A large amount of sludge will be produced in the process of chemical production. The sludge is composed of non degradable substances in sewage treatment and dust produced in the production. With the increasing attention to environment in China, the requirements for sewage treatment in the chemical industry are increasing high, so the chemical enterprises need to properly disposes the sludge.

In the past, the sludge was naturally air dried. With the improvement of production efficiency, this method is obviously too limited and backward. At present, mechanical dewatering technology has been used in most of chemical enterprises. However, the dewatering efficiency, effect and treatment cost of mechanical dewatering technology need to be improved, which is the intention of this article.

1. Overview of mechanical dewatering technology

Pretreatment is necessary when using the mechanical dewatering technology. Pretreatment includes sludge concentration, sludge volume reduction and sludge dewatering property improvement. In order to improve sludge dewatering property, there are two methods: heat treatment and adding chemical reagents (coagulant, inorganic salt). After pretreatment, the sludge can be dewatered mechanically. The mechanical dewatering technology includes filtration and centrifugation.

1.1 Filtration

The sludge is filtered into solid phase and liquid phase through the filter cloth and filter paper. The solid phase needs to be further dried, and the liquid phase needs to be purified.

1.2 Centrifugation

The sewage is separated by high-speed centrifuge. Due to the different density of the solid phase and liquid phase, when the sewage is fed into the centrifuge, it will be separated by the centrifugal force and discharged from different outlets.

Both filtration and centrifugation require a large number of devices. The former has good filtration effect and high dewatering effect, which is 60%-70%. However, its disadvantages are low production efficiency, large area, complex operation and more workers. The latter is automatic, needs less devices, and the dewatering effect is about 80%. Its disadvantages are high cost and high requirements of sludge pretreatment.

2. Development of mechanical dewatering technology

There are two development space of mechanical dewatering technology: simplification of sludge dewatering process and upgrading of mechanical equipment.

2.1 Simplification of sludge dewatering process

The traditional process of sludge mechanical dewatering technology is: sludge→sludge pretreatment→non-toxic treatment (chemical reagents)→filtration or centrifugation→disposal (agricultural, incineration or landfill). In the process, there is a large space for simplification in sludge pretreatment and non-toxic treatment. With the development of science and technology, the research of chemical reagents are progressing day by day, so it is expected to develop high-efficiency chemical reagents for sludge pretreatment and no-toxic treatment in the future.

2.2 Upgrading of mechanical equipment

With the development of science and technology, the upgrading of mechanical equipment is faster and faster. In the past, the mechanical equipment covers a large area, has low dewatering efficiency and poor dewatering effect. Now, the mechanical equipment covers a small area, is easy to operate, has high dewatering efficiency and good dewatering effect. In the foresee future, the will be new development of sludge mechanical equipment.

3. Dewatering trend of sludge dewatering technology

In the 21st century, biotechnology develops rapidly and is widely used. There are many research results in the field of biology, among which the research results in the field of microorganism can be applied to wastewater treatment and sludge dewatering in chemical enterprises. The efficiency and effect of sludge dewatering can be improved by integrating biotechnology into sludge dewatering technology. Different microorganisms have different features, there are a lot of organic substances in the sludge of chemical enterprises, this kind of environment is very suitable for microbial action. Microorganisms can decompose organic macromolecules into small molecules, and convert toxic polymers into non-toxic or low-toxic small molecules. In addition, microorganisms can improve the sludge dewatering property, so that the filtration or centrifugation can be easier to carry out. Generally speaking, the future development trend of sludge dewatering technology is to integrate biotechnology with organic technology, which is more efficient and lower cost.

The by-products of sludge dewatering will be widely used to realize resource reuse. There are a large amount of organic substances and nutrients in the chemical sludge. After non-toxic treatment and low-toxic treatment, the dried sludge has a high utilization value. At present, some dried sludge are used as fertilizers in agriculture, the practice has proved that the fertilization effect is excellent. Some dried sludge are used as materials for combustion. The dried sludge can be used to fill the foundations and strengthen the buildings. Generally speaking, with the development of industry, the dried sludge will be more widely used.