Surface Water Treatment Systems

An essential component in any surface water management system (SuDS) for non potable re-use is surface water treatment. Hard surfaces exposed to traffic will carry a greater range of diffuse pollution than water collected from a roof. There are greater concentrations of sediment particles, hydrocarbons (oils) from vehicles and dissolved heavy metals, predominantly copper and zinc, from exhausts and brakes that runoff from these areas. This runoff needs to be treated before it can be re-used.

BS8515 does not preclude the use of surface water for re-use but it does make reference that this run off will require a higher level of treatment than roof water before it can be re-used. The potential use of surface water can significantly improve water yield and therefore efficiency of any re-use system.

Traditionally oil separators have been used to remove gross contaminants from run-off,  however the Water Framework Directive WFD places greater requirements on industry to use surface water treatment systems to improve water quality. In urban environments the use of vegetated infrastructure to achieve these  targets can be very challenging.

Recent changes in SuDS legislation and planning conditions together with revised industry guidance through C753 The SuDS Manual and Sewers for Adoption 8th Edition have led to the introduction of a wider range of  manufactured treatment systems that are more reliable in removing the main pollutants that have previously excluded surface water from being used as part of a rainwater harvesting system.