Wastewater Treatment Performance of Earthworm Biofilter with Filter Media of Quartz Sand and Ceramic Pellet

Wastewater treatment performance by earthworm biofilter with different filter medias of quartz sand and ceramic pellet was studied. It was found that in five runs, ceramic pellet filter bed put up better ability of resisting high hydraulic loading and low temperature to keep stable wastewater treatment effect. Under the same conditions, ceramic pellet filter bed could remove organic matters and nutrients more efficiently than quartz sand filter bed. Its average removal of COD, BOD₅ and NH₄ ⁺-N were 40.31%, 54.34% and 39.47% respectively, while that of quartz sand were 28.52%, 41.01% and 23.18%. Wastewater treatment was realized when earthworm grew in filter bed. Therefore living environment provided by filter media affected wastewater treatment effect directly. Observation of the body wall tissue of earthworms by scanning electronic microscope (SEM) indicated that the corneum, epidermis and central muscle were injured slighter in ceramic pellet filter bed than in quartz sand filter bed. The character of ceramic pellet met the request for need of earthworms´ life activities more. The effect of earthworms´ physiological activity in different filter beds on organic matter degradation was also investigated and the results showed earthworms´ digestion quantity and rate in ceramic pellet filter bed were higher than that in quartz sand filter bed.