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The aim of this study is to evaluate the performance of coagulation and flocculation (C/F) process and economic analysis for the advanced primary treatment in order to obtain a semi-closed water circuit in the pulp mills in the cardboard recycling industry. Since the high water quality level is not required in the pulpers, the dosages in this research were determined without pH changes or adjustment to decrease the capital and operational expenditures. The results showed that FeCl3 with the concentration of 2000 mg/L gave the best quality when coagulants were used solely. Moreover, using alum with the concentration of 1500 mg/L provided acceptable quality for the effluent re-circulation and the removal/reduction percentages of 42, 82, 71 and 97 were achieved for chemical oxygen demand (COD), total suspended solids (TSS), turbidity and colour, respectively. It was also found that the combination of coagulants did not improve the process performance significantly. The best combination was ferric chloride (500 mg/L) and alum (2000 mg/L) with the efficiency of 47% and 98% in terms of COD and colour removal/reduction, respectively, while the best couple in TSS removal was FeCl3 (500 mg/L) and CaCO3 (500 mg/L) with the efficiency of 88%. The chemicals coupled with cationic polyacrylamide (C-PAM) did not enhance the quality of pre-treated solutions when the settling time reduced up to 15 minutes. The cost analysis also showed that alum is the most cost-effective coagulant with the costs in the range of 0.06–0.12 $/kg removed TSS, 0.06 to 0.11 $/kg removed COD and 0.06–0.1 $/m3·reduced NTU whereas calcium carbonate is the economic coagulant regarding colour reduction with the cost of 0.003 $/m3·reduced unit and more than the reduction efficiency of 90%. [ABSTRACT FROM AUTHOR]

In this paper, an orthogonal basis for the space of linear splines based on linear B-splines is introduced. Some properties and modifications of this basis are investigated, then operational matrices of integration in collocation points are obtained using stable formula. Theoretical considerations are discussed. Applications to the numerical solutions for some linear and nonlinear inverse problems are given, in which the approximations are obtained using the first and second integrals of orthogonal linear splines that lead to an efficient solution procedure. For solving linear problems, the proposed method is combined with the Tikhonov regularization. Also, the trust-region-dogleg method is used for nonlinear equations. Numerical results validate the effectiveness of the orthogonal linear spline basis for linear and nonlinear inverse problems. [ABSTRACT FROM AUTHOR]

This study evaluates the bio-treatability performance and kinetic models of full-scale horizontal subsurface flow constructed wetland used for the tertiary treatment of composite industrial effluent characterized by high-salt content ranging from 5830 to 10,400 µS/cm and biochemical oxygen demand (BOD5): chemical oxygen demand (COD) ratio below 0.2. The wetland vegetated with Phragmites australis was operated in a semi-arid climate under an average hydraulic loading rate of 63 mm/d. The results of a 4-year operation calculated based on the concentration of pollutants showed that the average removal efficiency of COD, BOD5, and total suspended solids (TSS) were 17.5, 5.1, and 11.2%, respectively. The system reduced up to 6.5 ± 0.7% of electrical conductivity presenting poor phyto-desalination potential without considering the contribution of evapotranspiration in water balance in contrast to satisfying performance for heavy metals reduction. The comparison of the kinetics of organic matter removal obtained by the first-order and Monod models paired with continuous stirred-tank reactor and plug flow regime showed that Monod-plug flow model provided the best fit with the constants of 2.01 g COD/m2·d and 0.3014 g BOD5/m2·d with the best correlation coefficient of 0.610 and 0.968 between the predicted and measured concentrations, respectively. The low kinetic rates indicate that the process is capable of effluent polishing instead of purification due to the presence of organic compounds recalcitrant to biodegradation and a high level of salinity. [ABSTRACT FROM AUTHOR]