What are the treatment methods of reclaimed water reuse
1、 Classification by use
There are three treatment methods for reclaimed water due to different uses
1. One is to treat it to the standard of drinking water and directly reuse it in daily life, that is to realize the direct recycling of water resources. This kind of treatment method is suitable for areas with extreme lack of water resources, but it has high investment and complex process;
2. The other is to treat it to the standard of non drinking water, which is mainly used for water not in direct contact with human body, such as toilet flushing, floor and car cleaning, greening and sprinkling, fire fighting, industrial common water, etc. This is the usual way of reclaimed water treatment.
3. In industry, the reclaimed water reuse technology can be used to re treat the industrial sewage meeting the discharge standard. Generally, softener, RO, EDI / mixed bed and other equipment will be added to make it reach the level of softened water, purified water and ultra pure water. It can be used for industrial recycling to save capital and protect the environment.
2、 Classification by treatment method
According to the treatment method, the reclaimed water treatment process is generally divided into three types
1. Physical treatment
The membrane method is suitable for large changes in water quality.
The characteristics of this process are: compact device, easy to operate, and less affected by load changes.
Membrane filtration method is under the action of external force, the separated solution flows along the surface of the membrane at a certain flow rate, the solvent, low molecular weight substances and inorganic ions in the solution enter the low pressure side through the membrane from the high pressure side, and are discharged as filtrate; while the high molecular weight substances, colloidal particles and microorganisms in the solution are intercepted by the ultrafiltration membrane, and the solution is concentrated and discharged in the form of concentration.
Evaporative heat method: applicable to any water quality.
The features of this process are: high stability, easy maintenance, long service life, simple operation, and no influence on equipment operation due to water quality fluctuation.
Evaporation heat method is to separate pure water and salt solid by heating and evaporating the solution to boiling point in the evaporation body. Pure water is condensed into pure water in the form of steam, and the concentrated liquid forms salt solid through continuous circulation evaporation. Pure water quality can be reused by a series of filtration measures.
2. Physicochemical method
It is suitable for the situation that the sewage quality changes greatly. The commonly used methods are: sand filtration, activated carbon adsorption, flotation, coagulation and sedimentation. The characteristics of this process are: using hollow fiber ultrafilter for treatment, advanced technology, compact structure, less land occupation, intermittent operation of the system, simple management.
3. Biological treatment
It is suitable for wastewater with high organic matter content. Generally, activated sludge process, contact oxidation process (as shown in the figure), biological turntable and other biological treatment methods are used. It can be used alone or combined with several biological treatment methods, such as contact oxidation + biofilter; biofilter + activated carbon adsorption; rotary table + sand filtration and so on. This process has the advantages of strong adaptability to hydraulic load variation, less sludge production and easy maintenance and management.
At present, some countries and regions are excessively and uncontrollably developing water resources, but at the same time, the awareness of environmental protection is relatively poor, so that the surface water and groundwater are polluted to varying degrees, so that the supply of fresh water with good water quality is limited; secondly, the fresh water source to be developed is far away from the centralized water supply point, and the one-time investment cost is high Some water shortage areas are unable to expand water supply capacity. To the extent of non drinking, the concept of reclaimed water is introduced here. Reclaimed water is to reuse the high-quality miscellaneous drainage (excluding feces and kitchen drainage), miscellaneous drainage (excluding feces sewage) and domestic sewage (waste) that people used in life and production after collection and regeneration treatment. It is used as miscellaneous water for ground cleaning, watering, car washing, air conditioning cooling, toilet flushing, fire fighting and other non-contact with human body. Because its water quality index is lower than the standard of drinking water in urban water supply, but higher than the standard of allowing sewage to be discharged into surface water, that is, its water quality is between the standard of drinking water quality and that of allowing sewage to be discharged, so it is named "reclaimed water".
Reclaimed water development and reuse technology has been developed rapidly, and has been widely used in the United States, Japan, India, Britain and other countries (especially Japan). According to the characteristics of their own countries and regions, these countries have determined the reclaimed water reuse technology suitable for their national conditions and national strength, which makes the reclaimed water reuse technology more and more perfect. In China, this technology has been attached great importance by governments at all levels and relevant departments, and has done a lot of theoretical research and practical work on the reuse of building reclaimed water. In many cities in China, such as Shenzhen, Beijing, Qingdao, Tianjin, Taiyuan, etc., the operation of reclaimed water projects has been carried out, and remarkable results have been achieved. China's state-owned industrial enterprises and some private enterprises, such as enterprises with serious pollution and more use of water resources, have built reclaimed water reuse projects, contributing to the national call for low-carbon production and energy conservation and emission reduction.