title: Effects of earthworms on surface clogging characteristics of intermittent sand filters.
abstract: Intermittent sand filters (ISFs) are effective and economical in treating wastewater, but they are easy to clog up. To explore a feasible and simple method to alleviate clogging, two pilot-scale ISFs were constructed, one of which contained earthworms and the other did not. During the operation, the effects of earthworms on the hydraulic behaviour of ISFs were investigated. The results showed that both ISFs exhibited good performance in wastewater treatment. However, they showed different hydraulic characteristics although operated at the same organic loading rate (approximately 300 g m(-2) d(-1)). The ISF without earthworms clogged only after 53 d operation, and was partially recovered after 7 d resting, but after that, clogging occurred again, and more rapidly than the initial clogging event (40 d). However, water on the medium surface of the ISF with earthworms was not observed during the whole experiments. In addition, 11-13% of effective porosity and 0.015-0.026 cm s(-1) of infiltration rate were measured in the upper 20 cm of the ISF at the end of the experiments. The facts demonstrated that earthworms played a positive role in alleviating clogging and earthworms fed filter could alleviate surface clogging effectively.
authors.affiliation: College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China.
authors.forename: Dong-bo
authors.initials: DB
authors.lastname: Wang
authors.forename: Zi-yun
authors.initials: ZY
authors.lastname: Zhang
authors.forename: Xiao-ming
authors.initials: XM
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.forename: Yan
authors.initials: Y
authors.lastname: Ding
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Qi
authors.initials: Q
authors.lastname: Yang
authors.forename: Tian-jing
authors.initials: TJ
authors.lastname: Zeng
authors.forename: Jian-bin
authors.initials: JB
authors.lastname: Cao
authors.forename: Xiu
authors.initials: X
authors.lastname: Yue
authors.forename: Ting-ting
authors.initials: TT
authors.lastname: Shen
authors.forename: Guang-ming
authors.initials: GM
authors.lastname: Zeng
authors.forename: Jiu-hua
authors.initials: JH
authors.lastname: Deng
authors.forename: Xun
authors.initials: X
authors.lastname: He
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D005374:Filtration; D009835:Oligochaeta; D012822:Silicon Dioxide
chemical_list: D012822:Silicon Dioxide