The objectives of this study were to inquire the feasibility of the removal of Cr(VI), Pb(II), Zn(H) by coagulation process and to determine the effect of the humic acid on the removal of the aforesaid heavy metals. The results indicated while the removal of Cr(VI) using coagulant of ferrous sulfate was very effective, using alum and ferric chloride was ineffective. The removal of Pb(II) and Zn(II) using alum and ferric chloride was very effective and the higher the pH the better the removal efficiency. The removal of Cr(VI) using alum could be benefited by the input of humic acid. However, the removal of Pb(II) could be obstructed when the humic acid was not completely removed by coagulation. As the pH was greater than 8, the removal of Zn(H) was impeded by the input of the humic acid. In contrast, as the pH was less than 8, the removal of Zn(II) was improved. 混凝沉澱程序是給水廠中對濁度及色度去除的重要處理單元之一，本研究主要係藉此一處理程序來探討對重金屬鉻、鉛、鋅之去除效果以及腐植酸對其處理效果之影響。試驗結果發現硫酸亞鐵對六價鉻之去除效果極佳，硫酸鋁及氯化鐵對六價鉻之去除效果則很差。而氯化鐵及硫酸鋁對二價鉛及二價鋅之去除效果則很好，且隨pH值的增加而愈佳。腐植酸有助硫酸鋁去除六價鉻；而對於鉛，則在腐植酸未完全去除前，對鉛之去除有所妨礙，但當腐植酸可完全被去除時，則腐植酸對鉛之去除甚有助益。腐植酸之pH值大於8時，妨礙了鋅之去除，然在pH值小於8時， 則能增進鋅之去除。平衡滲析試驗結果發現六價鉻、二價鉛、二價鋅與腐植酸錯合程度係隨pH值升高而增加，三者錯合能力大小依序為二價鉛、二價鋅、六價鉻。
