Technical and Economic Comparison between two Marble Industry Wastewater Treatment Systems

Abstract

Marble wastewater slurry was treated at two different industrial sites at Shaq Al-Thoaban region using conventional coagulation/sedimentation (C/S) and dissolved air floatation (DAF) treatment techniques. In the first treatment unit polyacrylamide (PAM) coagulant was used with a dose of 50 mg/lit and this reduced the average total suspended solids (TSS) influent from 6521.25 mg/lit to 177.50 mg/lit yielding an average removal efficiency of 97.28%. In the second DAF treatment unit no any chemical was used for pretreatment and the resulting average removal efficiency achieved was 95.41%. The pH and EC values of the treated wastewater were negligible and in the neutral range. The average turbidity values recorded were 34.25 NTU and 50.75 NTU respectively. Furthermore, economic & technical comparison with regards initial costs, operation & maintenance requirements, environmental impact and settled sludge reuse favored the use of the DAF treatment unit although it recorded a 1.87% drop in TSS removal compared with the C/S treatment unit. The cost of the coagulant used in the first treatment system amounted to a 70% increase in the O & M costs compared to the second system.