It is possible to remove heavy metals and organic compounds at the same time when they are in high concentration and treated with cast iron chippings. The waste water was made to react with the iron chippings and then its pH adjusted to 9.5±0.4, the precipitation would occur by coagulation. Let the supernatant flow through an iron chippings bed and then adsorbed by cinder. After this treatment, all the indexes of heavy metals and COD could reach the national discharge standard (i. e. COD < 10mg/L, total chromium < 0.05mg/L, copper < 0.5mg/L, lead < 0.5mg/L and tin < 0.5mg/L).

The waste water was treated twice with iron chippings. At first time the reaction time of waste water with iron chippings was controlled within 60- 90min; the consumption amount of iron chippings was controlled within 0.6 - 0.8g/L and pH was adjusted to 9.5±0.4 with lime. Then all the Cr³⁺, Cu²⁺, Pb²⁺ and Sn²⁺ were precipitated in hydroxides, so that the concentration of heavy metals was lower than the national discharge standard. Besides, the organic compounds in waste water were also absorbed on the particles of hydroxides of Fe²⁺ and heavy metals and removed. The removing extent of COD could come to 81.08% - 84.80%. The waste water which had passed the first processing was again passed through an iron chippings bed, and allowed to stay there for 30 - 60min, After that the content of organic compounds was reduced further; the removing extent of COD could reach 78.5% - 85.31%.

The characteristics of this treatment are simple technology, reasonable combination, convenient operation, low material cost, less investment for engineering, and good disposal effect. Iron chippings and cinder are all waste of industry, so according to this method to control waste by waste is achieved.

The optimum amount of iron chippings to be used and the reaction time were studied. The mechanism was also explained.