USA As Represented by Secretary of the Navy

Bingham Y Pan

Teh Fu Yen

Henry P Sheng

Jau R Chen

An integrated process for treatment of wastewater from steam boiler clean operations, containing sodium nitrite and also usually heavy metal ions such as Cu, Fe, Pb, Cr, Cd, Zn and Ni, as well as suspended solids and sludge, to remove the nitrite, substantially reduce the amount of such metal ions and remove suspended solids and sludge in the treated wastewater. The process comprises adding sulfamic acid to the wastewater, particularly in about stoichiometric proportions with respect to sodium nitrite to form gaseous nitrogen. The reaction takes place at ambient temperature and atmospheric pressure. An alkali such as sodium hydroxide is added to the resulting solution in amount sufficient to raise the pH thereof to about 10, and precipitating the metal ions. The precipitates and suspended solids and sludge are removed from the resulting wastewater by settling and filtration, and the wastewater free of nitrite and of substantially reduced metal ion content and free of suspended solids as well as sludge, is in condition for discharge to sewers.

Treatment of sodium nitrite-containing boiler wastewater

Process for treating wastewater containing citric acid and triethanolamine nd heavy metals by subjecting the wastewater to treatment with hydrogen peroxide and ultraviolet light (UV) and in the presence of ferrous ion as catalyst, to substantially decompose the citric acid and the triethanolamine. Wastewater generated from ship bilge cleaning and containing up to 10% citric acid or up to 5% triethanolamine, or mixtures thereof, can thus be subjected to UV/H.sub.2 O.sub.2 treatment with ferrous ion in a concentration thereof of about 20 to about 100 ppm, without forming chelates of iron and other heavy metals with citric acid or with triethanolamine, to decompose up to 90% or more of the citric acid and triethanolamine.

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Claremont, CA, United States of America

Bingham Y Pan