1. Dead end filtering
When the suspended solids, turbidity and COD values are low, such as clean surface water, natural mountain spring water and other water bodies, or there are very strict pre-solutions before ultrafiltration, such as ultrafiltration water filter and so on. At this time, ultrafiltration can be operated in accordance with the method of full filtration/dead-end filtration. When the source water enters hollow fiber ultrafiltration membrane, no concentrated water is discharged, and the operating utilization rate is 100%.
The characteristics of dead-end filtration: It is suitable for influent water with low suspended solid content and low environmental pollution content. It usually requires high previous solutions and low water flux. The processing technology is simple, the processing technology operation flexibility is poor, it is not suitable for the situation of large influent conversion, the cleaning is difficult, and the operation energy consumption is low. Hollow fiber ultrafiltration membrane is mainly manifested by environmental pollution and high cleaning frequency.
2. Cross-flow filtration
When the content of influent suspended solids and colloidal solution is not high, cross-flow filtration can be performed. The source water enters hollow fiber ultrafiltration membrane, and the concentrated water is discharged from the concentrated water of the membrane tube in a certain proportion. Most of the product water is produced from the ultrafiltration port, and the operating utilization rate is generally 90%-99%, which is determined by the source water particle concentration.
The characteristics of cross-flow filtration: suitable for influent with low solid suspended solids and environmental pollution content, low energy consumption, high water flux, flexible processing technology, and large suspended solids carrying capacity.
3. Circulating filtration at the concentrated water end
When the content of suspended solids and colloidal solution in the raw water is high, in most sewage treatment, it is necessary to reduce the recovery rate to maintain the high flow rate inside the fiber, resulting in a large amount of sewage. In order to better prevent waste and improve utilization, the discharged concentrated water enters uf membrane module again, that is, in the circulation mode, the influent water is continuously circulated on the membrane surface. The high circulating water flow rate prevents the accumulation of particles on the membrane surface and increases了流。 The flux. Since most of the influent water becomes circulating concentrated water, and a small part of the influent water becomes product water, in order to better obtain the same output rate, higher energy consumption is required.
The characteristics of concentrated water end circulation filtration: suitable for high solid suspension content, high energy consumption content, high operating energy consumption, and slow water permeability flux loss.