Author: Site Editor Publish Time: 2022-12-26 Origin: Site
Urban wastewater treatment and urban water supply are the main application sites for membrane water treatment technology. The majority of membrane urban water supply plants use microfiltration membranes, with some plants with high effluent targets using both microfiltration and reverse osmosis membranes, and nanofiltration plants have also been on the rise in recent years.
The vast majority of membrane urban wastewater treatment plants use MBR technology. From the data, the large-scale municipal MBR application and the change in scale of membrane municipal water treatment plants are highly consistent with the trend in the output value of the membrane water treatment industry as a whole, and it can be assumed that the application of MBR membrane technology has played a leading role in the rapid growth of the output value of membrane water treatment.
Water treatment is divided into primary treatment, secondary treatment and deep treatment. The main purpose of primary treatment is to remove suspended solids, often using physical methods, the removal rate of BOD5 is generally in the range of 20%-30%; secondary treatment is to further remove colloids and dissolved pollutants in the sewage, often using biological methods, the removal rate of BOD5 in more than 90%; deep treatment to achieve higher treatment and discharge requirements or reuse of sewage as the purpose.
Membrane technology is often used to treat secondary treatment activated sludge effluent, or the membrane treatment system is placed directly in the biochemical pond, i.e. membrane bioreactor (MBR), replacing the original secondary sedimentation tank, flocculation sedimentation tank and other links.
(1) Excellent effluent quality: MBR technology has excellent and stable effluent quality, with suspended solids and turbidity close to zero. It has certain advantages over traditional processes in terms of removal of hard-to-degrade organic matter, disinfection and ecological stability.
(2) Small footprint: MBR reactors can maintain high concentrations of microorganisms within the disposal unit, high volumetric load, and greatly reduce the footprint compared to traditional biological processes, which is an important reason why some municipal wastewater projects currently choose MBR.
(3) Strong resistance to water quality impact: due to the efficient retention effect of the membrane, microorganisms can be completely retained in the bioreactor, which is conducive to the slow-proliferating microorganisms being retained, growing and multiplying in the reactor, making the system more resistant to water quality impact.
(4) Less residual sludge: the system operates under high volumetric load, low sludge load and long sludge age, with low sludge yield, which can reduce the cost of sludge treatment.
5) Easy start-up: the system creates growth conditions for the residence and reproduction of various microorganisms, enriching the microbial phase in the reactor and shortening the domestication cycle, thus allowing MBR to start up operation in a short period of time.
However, MBR technology is also faced with challenges in the promotion and application process, such as high energy consumption, high costs, high management requirements and difficulties in the treatment of residual sludge. In terms of economics, the investment cost of MBR technology is high.
According to statistics, the average total investment cost of all municipal wastewater treatment plants is about 2200 yuan per ton of water, while the total investment cost of MBR ton of water is 2100-7000 yuan, an average of about 3800 yuan, direct engineering costs of 2000-4500 yuan (including civil construction, installation, membrane systems and equipment), the difference in investment costs and application areas, project construction period, membrane module manufacturers, structural forms, etc. have The investment cost varies depending on the application area, project construction period, membrane module manufacturer and structure form.