Gas tanks on waste water treatement plants (WWTP) were solely built in low pressure technique until 1980s.
To lower investment costs from this point on the technique of pressureless gas storages were introduced. At the time in the farming sector the first biogas plants occured.
Pressure less gasholders seem to be an interesting low cost alternative in comparison to low pressure gasholders at first site. On closer inspection the operating company (WWTP etc.) has to oppose the lower asset costs of the pressure less gasholder against lower security standards and further assets costs in the field of gas fans as well as higher operating costs and inspection costs.
The documents which are provided on this site are specialy focused on plant security.
In particular the security standards of low pressure gasholders are compared with those of pressureless gasholders.