How to ensure the stable operation of high-salt wastewater biochemical system?
Date:
2023-10-30
Direct discharge of these high-salinity wastewaters will cause great harm to the natural environment, causing pollution of natural water bodies and increased salinity, or causing problems such as soil salinization and compaction. Because the salt in high-salinity wastewater cannot be removed through the natural biodegradation process, the salt problem must be solved in the treatment of high-salinity wastewater, or a solution must be sought after harmless treatment.
In general, industrial brine has the characteristics of large discharge volume, wide sources, high salt content, complex composition, and large differences in the brine produced by different industries.
So how to deal with these high-salinity wastewater?
In addition to high concentrations of salt substances, high-salinity wastewater also contains high concentrations of organic matter, nitrogen, phosphorus and other pollutants. The water quality is complex and difficult to treat. The current treatment methods mainly include physical, chemical and biological methods. Among these three methods, the biochemical method is the most economical, efficient and harmless, so this article focuses on introducing the use of biochemical methods to treat high-salinity wastewater.
How to treat high-salinity wastewater by biochemical method
The biochemical method generally includes the activated sludge method, the biofilm method, etc. It uses microorganisms in the natural environment (ammonifying bacteria, nitrifying bacteria, denitrifying bacteria, etc.) to oxidize and decompose nitrogen-containing organic matter in the wastewater and convert it into stable and harmless nitrogen gas, water, etc.
In order to ensure the normal operation of the biochemical system, it is usually necessary to maintain parameters such as dissolved oxygen, pH, temperature, and salinity within a range suitable for the survival of microorganisms. High-salt wastewater often inhibits the growth and reproduction of microorganisms due to excessive salt content.
How to stabilize the biochemical system?
Inorganic salts play an important role in promoting enzyme reactions, maintaining membrane balance and regulating osmotic pressure during microbial growth. Microorganisms can be divided into four categories according to their optimal salt concentration: non-halophiles, weak halophiles, moderate halophiles and extreme halophiles.
Among them, halophiles have special cell structures and physiological functions, and their cell membrane structures and intracellular solutes can adapt to high-salt environments and survive in high salt concentrations. At present, in the research on the effect of salt content on the removal of organic matter in wastewater at home and abroad, most results show that when high-salinity salt tolerance acclimation or halophiles are not inoculated, the salt content in the wastewater increases and the organic matter removal efficiency decreases.
The main reasons for the decrease in pollutant removal rate caused by increased salt content may be the following:
Why does pollutant removal rate decrease as salt content increases?
The salting out effect is enhanced, the activity of microbial enzymes is reduced, and the decomposition of ATP, the direct energy source, is inhibited, resulting in a slowdown in microbial metabolism and a weakening of degradation capacity;
Microorganisms may secrete more extracellular polymers to attenuate salt toxicity;
As the osmotic pressure increases, the lysis of microorganisms is enhanced, a large number of intracellular components are released, and non-salt-tolerant microbial cells self-destruct, causing a large number of intracellular components to be released, allowing the organic matter in the cells to enter the wastewater, causing a temporary increase in COD in the water.
Therefore, if the biochemical system wants to ensure normal and stable operation in the presence of high-salt wastewater, it needs to undergo high-salinity salt-tolerant acclimation or be inoculated with halophilic bacteria; the former spends a lot of time naturally screening halophilic bacteria, and the latter directly inoculates halophilic bacteria, which greatly shortens the startup time and improves the salt tolerance of the biochemical system.
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