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Abstract
The removal of biodegradable ozonation by-products was evaluated at pilot-scale using one conventional biofilter containing sand and anthracite and five fixed bed biofilm reactors (FBBRs) containing plastic media. Four of the FBBRs incorporated chemical or environmental optimization strategies (light restriction, chloramine, hydrogen peroxide, and nutrients) to either promote healthy biomass or minimize macrofauna proliferation. Conventional media biofiltration consistently removed assimilable organic carbon (AOC) by a maximum of 70% and was not susceptible to snail grazing. The control FBBR reduced AOC by a maximum of 60%, but dropped to zero following snail grazing on established biomass. Adenosine triphosphate (ATP) was used to quantify viable biomass attached to plastic media (tATP) and aqueous biomass in the column effluent (cATP). The control FBBR averaged 61 ng tATP/cm3 of attached biomass compared to chloramine (7 ng tATP/cm3), hydrogen peroxide (21 ng tATP/cm3), dark conditions (45 ng tATP/cm3), and nutrients (61 ng tATP/cm3). Hydrogen peroxide (1.8 mg/L) and light restriction strategies precluded dark algae and chironomids, but allowed snail development. None of this biota was observed in the presence of chloramine (0.20 mg/L). While the conventional biofilter and control FBBR produced similar AOC removals, FBBRs were sensitive to hydraulic disruptions and susceptible to grazer organisms.