Treatment Of Oily Wastewater By Demulsification/Flocculation

The inadequate processing of oily wastewater doesn’t only creat lots of waste of resources, and it’s also the cause of severe environmental damage. Therefore, how to effectively deal with oily water has become an urgent issue that needs to be settled in the petroleum industry. In this paper, the demulsification/flocculation process is used to deal with oily wastewater which is very difficult to treat, a novel sewage treatment agent YL-7 is developed through compounding demulsifier with flocculants. At an YL-7 dosage of 110-320 mg/L at 50℃ for 90 min, the oil removal efficiency reaches 92.0-96.7%. Microorganism flocs (extracted from oily wastewater from A oilfield) with high negative zeta potential enhance the stability of O/W emulsion. In order to reduce the dosage of sewage treatment agent, a new high efficient NP-22 is developed by compounding YL-7 with organic silicone surfactants 321. At an NP-22 dosage of 60-90 mg/L at 45℃ for 90 min, the oil removal efficiency reaches 90.7-95.3%. The mechanisms of YL-7 and NP-22 are discussed by measuring oil content, droplet distributions, zeta potential, and interfacial tension. The demulsifier of YL-7 can replace the active components of o-w interface and neutralize the negative charge of the oil droplet surface, while flocculants of YL-7 mainly neutralize charge, bridge and sweep flocs during the flocculation process. The organic silicone surfactants 321 of NP-22 can effectively reduce the o-w interfacial tension and interfacial film strength, so as to better promote the demulsification/flocculation effect of YL-7 and reduce the dosage of the water treatment agent. Through introducing YL-7 and NP-22 into oily wastewater treatment of vacuum distillation tower from X oil refineries, the results show that the oil removal rate reached 84.0% and 80.1% respectively after adding 40 mg/L YL-7 and 15 mg/L NP-22. The dosage and treatment performance of YL-7 and NP-22 are superior to the original use of agents, indicating that they can be widely used in various types of oily wastewater treatment. To reduce the time of oily wastewater treatment, the Fe3O4 magnetic nanoparticles are prepared by chemical coprecipitation, and the composition and morphology are characterized by IR, Raman, XRD, TEM, SEM. Experiments show that the oil removal efficiency reaches 93.3% within 10 min after adding 200 mg/L Fe3O4 magnetic nanoparticles and 150 mg/L demulsifier in magnetic field.What’s more, the Fe3O4 magnetic nanoparticles can be reused after using ethanol ultrasonic extract. It is of great significance for special occasions such as offshore oilfield which have higher request for treatment time of oily wastewater...