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.
Effluent sewer
Another problem area is a place where there are many homes or businesses at or near the lowest elevation in the area, such as sea level for a coastal city. Typically, waste is pumped uphill under low pressure to the main sewer line in such situations, either after it has been through a septic tank or after it has been ground up into a slurry by a grinder. Grinding can be done when the waste of many homes or businesses is combined or smaller grinders can be installed at each home or business. A disadvantage of using grinders is that they require electricity, and a disadvantage of using septic tanks is that they require solid waste buildup to be removed every one to three years, depending on the size of the tank and the number of people using the system.