{HEAD ~ The microbial fuel cells} can be operated as {TAIL ~ monitors}, filtration devices, and sensors 
operated as
{ HEAD ~ The microbial fuel cells } can be operated as { TAIL ~ monitors } , filtration devices , and sensors
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH