A compact reactor system for processing grey water and its reutilization for flushing toilet bowls

In this contribution, a compact reactor system is presented that enables efficient processing of grey water in order to facilitate its reutilization for flushing toilet bowls. The treatment of collected grey water is performed in combination with an aerobic/anoxic biological process carried out in a submersed bioreactor with immobilized biomass for the removal of dissolved organic substances, and a procedure of adjusting the concentration of microorganisms in the liquid phase by using a simple technique of flow-through ultraviolet-light based disinfection. In this system which operates at ambient temperature as a semi-continuous recycle reactor, significant removal of organic matter was achieved (conversions up to 65%, expressed as total organic carbon) without the occurrence of malodour. A low concentration of dispersed microorganisms was measured in treated grey water; importantly, no coliforms were accumulated in the unit.