Handling of grey wastewater - test of a method for hazard identification

摘要

A method for hazard and problem identification is tested on reuse of grey wastewater for toilet flushing. The grey wastewater is treated in a biological sand filter prior to the planned reuse. Xenobiotic organic compounds and the heavy metals originate from personal care products that are used in or on the human body, health hazards related to these components are therefore not considered relevant. Besides, skin contact with and inhalation of recycled grey wastewater is very limited, in this case. The health hazard will instead be exposure to infectious microorganisms. The presence of microorganisms in general can constitute a problem since growth of microorganisms may cause bad odour and colouring. Geochemical modelling showed that there is a possibility for oversaturation of iron-hydroxides, which can cause Fe(hydr)oxide to precipitate, with the possible effect of clogging as well as discolouring of the toilet bowl. No problem with corrosion could be identified. The potential problems of foaming are expected to be reduced by biological treatment in the sand filter.