Reclaimed water is an important way to solve the crisis of urban water resources and the fundamental way to coordinate urban water resources and water environment. The treatment and reuse of domestic sewage can not only reduce the exploitation of groundwater, but also bring us certain economic benefits. Reclaimed water refers to non potable water that has been treated to meet the specified water quality standards and can be used for various purposes such as domestic, municipal, and environmental purposes. Because its water quality index is lower than the water quality standard for drinking water, but higher than the water quality standard for allowed discharge of sewage, it is in between the two, so it is called "reclaimed water".
Due to the "water crisis", many countries and regions are actively working to consolidate and strengthen their awareness of water conservation, as well as researching the regeneration and reuse of urban wastewater. Urban sewage reuse refers to the treatment and reuse of water used by urban residents in their daily lives and production. There are two different levels of reuse: one is to treat wastewater to a drinkable level, while the other is to treat wastewater to a non drinkable level. For the former, due to its high investment and complex process, it is generally not commonly used in non water scarce areas. Most countries treat wastewater to a non potable level, which leads to the concept of reclaimed water. Reclaimed water is also used to recycle high-quality miscellaneous wastewater (excluding feces and kitchen drainage), miscellaneous wastewater (excluding fecal sewage), and domestic sewage (waste) that people have used in their daily lives and production. It is used for floor cleaning, watering plants, car washing, air conditioning cooling, toilet flushing, firefighting, and other miscellaneous water that does not come into direct contact with the human body.
The membrane bioreactor (MBR) has been applied in multiple reclaimed water reuse projects due to its high treatment efficiency, good effluent quality, compact equipment, small footprint, easy implementation of automatic control, and simple operation and management.
Reclaimed water equipment is a new type of biochemical water treatment equipment specially developed for the reuse of industrial and domestic sewage. It breaks the traditional process used in reclaimed water treatment facilities and applies the international new membrane technology process to reclaimed water treatment, thus forming the current new reclaimed water treatment technology. Its effluent quality is excellent and stable, suitable for non drinking water places such as flushing toilets, green spaces, car washing, and supplementing ornamental water bodies, greatly utilizing water resources and reducing environmental pollution.
Applicable industries for reclaimed water reuse:
The required inlet water quality for washing wastewater treatment, hospital wastewater treatment, hospital wastewater treatment equipment, and hospital wastewater treatment projects is: BOD ≤ 500mg/l, CODcr ≤ 1500mg/l, T-N ≤ 60mg/l, SS ≤ 400mg/l. The main indicators of the treated wastewater are: chromaticity ≤ 40 degrees, COD ≤ 50ppm BOD≤10ppm、SS≤10ppm 、PH≤6.5~9、LAS≤1ppm
Total coliform count ≤ 3, total bacterial count ≤ 100/L, free residual chlorine ≥ 0.2ppm, and no unpleasant sensation in the effluent.
Characteristics of reclaimed water reuse technology:
(1) It can efficiently perform solid-liquid separation, separating suspended substances, colloidal substances, and microbial communities lost from biological units in wastewater from purified water. The separation process is simple, occupies a small area, has good effluent quality, and generally does not require tertiary treatment for reuse.
(2) It can maintain a high concentration of biomass in the biological treatment unit, greatly increasing the volumetric load. At the same time, the high efficiency of membrane separation greatly shortens the hydraulic retention time of the treatment unit, and correspondingly reduces the footprint of the bioreactor.
(3) Due to its ability to prevent the loss of various microbial communities, it is beneficial for the growth of slow growing bacteria (such as nitrifying bacteria), thereby facilitating the smooth progress of various metabolic processes in the system.
(4) Extending the residence time of some macromolecules that are difficult to degrade organic compounds is beneficial for their decomposition.
(5) Membrane treatment technology, like other filtration and separation technologies, is prone to clogging as a filtration medium during long-term operation. The flow rate of water through the membrane gradually decreases over time. Effective backwashing and chemical cleaning can slow down the decrease in membrane flux and maintain the effective service life of MBR systems.
(6) MBR technology has been successfully applied in urban sewage treatment projects due to its simple process, convenient operation, and ability to achieve fully automated operation and management.
Process flow of reclaimed water reuse:
Raw water → Grid → Regulating tank → Lift pump → Bioreactor → Circulating pump → Membrane module → Disinfection device → Reclaimed water storage tank → Reclaimed water use system.