Mechanisms and regulations of GAC/GDM hybrid process for rural drinking water treatment

Abstract:

High energy consumption, complex operation, large amount of operation and maintenance, and high cost restrict the development and extensive application of drinking water treatment technology in rural areas. In this study, the ultra-low pressure gravity-driven membrane (GDM) filtration technology was specifically developed, which has the advantages of simple operation, low maintenance, low energy consumption, and chemical free. To further improve the removal efficiency of pollutants, we constructed a hybrid process of granular activated carbon (GAC) slow filter and GDM (GAC/GDM). Results show that pretreatment by GAC slow filter could significantly improve the removal efficiency of UV₂₅₄, dissolved organic carbon (DOC), and ammonia nitrogen, with the average removal efficiency of 75%, 86%, and 90%, respectively. Meanwhile, the membrane flux was improved by 32% compared with GDM control. The regulation effect of either water cycle (CGAC/GDM) or weak aeration (AGAC/GDM) on the performance of the hybrid process was investigated. During long-term filtration, compared with GDM control, the stable flux of CGAC/GDM and AGAC/GDM was increased by 36% and 49%, respectively. However, the removal efficiency of DOC and UV₂₅₄ in CGAC/GDM and AGAC/GDM declined slightly compared with GAC/GDM, since water cycle and weak aeration increased the concentration of dissolved oxygen in the feed water before GDM filtration, which promoted the hydrolysis of organic pollutants retained within the bio-cake layer on the membrane surface by the microorganisms. Therefore, the proposed GAC/GDM hybrid process can simultaneously improve the stable flux level and pollutant removal, which will provide theoretical and technical support for the development and application of membrane filtration technology in the rural areas.