Removal of calcium ion from wastewater using waste activated sludge and artificial zeolites

Removal of calcium from wastewater was carried out using waste activated sludge and artificial zeolites. The effects of parameters such as pH, temperature, reaction time and sorption duration on removal rate of Ca2+ were studied. The results show that solid-to-liquid ratio is the most important factor on the removal of Ca2+, pH and temperature have obvious influences on the process, and reaction time has little effect on removal rate of Ca2+ after reacting for 10 min. The removal rate of Ca2+ increases with increasing solid-to-liquid ratio under conditions of 25°C, initial pH 8.04, reacting for 1h. 80.38% of the initial Ca2+ content (solution containing 801.60 mg/L of Ca2+) is removed under condition of solid-to-liquid ratio of 3:100, and terminal concentration of Ca2+ of 157.31 mg/L. The increase of temperature is advantageous to the removal of Ca2+, the removal rate of Ca2+ rises from 77.30% to 90.71% with temperature enhancing from 20°C to 45°C. The removal of Ca2+ is finished in 50 min. According to the IR spectrum of artificial zeolite, chemical biosorption takes main effect on the removal of Ca2+.