Microplastics (MPs) from industrial activities remain poorly understood, particularly in wastewater systems serving e-waste dismantling. This study investigated a full-scale wastewater treatment plant (WWTP) in Guiyu, China, through four seasonal sampling campaigns covering two parallel treatment trains: an anaerobic-anoxic-oxic (A/A/O) oxidation ditch–secondary clarification train and an A/A/O oxidation ditch–membrane bioreactor train. MPs were quantified and characterized by micro-Raman spectroscopy, and their process fate, source-related fingerprints, associations with phthalate esters and organophosphate esters, and screening-level hazard redistribution were evaluated. The raw influent contained 6637.3 ± 927.4 MPs/L, substantially exceeding typical municipal WWTP levels. Both treatment trains reduced aqueous MP concentrations by 2–3 orders of magnitude, but most removed particles were transferred to sludge rather than eliminated. E-waste-related engineering polymers and angular fragments with sharp edges dominated the influent and sludge. Their co-occurrence with multiple plastic-associated organic contaminants supported an integrated polymeric, morphological, and chemical source-fingerprint inference for e-waste-related MPs. Hazard screening further indicated that treatment reduced the aqueous hazard-weighted MP burden while redistributing the dominant burden to sludge. These findings highlight the need to consider source fingerprints and sludge accumulation in assessing and controlling industrial MP pollution.