Physiochemical, Instrumental and thermal characterization of the post coagulation sludge from paint industrial wastewater treatment

Abstract

Most sludge generated from water treatment plants is toxic. One of such sludge as focused on this work is paint wastewater treatment sludge from coagulation-flocculation process. Due to the problem of sludge disposal, post coagulation sludge was characterized via physical, instrumental and thermal characterization to suggest possible treatment methods to avert disposal of toxic wastes into the environment. Post coagulation sludge recovered after jar-test experiment has high settleability index with Sludge Volume Index ˂ 80. The best sludge volume index of 11 was obtained at sludge solid concentration of 2264.3 mg/l. Post coagulation sludge has pH of 6.83, Volatile Solid of 77% of the total solid (2210 mg/l) and Carbon: Nitrogen value of 26:1. The Biological Oxygen Demand - Chemical Oxygen Demand ratio of 0.7 shows that post coagulation sludge is moderately toxic. CHNX analysis shows that post coagulation sludge contains majorly calcium (35.54%), oxygen (30.2%), carbon (9.25%) and sodium (7.74 (aluminum (3.05%), silicon (3.14%) and titanium (3.69%)) and some trace elements. The prominent functional groups include =C–H in-plane bending of alkene aliphatic compound at 1403 cm−1, carboxylic group at 3000 cm−1, cellulose –OH stretching vibration group at 3476 cm−1,NH stretching of amine group within 3300–3500 cm−1 among others in trace forms. 10% reduction in weight was observed via thermo-gravimetric analysis (TGA). The mid-point glass temperature was 45 °C, while the melting point was 175 °C. In addition, PCS turns to ashes above 300 °C. Based on the results; Post coagulation sludge can be managed via, biological treatment methods, anaerobic digestion and by thermal degradation.