Hangzhou’s chemical fiber sector has long grappled with a stubborn adversary: wastewater so laced with acids and stubborn organics that traditional bioreactors shut down before they even start. But a team led by Lin Baochun, chief engineer at Hangzhou Yishui Environmental Engineering, has just delivered a playbook that turns that liability into an asset.
Inside a 1,200 m³/day plant on the city’s outskirts, a hybrid beast of split-stream pretreatment, dissolved-air flotation, UASB digesters and two-stage anoxic–oxic tanks now handles polyester fiber effluent that once defied treatment. “We had influent COD above 2,000 mg/L and a B/C ratio of only 0.3,” Lin recalls. “Standard activated sludge would just flat-line.” The breakthrough was stitching together acid-resistant acidification, staged anaerobic–aerobic metabolism, and a final punch of catalytic ozonation plus UF/RO polishing. “The ozonation step is the real game-changer,” Lin notes. “It slices the remaining refractory aromatics and lifts the B/C ratio so the downstream membrane sees clean water, not a chemical soup.”
Commercial fallout is immediate. With effluent routinely below 50 mg/L COD, 1.5 mg/L NH₃-N and 0.3 mg/L TP—all while reusing 90 % of the flow for cooling towers—the plant has slashed municipal discharge fees and cut fresh-water purchases by the same margin. For energy-intensive polyester plants eyeing carbon-neutral pledges, that translates to lower grid draw for abstraction and a measurable drop in Scope 2 emissions.
What makes the design portable is its modularity. A single skid can scale from 500 m³/day to 5,000 m³/day with minimal re-engineering, letting smaller fiber producers leapfrog legacy systems. Lin’s group is already fielding inquiries from plants in Jiangsu and Guangdong, where provincial water quotas are tightening faster than national standards.
Published in Gongye shui chuli (Industrial Water Treatment), the paper quietly signals a shift: when wastewater is too “difficult,” the answer may no longer be bigger clarifiers or stronger chemicals, but tighter choreography between unit processes. For an industry that once treated every drop as waste, that’s a quiet revolution.