Environmental protection project for coking wastewater treatment

It’s about the recovery and treatment of cold coking water, and so on!

I really haven’t done it before; could some expert come and give me some guidance?

Our company has installed a wastewater treatment system for coking wastewater; it is operating stably at present, and the treated water is used to quench coke in the coke ovens. Meanwhile, a three-stage water purification system has been installed recently, which is primarily used to treat clean wastewater, with the treated water serving as a supplement to the process cooling water. Together, these two systems handle the wastewater generated by the coking plant, ensuring zero wastewater discharge from the company.

My coking plant installed two systems for treating cyanide-containing wastewater in 2006, but their performance was very poor. The inlet COD is 5100 mg/l and the ammonia nitrogen level is 500 mg/l; the outlet COD is 1000 mg/l while the ammonia nitrogen level is just over 100 mg/l. I would like to ask everyone how to deal with this?

5# sunguozhu_56 Based on past experience, it’s possible that the tank capacity is too small, resulting in a short residence time. There is also the issue of backflow. Since the wastewater is highly toxic, increasing the recirculation rate helps to dilute it to some extent. There are also issues related to aeration and pH, which need to be adjusted according to the specific circumstances

Currently, there are very few facilities in China that handle coking wastewater effectively. The reason for this is poor pretreatment; more precisely, nitrogen, phenols, and other substances present in coking wastewater cannot be recovered properly, which in turn results in suboptimal outcomes from the subsequent biochemical treatment processes. The main reason behind this is the high costs and investment required for such treatment, which prevents many manufacturers from implementing it. In fact, after treatment, coking wastewater can be reused for quenching coke, enabling recycling with almost no discharge ； There is also circulating water used for dust removal in steel mills; however, due to its high alkalinity, acid treatment is required, and the requirements for scale inhibitors are quite high as well, otherwise scaling can easily occur in pumps and pipes.

Here is an article on advanced treatment using membrane technology for your reference. Research on Advanced Treatment and Reuse of Coking Wastewater by Membrane Technology Abstract: An experimental study was conducted on the advanced treatment and reuse of coking wastewater using a pilot-scale (5–10 m3/d) “A2/O membrane bioreactor + RO” combined process. The test results show that this process achieves excellent treatment efficiency, and the MBR and RO systems can operate stably over the long term. When the average inlet CODcr concentration is as high as 3000 ppm and the NH3-N concentration is 220 ppm, the CODcr in the effluent of the MBR system

In addition, there are also some issues associated with the use of membrane treatment and advanced oxidation technologies for the advanced treatment of coking wastewater. The main problems include: (1) If membrane treatment technology is employed for advanced treatment, a secondary water treatment process is required; after the membrane separates the treated water, it results in two streams of water – one stream is water that can be reused directly, accounting for 75% of the total water volume； The other portion consists of concentrated wastewater with high levels of COD and salts, accounting for 25% of the total water volume; this water requires secondary treatment. Experts suggest that activated carbon adsorption can be used to remove COD from this portion of wastewater; however, this method presents issues such as the regeneration of activated carbon. Some scholars propose that this wastewater should be recycled back into the secondary treatment process, thereby avoiding further treatment steps, but the impact on water quality requires further research and evaluation. (2) If advanced oxidation processes are used for advanced treatment, the COD level first decreases and then increases, possibly because the intermediate products generated by advanced oxidation constitute new COD. Experts suggest that the COD value determined by the potassium dichromate method has certain limitations, and using the TOC value might be more appropriate.