Are There Any Tests to Ensure Grey Water is Safe?

Testing for Bacterial and Viral Contaminants

Grey water reused for irrigation should be tested for E. coli, which is a common indicator of fecal contamination. Sampling should be taken from the grey water source before treatment and after treatment. Recommended testing methods include the multiple-tube fermentation (MTF) test and the Colilert-18 test. These tests are used to detect E. coli at concentrations of less than 1 CFU/100mL. The results of these tests should be used to adjust treatment processes to achieve safe levels of bacterial contamination.

Chemical Contaminant Testing

In addition to bacterial and viral contaminants, grey water reused for irrigation should also be tested for chemical contaminants. Common chemical contaminants include heavy metals (such as lead and mercury), pesticides, and household chemicals. Sampling should be taken from the grey water source before treatment and after treatment. Recommended testing methods include inductively coupled plasma mass spectrometry (ICP-MS) for heavy metals and gas chromatography-mass spectrometry (GC-MS) for pesticides and household chemicals. The results of these tests should be used to adjust treatment processes to achieve safe levels of chemical contamination.

Treatment and Disinfection Methods

To ensure grey water is safe for reuse, it must be properly treated and disinfected. Recommended treatment and disinfection methods include mechanical filtration, UV disinfection, and ozone disinfection. Mechanical filtration can remove up to 99.9% of particulate contaminants, while UV disinfection can kill up to 99.9% of bacterial and viral contaminants. Ozone disinfection can also kill up to 99.9% of bacterial and viral contaminants, while also removing chemical contaminants. The type and level of treatment and disinfection required will depend on the intended use of the grey water and the results of testing.