TOC in Pretreatment

[waterweasel]

Am working on a pretreatment train and am experiencing significant increase in TOC across the multimedia filter beds. Water is chlorinated for breakpoint chlorination and enters the filter bed (sand and anthracite) with about 9 ppm free chlorine.

We see TOC jumping from around 1.3 to 9 through the filter bed. The phenomenon is identical on both trains.

Is the high chlorine level breaking down the anthracite?

Thanks