Flocculant is one of the most commonly used chemicals in sewage treatment. Also widely used in other industries. It is mainly divided into three categories: inorganic flocculants, organic flocculants, and natural polymer flocculants. In terms of contact and understanding, most people are relatively familiar with inorganic flocculants and natural polymer flocculants. They are cheap but have secondary pollution problems. Natural polymer flocculants, although environmentally friendly, are expensive and not familiar to people, but There are exceptions such as microbial flocculants. People have long discovered that microorganisms have flocculation.
Microbial flocculant is a new type of water treatment agent that is safe, efficient, and naturally degradable, and is extracted and purified from microorganisms or their metabolites using biotechnology. The ingredients Including glycoproteins, cellulose, proteins and DNA. It has also attracted more and more people’s attention, and has shown a trend of gradually replacing traditional flocculants. Currently, microbial flocculants on the market are mainly used to treat high-COD organic wastewater and dye wastewater, decolorize them, and restore activated sludge settling capacity.
Principle of action of microbial flocculant
Electric neutralization principle: The surface of suspended particles in the water body has a negative charge , Particles of the same sex repel each other, and the surface of the microbial flocculant is positively charged, which will neutralize the negative charge, causing the suspended particles to undergo magnetic collision and agglomerate and precipitate.
Sweeping principle: Microbial flocculantAfter being dissolved in the water body, it forms a network-like floc, which can be quickly caught under the action of gravity and sweep up smaller suspended particles in the water body.
Adsorption bridging mechanism: flocculant macromolecules rely on ionic bonds and hydrogen Bonds and van der Waals forces adsorb multiple colloidal particles at the same time, creating a bridging effect between particles, thereby forming a network-like three-dimensional structure and precipitating.
Features of microbial flocculants
High efficiency: at the same dosage, the use efficiency of microbial flocculant is high Compared with conventional flocculants such as iron salt and aluminum salt.
Non-toxic: microbial flocculants are natural organic high-density flocculants. Safe and non-toxic, will not affect sludge.
No secondary pollution: the flocculants produced by microorganisms have complex and diverse components. It varies with different strains of bacteria. It is biodegradable and can degrade by itself, so it will not cause secondary pollution.
Wide range of applications: objects that can be treated include activated sludge, charcoal, Ink, river bottom sediment, printing and dyeing wastewater, etc.
Short production cycle: microorganisms grow and reproduce quickly, are prone to mutation and distribution It is widely sourced and has a very short production cycle.
Application of microbial flocculants in wastewater treatment
In river water treatment Research on its application has shown through experiments that when flocculants produced by isolated and screened Bacillus are used to treat higher turbidity river water, the technical indicators after treatment are significantly better than conventional flocculants such as PAC.
Relieve sludge bulking: By adding microbial flocculants to activated sludge, the volume index of activated sludge will decrease, thereby eliminating sludge bulking and restoring the settling capacity of activated sludge. For example, when treating the sublimation of licorice pharmaceutical wastewater, by adding a certain amount of microbial flocculant into the formed expanded sludge, the SVI of the sludge quickly dropped from 290 to 50, thereby eliminating sludge expansion and restoring activated sludge settlement. Ability effects.
Decolorization of printing and dyeing wastewater: The composition of printing and dyeing wastewater is relatively complex, has high chroma, and contains difficult-to-degrade surfactants. For example, the use of white rot fungi to treat dye wastewater is a current research hotspot.
Enrichment of heavy metals: many microbial flocculant-producing bacteria have Ability to adsorb heavy metal ions.
With the continuous improvement of people’s understanding of water treatment, chemical flocculants The possible secondary pollution caused by residues has attracted much social attention, which gives microbial flocculants an excellent opportunity to enter the market. However, the composition of my country’s productive wastewater is becoming increasingly complex, and the adaptability of microbial flocculants is also facing tests.
Future research on microbial flocculants may focus on the following Several aspects:
1. On the physical and chemical properties of microbial flocculants and the properties of flocculating groups Study of structure, flocculation performance, flocculation kinetics and factors affecting flocculation.
2. Choose to use alternative microbial culture media to optimize microbial flocculation The production route of the agent can be used to reduce production and use costs and achieve large-scale application.
3. The combined application of microbial flocculants and various flocculants, Realize the complementary advantages of various flocculants and increase efficiency and save energy.
4. Through genetic engineering technology, the pollution factor degradation plasmid is introduced into the engineering strain to achieve flocculation. , sedimentation and degradation, expanding the application prospects of flocculants.
