The ornamental design for an airtreatmentsystemfilter, as shown and described.
FIG. 1 is a perspective view of the air treatment system filter embodying the new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left-side view thereof; and,
FIG. 7 is a right-side view thereof.
FIGS. 1-7 may show features of the air treatment system filter in broken lines. The broken lines depict environment and do not form any part of the claimed design, the broken lines immediately adjacent the solid-line portions of the design form the boundary of the design and form no part of the claimed design.