基于改性凹凸棒土的强化混凝处理高藻低浊原水工艺

Effects of an enhanced coagulation process by modified attapulgite on treatment of low turbidity and high algae-laden water

针对水厂低浊高藻水的处理难题,研究了改性凹凸棒土(改性凹土)联合聚合氯化铝(PAC)强化混凝的除藻除浊效果。设计实验原水条件为叶绿素a(chl-a)浓度为98.58~110.35μg/L,浊度(5.6±0.5)NTU。考察了PAC和改性凹土的复配投加量、混凝沉淀时间、pH、投加顺序、搅拌速率等工艺参数对Chl-a和浊度耦合去除效果的影响。结果表明,'PAC+改性凹土'对Chl-a和浊度的去除效果明显优于单投PAC的效果。当PAC投药量12 mg/L,改性凹土投药量10 mg/L,沉淀时间20 min时,对Chl-a和浊度的去除率可分别达到92.5%和89.2%,可至少减少40%的PAC投量,且形成的矾花密实,沉降速度快,去除效率高。最适pH范围为7~8。投加顺序应为先投加改性凹土,混合搅拌转数宜慢速,可控制为50 r/min。

In order to solve the difficulty in water treatment for low turbidity and high algae-laden water,the removal effect of algae and turbidity by an enhanced coagulation of modified attapulgite and polyaluminium chloride( PAC) was studied. At the same time,the impacts of dosage,settling time,pH,dosing sequence and stirring velocity on the coupling removal result of algae and turbidity were also discussed. The chlorophyll A( chl-a) of raw water in this experiment ranged from 98. 58 ug /L to 110. 35 ug /L,and the turbidity was( 5. 6 ± 0. 5) NTU.The experimental results showed that the removal efficiency of algae and turbidity by using PAC combined with modified attapulgite was much better than using PAC only. When the dosage of PAC was 12 mg /L and modified attapulgite was 10 mg /L,optimal settling time set as 20 minutes,92. 5% of chl-a and 89. 2% of turbidity of raw water could be removed. Compared with traditional process which only use PAC,the dosage of PAC of combination process was reduced 40%,the flocs were denser,settling velocity was faster. When PAC combined with modified attapulgite was used to remove algae and turbidity,the most appropriate pH value ranged from 7 to 8,and the modified attapulgite should be dosed two minutes earlier before dosing PAC,and mixed and stirred at a low speed of 50 r /min.