Van Cuyk Sheila, Siegrist Robert L
Environmental Science and Engineering, Colorado School of Mines, Golden, CO 80401, USA.
Water Res. 2007 Feb;41(3):699-709. doi: 10.1016/j.watres.2006.07.021. Epub 2006 Sep 8.
The column studies presented in this paper simulated the infiltrative surface of onsite wastewater systems where effluent is applied and where a biomat may form. Two bacteriophages, MS-2 and PRD-1, were used as surrogates for human pathogenic enteric viruses during two tracer tests. A vacuum manifold was used to simulate the drainage effects of an underlying unsaturated soil profile, allowing for the collection of percolate samples at 4 cm immediately below the infiltrative surface. The impact of effluent applied (septic tank effluent (STE) or a simulated ground water), soil type (medium sand or sandy loam), hydraulic loading rate (5 or 25 cm/day) and method of application (four equivalent daily doses or 24 equivalent micro-doses per day) on the removal of viruses were investigated. These unsaturated mini column experiments demonstrated that the removal of viruses within an infiltrative surface zone (of approximately 4 cm) generally improved over time under the conditions studied. An exception occurred in sand-filled columns dosed with STE where the removal of PRD-1 decreased after a period of effluent application. Statistical analysis conducted on the calculated percent removal demonstrated that the quality of the effluent applied to the infiltrative surface is important for removal of MS-2 and PRD-1. Hydraulic loading rate also proved important in the removal of viruses. At the time of tracer test 2, columns dosed at the higher HLR (25 cm/day) had higher percent removals for both MS-2 and PRD-1. Soil type altered the removal of PRD-1 at the time of the second tracer test, at which time sandy loam had higher removal rates for PRD-1. No significant differences were observed between columns dosed four times daily and those dosed 24 times daily for either bacteriophage at either of the tracer test time points. These data suggest that over a relatively short period of operation the infiltrative surface of soil based wastewater treatment systems can achieve much higher removal then initially measured shortly after startup.
本文中所呈现的柱实验研究模拟了现场废水处理系统的渗透表面，废水在此处施加，且可能形成生物膜。在两次示踪试验中，使用了两种噬菌体MS-2和PRD-1作为人类致病性肠道病毒的替代物。使用真空歧管模拟下层非饱和土壤剖面的排水效果，以便在渗透表面正下方4厘米处采集渗滤液样本。研究了施加的废水（化粪池出水（STE）或模拟地下水）、土壤类型（中砂或砂壤土）、水力负荷率（5或25厘米/天）以及施加方法（每天四次等量剂量或每天24次等量微剂量）对病毒去除的影响。这些非饱和小型柱实验表明，在所研究的条件下，渗透表面区域（约4厘米）内病毒的去除率通常会随着时间的推移而提高。一个例外情况是，在装有STE的砂柱中，在施加一段时间废水后，PRD-1的去除率下降。对计算出的去除百分比进行的统计分析表明，施加到渗透表面的废水质量对于MS-2和PRD-1的去除很重要。水力负荷率在病毒去除方面也被证明很重要。在示踪试验2时，以较高水力负荷率（25厘米/天）投加的柱中，MS-2和PRD-1的去除百分比更高。在第二次示踪试验时，土壤类型改变了PRD-1的去除情况，此时砂壤土对PRD-1的去除率更高。在任何一个示踪试验时间点，对于两种噬菌体而言，每天投加四次的柱和每天投加24次的柱之间均未观察到显著差异。这些数据表明，在相对较短的运行期内，基于土壤的废水处理系统的渗透表面能够实现比启动后不久最初测量时更高的去除率。
