High-efficiency cleaning technology and lifespan prediction for the ceramic membrane treating secondary treated effluent.

Chemical cleaning is one of the key technical means to control membrane fouling, restore membrane flux and ensure the stable operation of membrane systems. In the experiment, the six most representative chemical cleaning agents for ceramic membranes, such as sulfuric acid (H2SO4), sodium hydroxide (NaOH), sodium hypochlorite (NaClO), ethylenediaminetetraacetic acid disodium salt (EDTA-Na2), sodium dodecyl sulfate (SDS) and nonylphenol polyoxyethylene ether (OP-10), were used as research objects. The cleaning effect of the two-step combined cleaning of chemical cleaning agents on the fouled membrane was systematically investigated. Results showed that the order of the chemical cleaning agent had a significant effect on the cleaning effect. The best chemical cleaning program was determined to be NaClO first and then SDS: the fouled ceramic membrane was soaked in NaClO solution at 0.15% for 2.5 h and further soaked in SDS solution at five times its own critical micelle concentration for 2.5 h. The predicted long-term lifespan of the ceramic membranes was 4.91 years. Scanning electron microscopy-energy spectrum analysis showed that the surface roughness of the cleaned ceramic membrane was slightly higher than that of the new membrane. The contact angle was slightly lower than that of the new membrane.

Study on pickling technology to control fouling of ceramic membrane treating secondary treated effluent.

The application of membrane technology in the field of water treatment was increasingly widespread, but membrane fouling still restricted its development, and the membrane needed to be chemically cleaned. This research focused on the high-efficiency pickling technology of ceramic membrane, and developed the cleaning technology of ceramic membrane in cooperation with surfactant. In the experiment, the municipal secondary effluent was used as the raw water, and the single-step, mixed and step-by-step cleaning effects of three strong acids, three weak acids and surfactants on ceramic membranes and polyvinylidene difluoride (PVDF) membranes were investigated. For ceramic membrane, the optimal cleaning combination was H2SO4 first and then DTAC, and the flux recovery rate could reach 96.94%; for PVDF membrane, the optimal cleaning combination was HNO3 first and then H2SO4, and the flux recovery rate could reach 93.72%. In addition, the surface of initial, polluted, and cleaned membranes were analyzed by scanning electron microscope and contact angle, and the fouling mechanism of the ceramic membrane was analyzed. The results showed that through physical cleaning and chemical cleaning, most of the pollutants on the membrane surface and pores were removed. The cleaning method can effectively control the membrane pollution.