Fluorescent penetrant is used for the cleaning process of precision machine parts in non-destruc-tive testing (NDT). Wastewater will be produced in that course with high chemical oxygen demand (COD) (1000–15,000 mg/L), high mineral oil (300–3000 mg/L) and high chroma (600–2000). This liquid waste has a serious influence on the environment due to its’ stronger biological toxicity and higher virulence. When the oil content exceeds 0.01 mg/L in water, the water will lack oxygen and lead aquatic plants and animals to die, thus create badly wate...
