Wastewater can be divided into two kinds: domestic wastewater and industrial wastewater.Domestic wastewater can be treatedsatisfactorily by traditional activated-sludge process, which is usedwidely in urban sewage treatment plantsHowever, industrial wastewater, often containing toxic substances,
creates a great problem for this process due to a lack of effective
degrading bacteria in activated sludge.The quality of industrial wastewater often exhibits
to be inflexible for biodegradation (BOD5/COD < 0.2–0.3).
Moreover, some kinds of toxic substances may poison the
microbial community in the system and make activated sludge