Flocculants play a very important role in the process of sludge dewatering, the flocculants are used to quickly separate the floating small particles in the sewage. However, in terms of the current use of common flocculants, there is a adverse consequence, which will lead to water pollution. Although the small particles in the sewage have been purified, there will be a small number of toxicity in the purified water. In order to avoid it, microbial flocculants can be used. The microbial flocculants not only have the better effect in particles sedimentation, but also do not produce toxin.

1. Characteristics of microbial flocculants

At present, inorganic salts, polymers and organic polymer compounds are commonly used in sludge dewatering. Compared with them, the advantages of microbial flocculants are as follow:

1.1 High efficiency

High efficiency is an outstanding characteristic of microbial flocculants. Generally speaking, only a small number of microbial flocculants can realize the same effect as a large number of inorganic salts, polymers and organic polymer compounds.

1.2 Safety and non-toxic

The microbial flocculants are mainly composed of natural organic polymers, which are microbial secretions. Many experiments show that the microbial flocculants do not contain any toxicity, and will not cause toxic damage to the water.

1.3 No secondary pollution

There will be a variety of residues difficult to decompose after using inorganic salts, polymers and organic polymer compounds. These residues will cause secondary pollution to the water, and some flocculants that do not participate in the reaction may also cause secondary pollution. Correspondingly, the microbial flocculants will also produce some residues, but these residues are some organic macromolecule substances, which are easy to be degraded by some microorganisms in the water and will not pollute the water. Even if there are some unresponsive microbial flocculants, they will be degraded to avoid secondary pollution.

2. Control measures of microbial flocculants in sludge dewatering

2.1 Decolorization of sewage

In essence, the main reason for sewage color rendering is that there are some color rendering substances and molecules in the water. The microbial flocculants are used to remove these molecules so as to achieve the purpose of sewage decolorization. Many studies have shown that the current microbial flocculants can decolorize almost all colored sewage. In addition, NOC-1 microbial flocculant has a significant decolorization effect on some sewage mixed with pigment and alkaline fuel. Its decolorization rate is higher, and it can even obtain completely transparent solution.

2.2 Treatment of emulsion

At present, emulsion is also a common type of industrial production and domestic sewage, and its main form of existence is oily sewage. For example, industrial sewage discharged during the process of exploitation and production of industrial oil, the sewage discharged from the mechanical processing or maintenance industry, the sewage discharged from the catering industry, are all common emulsion. By using the microbial flocculants, the oily substances in the emulsion will be quickly separated. The amount of microbial flocculants is very small, but the separation effect is very good, so the cost of using microbial flocculants in emulsion treatment is very low.

2.3 Improvement of sludge settling performance

In sewage treatment, activated sludge process is usually used. But after its use, the activated sludge will more or less cause the sewage pollution again because it is difficult to be completely degraded. By using the microbial flocculants, it can not only promote the sedimentation of the sludge, reduce the volume of the sludge, but also can improve the clarity of the sewage.

3. Conclusion

In summary, microbial flocculants have many advantages over inorganic salts, polymers and organic polymer compounds in sludge dewatering.