Microcosm-scale experiments were conducted in replicated reciprocating fill-and-drain biofilter systems to evaluate treatment efficacy of several substrates as compared to a no-substrate control (2-cell reciprocating lagoon). The three substrates (rock, bioballs and a non-woven textile
fiber (geo-mat), were tested in two treatment configurations (systems with and without a paired lagoon cell). Concentration dynamics were monitored over a 96 hour period to determine removal rates for chemical oxygen demand (COD), total ammonia nitrogen (TAN), nitrate-nitrogen (NO3-N), and
soluble ortho-phosphate (P04-P). With respect to COD and TAN removal rates, results revealed that paired reciprocating configurations containing one lagoon cell and one substrate-filled cell were nearly as effective as configurations containing two substrate-filled cells. COD removal ranged
from 73% (lagoon only control) to 97% for treatments with substrates. COD removal was consistently high for all substrates and system configurations (93–97%). Treatments with rock substrate or geo-mat were more effective at removing TAN (91–99%) than treatments with bioballs alone
(65%) or the lagoon control (21%). Nitrate nitrogen increased progressively over time as a function of treatment specific ammonia oxidation and as an indication of carbon limitation. Phosphorus removal over the four day trial averaged 42 and 69 percent respectively in lagoon/rock and rock/rock
treatment configurations. Phosphorus removal was less than 15% for treatments containing bioballs or geo-mat, irrespective of treatment configuration.
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