ABSTRACT
Historically, it was common to see schematics that showed the water treatment scheme in detail and an arrow at the end that simply said “sludge to disposal” (Neyens et al., 2004). However, presently the situation is altogether different as increasing sludge production and its proper management is a big challenge for waste management authorities mainly due to increasingly stringent sludge reuse and disposal regulations. The population explosion resulting in the generation of wastewater volume, which is triggering to increased wastewater treatment facilities. Activated sludge process is a generalised secondary treatment system with a fact that over 90% wastewater treatment systems are using the conventional activated sludge process. The worldwide sludge generation is about 50 million tonnes dry solids per year, which will increase upto 83 million tonnes of dry solids by 2017. The main bottlenecks in sludge management are:
Sludge treatment and disposal accounts 40–60% cost of total plant operation cost
Land application of sludge is restricted by pathogens, emerging contaminants, heavy metals etc.
Incineration is an efficient method in sludge volume reduction but high capital cost, ash generation and discharges of heavy metals, CO2 and N2O to the atmosphere are the main issues
Landfills are facing pressure due to high building, operational and land cost, and emissions and loss of resource
