During the process of groundwater source heat pump recharge, microbial blockage represented by Escherichia coli is one of the important causes of ground subsidence, and studying its blockage characteristics is of great practical significance. We studied the “sedimentation detachment” characteristics of Escherichia coli when the direction of seepage and fluid velocity changed using a self-developed sand layer clogging device. The experimental results showed that： 1） Escherichia coli blockage exhibited a saddle shape under three different flow rates, with concentration changes increasing first and then decreasing, and then decreasing again after a correction. Among them, the blockage of Escherichia coli at the throat has a certain degree of dependence, which affects the efficiency of reinjection; 2） After changing the direction of seepage and increasing the flow rate, the dynamic balance of “sedimentation detachment” of Escherichia coli is disrupted, and the concentration of Escherichia coli decreases. The Escherichia coli that originally deposited in the pores are driven to migrate by external forces. By monitoring the liquid sample at the outlet, it was found that there was a significant increase in concentration values. Based on engineering practice, if the method of backflushing is used to treat the wellbore blocked by Escherichia coli, excessive cleaning time may cause new blockages, which may not meet the requirements of thorough cleaning of the wellbore. Therefore, it is necessary to control the reasonable time of backflushing.
Key words
Escherichia coli /
water source heat pump /
sedimentation detachment /
sand and gravel /
clogging /
microorganism
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