INVESTIGATION OF THE COAGULATION METHOD FOR WASTEWATER TREATMENT FROM FLUORINE AND MECHANICAL IMPURITIES IN THE PRODUCTION OF AMMOPHOS

Abstract

The paper presents the results of a study of the coagulation wastewater treatment process for the production of ammophos containing fluorine ions (up to 150-200 mg/l) and finely dispersed mechanical impurities (phosphogypsum, unreacted raw materials). The relevance of the topic is due to the need to reduce the toxicity of fluorinated wastewater to the maximum permissible concentration (for fluorine no more than 1.5 mg/l) and to extract the solid phase before dumping or reuse of water in circulation.

It was found that with a coagulant dose of 200-300 mg/l and pH adjustment with lime milk, the residual fluorine concentration decreases to 1.2–1.4 mg/l, and the suspended solids content decreases to 15-20 mg/l (purification efficiency 92-95%). Optimal modes and settling conditions have been identified, ensuring stable quality of clarified water.

Laboratory studies using soda ash have purified EFA from fluoride compounds using a soda ash–based coagulant at a pulp pH of 4.9 - 5.0. Filtered pulp with a fluorine content of about 0.03% can be used as calcium sodium phosphate, in particular as feed phosphates, corresponding to the standards for the amount of fluorine.