Utilization of autoclaved aerated concrete solid waste as a bio-carrier in immobilized bioreactor for municipal wastewater treatment

Autoclaved aerated concrete waste (AACW) resulted from construction and demolition was used as a bio-carrier in a passively aerated biological filter (PABF) treating municipal wastewater. Physical, chemical and morphological characterization of AACW were carried out in terms of X-ray diffraction, surface area, porosity, scanning electron microscopy and energy-dispersive X-ray. Results showed that the main crystalline phases in AACW are mainly oxides of SiO2, CaO and Al2O3 beside hydrous silicates (Ca5Si6O18H2). In addition, AACW has a rough surface with a high specific surface area of 42.8 m(2)/g. Different from commercially available bio-carriers, AACW has an open macro-porous structure that is suitable for immobilizing microorganisms. The use of AACW as a bio-carrier in a pilot scale PABF reactor improved greatly the removal of organic and inorganic pollutants. Average removal values of chemical oxygen demand, biochemical oxygen demand and total suspended solids were 90%, 92% and 89% with corresponding average residual values of 36.4, 17.2, 11.3 and 3.3 mg/L. Results indicated that the potential of using AACW as a bio-carrier in a PABF is recommended and it provides a promising approach to utilize construction and demolition solid waste.