Types of carbon sources and their advantages and disadvantages (what are the types of carbon sources)
At present, commonly used carbon sources on the market include methanol, acetic acid, sodium acetate, flour, glucose, biomass carbon sources, sludge hydrolysis supernatants, beer wastewater and landfill leachate. In the application process, it is necessary to choose the appropriate carbon source according to the actual engineering situation. This article compares various commonly used carbon sources and analyzes their advantages and disadvantages:
(1) Methanol
As an external carbon source, methanol is generally considered to have the advantages of low operating cost and low sludge yield. When using methanol as a carbon source, when the carbon-nitrogen ratio > 5, a better carbon-nitrogen ratio of >5 can be obtained, but there are three disadvantages:
1. As a chemical agent, the cost is relatively high;
2. The reaction time is slow, and methanol cannot be utilized by all microorganisms. The addition of methanol requires a certain period of adaptation until it is fully enriched and fully utilized. It is used for emergency carbon source addition in sewage treatment plants, and the effect is not good.
3. Methanol has a certain toxic effect, and the long-term use of methanol as a carbon source will also have a certain impact on tailwater discharge.
(2) Sodium acetate
The advantage of sodium acetate is that it can react immediately to the denitrification process and can be used as an emergency treatment for water plants.
It is generally believed that the denitrification rate of ethanol is not as high as that of methanol, but because it is non-toxic, the sludge production is similar to methanol, and it can be considered as an alternative carbon source for methanol. When ethanol is the carbon source and nitrate is the electron acceptor, the best c/n = 5, the lack of carbon source will cause nitrite accumulation.
The following three disadvantages should be considered when using sodium acetate:
1. Sodium acetate is mostly 20%, 25%, 30% liquid, due to its low equivalent cod, high transportation costs, can not be transported over long distances.
2. The sludge production is large, and the cost of sludge treatment increases;
3. The price is relatively high, so it is almost impossible to add sodium acetate on a large scale in sewage treatment plants.
(3) Glucose
Glucose, as a representative carbohydrate, has a good therapeutic effect as an external carbon source. However, as a multimolecular compound, it is easy to cause a large number of bacteria to multiply, causing the sludge to expand, increasing the cod value of the effluent, and affecting the quality of the effluent. At the same time, carbohydrates are more likely to produce nitrite nitrogen accumulation than alcohol carbon sources. Therefore, it is not recommended to use glucose in large quantities as an external carbon source.
The type of glucose of the carbon source
shortcoming:
1. It needs to be prepared into a solution on site, with high labor intensity and poor dosing accuracy, and cannot be used for large-scale sewage treatment plants.
2. Industrial glucose contains a lot of impurities, and food glucose is expensive.
(4) Biomass carbon sources
With the increase in the requirements for wastewater denitrification, a new enterprise specializing in carbon source production has emerged. Through the principle of bioengineering, they ferment some sugars and agricultural wastes to produce non-toxic and harmless biological products, the main components of which are small molecule organic acids, alcohols and sugars. Compared with a single chemical, it is easier to be used by microorganisms, and the cost of use is cheaper than that of a single chemical, so it has a very high price performance ratio.
、
The type of carbon source is a composite carbon source
Product stability needs to be improved, and the equivalent cod of each batch of products needs to be detected before use.
(5) Sludge hydrolysis supernatant
Biotransformation volatile acid VFA comes from sludge hydrolyzed supernatant. Due to the high rate of VFA denitrification generated by hydrolysis, the carbon source can be directly provided by the sewage treatment plant, reducing the amount of sludge and the problem of carbon source transportation, which is currently a more favorable carbon source.
At present, there are many different conclusions about the hydrolytic utilization of sludge as an exogenous carbon source, but it is generally accepted that sludge hydrolysis utilization as a source of denitrified carbon is a valuable method.
In addition, if the hydrolyzed sludge is directly used as an external carbon source, the release of nitrogen and phosphorus during the hydrolysis of the sludge should also be considered. If this part of nitrogen and phosphorus is added to the sewage in the form of a carbon source, it will inevitably increase the nitrogen and phosphorus load of the sewage treatment plant. How to solve this problem is another major problem in the utilization of sludge hydrolysate.
This article is reproduced in: http://www.cltep.com/news/hydt/942.html