Water Research ( IF 12.8 ) Pub Date : 2017-11-08 , DOI: 10.1016/j.watres.2017.11.020 Sarah E. Keithley , Mary Jo Kirisits
Extracellular polymeric substances (EPS) are an important parameter in drinking-water biofilters, and, to date, this is the first study to compare protocols from the literature for extracting EPS from granular filter media. Five extraction protocols were compared, and one was improved by varying the type of initial physical treatment and the shaking intensity, temperature, and time of incubation. Extracting EPS from granular filter media in triplicate by combining 2 g (wet weight) of filter media with 10 mL of extraction buffer (10 mM Tris, 10 mM EDTA, 2.5% NaCl, pH 8), vortexing for 1 min, and incubating for 4 h at 35 °C with shaking at 200 rpm yielded significantly higher EPS polysaccharide and/or protein concentrations than did protocols from the literature. This improved protocol extracted a significant fraction of the biofilm attached to sand but was less effective on biofilm attached to anthracite or granular activated carbon (GAC). A survey of 11 full-scale biofilters from the U.S. and Canada revealed that EPS polysaccharide and protein concentrations can vary over one order of magnitude, from 0.02 to 0.60 mg glucose/g total solids (TS) and 0.27–3.38 mg bovine serum albumin/g TS, respectively. Backwashing significantly lowered the biomass and EPS polysaccharide concentrations, but the majority of the biofilm remained attached to the filter media after backwashing, as expected. The fraction of EPS polysaccharides and proteins removed during backwashing did not differ between anthracite and GAC biofilters. The improved EPS extraction protocol can be utilized to investigate the role of EPS in biofilter performance.
中文翻译:
从粒状滤料中提取细胞外聚合物的改进方案
细胞外聚合物(EPS)是饮用水生物滤池中的重要参数,迄今为止,这是第一项比较文献中从粒状滤池中提取EPS的方案的研究。比较了五种提取方案,并通过改变初始物理处理的类型以及摇动强度,温度和孵育时间进行了改进。通过将2 g(湿重)过滤介质与10 mL提取缓冲液(10 mM Tris,10 mM EDTA,2.5%NaCl,pH 8)合并,一式三份,从颗粒状过滤介质中提取EPS,涡旋1分钟,然后温育在35°C下以200 rpm摇动4 h产生的EPS多糖和/或蛋白质浓度明显高于文献中的方案。这种改进的方案提取了附着在沙子上的大部分生物膜,但对附着在无烟煤或颗粒状活性炭(GAC)上的生物膜效果不佳。对来自美国和加拿大的11种全尺寸生物滤池的调查显示,EPS多糖和蛋白质的浓度可以变化一个数量级,从0.02至0.60 mg葡萄糖/ g总固体(TS)和0.27–3.38 mg牛血清白蛋白/ g TS分别。反冲洗可显着降低生物量和EPS多糖的浓度,但正如预期的那样,反冲洗后大多数生物膜仍保持附着在过滤介质上。在无烟煤和GAC生物滤池之间,在反冲洗过程中去除的EPS多糖和蛋白质的比例没有差异。