Is the biodegradability of sewage good? Share four identification methods

The biodegradability of wastewater, also known as the biodegradability of wastewater, refers to the difficulty of biodegradation of organic pollutants in wastewater. This is one of the important characteristics of wastewater. Some wastewater contains organic compounds that are easily decomposed and utilized by microorganisms, while others contain organic compounds that are difficult to degrade or even inhibit microbial growth. The biodegradability of these organic compounds and their relative content in wastewater determine the feasibility and difficulty of using biological treatment (usually referred to as aerobic biological treatment).
The determination of the biodegradability of wastewater treatment objects is of great significance for selecting wastewater treatment methods, determining important process parameters such as the inflow of biochemical treatment sections, and organic load. The methods for determining biodegradability at home and abroad can be roughly divided into aerobic respiration parameter method, microbial physiological index method, simulation experiment method, and comprehensive model method.
1、 Aerobic respiration parameter method
In the aerobic process of degrading organic pollutants, microorganisms not only undergo changes in water quality indicators such as COD (chemical oxygen demand) and BOD (biochemical oxygen demand), but also consume O2 and generate CO2. The aerobic respiration parameter method utilizes the above facts to determine the biodegradability of a certain organic pollutant (or wastewater) by monitoring water quality indicators such as COD and BOD, as well as changes in O2 or CO2 content (or consumption and generation rate) during respiratory metabolism. According to the water quality indicators used, they can be mainly divided into: water quality indicator evaluation method, microbial respiration curve method, and CO2 generation measurement method.
2、 Microbial physiological indicator method
When microorganisms come into contact with wastewater, they utilize organic matter in the wastewater as a carbon source and energy source for metabolism. By observing the changes in important physiological and biochemical indicators during microbial metabolism, the biodegradability of this type of wastewater can be determined. At present, the physiological and biochemical indicators that can be used as the basis for judgment mainly include dehydrogenase activity and adenosine triphosphate (ATP).
3、 Dehydrogenase activity index method
The oxidative decomposition of organic matter by microorganisms is completed with the participation of various enzymes, among which dehydrogenase plays an important role: catalyzing the transfer of hydrogen from the oxidized substance to another substance. Due to the sensitivity of dehydrogenase to toxins, its activity (ability to activate hydrogen per unit time) decreases when toxins are present. Therefore, dehydrogenase activity can be used as an indicator to evaluate the ability of microorganisms to decompose pollutants: if the activity of microbial dehydrogenase grows in a culture medium with a certain wastewater (organic pollutant) as the substrate, it indicates that microorganisms can degrade that wastewater (organic pollutant).
4、 ATP indicator method
The process of microbial oxidation and degradation of pollutants is actually an energy metabolism process. Adenosine triphosphate (ATP) is a substance that stores energy in microbial cells. Therefore, the level of ATP in cells can be measured to reflect the activity of microorganisms, and it can be used as an indicator to evaluate the ability of microorganisms to degrade organic pollutants. If the activity of ATP in microorganisms growing in a culture medium with a certain wastewater (organic pollutant) as the substrate increases, it indicates that microorganisms can degrade that wastewater (organic pollutant).
Simulation experiment method
Simulation experiment method refers to the method of directly simulating the actual wastewater treatment process to determine the feasibility of wastewater biological treatment. According to the degree of approximation between simulated and actual processes, it can be roughly divided into culture medium determination method and simulated biochemical reactor method.
The culture medium determination method, also known as the shaking table test method, involves filling a series of triangular flasks with a certain pollutant (or wastewater) as a carbon source culture medium, adding appropriate nutrients such as N and P, adjusting the pH value, and then inoculating one or more microorganisms (or domesticated activated sludge) into the flasks. The triangular flasks are placed on a shaking table for oscillation, simulating the actual aerobic treatment process, Continuously monitor changes in the physical appearance (concentration, color, odor, etc.) of the culture medium in a triangular flask during a certain stage, as well as changes in microorganisms (bacterial species, biomass, and biomass), and changes in various indicators of the culture medium, such as pH, COD, or concentration of a certain pollutant.
The simulated biochemical reactor method is carried out in a model biochemical reactor (such as an aeration tank model), by simulating the reaction conditions of actual sewage treatment facilities (such as an aeration tank) in the biochemical model, such as MLSS concentration, temperature, DO, F/M ratio, etc., to predict the removal efficiency of various wastewater in sewage treatment facilities and the impact of various factors on biological treatment.
The comprehensive modeling method is mainly aimed at determining the biodegradability of a certain organic pollutant through computer simulation to predict the biodegradability of new organic compounds. The main models include BIODEG model, PLS model, etc.
The comprehensive modeling method relies on a large biodegradability database of known pollutants (such as the EU's EINECS database), and the simulation process is complex and costly. It is mainly used to predict the biodegradability of new compounds and the degradation pathways after entering the environment.
In addition to the above methods for determining biodegradability, many other methods have been developed in recent years, such as using multi-stage filtration and ultrafiltration methods to obtain the particle size distribution PSD and COD distribution of wastewater as indicators for predicting biodegradability; Joint evaluation of the biodegradability of wastewater using the biological activity value of a certain end product in the biochemical reaction based on oxygen consumption; Using an empirical flowchart to predict the biodegradability of a certain organic pollutant.