反冲洗对4种换炭模式下生物活性炭层生物量和水质指标的影响

Influence of Backwashing on Biomass in BAC Layer and Water Quality Parameters under 4 Modes of Used Carbon Substitution

以水厂砂滤池出水作为生物活性炭柱的反冲洗水,研究了4种换炭模式下反冲洗前后炭层中生物量和出水水质指标的变化情况。结果表明,旧炭(已经运行使用3年的颗粒炭)的装填比例对炭层中生物量和出水水质指标均有不同程度的影响。通常情况下,全新炭柱上的生物量略高于旧炭,但反冲洗后旧炭比例高的炭柱生物量损失率更低。气水先后反冲洗后总生物量的损失率比单独水冲后总生物量的损失大,但附着生物量的损失基本不变,说明生物活性炭池可尝试使用单独水反冲洗。除高锰酸盐指数(COD_(Mn))变化不明显外,紫外吸光度(UV_(254))、可溶性有机碳(DOC)、生物可降解溶解性有机碳(BDOC)、生物不可降解溶解性有机碳(NBDOC)和三卤甲烷生成潜能(THMFP)的去除率在反冲洗后均有不同程度的上升。因此,反冲洗有利有弊,它既能冲刷掉部分附着在活性炭上的生物膜,对生物的冲刷力较强,同时又能恢复活性炭的吸附能力,使有机物的去除效果增强。反冲洗对填装精制新炭的4#炭柱炭层的吸附容量的恢复力最强,但其生物量的损失率却最大,说明相对于填装粗制新炭的3#炭柱,4#炭柱上的生物系统抵抗水力冲刷能力相对较弱,因此,精制或粗制炭的选择应根据活性炭池是主要发挥其吸附能力还是生物降解能力的需要进行。

Taking the outflow of sand filter of the water treatment plant(WTP)as the backwashing water of the biological activated carbon column,the effects of backwashing on biomass in carbon layer and outflow parameters under four modes of carbon substitution were studied.The results showed that the loading ratio of worn carbon had an influence on biomass and outflow indices to different extents.Generally,the biomass on the new carbon was slightly higher than that of worn carbon(granular charcoal that had been in use for three years),while the biomass loss rate of carbon column with high proportion of worn carbon after backwashing was lower.The loss rate of total biomass after air-water backwashing was greater than that after water backwash alone,but the loss of attached biomass was basically unchanged,indicated that the use of water backwashing alone could be attempted in the biological activated carbon pool.While the change of COD_(Mn) in the outflow was not obvious,the removal rates of UV254,DOC,BDOC,NBDOC and THMFP all increased to different extents after backwashing.Therefore,backwashing had both advantages and disadvantages.It could not only flush out some biofilms attached to the activated carbon,but also had a strong scouring force on microorg anism.At the same time,it could restore the adsorption capacity of activated carbon and enhanced the removal effect of organic matter.Backwashing had the strongest recovery ability on the adsorption capacity of the carbon layer of the 4#carbon column filled with refined new carbon,but its biomass loss rate was the highest,indicated that compared to the 3#carbon column filled with crude new carbon,the biological system on the 4 # carbon column had relatively weak resistance to hydraulic erosion. Therefore, the selection of refined or crude activated carbon shouldbe based on whether the activated carbon tank mainly utilizes its adsorption capacity or biodegradation ability.