  We use new UV and optical spectra and an archival HST-WFPC2 image to study
the z_a~z_e absorber in the z_e = 0.20 QSO PKS 2135-147. The UV spectra,
obtained with HST-FOS, show strong z_a~z_e absorption lines of C IV, N V, O VI,
Ly-alpha and Ly-beta. The z_a~z_e line profiles are resolved, with deconvolved
FWHM of 270 to 450 km/s. Lower limits on the total column densities are of
order 10^15 cm-2 for all ions. If the absorber is photoionized by the QSO and
the derived relative columns in C IV and H I are roughly correct, then the
metallicity must be at least solar. The location of the z_a~z_e absorber
remains uncertain. Two ~L_* galaxies in a small cluster centered on PKS
2135-147 lie within 36h^{-1} kpc projected distance and have redshifts
consistent with causing or contributing to the z_a~z_e lines. The extensive
halo of the QSO's host galaxy could also contribute. Calculations show that the
QSO is bright enough to photoionize gas up to O VI in the low-density halos of
the host and nearby cluster galaxies. Nonetheless, there is indirect evidence
for absorption much nearer the QSO, namely (1) the derived high (albeit
uncertain) metallicity, (2) the relatively strong N V absorption lines, which
might be caused by a higher nitrogen abundance in the metal-rich gas, and (3)
strong, lobe-dominated steep-spectrum radio emission, which is known to
correlate with a much higher incidence of (probably intrinsic) z_a~z_e lines.
We propose that the CIV/NV/OVI line ratios can be used as a general diagnostic
of intrinsic versus intervening absorption, as long as the line saturation
effects are understood.
