Reducing the natural color of membrane bioreactor permeate with activated carbon or ozone.

The suitability of two membrane bioreactors for on-site wastewater treatment and reuse in Switzerland was investigated. The treated wastewater was used for toilet flushing and gardening, with water recycling rates of 30% (single family house) and almost 100% (toilets in a cable car station) respectively. Due to the recycling, an increase in a natural yellowish-brown color was observed, leading to double flushing of the toilets, higher cleaning requirements and increased permeate production.