Effects of earthworms on surface clogging characteristics of intermittent sand filters.
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.
Wang
Dong-bo
DB
College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China.
Zhang
Zi-yun
ZY
Li
Xiao-ming
XM
Zheng
Wei
W
Ding
Yan
Y
Yang
Bo
B
Yang
Qi
Q
Zeng
Tian-jing
TJ
Cao
Jian-bin
JB
Yue
Xiu
X
Shen
Ting-ting
TT
Zeng
Guang-ming
GM
Deng
Jiu-hua
JH
He
Xun
X
D000818:Animals; D004784:Environmental Monitoring; D005374:Filtration; D009835:Oligochaeta; D012822:Silicon Dioxide
D012822:Silicon Dioxide