我国砂型铸造行业水污染现状调查

Investigation of Water Pollution in China's Sand Molding Foundry Industry

较为全面和系统地调查了7个铸造企业的废水水质,调查发现,各工部中,污染非常严重的是失蜡精密铸造废水,氨氮浓度高达37 008 mg/L;其余工部中,仅部分电炉冷却水和热处理冷却水存在部分指标(p H,化学需氧量COD)超标。采用水玻璃砂铸造的企业,旧砂湿法再生过程中产生的废水污染也较严重,废水呈现出强碱性,平均p H值达到了11.01,平均悬浮物SS浓度达到984 mg/L,平均总磷TP浓度达到3.26 mg/L。水玻璃砂铸造包括二氧化碳硬化和酯硬化工艺,采用酯硬化工艺的企业旧砂湿法再生废水COD高达10 703 mg/L;而采用二氧化碳硬化的企业旧砂湿法再生废水COD仅为60 mg/L。在对采用水玻璃砂湿法再生工艺的企业调研中发现,部分使用废水处理设施的企业废水处理后水质情况改善不大,处理效果并不明显。各企业排放的废水中总Cr浓度都没有超过《城镇污水处理厂污染物排放标准》中的0.1 mg/L限值。

This study comprehensively and systematically investigated the wastewater quality in China＇s foundry industry. It was found that the wastewater of lost wax casting was heavily polluted with NH＋4-N （up to 37 008 mg/L） for which a combined physical and chemical treatment was required. In the rest samples, only some of electric furnace cooling water and heat treatment cooling water were found exceeded national wastewater standards （pH and COD not meet）, which should be noticed. The wastewater from wet reclamation of sodium silicate used sand was also heavily polluted with the average pH value 11.01, SS 984 mg/L and TP 3.26 mg/L. For such wastewater adding acid followed by coagulation and sedimentation treatment was required. Sodium silicate sand castings usually use carbon dioxide process or ester cured process. Wastewater from wet reclamation of the later one showed high Chemical Oxygen Demand up to 10 703 mg/L, thus a biochemical treatment after coagulation and sedimentation process was required. Meanwhile for carbon dioxide process the COD was only 60 mg/L. Wastewater treatment facilities were found in some foundry companies, but the wastewater quality does not improve significantly. The all wastewater was tested in the study, none of the total Cr concentrations exceeded 0.1 mg/L.