In wastewater treatment, how can COD levels be reduced quickly and conveniently?

COD is an umbrella term for Chemical Oxygen Demand; it represents the amount of oxygen required to oxidize the oxidizable substances present in water. COD is not a single substance, and the substances that contribute to COD vary depending on the type of wastewater. Each case must be analyzed on its own. What the original poster is looking for is likely not achievable. Wastewater treatment is a complex issue; if a simple and effective method were found to reduce COD, then we would all lose our jobs.

It’s fine as long as the main components are organic macromolecules! Pre-treatment with a flocculant can achieve a removal rate of over 60%. But if small molecules are the dominant component, it won’t work; the efficiency may drop to less than 30%. Of course, in either case, only a portion can be removed; to meet the standards, secondary treatment is necessary.

It’s fine as long as the main components are organic macromolecules! Pre-treatment with a flocculant can achieve a removal rate of over 80%. But if small molecules are the dominant component, it won’t work; the efficiency may drop to less than 30% ； To quickly reduce the COD level, simply add strong oxidants – and the problem is solved right away. The faster the COD level drops, the faster money is spent! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! (But it can still be used if only reducing COD is needed and the water volume is small.)

This is a systematic project; it cannot be achieved with a simple method

It’s too general; specific issues need to be analyzed on a case-by-case basis.

Different sources of wastewater require different treatment methods; it’s not something that can be solved simply by adding some chemicals.

The question posed by the original poster is a bit vague; the ideal methods for removing COD from different types of wastewater vary. For high-concentration organic wastewater, advanced anaerobic treatment methods (such as UASB), followed by oxygen-consuming treatment processes (such as oxidation ditches, SBRs, etc.), can yield good results ； For urban wastewater, biological treatment methods have lower costs ； For special wastewater containing heavy metals, toxic substances, etc., only physical and chemical treatment methods (such as reverse osmosis) can achieve a good COD removal rate. Furthermore, costs are also directly related to the scale of wastewater treatment; therefore, to remove COD in an economical and efficient manner, it is necessary to take into account both the characteristics of the wastewater and the scale of treatment.

The questions raised upstairs are incomplete; in my opinion, they are not accurate. By the time wastewater treatment reaches the COD treatment stage, strict restrictions have been imposed on the sources of such wastewater, and preliminary pretreatment has essentially already been carried out. It might be due to issues with the water supply, which contains heavy metals and toxic substances; however, this is no longer within the scope of consideration, as it requires specialized techniques and treatment methods. Compared to existing anaerobic treatment methods (such as UASB), the technologies for aerobic treatment (oxidation ditches, SBRs, etc.) are subject to limitations in terms of scale and cost, as well as factors such as floor space and location. For large-scale municipal sewage or large wastewater treatment plants, this can be disregarded. For small and medium-sized treatment units, with a daily treatment capacity of several thousand to ten thousand cubic meters, this is essentially at the enterprise-level of treatment. The three key factors for such installations become apparent: land area required, cost (both unit cost and total investment cost), and the level of treatment achieved (the standard to which the treated water can meet). The problem is serious, which is why it took a long time before it was brought up for discussion. I have also conducted research on this; there aren’t many methods available, and the results are average at best. Come and take a look to see if there are any better solutions, so we can all use them as a reference. The treatment method developed by myself is as follows: first, use iron-based flocculants + PAM, followed by anaerobic treatment and aerobic treatment before discharging the water into rivers – the treatment capacity is 15 WM/h, and the cost is around 3.0 yuan per ton; however, it requires a large amount of space, making it unsuitable for use on an industrial scale.