Removal of heavy metals from wastewater using cost effective method: Determining optimal strategic conditions and system modeling using response surface methodology

Abstract

Lead and cadmium are among the heavy metals that result in the highest environmental hazards because of their widespread use, toxicity and distribution. These metals can cause complications such as poisoning and short-term and long term genetic effects. This study aimed to evaluate the removal efficiency of heavy metals of lead and cadmium from wastewater using stabilization ponds. Since such refining systems are important in economical and efficiency terms in developing countries, in this experimental study, anaerobic, facultative and maturation 60-L stabilization ponds were applied at retention times of 1–3 d in anaerobic pond and 3–9 d in the facultative and maturation pond with 1–50 mg/L initial concentration of lead and cadmium to remove chemical oxygen demand (COD), biochemical oxygen demand (BOD5), lead and cadmium on three levels in response surface methodology. Heavy metals were measured using atomic absorption spectrometers. According to results, maximum removal efficiency of COD, BOD5, lead and cadmium were 52.88, 65.5, 83.78 and 90.83%, respectively, in anaerobic stabilization pond. Carbon removal efficiency was directly attributed to hydraulic retention time and was inversely related to the initial concentrations of lead and cadmium. The efficiency of anaerobic stabilization pond was higher compared to that of facultative and maturation ponds. This system can be used instead of expensive and complex systems such as active sludge system and so on, due to its good features such as flexibility, ease of implementation, easy operation and fairly good performance in order to treat industrial wastewater containing heavy metals.