Views: 508 Author: Site Editor Publish Time: 2024-03-21 Origin: Site
| Wastewater Type | Oil and emulsion |
| Implementation time | |
| Processing scale | 10m3/H |
| Project name | Oil and emulsion project for a fuel recycling enterprise in Zhejiang |
| Product name | RDAF High Efficiency Dissolved Air Flotation |
| Process | air flotation /UASB /Fenton /AO |
A fuel recycling enterprise in Zhejiang mainly manufactures and processes recycled fuel oil, lubricating oil, and waterproof coatings (except hazardous chemicals). To ensure the quality of the enterprise's products, reduce the enterprise's energy consumption, and reduce the emission of "three wastes," it is planned to carry out the technical transformation of the plant, dismantle or eliminate all the original old equipment, rebuild (newly build) a set of recycled base oil production equipment, and build a supporting sewage treatment station.
The enterprise's wastewater is divided into production wastewater and domestic sewage. Production wastewater mainly includes oil-water separation wastewater, vacuum pump wastewater, ground washing wastewater, and initial rainwater. The water quality and water volume are shown in Table 1. The total wastewater is 9.5 m3/d, of which initial rainwater is 1.7 m3/d and oily wastewater is 7.8 m3/d. After on-site investigation and water quality analysis, it was found that the COD value in the oily wastewater in the plant area is high, and most of the oil in the wastewater exists in the form of dispersed oil, emulsified oil, and dissolved oil, with less floating oil. There are no other sewage treatment facilities in the plant area except the pretreatment tank. Therefore, the technical transformation mainly focuses on the problems of high COD, dispersed oil, emulsified oil, and dissolved oil content.
| Wastewater Type | Water volume/(m3·d－1) | COD/( mg·L－1) | Petroleum/(mg·L-1) |
| Oil-water separation wastewater | 4.9 | 90000 | 500 |
| Floor washing wastewater | 0.9 | 1000 | 100 |
| Vacuum pump wastewater | 3.0 | 800 | 100 |
| Initial rainwater | 1.7 | 300 | - |
Tab． 1 Wastewater quality and quantity
management department, the plant will be equipped with a sewage treatment station. After completing the project, it will have an annual production capacity of 3.5 × 104 t/a of waste mineral oil regeneration base oil. According to the requirements of the enterprise, the project wastewater is pre-treated by the plant sewage station to meet the indirect discharge standards of the "Petroleum Refining Industry Pollutant Emission Standard" (GB 31570-2015) and the third-level standard of the "Comprehensive Sewage Emission Standard" (GB 8978-1996). The designed water treatment volume is 15 m3/d. The designed inlet and outlet water quality are shown in Table 2.
| Project | pH | COD/( mg·L－1) | SS/( mg·L－1) | Petroleum/(mg·L-1) | |
| Water inlet | Oily wastewater | 6~9 | 9000 | 500 | 500 |
| Initial rainwater | 6~9 | 300 | 150 | 40 | |
| Water outlet | Level 3 pipe standard | 6~9 | 500 | 400 | 30 |
Tab． 2 Design influent and effluent quality
Dispersed oil and emulsified oil in oily wastewater are difficult to separate by gravity separation. Therefore, the tiny bubbles generated by dissolved air flotation can be used to adhere to the fine oil particles in the wastewater and float them up, thereby achieving the effect of oil-water separation. At the same time, alkali, aluminum sulfate and coagulant aids are added to break the emulsion and improve the flotation effect.
During the trial operation phase, the wastewater treatment effect remained stable after one month. The influent COD was 4200-9600 mg/L, the petroleum was 120-328 mg/L, and the SS and pH values met the design influent requirements; the effluent COD was 122-458 mg/L, the petroleum was 7-13 mg/L, the SS was 30-98 mg/L, and the pH value was 6.44-8.61. The effluent indicators were better than the design requirements. The average COD removal rate was ＞95.10%, and the petroleum removal rate was ＞95.25%.
