Bioflocculant Efficiency for Wastewater Treatment

Wastewater samples were collected from KwaDlangezwa Wastewater Treatment Plant and Tendele Coal Mine Wastewater Plant in KwaZulu-Natal, South Africa. Parameters such as total nitrogen (N), biochemical oxygen demand (BOD), phosphorus (P) and chemical oxygen demand (COD) were measured before and after treatment with the bioflocculant. The measurements were performed using a spectrophotometer (Spectro-quant Phero 300, Merck KGaA, Darmstadt, Germany) and a pH meter (Eutech Instruments pH 700, Singapore) [36 (link)]. About 3 mL of 1% (w/v) AlCl₃ ions and 2 mL of 0.4 mg/mL bioflocculant solution were mixed with 100 mL of wastewater sample in a 250 mL conical flask. The mixtures were agitated at 200 rpm for 3 min, and the speed was thereafter reduced to 40 rpm for 5 min. The flasks were left at room temperature to stand for 10 min for sedimentation. For comparison, conventional flocculants such as alum and ferric chloride (0.4 mg/mL) were used. Thereafter, the percentage removal efficiency of the bioflocculant on; N, BOD, P and COD was measured by reading the optical densities at 680 nm. The following formula was used to calculate the bioflocculant removal efficiency [37 (link)];
$$\mathrm{Removal} \mathrm{efficiency} \left(\mathrm{RE}\right) (\%)=\left[\frac{Co-C}{Co}\right] \times 100,$$
whereby Co and C are the values before and after the flocculation process measured at 680 nm, respectively [38 (link)].