What are the main technologies and applications in the field of water purification wastewater treatment and high concentration material filtration and

At present, the technologies widely used in sewage treatment in China include oxidation ditch process, SBR process, CASS process, contact oxidation process, biological aerated filter (BAF) process, MBR process, and rapid separation biological treatment technology. The above methods each have their own advantages and disadvantages. The selected main methods are described as follows:

CASS process

The CASS (Cyclic Activated Sludge System) process is one of the internationally recognized advanced processes for treating domestic sewage and wastewater in recent years. Its basic structure is: based on the sequencing batch reactor (SBR), the reaction tank is designed in two parts along the length of the tank, with the front part being the biological selection zone, also known as the pre reaction zone, and the rear part being the main reaction zone. The rear part of the main reaction zone is equipped with an adjustable automatic skimming device. The aeration, sedimentation, and drainage processes of the entire process are cyclically operated in the same tank, eliminating the need for the secondary sedimentation tank and sludge reflux system of conventional activated sludge processes; Simultaneously capable of continuous water intake and intermittent drainage.

MBR process

Membrane bioreactor (MBR) is a new water treatment technology that combines membrane separation units and biological treatment units, and has developed rapidly in recent decades. This process replaces the secondary sedimentation tank in the activated sludge process with hollow fiber membranes for solid-liquid separation, effectively achieving the goal of sludge water separation. The efficient interception effect of the membrane can effectively intercept nitrifying bacteria, allowing them to be completely trapped in the bioreactor, enabling the nitrification reaction to proceed smoothly, effectively removing ammonia nitrogen, avoiding sludge loss, and also intercepting large molecular organic matter that is difficult to degrade at the moment, prolonging their residence time in the reactor, and maximizing their decomposition.

However, the MBR process still has the following drawbacks: high membrane cost, short service life of membrane components, and the need for replacement within 2-3 years; Easy to cause membrane fouling; High energy consumption, in order to increase membrane flux and reduce membrane fouling, it is necessary to increase the flow rate and flush the membrane surface, resulting in higher energy consumption of MBR compared to traditional biological treatment processes.

Rapid biological processing technology

Rapid biological treatment technology is a new type of wastewater treatment technology. The principle of this technology is to use the "flow" principle in fluid mechanics to break through traditional biological treatment methods, transforming the single biological environment in the treatment system into a variable biological environment, allowing sewage to undergo multiple anaerobic and oxygen consuming reactions in the collection body, and the treatment process does not require sedimentation tanks, backwashing, and sludge treatment systems. The core of the rapid separation biological treatment technology is the "rapid separation biochemical ball", which serves as a biological carrier and is filled in a specially designed rapid separation biochemical pool. The biofilm attached to it is the main functional substance of the biochemical treatment system. The quick separation bio ball can be used normally for 30 years without replacement, saving a lot of replacement and maintenance costs compared to traditional bio fillers.

Development trend of sewage treatment technology

1. Wastewater treatment processes with denitrification and phosphorus removal functions are still the focus of future development

The "Pollutant Discharge Standards for Urban Sewage Treatment Plants" (GB18918-2002) have clear requirements for effluent nitrogen and phosphorus. Therefore, existing urban sewage treatment plants need to be renovated to increase facilities for removing nitrogen and phosphorus pollutants from sewage, in order to meet the national emission standards. Newly built sewage treatment plants must be constructed in accordance with the standard GB18918-2002. At present, research on the mechanism, influencing factors, and processes of biological nitrogen and phosphorus removal in wastewater has become a hot topic, and some new and reformed processes have been proposed.

Such as MSBR, inverted A2/O, UCT, etc., and actively introducing new foreign processes.

Such as OCO, OOC, AOR, AOE, etc. For denitrification and phosphorus removal processes, future development requirements are not limited to high nitrogen and phosphorus removal rates, but also require stable and reliable treatment effects, flexible process control and adjustment, and cost savings in investment and operation. At present, biological phosphorus and nitrogen removal processes are developing towards this simple, efficient, and economical direction.

2. Efficient, low investment, low operating costs, mature and reliable sewage treatment processes are the preferred processes for future sewage treatment plants

China is a developing country with a relatively backward level of economic development. Faced with increasingly severe environmental pollution, the country is intensifying efforts to treat sewage. The fundamental measure to solve urban sewage pollution is to build secondary urban sewage treatment plants with biological treatment as the main process. However, building a large number of secondary urban sewage treatment plants requires significant investment and high operating costs, which is a heavy burden for China. At present, the construction of sewage treatment plants in China is difficult to carry out due to a lack of funds. Some completed sewage treatment plants have been unable to operate normally due to high operating costs or a lack of professional operation and management personnel. Therefore, research on high-efficiency, low investment, low operating cost, mature and reliable sewage treatment processes is a key research direction in the future.

3. Research on the process applicable to small town sewage treatment plants

Developing small towns is a necessary path for China's urbanization process and a strategic choice for the urbanization path with Chinese characteristics. From 1978 to 2000, the number of established towns in China increased from 2178 to 20312, and currently there are nearly 48000 small towns of various sizes and natures. If we only focus on the construction of sewage treatment projects in large and medium-sized cities and ignore the sewage treatment of so many small towns, then China's sewage treatment cannot achieve the predetermined goals. And for the sewage treatment in small towns, there are a series of problems: the characteristics of sewage in small towns are different from those in big cities; Shortage of funds in small towns; Lack of operational management personnel, etc. Therefore, the sewage treatment process in small towns should have low infrastructure investment, low operating costs, relatively easy operation and management, and high operational reliability. The current research direction for processes applicable to small town sewage treatment plants is to compare and select processes suitable for small town sewage treatment plants from existing processes, while developing new processes suitable for small town sewage treatment plants.

4. Research on sewage treatment processes with low sludge production and stable sludge production

At present, the treatment of sludge generated by sewage treatment plants is also a key and difficult point in China's sewage treatment industry. In 2003, the total sewage treatment capacity of urban sewage plants in China was about 95.9562 × 108/a, and the average solid content of urban sewage was 0.02%. Therefore, the wet sludge production was 965.562 × 104 t/a. Moreover, the composition of sludge is very complex, containing various harmful and toxic components. If the sludge with such a large production and containing a large amount of toxic and harmful substances is not effectively treated and discharged into the environment, it will cause great damage to the environment.

The current situation of sludge treatment and disposal in China is not optimistic: according to statistics, only 25.68% of the urban sewage treatment plants that have been built and operated in China have sludge that has been concentrated, digested and stabilized, and dried and dehydrated. 55.70% of the sewage plants do not have sludge stabilization treatment, and about 48.65% of the sewage plants do not have sludge drying and dehydration treatment. This indicates that more than 70% of sewage treatment plants in China do not have complete sludge treatment processes. An effective solution to this problem is to adopt sewage treatment processes with low sludge production and stable sludge, which can reduce the amount of sludge generated at the source and obtain stable residual sludge, thereby reducing the burden of subsequent sludge treatment. At present, some processes in China can achieve this, such as biological contact oxidation process, BIOLAK process, hydrolysis aerobic process, etc. However, systematic research on sewage treatment processes with low sludge production and stable sludge has not yet begun.