The reclaimed water treatment technology for wastewater is based on the global shortage of water resources and the pollution caused by wastewater discharge. The reuse of urban sewage treatment not only reduces the pollution level caused by direct sewage discharge, but also can recycle water resources to a large extent. It can be said to be a major move in water resources. For a city, the introduction of a reclaimed water system is not only a highlight of the city but also an environmental protection calling card for reclaimed water utilization. This is still a very attractive person who is increasingly aware of environmental protection in today's society.
There are problems with the technology of reusing reclaimed water from sewage
Although the technology for reusing reclaimed water is relatively mature at present, there are still some problems, mainly manifested in the high investment cost in the initial stage of development. The price of reclaimed water abroad is approximately 80% of that of tap water. However, the cost of reclaimed water in our country is relatively high. Some small-scale reclaimed water reuse projects even exceed the price of tap water and have no competitive advantage. In addition, the water source is unstable and the facilities are not fully utilized, resulting in high operating costs. Technical security needs to be improved. For instance, the application of ultraviolet oxidation technology in the advanced treatment of secondary effluent has the characteristics of simple process and thorough degradation. However, it is necessary to ensure sufficient hydraulic retention time, promptly clean the dirt in the reactor, and guarantee the high degradation and sterilization performance of the ultraviolet lamp. A high dose of ozone is also required. However, excessive ozone will produce certain oxidation by-products, leading to an increase in the ecological toxicity of the effluent. In membrane technology production water, excessive strength and overload operation can cause mechanical damage to the membrane and lead to leakage. When the pollution is severe, membrane fouling will increase the osmotic pressure on the membrane surface, reduce the mass transfer force, increase the resistance of membrane separation, and damage the membrane separation function. The sbr process requires a longer hydraulic retention time and better phosphorus removal effect. Poor.
Technologies and processes for reusing reclaimed water from sewage
1. Wastewater reuse technology
The development of wastewater reuse technology is based on the advancement of advanced water treatment technologies. The development and application of reuse technology are much more flexible than those of drinking water treatment technology. The combination methods of treatment units and specific technological processes are more diverse than those of drinking water treatment technology. The removal effect of primary sewage treatment technology on pollutants in sewage is limited. Generally, in order to meet the requirements that are lower than the water quality standards for reuse, the effluent can be effectively removed through advanced treatment. Therefore, the general wastewater reuse technology is based on the primary effluent, and the subsequent treatment processes include coagulation sedimentation, biological treatment, filtration, disinfection, membrane treatment and other treatment technologies.
2. Reclaimed water treatment process
During the coagulation and sedimentation process, coagulation includes coagulation, reaction, flocculation and coagulation, and the dosage of coagulant is much larger. When microflocculation is combined with the filtration process, coagulation only includes the mixing stage, the reaction stage and the microflocculation stage, and the dosage of coagulant is relatively small. Carry out general filtration, microfiltration and ultrafiltration. Common filtration devices include common rapid filters, mechanical pressure filters, honeycomb filters, precision sintered rod filters, membrane reactors, etc. Among them, ultrafiltration devices are membrane reactors, which can be classified into hollow fiber membranes, plate membranes, tubular membranes, etc. according to the membrane form. Microfiltration and ultrafiltration are generally used for small-scale water reuse. According to the aerobic classification of microorganisms, the biofilm method and the activated sludge method, the anaerobic and aerobic methods were classified, and the aerobic activity of microorganisms was divided into the anaerobic and aerobic methods. The commonly used devices mentioned include biological contact oxidation devices, biological rotating discs, activated sludge tanks, hydrolysis acidification tanks, etc. In addition, an integrated device or a combined device is also provided, such as a membrane bioreactor as the main process of biological treatment, etc.
Analysis and Application of Reclaimed Water Treatment Technology
1. Physical and chemical treatment and process analysis
Physicochemical treatment is a comprehensive method for treating sewage through chemical coagulation reactions and physical sedimentation, adsorption, filtration, disinfection, etc. The basic method combining coagulation sedimentation (air flotation) technology with activated carbon adsorption technology is adopted. By adding flocculants and coagulant AIDS and thorough stirring, the coagulation effect is achieved. Then, after sedimentation, filtration and disinfection treatment, the reuse standard is met. This treatment method is mainly used for dealing with high-quality impurity emissions and can operate intermittently without the need for sludge treatment. It is applicable to the treatment of small-scale reclaimed water projects. Its main features are short processing technology, simple operation and management, and relatively small floor area. However, compared with biological treatment, the operating cost of traditional Chinese medicine is high. The effluent quality is affected by the type and dosage of coagulant and has certain fluctuations. Its removal effect on organic matter is relatively poor.
2. Biophysical and chemical treatment and process analysis
Biological treatment methods include aerobic microbial, anaerobic microbial and facultative microbial treatment. Biological treatment methods involve the steps of decomposing wastewater into substances containing large amounts of organic and inorganic matter by utilizing the adsorption and oxidation of microorganisms. It is widely used in water engineering to degrade organic matter in water and meet the organic matter content standards in water quality. The biochemical treatment method of the present invention is a treatment method combining biological treatment and chemical methods. After the sewage undergoes biological treatment, it undergoes chemical coagulation reaction, sedimentation, filtration and disinfection. This treatment method is mainly used to treat sewage containing heavy organic pollutants and is suitable for the treatment of large-scale reclaimed water projects. Its main features are good effluent quality and relatively low operating costs. Especially for large-scale sewage treatment projects, their disadvantages include high requirements for sludge treatment, easy generation of odors, complex operation and management, and large land occupation.
3. Analysis of Reverse Osmosis Technology and Process
When the pressure and temperature are the same, the chemical potential of the concentrated solution is greater than that of the dilute solution. Therefore, the direction of solvent flow is from the dilute solution to the concentrated solution. When dynamic equilibrium is reached, the pressure is the osmotic pressure of the solution. When pressure is applied to one side of the concentrated solution and the pressure is greater than the osmotic pressure, the chemical potential of the concentrated solution is lower than that of the dilute solution, and the solvent flows towards the dilute solution. This process is the opposite infiltration process. Reverse osmosis (RO) is a highly effective membrane separation operation unit, and the semi-permeable membrane is the key to the entire technology. The anti-fouling performance and light transmittance of the membrane module determine the treatment efficiency of the entire process. Reverse osmosis technology can not only remove salt from water, but also eliminate particles, organic matter and colloidal substances in water, which cannot be achieved in other processes. In order to prevent the membrane module from being damaged and ensure the long-term safe operation of R0, it is necessary to carry out pretreatment on it. This treatment method is mainly used for the treatment of wastewater with high salt content and is suitable for the treatment of medium-scale reclaimed water projects. Its main features are good and stable effluent quality, while the disadvantages are large investment and high operating costs.
Conclusion
To sum up, reclaimed water reuse technology is a practical and effective water-saving technology. The wide promotion of this technology can save precious drinking water resources and to a large extent alleviate the contradiction between urban water supply and demand. It has good social and economic benefits and broad application prospects.
