Waste activated sludge dewaterability: comparative evaluation of sludge derived from CAS and MBR systems

Sludge dewatering represents, nowadays, one of the greatest operational cost to wastewater treatment cycle. Physical–chemical and biological parameters are recognized to influence the sludge dewaterability. However, many authors agree in identifying the sludge origin as one of the main aspect involved in sludge dewaterability. Indeed, the sludge origin such as the processes involved in liquid–solid separation, seriously affect the sludge features. In order to elucidate the key factors influencing the dewaterability process, the present work is aimed to investigate the influence of the treatment plant lay-out on sludge dewaterability. The analyzed sludge samples were derived from four conventional activated sludge and two membrane bioreactor wastewater treatment plants. Experimental investigation was focused to highlight difference in sludge dewaterability derived from the application of European Standards adopted for sludge characterization. The achieved results confirmed the complexity of the inter-relationships between many factors affecting the sludge dewaterability.