In German Patent Document DE 36 41 365 C2, an apparatus for the cleaning and treatment of contaminated water is described which utilizes electroflotation. In electroflotation, iron and aluminum electrodes are consumed by the electrolysis, i.e. are sacrificial electrodes which are used to treat the waste water passing between sets of metal plates forming a cascade of electrodes.
The alternating iron and aluminum plates can achieve flotation in a wide pH range without the addition of chemicals and can bring about sufficient clarification or cleaning of the water.
During the electroflotation step, metals are oxidized in the waste water and can form precipitates, emulsions can be broken and oil components converted to a foam phase. In practice, fine gas bubbles are produced by an electrolytic action by the electrodes, which form anodes and cathodes, in the waste water which constitutes an electrolyte. Liberated oxygen serves to oxidize substances in the waste water. The release of iron and aluminum into the solutions provides flocculating agents which cause contaminants to fall to the bottom while gas bubbles may produce a foam bed at the top. A clean phase forms between the upper foam bed and the heavier dirty component at the bottom.
Prior processes for electroflotation operate with continuous direct current, the electrodes being dissolved in conjunction with the electrolysis.