Occurrence and removal of polycyclic aromatic hydrocarbons in real textile dyeing wastewater treatment process

In this work, the occurrence and removal of polycyclic aromatic hydrocarbons (PAHs) were investigated in a combination process of anoxic baffled reactor (ABR)-hybrid coagulation/membrane bioreactor (HCMBR) for real textile dyeing wastewater treatment. It was found that the target compounds except for the chrysene, benzo(b)fluoranthene, dibenzo(a,h)anthracene, and benzo(g,hi)perylene occurred widely in raw textile dyeing wastewater, treated effluent and sludge samples. In the raw wastewater, two-ring naphthalene was the dominant compound, while three-ring PAHs predominated in the final effluent. The dominant compounds in the raw sludge samples were phenanthrene, while they were pyrene and indeno(1,2,3-cd)pyrene for final discharge sludge. The combination process achieved over 88% removal for all the PAHs. Low molecular weight (LMW) PAHs might be mainly removed by volatilization, adsorption, and sedimentation in the ABR treatment unit. High molecular weight (HMW) PAHs might be mainly removed by adsorption and sedimentation processes after coagulation and solid-liquid separation in the HCMBR treatment unit. The final discharge of treated textile dyeing wastewater and sludge was biologically safe based on the toxicity evaluation test.