对混凝沉淀法分散式饮水除砷的研究

采用混凝沉淀法进行分散式饮水除砷试验。结果表明,当水样中五价砷［Ａｓ（Ⅴ）］含量为１．０ｍ ｇ／Ｌ时,不调节ｐＨ值（ｐＨ７．８２）,直接投加５０ｍ ｇ／Ｌ硫酸铁,室温下沉淀静置１２ｈ,可使倾析液残留砷含量低于０．０５ｍ ｇ／Ｌ。如沉淀反应后静置３０～４０ ｍ ｉｎ 即过滤,则只需投加３０ｍ ｇ／Ｌ的硫酸铁或４０ｍ ｇ／Ｌ的硫酸铝即可达到同样的除砷效果。随着投加量的增加,２种混凝剂对砷的去除率均升高,当水样Ａｓ（Ⅴ）≤１．０ｍ ｇ／Ｌ和≤０．５ｍ ｇ／Ｌ时,分别投加３０ｍ ｇ／Ｌ 硫酸铁和硫酸铝,过滤后可使残留砷含量达到现行饮水卫生标准（＜０．０５ｍ ｇ／Ｌ）。在水样处于不同ｐＨ 值、水温、浊度、硬度等条件下硫酸铁的除砷性能较硫酸铝稳定。一般情况下,沉渣中的砷不会再次进入水中

Study on the removal of arsenic from drinking water by coagulants

The coagulation method for removing arsenic in drinking water from dispersed water supply was tested. The results showed that the remained arsenic [As(V)] in decanted water could be lower than 0.05 mg/L by directly putting 50 mg/L ferric sulfate into water samples without adjusting pH value (pH 7.82) and settling for 12 hours in room temperature while the original As(V) concentration was 1.0 mg/L. The same removal efficacy could be achieved by putting 30 mg/L ferric sulfate or 40 mg/L aluminum sulfate and filtering after 30-40 min settlement. The removal rates were raised with the increased concentration of coagulants in water. The remained As(V) in filtered water could meet the valid health standard of drinking water (< 0.05 mg/L) when the original concentrations of As(V) were 1.0 mg/L and 0.5 mg/L by using 30 mg/L ferric sulfate and aluminum sulfate respectively. Furthermore, ferric sulfate was more efficient than aluminum sulfate at varied of pH value, water temperature, turbidity and hardness of water, etc. Generally, arsenic in coagulated sludge would not release into water again.