It´s not easy to estimate the complete impact of surfactants to the environment. There are too many surfactants to ana small Lysis them. But it would be enough valuable that we can judge the initial impact of key surfactants including ethoxylated nonionic surfactants which are used in the major industries to activated sludge in wastewater treatment. Becaus the initial shock to the activated sludge is the very serious problem that must be avoided in the fields. Among the ethoxylated nonionic surfactants, NP 8 EO is still used vastly even though it has some serious environmental problems. According to the many = bibliographies on the effect of surfactants, especially ethoxylated nonionic surfactants to environment from a lot of Eternizes and the results from the bench scale tests on the initial impacts of NP 8 EO to activated sludge comparing with LAS and QAC, the conclusions are as follows
1. Conclusion from literatures
1-1. The biodegradability of nonionic surfactants increases depending on the straight degree of hydrophilic group. But it decreases as the EO, PO added and molecular weight increase: Especially proxilated ones are more difficult to be bioderaded than the ethoxylated ones.
1-2. The toxicity of nonionic surfactants increases while the EO added increases.
2. Conclusion from bench scale test
2-1. The system in aeration tank is splitted off after 50 hours´ aeration when 30mg l of QAC is injected and repeat after 17 hours´ aeration when 50mg/I of QAC injected. But the system is seperated after 45 hours´ aeration when 50mg/i of NP 8 EO isdosed.
2-2. At 30rngll of surfactants concentration, LAS doesn´t affect the major damage to activated sludge for relatively long time, but QAC and NP 8 EQ have the considerable damage that the useful microbes in the activated sludge diminish.
2-3 The concentration curves of MISS for all kinds and concentrations of surfactants show icreasion in first 5 - 20 hours and decreasion after 20 hours.
2-4 The impact of surfactants to activated sludge for reducing CON. are different. The impact of NP 8 EO is smaller than that of QAC but bigger than that of LAS.
3. Conclusion from the conbined view.
The initial impact of NP 8 EQ is remarkably bigger than that of LAS but smaller than QAC: It means that at only 30mg/l, NP 8 EO appears the negative effects obviously to the activated sludge within 45 hours. Therefore it would be necessary that the pre-treatment for removing the excessive NP 8 EO from the influents is accepted or the other nonionic surfactants are recommended.
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