Abstract
Every year increasing amounts of industrial waste are generated worldwide. Depending on their characteristics, wastes can represent an important source of secondary raw materials in order to replace natural resources. The growing amount of carbide lime waste (CLW), a by-product of acetylene production, has resulted in environmental problems. In the present study, the potential use of CLW for wastewater treatment was investigated. The main characteristics of the CLW were determined. Chemical and X-ray diffraction analyses indicated that CLW was similar in chemical and mineralogical compositions to industrial lime, except for the presence of carbon in the waste. Morphological and elemental chemical analyses by scanning electron microscopy and energy dispersive X-ray spectrometry revealed that CLW particles differ from industrial lime by the presence of carbon formations. The use of CLW was evaluated in the treatment of Annaba city wastewater effluent. CLW was found to be the suitable for the treatment of Annaba city wastewater for an optimal dose of 850 mg L-1. Percentage removal efficiency for turbidity, total suspended solids (TSS), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5) was found to be 96, 98.2, 90 and 84.5%, respectively. Residual turbidity in supernatant was 4.5 NTU and total residual bacteria was 68 CFU mL(-1). Algerian effluent quality standards for TSS and COD were met after treatment. However, BOD5, bacterial level and pH were high, emphasizing the need of pH adjustment and secondary treatment for the Annaba city effluent. The precipitation of heavy metals with CLW has been shown to be successful in reducing the level of soluble heavy metals in aqueous solution. The removal of heavy metals was enhanced at pH ranges 10-11 for zinc, 9.2-11.6 for lead, 4-11.8 for iron and 7-11.8 for copper. The results revealed that CLW can be effectively used in wastewater treatment.