The actual and potential benefits of anaerobic wastewater treatment when implemented at the core of a sustainable and non-vulnerable environmental protection programme are described. The paper focuses on the anaerobic sludge bed (and in particular the expanded granular sludge bed (EGSB)) reactor concept. Start-up of these systems is shown to be rapid, within a few days with granular seed sludges, and they may be applied across a wide range of conditions and strengths of wastewater. EGSB systems are particularly suited to low temperatures (10°C) and very low strengths (<<1000mg/1) and for the treatment of recalcitrant or toxic substrates.