Based on the problems of decentralized water supply and conventional ultrafiltration process

a gravity-driven membrane (GDM) filtration process was developed

which combined the dual rejections between bio-cake layer and ultrafiltration membrane and had the advantages of no cleaning

no chemical supply

simple operation

low energy consumption

and low maintenance. Results showed that flux stabilizations of GDM were observed during the long-term treatments of river water

reservoir water

and synthesized water

indicating the practical universality of GDM process in treating different types of water resources. The operating conditions

including raw water quality

operating pressure

membrane configuration type

membrane material

membrane pore size

temperature

intermittent filtration

and pre-treatment

affected the structures and compositions of bio-cake layer formed on the membrane surface

and consequently exerted impacts on the stable flux of GDM and its membrane fouling characteristics. Flux stabilization of GDM process was mainly determined by the structures and compositions of bio-cake layer regulated by the biological activities. The bio-cake layer with rougher structures

more abundant pores

and less extracellular polymeric substance (EPS) excretions

could contribute to a higher stable flux in long-term GDM filtration. Compared with conventional ultrafiltration process

the bio-cake layer formed on the surface of GDM could efficiently enhance the removal performance for turbidity

assimilable organic carbon (AOC)

and ammonia. In addition

pre-treatment of slow filter could effectively modify the structural characteristics of bio-cake layer

improve the stable flux of GDM

and enhance the removal performance. The findings of this paper are expected to promote the extensive applications of ultrafiltration technology in decentralized drinking water supply.