A sequencing biofilm reactor for the treatment of chlorinated solvents using methanotrophs

Abstract

ABSTRACT: Laboratory experiments were conducted with a sequencing, packed‐bed bioreactor that was seeded with the methanotroph, Methylosinus trichosporium OB3b. The reactor cycled between a growth mode, in which methane and oxygen were supplied from the gas phase, and a degradation mode, in which water containing chloroform at 100 µg/L was treated in the absence of methane. When the influent was supplemented with formate, chloroform degradation was as great as 90% at an empty bed retention time of approximately 90 minutes. The degradation rate remained stable for several days, but steadily declined thereafter. In the absence of formate, the initial degradation rate was smaller and declined more rapidly than in the presence of formate. Mathematical modeling demonstrated that the pseudo‐first‐order rate constants for chloroform degradation in the reactor were about two orders of magnitude smaller than those measured in suspended growth, batch kinetic studies. The sequencing reactor performed better than a packedbed, continuous‐flow reactor, because a larger, more evenly distributed biomass could be established in the sequencing reactor.