Septic tank
While a properly maintained and located septic tank does not pose any more environmental problems than centralized municipal sewage treatment, certain problems can arise with septic tanks in unsuitable locations. Since septic systems require large drainfields, they are not suitable for densely built areas.
Lee Tunnel
This long tunnel, of diameter , running from deep at Abbey Mills down to deep at its terminus at Jenkins Lane, East Ham, will capture , or 16 million tonnes, of sewage annually from the single largest polluting CSO in London. This sewage would otherwise flow straight into the River Lea, the Thames Tideway and eventually the Thames Estuary. However, the sewage is now pumped up to the Beckton Sewage Treatment Works – the largest sewage treatment works in Europe – and the resultant clean water emptied into the River Thames. The reason for starting at −75 m is to be ready to collect sewage from the lowest point of the Thames Tideway Tunnel, which is under construction and intended to connect.