Hydrotherapy is a part of medicine, in particular of occupational therapy and physiotherapy, that involves the use of water for pain relief and treatment. [wikipedia]
Professional carwashing is a "non-point source" of discharge that has the ability to capture these contaminants, normally in interceptor drains, so the contaminants can be removed before the water enters sanitary systems.
The wax in a lava lamp used to contain carbon tetrachloride to help it sink in water, however carbon tet was banned in the U.S. in 1970 and the new compound has been kept a trade secret.
