process (Roa-Morales et al, 2007). The high organic load of pasta industry represents a major environmental problem. With the establishment of more stringent regulations concerning wastewater treatment, there has been a growing interest in the development of
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