METHOD OF REUSING WASTE WATER SLUDGES CONTAINING MIXTURES OF HEAVY METAL HYDROXIDES AND/OR HYDROXOCARBONATES Russian patent published in 1999 - IPC

FIELD: waste water treatment. SUBSTANCE: invention relates to waste waters produced at metalworking enterprises, which are reused as raw additives in production of concrete products. Mixes of natural limestone and clay needed for concrete production, are modified with waste water sludges replacing 5-35% of calculated amount of clay with equivalent summary amount of aluminum, iron, and chromium. Components are mixed and fired at 1450-1500 C until residual content of free calcium oxide is no higher than 0.5 wt %. Firing product is cooled, crushed, and used to prepare concrete. EFFECT: reduced environmental danger of waste- containing concrete due to increased resistance of concrete products against leaching of toxic heavy metal ions by natural water. 3 tbl, 3 ex