Integrated ferrate and calcium sulfite to treat algae-laden water for controlling ultrafiltration membrane fouling: High-efficiency oxidation and simultaneous cell integrity maintaining

To alleviate severe algal-source membrane fouling in the ultrafiltration (UF) process, calcium sulfite (CaSO3) integrated with ferrate (Fe(VI)) was proposed. With the integrated pre-treatment, the maximum removal rate of algae cells was improved to 91.19 %, and numerous larger flocs with great settleability were generated. The fluorescent organic components were effectively eliminated, as well as the dissolved organic matter decreased by 38.20 %. During the Fe(VI)/CaSO3 process, oxidation played a fateful role in fouling alleviation and promoted the in-situ coagulation efficiency. Compared with single Fe(VI) treatment, the oxidation capacity was strengthened through the formation of a series of reactive intermediates (involving Fe(V), Fe(IV), SO3 center dot-, SO5 center dot-, SO4 center dot- and (OH)-O-center dot), which were easy to be quenched by the cell-coated extracellular organic matter. Moreover, the consumption of all the oxidants was also remarkably accelerated, thereby the cell integrity was well-kept, and the intercellular organic matter (IOM) was not released. The IOM which already existed in water could also be eliminated, as well as the effluent safety was well guaranteed. During UF, the terminal J/J(0) was elevated to 0.87 at most from 0.10, and the fouling resistances were strikingly reduced. The algal foulants deposition was effectively decreased, and the contact angle of the fouled membrane was closer to the virgin membrane. The dominant fouling mechanism was also converted to intermediate and standard blocking without forming the cake layer.

Automated summary

To alleviate severe algal-source membrane fouling in the UF process, a combination of calcium sulfite (CaSO3) and ferrate (Fe(VI)) pre-treatment was proposed. The integrated pre-treatment improved the removal rate of algae cells and generated larger flocs with better settleability. The oxidation capacity was strengthened during the Fe(VI)/CaSO3 process, leading to enhanced fouling alleviation and in-situ coagulation efficiency.