Views: 508 Author: Site Editor Publish Time: 2024-03-25 Origin: Site
| Wastewater Type | Electroplating wastewater |
| Implementation time | 2018 |
| Processing scale | 240m3/d |
| Project name | Wastewater treatment project for an electroplating enterprise in Jiangsu |
| Product name | RDAF High Efficiency Dissolved Air Flotation |
| Process | Sand settling + oil separation + air flotation + coagulation sedimentation + biochemical + Secondary coagulation sedimentation + sand filter carbon filter unit |
An enterprise in Jiangsu Province is engaged in metal surface treatment and processing. It discharges wastewater in the product coating and pickling process, with a water volume of 240m3/d. The wastewater composition is complex, contains some heavy metal ions, and has a high COD concentration. For this reason, the enterprise has built a new set of wastewater treatment facilities, using the combined process of "sand settling + oil separation + air flotation + coagulation sedimentation + biochemical + secondary coagulation sedimentation + sand filtration carbon filtration unit." The project is running stably, and the effluent has met the urban greening water quality requirements in "Urban Wastewater Recycling Urban Miscellaneous Water Quality" (GB/T 18920-2002).
| Project | pH | BOD(mg/L) | Total dissolved solids (mg/L) | Total coliform bacteria (pcs/L) | Chroma | Zn²+ |
| Raw water | 2~3 | 300 | ＜1000 | 2500 | / | 40 |
| Outlet water | 6~9 | 10 | 20 | 1000 | ＜3 | 1 |
Table 1 Designed inlet and outlet water quality (except pH, unit: mg/L)
The wastewater first passes through the grit chamber to precipitate suspended solids, flows into the regulating tank for collection (the oily wastewater is deoiled in the oil separator), is pumped into the air flotation equipment through a water pump, and then flows into the primary coagulation sedimentation tank by gravity, so that the oil can meet the relevant discharge requirements. The clear liquid of the primary coagulation sedimentation tank removes COD in the water through the biochemical system, and the mud-water mixture is separated in the sedimentation tank. The biochemical effluent then passes through the secondary coagulation sedimentation, sand filter, carbon filter, and disinfection unit to meet reuse requirements. The sludge generated by the system is collected in the sludge thickening tank through the sludge pump and then pumped into the plate and frame mud press for treatment. The water content is less than 80%, and the filtrate is discharged into the regulating tank. The sludge is discharged into the sludge tank, dehydrated by the plate and frame filter press, and the mud cake is transported for disposal.
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.
1 set, installed power 2.5kW, integrated equipment, the flotation tank consists of a contact and separation tank. Wastewater is mixed with dissolved air water from the dissolved air tank in the contact tank, and the precipitated tiny bubbles contact and agglomerate with the pollutants in the wastewater. The agglomerates float on the water surface through the separation tank and can be scraped off. The treated wastewater flows out from the lower side of the baffle into the neutralization reaction tank.
The project was completed and put into operation in 2018. The average influent concentrations of pH, BOD, and turbidity were approximately 2.8, 830 mg/L, and 280, and the effluent concentrations were 7.8, 18 mg/L, and 9, respectively. Other indicators were also better than the design expectations.
